Dendritic cells and macrophages in the kidney: a spectrum of good and evil

Nature Reviews Nephrology | Review

 

Renal dendritic cells and macrophages are key factors in the initiation and propagation of renal disease and tissue regeneration. This Review discusses the common and distinct characteristics of dendritic cells and macrophages as well as current understanding of the renal-specific functions of these important phagocytic, antigen-presenting cell types in potentiating or mitigating intrinsic kidney disease.

 

Abstract | Renal dendritic cells (DCs) and macrophages represent a constitutive, extensive and contiguous network of innate immune cells that provide sentinel and immune-intelligence activity; they induce and regulate inflammatory responses to freely filtered antigenic material and protect the kidney from infection. Tissue-resident or infiltrating DCs and macrophages are key factors in the initiation and propagation of renal disease, as well as essential contributors to subsequent tissue regeneration, regardless of the aetiological and pathogenetic mechanisms. The identification, and functional and phenotypic distinction of these cell types is complex and incompletely understood, and the same is true of their interplay and relationships with effector and regulatory cells of the adaptive immune system. In this Review, we discuss the common and distinct characteristics of DCs and macrophages, as well as key advances that have identified the renal-specific functions of these important phagocytic, antigen-presenting cells, and their roles in potentiating or mitigating intrinsic kidney disease. We also identify remaining issues that are of priority for further investigation, and highlight the prospects for translational and therapeutic application of the knowledge acquired.

 

Rogers, N. M. et al. Nat. Rev. Nephrol. advance online publication 30 September 2014; doi:10.1038/nrneph.2014.170

Figure 1: The heterogeneous but overlapping phenotype and functions of renal DCs and macrophages.

DCs are traditionally described as mediators of immune surveillance and antigen presentation, and as the primary determinants of responses to antigens—through initiation of either immune effector-cell functions or the development of tolerance. Macrophages also function as innate immune cells, predominantly through phagocytosis and production of toxic metabolites. However, the classical paradigm of DC versus macrophage phenotypes and functions is increasingly indistinct within the kidney, as these cells exhibit overlapping surface markers, functional capabilities, and ontogenic pathways. This molecular and phenotypic overlap between cell types and subsets complicates their identification and evaluation. *Marker described only in humans. Abbreviations: B-ATF-3, basic leucine zipper transcription factor ATF-like 3; BDCA-1, blood dendritic cell antigen 1; CCR, CC chemokine receptor; CSF-1R, colony-stimulating factor 1 receptor; CX3CR1, CX3C chemokine receptor 1; DC, dendritic cell; DC-SIGN, dendritic-cell-specific ICAM-3-grabbing non-integrin; ECM, extracellular matrix; EMR1, EGF-like module-containing mucin-like hormone receptor-like 1; FcγR(II/III), low affinity IgG Fc region receptor (II/III); FLT3, fms-like tyrosine kinase 3; Gr-1, granulocyte-differentiation antigen-1; ICAM-1, intercellular adhesion molecule 1; ID-2, inhibitor of DNA binding 2; IL-4R, IL-4 receptor; IL-10R, IL-10 receptor; IRF, interferon regulatory factor; Ly6(C/G), lymphocyte antigen 6(C/G); SIRPα, signal-regulatory protein α (also known as tyrosine-protein phosphatase nonreceptor type substrate 1); STAT3, signal transducer and activator of transcription 3; ZBTB46, zinc finger and BTB domain containing protein 46.

Figure 2: The ontogeny of kidney-resident DCs and macrophages.

Bone-marrow-resident MDPs differentiate into monocytes that are released to the peripheral circulation under homeostatic and inflammatory conditions. MDPs also develop into CDPs, which subsequently differentiate to pre-DCs that can migrate from bone marrow to the renal interstitial compartment via the blood, with regular turnover. Under the influence of different chemokines and growth factors, the pre-DCs differentiate to form distinct, tissue-based DC subsets (broadly characterized as CX3CR1⁺ DCs or CD103⁺ DCs) that are capable of exodus to the draining lymph nodes where they can present antigens to B cells and T cells. Monocytes can also localize to the kidney under the influence of chemokines such as CCR2, and subsequently differentiate into DCs. Pre-DCs also give rise to pDC, although the presence of pDCs in kidneys of mice is disputed (dashed arrow). Abbreviations: B-ATF-3, basic leucine zipper transcription factor ATF-like 3; BDCA-(1/2), blood dendritic cell antigen (1/2); CCL(19/21), CC chemokine ligand (19/21); CCR(2/7), CC chemokine receptor (2/7); CDP, common dendritic cell precursor; CLEC4K, C-type lectin domain family 4 member K; CLEC9A, C-type lectin domain family 9 member A; CSF-1, colony-stimulating factor 1; CSF-1R, CSF-1 receptor; CX3CR1, CX3C chemokine receptor 1; DC, dendritic cell; DC-SIGN, dendritic-cell-specific ICAM-3-grabbing non-integrin; FLT3, fms-like tyrosine kinase 3; FLT3LG, FLT3 ligand; GM-CSF, granulocyte-macrophage colony-stimulating factor; Ly6(C/G), lymphocyte antigen 6(C/G); M-CSF, macrophage colony-stimulating factor; MDP, monocyte–DC precursor; pDC, plasmacytoid DC.

Figure 3: Renal DC function in health and disease.

DCs perform homeostatic functions, including induction of tolerance to peripheral antigens typically cleared by the glomerulus, such as albumin, and anti-infection immunosurveillance. Interaction of DCs with bacteria causes them to generate chemokines to attract effector cells, such as neutrophils. The kidney-resident DCs also operate to exacerbate (proinflammatory DCs) or mitigate (anti-inflammatory DCs) a wide range of parenchymal disease, and the role of these cells in disease might be determined by either tissue-resident cells or influxing cells and antigens. For example, the responsiveness and maturation state of DCs might be regulated by ongoing interactions with tubular epithelial cells. Abbreviations: AKI, acute kidney injury; DC, dendritic cell; IRI, ischaemia–reperfusion injury; LPS, lipopolysaccharide; NTN, nephrotoxic nephritis; SLE, systemic lupus erythematosus; T_H17, type 17 T-helper; UUO, unilateral ureteral obstruction.

Figure 4: Macrophages in renal disease.

Tissue-resident macrophages or infiltrating proinflammatory monocytes can become classically activated by exposure to danger-associated molecular patterns or proinflammatory cytokines to take on an M1 phenotype, associated with production of IL-12 and IL-23, engagement of T cells for antigen presentation, activation or exacerbation of profibrotic parenchymal changes, and direct and indirect tissue injury. M1 macrophages can be reprogrammed to become alternatively activated M2 macrophages by stimulation with anti-inflammatory cytokines, such as IL-10 or CSF-1, or ingestion of apoptotic cells. M2 macrophages might facilitate and coordinate restoration of tubular cell and, therefore, kidney tubule integrity following injury. M2 macrophages can also express anti-inflammatory mediators, such as HO-1 and IL-10, which act to limit tissue injury and promote resolution of inflammation, but might also drive pericyte and myofibroblast activation through production of TGF-β, galectin 3 and PDGF. Abbreviations: AKI, acute kidney injury; CSF-1, colony-stimulating factor 1; ECM, extracellular matrix; HO-1, haem oxygenase-1; ICAM-1, intercellular adhesion molecule 1; M-CSF, macrophage colony-stimulating factor; PDGF, platelet-derived growth factor; TGF-β, transforming growth factor β; Wnt7b, wingless-related MMTV integration site 7B.

Read More

Nanoscopy Wins Nobel

The Scientist » News & Opinion » Daily News               

Nanoscopy Wins Nobel

Eric Betzig, Stefan Hell, and William Moerner have won the 2014 Nobel Prize in Chemistry "for the development of super-resolved fluorescence microscopy."

 

By Tracy Vence | October 8, 2014

 





Eric Betzig (left), Stefan Hell (middle), and William

Moerner take home this year's Nobel Prize in Chemistry

for their work on super-resolved fluorescence

microscopy.

ILL. N. ELMEHED. © NOBEL MEDIA 2014; WIKIMEDIA COMMONS;

WIKIMEDIA COMMONS, K. LOWDER

Eric Betzig, Stefan Hell, and William Moerner have won the 2014 Nobel Prize in Chemistry “for the development of super-resolved fluorescence microscopy.”

 

Betzig, of the Howard Hughes Medical Institute’s Janelia Farm Research Campus in Ashburn, Virginia; Hell, of the Max Planck Institute for Biophysical Chemistry and the German Cancer Research Center; and Stanford University’s Moerner will share this year’s prize equally. The three are being honored for bringing “optical microscopy into the nanodimension,” enabling scientists to “study living cells in the tiniest molecular detail,” the Nobel Foundation said in its press release announcing the award.

 

In 2000, Hell developed a technique called stimulated emission depletion (STED) microscopy, which uses laser beams to home in on fluorescently glowing molecules, scanning a sample nanometer by nanometer to produce a high-resolution image. For this and other achievements, Hell shared a 2014 Kavli Award.

 

Working separately, Betzig and Moerner paved the way for single-molecule microscopy, in which interspersed molecules are fluoresced on and off such that, when the same area is imaged multiple times, superimposition of the resulting images results in nanolevel resolution. Betzig first used this method in 2006.

 

Bernd Rieger of the Delft University of Technology in the Netherlands said the three men “opened up a huge field of research [during] the last 8 to 10 years that made it possible to study molecular interactions with a light microscope, which is the work of most cell biologists. . . . They really made a big impact.”

 

“It’s a great recognition of Stefan’s work and a lot of work that’s been done over many years,” Mark Bates, a postdoc in Hell’s lab, said of his advisor’s Nobel. “The field of super-resolution fluorescence nanoscopy [was] first conceived by Stefan and then pushed forward by a lot of different groups around the world.”

 

“This isn’t something that was done 20 years ago and has matured now. We’re all still really excited about further developing these methods and applying them to different problems in biology. . . .  These are tools that are going to push forward the fields of neurobiology, cell biology, structural biology,” said Bates. For now, though, the nanobiophotonics department is abuzz with “a lot of people, a lot of champagne, and a lot of celebratory mood.”

 

Update (October 9, 8:19 a.m.): “Over the past 10 to 15 years there has been increasing use of optical methods to look at single molecules at the nano level,” said Catherine Lewis, director of the Division of Cell Biology and Biophysics at the National Institute of General Medical Sciences. “The advantage of this [approach] is that you can see the dynamics—molecules moving around, interacting with others, and where they are in the cell.”

 

Along with advances in instrumentation and fluorescent probes, as well as in computational techniques, the work of Moerner and his co-Laureates “has allowed scientists to observe and see individual single molecules in living cells in real time,” added Lewis. “I’m thrilled about this prize.”

Tags

Nobel Prize

 

 

 

 

Read More

Brain’s “Inner GPS” Wins Nobel

The Scientist » News & Opinion » Daily News               

Brain’s “Inner GPS” Wins Nobel

John O’Keefe, May-Britt Moser, and Edvard Moser have won the 2014 Nobel Prize in Physiology or Medicine “for their discoveries of cells that constitute a positioning system in the brain.”

 

By Molly Sharlach and Tracy Vence | October 6, 2014

 

Left to right: John O’Keefe; May-Britt Moser, Edvard Moser

UCL, DAVID BISHOP; WIKIMEDIA, THE KAVLI INSTITUTE/NTNU

John O’Keefe, May-Britt Moser, and Edvard Moser have won the 2014 Nobel Prize in Physiology or Medicine “for their discoveries of cells that constitute a positioning system in the brain.”

 

O’Keefe, a professor of cognitive neuroscience at University College London, will receive one half of this year’s prize. Husband-and-wife team May-Britt and Edvard Moser, both professors at the Norwegian University of Science and Technology (NTNU), will share the second half.

 

Together identifying an inner positioning system within the brain, O’Keefe is being honored for his discovery of so-called place cells, while the Mosers are recognized for their later work identifying grid cells.

 

“The discoveries of John O’Keefe, May-Britt Moser and Edvard Moser have solved a problem that has occupied philosophers and scientists for centuries,” the Nobel Foundation noted in its press release announcing the award: “How does the brain create a map of the space surrounding us and how can we navigate our way through a complex environment?”

 

Menno Witter, the Mosers’ colleague at NTNU’s Kavli Institute for Systems Neuroscience/Centre for Neural Computation, first met the pair in the 1990s when they were students at the University of Oslo; Witter was an assistant professor at VU University Amsterdam. 

 

Their work “is a very important contribution in terms of understanding at least part of the neural code that is generated in the brain that allows species—probably including humans—to navigate,” Witter told The Scientist. “We’re all very, very pleased, because it to us shows that what we’re doing . . . as a whole community is considered to be really important and prestigious. It is also, I think, a fabulous sign to the world that Norwegian science is really at a top level.”

 

Francesca Sargolini, a cognitive neuroscientist at Aix-Marseille University in France, worked with the Mosers when she was a postdoc. The lab had a “wonderful, stimulating atmosphere,” Sargolini told The Scientist. Discoveries made by O’Keefe and the Mosers have helped researchers understand “how the brain computes . . . information to make a representation of spaces, so we can use that information to move around in the environment and do what we do every day,” she added.

 

“This is a very well-deserved prize for John [O’Keefe] and the Mosers,” said Colin Lever, a senior lecturer in the department of psychology at Durham University in the U.K., who earned a PhD and continued postdoctoral research in O’Keefe’s lab.

 

“This is a fascinating area of research,” Lever continued. “What we’re discovering about the brain through spatial mapping is likely of greater consequence than just for understanding about space. . . . Indeed, it seems to support autobiographical memory in humans.”

 

Update (October 6, 11:57 a.m.): O’Keefe and Lynn Nadel met as graduate students at McGill University in Montreal. In 1978, when Nadel was a lecturer at University College London, the two coauthored the seminal book The Hippocampus as a Cognitive Map. “We pursued the spatial map story for some years together, and we still do so separately,” Nadel, who is now a professor of psychology at the University of Arizona, told The Scientist. “From my point of view, this award really recognizes the whole enterprise of looking at cognition in terms of brain function,” he added. “It’s pretty cool.”

 

Correction (October 6, 9:58 a.m.): This article has been updated to correct Witter's previous affiliation; he was at VU University Amsterdam when he first met the Mosers.

 

Read More

Total Lunar Eclipse On Wednesday Will Be a Rare 'Selenelion'

By Joe Rao, Space.com Skywatching Columnist   |   October 06, 2014 01:35pm ET





A photo of the first total lunar

eclipse of 2014 taken from

Arizona.

Credit: Ron Delvaux via The Virtual

Telescope Project

View full size image

Observers of Wednesday morning's total lunar eclipse might be able to catch sight of an extremely rare cosmic sight.

 

On Oct. 8, Interested skywatchers should attempt to see the total eclipse of the moon and the rising sun simultaneously. The little-used name for this effect is called a "selenelion," a phenomenon that celestial geometry says cannot happen.

 

And indeed, during a lunar eclipse, the sun and moon are exactly 180 degrees apart in the sky. In a perfect alignment like this (called a "syzygy"), such an observation would seem impossible. But thanks to Earth's atmosphere, the images of both the sun and moon are apparently lifted above the horizon by atmospheric refraction. This allows people on Earth to see the sun for several extra minutes before it actually has risen and the moon for several extra minutes after it has actually set. [How to See the Total Lunar Eclipse (Visibility Maps)]

As a consequence of this atmospheric trick, for many localities east of the Mississippi River, watchers will have a chance to observe this unusual sight firsthand. Weather permitting, you could have a short window of roughly 2 to 9 minutes (depending on your location) with the possibility of simultaneously seeing the sun rising in the east while the eclipsed full moon is setting in the west.

 

Regions of visibility

 

From Newfoundland, the start of the partial stages of the total eclipse begins about 30 to 45 minutes before moonset.

 

A growing scallop of darkness will appear on the upper left part of the moon when it sets as the sun is coming up. Across eastern Nova Scotia, only the lowermost portion of the moon will be in view as it drops below the western horizon. Farther to the west and south along the Atlantic seaboard, the moon will rise completely immersed in the Earth's shadow.

 

The map shows the visibility regions for the Oct. 8, 2014 total lunar eclipse, which is

the second of four consecutive total eclipses of the moon between 2014 and 2015.

Sky & Telescope Magazine released this viewing map.

Credit: Sky & Telescope Magazine

View full size image

Now you see it … now you don't?

Then again, sighting a selenelion might be problematic feat. Twenty-five years ago, in the August 1989 issue of Sky & Telescope, Bradley Schaefer, an astronomer who extensively studied the visibility of the moon when it was low in the sky, noted that the full moon only becomes visible when it is about 2 degrees up and the sun is about 2 degrees below the horizon.

So, depending on the clarity of your sky, you might have up to roughly 10 to 15 minutes before sunrise for the sky to still be dark enough, and the moon to be high enough above any horizon haze for it to be clearly visible. And keep in mind that this holds only for the uneclipsed portion of the moon. You might, however, be able to mitigate the effects of a brightening sky somewhat by using binoculars or a telescope.

If the moon is totally eclipsed prior to sunrise, you probably are going to have to scan the western horizon with binoculars as the twilight brightens in order to still detect some semblance of the Moon, which will somewhat resemble a very dim and eerily illuminated mottled softball.

This chart shows the times of the end-stages of a total lunar eclipse taking place on

Oct. 8, 2014.

Credit: Space.com/Joe Rao

View full size image

 

A peculiar moonset

A series of four total

lunar eclipses in a row

is called a tetrad. See

how four blood moons

of a total lunar eclipse

tetrad work in this

Space.com infographic.

Credit: By Karl Tate,

Infographics Artist

View full size image

 

People who live in those portions of the United States and Canada that are a few hundred miles inland from the Eastern Seaboard should have a good view of the Moon's emergence from the umbra somewhat later. The low, partially eclipsed Moon in deep-blue twilight should offer a wide variety of interesting scenic possibilities for both artists and astrophotographers. From Toronto and points south through the eastern Ohio Valley and into the Piedmont to the Florida Gulf Coast, a peculiar-looking, waxing crescent moon with its cusps pointing downward will appear to set beyond the western horizon.

 

Farther west, across the western Great Lakes and down through the Deep South to the Gulf of Mexico, the moon will appear to be notched on its lower right side by the shadow.

Going still farther west, the Moon will go down "full," but if the western horizon is haze-free, assiduous observers from much of Minnesota, western Iowa, eastern portions of Nebraska and Kansas as well as central sections of Oklahoma and Texas might still be able to detect a faint penumbral stain on the moon's lower right limb.

 

Editor's Note: If you snap an amazing picture of the Oct. 8 total lunar eclipse, you can send photos, comments and your name and location to managing editor Tariq Malik at spacephotos@space.com.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

 

Editor's Recommendations

• October's Lunar Eclipse Won't Be Unusually Dark | Video
• Moon Turns Red - Lunar Eclipse Time-Lapse Video
• The Moon: 10 Surprising Lunar Facts

Author Bio

                      

Joe Rao

 

Joe Rao is a television meteorologist in the Hudson Valley, appearing weeknights on News 12 Westchester. He has also been an assiduous amateur astronomer for over 45 years, with a particular interest in comets, meteor showers and eclipses. He has co-led two eclipse expeditions and has served as on-board meteorologist for three eclipse cruises. He is also a contributing editor for Sky & Telescope and writes a monthly astronomy column for Natural History magazine as well as supplying astronomical data to the Farmers' Almanac. Since 1986 he has served as an Associate and Guest Lecturer at New York's Hayden Planetarium. In 2009, the Northeast Region of the Astronomical League bestowed upon him the prestigious Walter Scott Houston Award for more than four decades of promoting astronomy to the general public.

Joe Rao on   

Read More

How Do You Get Herpes?

A cold sore on this patient’s lip was caused by the herpes simplex virus type 1 (HSV-1).
Credit: cdc.gov
View full size image 

Herpes, a very common viral infection, spreads by person-to-person contact.

 

The infection is caused by the herpes simplex virus (HSV), which comes in two forms: HSV-1, which usually results in oral herpes infections affecting the mouth and lips; and HSV-2, which usually causes genital herpes affecting the genitals and anus.

 

Both types of HSV spread primarily by physical contact with an infected person. Most people get HSV-2 during sexual intercourse (vaginal or anal). HSV-1 tends to spread to individuals in childhood, when an adult who carries the virus touches the child — for example, by pinching a baby's cheeks. Among adults, HSV-1 usually spreads by kissing.

 

However, HSV-1 can also spread to the genitals during oral sex, while HSV-2 infections in the genitals can spread to the mouth during oral sex.

 

About 50 to 80 percent of U.S. adults carry HSV-1 (oral herpes), while 20 percent of people age 12 and older have HSV-2. In many cases, however, individuals with the virus don't know they have it. In fact, an estimated 90 percent of people with HSV-2 don't know they're infected.

 

That's because many people carry herpes without showing any signs of it. One symptom of a herpes infection is the presence of sores around the mouth, genitals or anus. These sores appear during a so-called herpes "outbreak" but usually clear up on their own.

 

The virus, however, never goes away — once you've been infected with herpes, it sticks with you forever. Most of that time, it will be dormant, living in your nerve cells (instead of in the skin cells, where it can cause sores).

 

People with dormant herpes virus can still pass it to others, though outbreaks of herpes sores make transmission more likely. Using barriers like condoms and dental dams during sex can lower your risk of getting herpes, but they are not 100 percent effective.

 

By Michael Dhar, Live Science Contributor   |   February 25, 2014 02:10pm ET

Read More

GENETICS AND GENOMICS: MOBILE DNA ELEMENTS

A Long Line of LINEs

Different mechanisms repress mobile DNA elements in human embryonic stem cells depending on the elements’ evolutionary ages.

By Kate Yandell | September 1, 2014

 

ROUTES TO REPRESSION: The oldest LINE-1 transposons in the human genome are no longer transcribed due to the accumulation of mutations (1). DNA-binding proteins called KRAB-ZFPs and their partner KAP1 repress slightly younger LINE-1s, which originated in our ancestors’ genomes between 26.8 and 7.6 million years ago (2). KRAB-ZFPs have not evolved the ability to recognize more newly evolved transposons, which instead are repressed by methylation, possibly triggered by small RNAs called piRNAs (3).

THE SCIENTIST STAFF

EDITOR'S CHOICE IN GENETICS AND GENOMICS

The paper

N. Castro-Diaz et al., “Evolutionally dynamic L1 regulation in embryonic stem cells,” Genes Dev, 28:1397-409, 2014.


Transposable elements—chunks of DNA that copy and reinsert themselves throughout chromosomes—make up about half of the human genome. Long interspersed element-1s (LINE-1s) are among the few transposable elements that are active in humans, continuing to express and amplify their 6–7 kilobases of DNA. They are a key driver of evolution, accounting for 20 percent of the genome, but their out-of-control proliferation can also harm cells.

In germ and embryonic cells, the control of LINE-1 activity is especially important, as any changes to the genome will be magnified as the organism develops. In adult cells such control is usually exerted through DNA methylation, but embryonic cells undergo an epigenetic overhaul, and the marks that usually suppress LINE-1s may be missing.

In a recent study, molecular virologist Didier Trono and his colleagues from the École Polytechnique Fédérale de Lausanne in Switzerland uncovered a clue regarding how human embryonic stem cells silence LINE-1s. Their findings suggest that transcriptional repressors called KRAB-containing zinc finger proteins (KRAB-ZFPs) recognize specific sequences of some LINE-1s and recruit the protein KAP1 to prevent transcription of the transposons.

While KRAB-ZFPs can explain some of the transposon repression in embryonic stem cells, they don’t explain it all. LINE-1s are ancient components of the genome, continually evolving as animals’ cells adapt to successfully repress them. Knocking down KAP1 in human embryonic stem cells did not significantly affect the activity of evolutionarily old or young LINE-1s, but it increased the activity of the medium-age ones. The researchers conclude that KAP1 only suppresses LINE-1s that evolved and spread throughout the genome between 26.8 million and 7.6 million years ago.

It likely takes some time for organisms to evolve KAP1-mediated repression of LINE-1s. In the meantime, the researchers speculate, they evolve stopgaps for keeping the transposons under control. Prior to the evolution of the highly specific DNA recognition required for KAP1, small RNAs may trigger DNA methylation that silences LINE-1s, Trono’s team suspects.

“The idea of a first line of repression based on small RNAs that can be later extended to a tighter KAP1-mediated control is very appealing,” Iñigo Narvaiza and Rusty Gage of the Salk Institute for Biological Studies said in a joint e-mail. Gage, Narvaiza, and their colleagues, who were not involved in this study, had shown previously that a small RNA called piRNA suppresses activity of evolutionarily young LINE-1s in human pluripotent stem cells.

In support of the theory that DNA methylation is key for controlling young LINE-1s, when the researchers knocked down enzymes that methylate DNA, they found that the activity of newly evolved LINE-1s increased, while the activity of medium-age LINE-1s largely stayed the same. And a separate study published in the same journal issue as Trono’s article shows that piRNAs, previously known to repress LINE-1s via DNA methylation in mouse germ cells, can also repress them via histone modification.
 

Following millions of years of suppression, the oldest LINE-1s have largely lost their activity. “They’re so transcriptionally inert they actually don’t need to be controlled anymore,” says Trono.

 

Tags

transposons, transposable elements, methylation, genetics & genomics, evolution and embryonic stem cells

 

  

Read More

The Nutshell: FDA OKs siRNA Ebola Drug

FDA OKs siRNA Ebola Drug

The US Food and Drug Administration gives the green light to deploy an experimental short interfering RNA treatment against Ebola.

By Kerry Grens | September 23, 2014

WIKIMEDIA, RICHARD ROBINSON

Although TKM-Ebola, a short interfering RNA (siRNA) therapy to treat Ebola infection, has not been approved for use in humans, the US Food and Drug Administration (FDA) is allowing for “compassionate use” of the medication. In other words, even though a drug is not fully vetted, the dire circumstances of the patients justify risky measures. Tekmira Pharmaceutical, the drug’s manufacturer, announced in a press release yesterday (September 22) that the FDA and Health Canada will “allow the use of our investigational therapeutic in more patients.”

 

Already, Tekmira has provided the medication to several Ebola patients “and the repeat infusions have been well tolerated,” according to the statement. “However, it must be kept in mind that any uses of the product under expanded access, does not constitute controlled clinical trials.”

 

David Kroll at Forbes pointed out that the successful administration of TKM-Ebola in monkeys saved the animals from a strain of the virus that circulated in 1995. “On one hand, this shows that TKM-Ebola could be effective against a strain separated by almost 20 years, but is no guarantee that it will against the currently-circulating strain,” he wrote.

 

USA Today reported that one of the patients who has taken TKM-Ebola is Richard Sacra, a US physician who became infected in Liberia and is now being treated in Nebraska. Sacra also received a blood transfusion from another doctor who survived the infection after taking ZMapp, an experimental monoclonal antibody therapy. According to the news report, “While it’s too early to know if TKM-Ebola will work on more patients, [TKM-Ebola researcher Thomas] Geisbert said he’s encouraged [that] Sacra was able to take the drug safely. That’s no small feat, he said. Experimental drugs with unknown effects are usually tested in healthy people. Sacra was acutely ill when he received the drug.”

 

Forbes’s Kroll cautioned that given the limited supply of medication Tekmira has available to distribute, data from patients given compassionate use may not be sufficient to offer reliable insight into the effectiveness of the drug.

Tags

siRNA, RNAi, infectious disease, FDA, ebola, drug development and compassionate use

 

 

Read More

Latest News: How did the 'Berlin patient' rid himself of HIV?





Eric Risberg/AP Photo

 

Timothy Ray Brown, known by many researchers as "the Berlin patient," is the only person to have been cured of an HIV infection.

How did the 'Berlin patient' rid himself of HIV?

Researchers are closer to unraveling the mystery of how Timothy Ray Brown, the only human cured of HIV, defeated the virus, according to a new study. Although the work doesn’t provide a definitive answer, it rules out one possible explanation.

 

Brown remains one of the most studied cases in the HIV epidemic’s history. In 2006, after living with the virus for 11 years and controlling his infection with antiretroviral drugs (ARVs), he learned that he had developed acute myeloid leukemia. (The leukemia has no known relationship to HIV infection or treatment.) Chemotherapy failed, and the next year Brown, an American then living in Berlin, received the first of two bone marrow transplants—a common treatment for this cancer—and ditched his ARVs. When HIV-infected people stop taking ARVs, levels of HIV typically skyrocket within weeks. Yet researchers scouring Brown’s blood over the past 7 years have found only traces of the viral genetic material, none of which can replicate.
 
Today, researchers point to three different factors that could independently or in combination have rid Brown’s body of HIV. The first is the process of conditioning, in which doctors destroyed Brown’s own immune system with chemotherapy and whole body irradiation to prepare him for his bone marrow transplant. His oncologist, Gero Hütter, who was then with the Free University of Berlin, also took an extra step that he thought might not only cure the leukemia but also help rid Brown’s body of HIV. He found a bone marrow donor who had a rare mutation in a gene that cripples a key receptor on white blood cells the virus uses to establish an infection. (For years, researchers referred to Brown as “the Berlin patient.”) The third possibility is his new immune system attacked remnants of his old one that held HIV-infected cells, a process known as graft versus host disease.
 
In the new study, a team led by immunologist Guido Silvestri of Emory University in Atlanta, designed an unusual monkey experiment to test these possibilities.
 
Bone marrow transplants work because of stem cells. Modern techniques avoid actually aspirating bone marrow, and instead can sift through blood and pluck out the stem cells needed for a transplant to “engraft.” So the researchers first drew blood from three rhesus macaque monkeys, removed stem cells, and put the cells in storage. They then infected these animals and three control monkeys with a hybrid virus, known as SHIV, that contains parts of the simian and human AIDS viruses. All six animals soon began receiving ARVs (which respond better to SHIVs than SIV itself), and SHIV levels in the blood quickly dropped below the level of detection on standard tests, as expected.
 
A few months later, the three monkeys that had stored stem cells underwent whole body irradiation to condition their bodies and then had their own stem cells reinfused. After the cells engrafted, a process that took a few more months, the researchers stopped ARVs in the three animals and in the three controls. SHIV quickly came screaming back in the three controls and two of the transplanted animals. (One of the transplanted monkeys did not have the virus rebound but its kidneys failed and the researchers euthanized it.)
 
The team, which publishes its work online in PLOS Pathogens today, concludes that conditioning by itself likely cannot rid the body of the AIDS virus. Silvestri explains that the monkey study was a proof-of-principle experiment that cleanly isolated the effects of conditioning alone. “There’s no way to do this in humans,” he says.
 
 “It’s an important study and it’s a very useful model,” says Daniel Kuritzkes of Brigham & Women’s Hospital in Cambridge, Massachusetts, who wasn’t connected to the research.
Kuritzkes and colleagues are particularly interested in the experiment because two of their own HIV-infected patients with leukemia received bone marrow transplants from donors who did not have HIV-resistant cells. For several months after stopping ARVs, HIV remained at bay in both men, raising hopes that the resistant donor cells were not a factor. But the virus eventually returned in each patient. Kuritzkes suspects that the transplants did reduce the amount of HIV left in the patients’ bodies—known as the viral reservoir—but the virus resurfaced because it continued to copy itself and eventually overwhelmed the immune responses against it.
 
Although the study shows that conditioning by itself likely cannot eliminate an HIV infection, the study leaves open the possibility that graft versus host disease played a central role in Brown’s cure. Unlike Brown and Kuritzkes’s two patients, the transplanted monkeys received their own stem cells, which did not trigger a graft versus host response. “At the end of the day that might be an important component,” Silvestri says. He also thinks it might help reduce the reservoir size to treat monkeys with ARVs for longer than a few months.
 
Silvestri hopes to do future monkey experiments that test the different variables, including transplanting the animals with viral-resistant blood cells that mimic the ones that Brown received. “The best scientific studies raise as many questions as answers,” says Steven Deeks, a researcher and clinician at the University of California, San Francisco, who has treated and studied Brown. “Unfortunately, the heroic efforts that went into this study failed to provide a definitive answer regarding the riddles of the Berlin patient. The model will likely need to be further optimized, and at the very least, the macaques treated with antiretroviral therapy for longer periods of time. But I am confident the team will figure this out.”

By Jon Cohen               

25 September 2014 3:00 pm

 

     

Jon is a staff writer for Science.
Email Jon

 

Related content:

• Strategies against HIV/AIDS
• HIV resurfaces in 'Mississippi baby' many presumed cured
• Cure setbacks force HIV researchers to reset sights

Posted in Health

 

Read More

Ebola — A Growing Threat?

The recent emergence of Zaire ebolavirus in West Africa1 has come as a surprise in a region more commonly known for its endemic Lassa fever, another viral hemorrhagic fever caused by an Old World arenavirus. Yet the region has seen previous ebolavirus activity  (see map). 

In the mid-1990s, scientists discovered Côte d'Ivoire ebolavirus (now known as Taï Forest ebolavirus) as a cause of a single reported nonfatal case in a researcher who performed a necropsy on an infected chimpanzee. The episode initiated a major research investigation in and around the Taï Forest region — an effort that failed to identify the reservoir of this new Ebola species. Since that incident, West African countries have not reported any evidence of the presence of ebolavirus.

 

Ebolaviruses belong to the family Filoviridae, a taxonomic group of enveloped, nonsegmented, negative-strand RNA viruses that includes the genera marburgvirus and cuevavirus, with a single species each, and ebolavirus, with five distinct species (see  (see figure).Bundibugyo ebolavirus to approximately 50% for Sudan ebolavirus to 70 to 90% for Zaire ebolavirus.2 The virulence of Taï Forest ebolavirus is difficult to assess because there has been only a single recorded case, and the only identified Asian species, Reston ebolavirus, seems to cause asymptomatic infection in humans.

All known African ebolaviruses can infect humans and cause similar symptoms, but they vary in terms of disease progression and virulence, with case fatality rates ranging from less than 40% for

 

Humans infected with ebolaviruses commonly present initially with nonspecific symptoms such as fever, vomiting, and severe diarrhea, with visible hemorrhage occurring in less than half the cases,2 as in the current outbreak.1 Owing to poor infrastructure, biosafety concerns associated with processes of patient care and autopsy, and the essential focus on disease containment during outbreaks, there has been little empirical study to elucidate the pathogenesis or pathology of human ebolavirus infection. The closest surrogate disease models are cynomolgus and rhesus macaques, which show clinical signs of viral hemorrhagic fever when infected with most ebolaviruses. Zaire ebolavirus is uniformly lethal in these macaques, and experts have assumed that its pathology and pathophysiology closely resemble those of ebolavirus infections in humans; immunosuppression, increased vascular permeability, and impaired coagulation have been identified as hallmarks of the disease.2 Evidence of microscopic hemorrhage is usually found, but the degree of bleeding ranges from undetectable to acutely visible. The recently introduced term “Ebola virus disease” may not convey the seriousness of a viral hemorrhagic fever, a clinical syndrome that should trigger isolation guidelines that ensure appropriate case management and implementation of infection-control measures.

 

Ebolaviruses are zoonotic pathogens purportedly carried by various species of fruit bats that are present throughout central and sub-Saharan Africa. In contrast to marburgvirus, whose reservoir has been identified as Rousettus aegyptiacus fruit bats,3 ebolaviruses have not yet been isolated from bats that have molecular and seroepidemiologic evidence of infection. Introduction into humans most likely occurs through direct contact with bats or their excretions or secretions or through contact with other end hosts, such as the great apes. Since Reston ebolavirus has been discovered in pigs on the Philippine islands, the possibility that there may be interim or amplifying hosts should not be dismissed, as we further elucidate ebolavirus ecology.

 

Human-to-human transmission leads to outbreaks, which are often started by a single introduction from the wildlife reservoir or another end host and involve virus variants with little genetic diversity, as in the current outbreak in West Africa.1 Some recorded outbreaks, on the other hand, have stemmed from multiple introductions, which have resulted in greater genetic viral diversity among the subsequent distinct chains of human-to-human transmission. Within a given species, however, virus variants have been shown to have low genetic diversity, often less than a few percent, as illustrated by the new variant isolated from patients in Guinea.1 Such limited diversity generally leads to neutralizing cross-reactivity within the species.

 

Biologic characterization of various Zaire ebolaviruses, their case fatality rates, and their virulence in animal models have so far failed to provide convincing evidence of obvious differences in pathogenicity. Thus, it should be assumed that the new West African variant is not more virulent than previous Zaire ebolaviruses; a case fatality rate of about 70%, if confirmed, might even indicate lower virulence. The finding that the Guinea variant resides at a more basal position within the clade than previously known Zaire ebolaviruses 1 argues against an introduction from Central Africa and instead supports the likelihood of distinct evolution in West Africa. These findings reinforce the hypothesis that ebolaviruses have a broader geographic distribution than previously thought.

 

There is currently no licensed prophylaxis or treatment for any ebolavirus or marburgvirus infection; therefore, treatment is merely supportive.2 Over the past decade, however, multiple countermeasure options have shown promising efficacy in macaque models of filoviruses, and some of the approaches have completed or are at least nearing phase 1 clinical trials in humans.4

 

The current front-runner for therapeutic intervention seems to be antibody treatment, which has been successful in macaques even when antibodies are administered more than 72 hours after infection. Treatment approaches involving modulatory RNA (i.e., small interfering RNAs or phosphorodiamidate morpholino oligomers) are following close behind, along with a promising synthetic drug-like small molecule, BCX4430.5 The most promising vaccine approaches are based on recombinant technologies, such as virus-like particles produced through plasmid transfection and replication-incompetent and -competent viral vectors.4 Among the latter, vesicular stomatitis virus vectors have shown efficacy within 24 to 48 hours after infection in rhesus macaques.

 

In the absence of effective intervention strategies, diagnosis becomes a key element in our response to ebolavirus infection.2 Detection rests largely on molecular techniques utilizing multiple reverse-transcriptase–polymerase-chain-reaction assays that can be used at remote outbreak sites. Antigen detection may be performed in parallel or serve as a confirmatory test for immediate diagnosis, whereas assays for detection of antibodies (e.g., IgM and IgG) are secondary tests that are primarily important in surveillance. Molecular detection strongly depends on sequence conservation, and established assays may fail when applied to new variants, strains, or viruses. Therefore, real-time sharing of information, particularly sequence data, is absolutely critical for our response capacity, since any delay could have disastrous consequences for public health. In addition, diagnostics remain essential for the time-consuming process of tracing contacts during an outbreak and for overcoming the obstacles to reintroducing survivors into their community.

 

The latest outbreak of Zaire ebolavirus in West Africa again has shown the limited ability of our public health systems to respond to rare, highly virulent communicable diseases. The medical and public health sectors urgently need to improve education and vigilance. And rapid, reliable diagnostic procedures must be implemented in key regions within or closer to the areas where these viruses are endemic so that local public health systems do not have to rely on distant reference laboratories, which should play a more confirmatory role in the future. Moreover, to optimize diagnostic-response capabilities, it is essential that information be shared in real time, as it was during the pandemic of the severe acute respiratory syndrome and during recurrent outbreaks of influenza.

 

Despite years of research on ebolaviruses and marburgviruses, it is still not possible to administer vaccines or treatments to the at-risk population or medical aid teams. If we are to practice cutting-edge medicine, rather than simply outbreak control, we need to advance leading approaches toward approval and licensing. This gap should close over the next several years — if we can continue making progress before Ebola (or a related virus) strikes again.

Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.

This article was published on May 7, 2014, and updated on May 22, 2014, at NEJM.org.

Source Information

From the Laboratory of Virology, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratories, Hamilton, MT.



 

Read More

mRNA-based therapeutics — developing a new class of drugs

Nature Reviews Drug Discovery | Review

The therapeutic potential of in vitro-transcribed mRNA (IVT mRNA) extends from prophylactic and therapeutic vaccines to applications such as protein replacement and genome engineering. In this Review, the authors describe the recent developments in the IVT mRNA field, discuss the class-specific challenges with regards to translating IVT mRNA into a biopharmaceutical, and provide an overview of IVT mRNA drugs in development for different indications.

Key points

• Messenger RNA (mRNA) is a pivotal molecule of life, involved in almost all aspects of cell biology.
• As the subject of basic and applied research for more than 5 decades, mRNA has only recently come into the focus as a potentially powerful drug class able to deliver genetic information. 
• Synthetic mRNA can be engineered to resemble mature and processed mRNA molecules as they occur naturally in the cytoplasm of eukaryotic cells and to transiently deliver proteins. 
• Recent advances addressed challenges inherent to this drug class and provided the basis for a broad spectrum of applications 
• Besides cancer immunotherapies and infectious disease vaccines novel approaches such as in vivo delivery of mRNA to replace or supplement proteins, mRNA-based induction of pluripotent stem cells, or mRNA-assisted delivery of designer nucleases for genome engineering rapidly emerged and entered into pharmaceutical development. 
• This Review gives a comprehensive overview of the current state of mRNA drug technologies, their applications and crucial aspects relevant to mRNA based drug discovery and development.

Abstract:

In vitro transcribed (IVT) mRNA has recently come into focus as a potential new drug class to deliver genetic information. Such synthetic mRNA can be engineered to transiently express proteins by structurally resembling natural mRNA. Advances in addressing the inherent challenges of this drug class, particularly related to controlling the translational efficacy and immunogenicity of the IVTmRNA, provide the basis for a broad range of potential applications. mRNA-based cancer immunotherapies and infectious disease vaccines have entered clinical development. Meanwhile, emerging novel approaches include in vivo delivery of IVT mRNA to replace or supplement proteins, IVT mRNA-based generation of pluripotent stem cells and genome engineering using IVT mRNA-encoded designer nucleases. This Review provides a comprehensive overview of the current state of mRNA-based drug technologies and their applications, and discusses the key challenges and opportunities in developing these into a new class of drugs.

Figure 1: (Timeline): Key discoveries and advances in the development of mRNA as a drug technology

CAR, chimeric antigen receptor; Cas9, CRISPR-associated protein 9; CRISPR, clustered regularly interspaced short palindromic repeat; DC, dendritic cell; dsRNA, double-stranded RNA; iPSC, induced pluripotent stem cell; RSV, respiratory syncytial virus; ssRNA, single stranded RNA; TALEN, transcription activator-like effector nuclease; TLR, Toll-like receptor. 

Figure 2: Principles of antigen-encoding mRNA pharmacology.

a | A linearized DNA plasmid template with the antigen-coding sequence is used for in vitro transcription. The in vitro transcribed mRNA contains the cap, 5′and 3′ untranslated regions (UTRs), the open reading frame (ORF) and the poly(A) tail, which determine the translational activity and stability of the mRNA molecule after its transfer into cells. b | Step 1: a fraction of exogenous mRNA escapes degradation by ubiquitous RNases and is spontaneously endocytosed by cell-specific mechanisms (for example, macropinocytosis in immature dendritic cells) and enters endosomal pathways. Step 2: release mechanisms of mRNA into the cytoplasm are not fully understood. Step 3: translation of mRNA uses the protein synthesis machinery of host cells. The rate-limiting step of mRNA translation is the binding of the eukaryotic translation initiation factor 4E (eIF4E) to the cap structure 222, 223. Binding of the mRNA to ribosomes, the eukaryotic initiation factors eIF4E and eIF4G, and poly(A)-binding protein, results in the formation of circular structures and active translation 224. Step 4: termination of translation by degradation of mRNAs is catalysed by exonucleases 225, 226. The cap is hydrolysed by the scavenger decapping enzymes DCP1, DCP2 and DCPS 32, followed by digestion of the residual mRNA by 5′–3′ exoribonuclease 1 (XRN1). Degradation may be delayed if the mRNA is silenced and resides in cytoplasmic processing bodies 227. Alternatively, endonucleolytic cleavage of mRNA in the exosome may occur 228, 229, 230. The catabolism of abberant mRNA (for example, mRNA with a premature stop codon) is controlled by various other mechanisms 231. Step 5: the translated protein product undergoes post-translational modification, the nature of which depends on the properties of the host cell. The translated protein can then act in the cell in which it has been generated. Step 6: alternatively, the protein product is secreted and may act via autocrine, paracrine or endocrine mechanisms. Step 7: for immunotherapeutic use of mRNA, the protein product needs to be degraded into antigenic peptide epitopes. These peptide epitopes are loaded onto major histocompatibility complex (MHC) molecules, which ensure surface presentation of these antigens to immune effector cells. Cytoplasmic proteins are proteasomally degraded and routed to the endoplasmic reticulum where they are loaded on MHC class I molecules to be presented to CD8+ cytotoxic T lymphocytes. MHC class I molecules are expressed by almost all cells. Step 8: in antigen-presenting cells, to obtain cognate T cell help for a more potent and sustainable immune response, the protein product needs to be routed to MHC class II loading compartments. This can be accomplished by incorporating routing signal-encoding sequences into the mRNA. Moreover, exogenous antigens that are taken up by dendritic cells can also be processed and loaded onto MHC class I molecules by a mechanism that is known as cross-priming 232. Step 9: protein-derived epitopes can then be presented on the cell surface by both MHC class I and MHC class II molecules. 

Figure 3: Tuning mRNA drug dose pharmacokinetics.

a | Key structural elements of in vitro transcribed (IVT) mRNA and strategies for their modifications. b | Depending on which elements (for example, modification of caps, untranslated regions (UTRs) or poly(A) tails) are used alone or in combination, the duration and kinetic profile of expression of the protein product can be modulated and fine-tuned. eIF4E, eukaryotic translation initiation factor 4E; IRES, internal ribosome entry site; ORF, open reading frame. 

Figure 4: Inflammatory responses to synthetic mRNA.

In vitro transcribed (IVT) mRNA is recognized by various endosomal innate immune receptors (Toll-like receptor 3 (TLR3), TLR7 and TLR8) and cytoplasmic innate immune receptors (protein kinase RNA-activated (PKR), retinoic acid-inducible gene I protein (RIG-I), melanoma differentiation-associated protein 5 (MDA5) and 2′–5′-oligo adenylate synthase (OAS)). Signaling through these different pathways results in inflammation associated with type 1 interferon (IFN), tumour necrosis factor (TNF), interleukin-6 (IL-6), IL-12 and the activation of cascades of transcriptional programmes. Overall, these create a pro-inflammatory microenvironment poised for inducing specific immune responses. Moreover, downstream effects such as slow-down of translation by eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, enhanced RNA degradation by ribonuclease L (RNASEL) over expression and inhibition of replication of self-amplifying mRNA are of relevance for the pharmacokinetics and pharmacodynamics of the IVT mRNA. IRF, interferon regulatory factor; ISRE7, interferon-stimulated response element; MAVS, mitochondrial antiviral signaling protein; MDA5, melanoma differentiation-associated protein 5; MYD88, myeloid differentiation primary response protein 88; MX1, myxovirus (influenza) resistance 1; NF-κB, nuclear factor-κB; TRIF, Toll-IL-1 receptor domain-containing adapter protein inducing IFNβ.

Figure 5: Differences in siRNA, pDNA and mRNA technologies in tissues with non-fenestrated or fenestrated capillaries.

All three nucleic acid-based drug modalities are applied as nanosized drug formulations for systemic delivery and reach organs via capillary systems with either non-fenestrated (a) or fenestrated (b) capillaries. The primary pharmacological effect of small interfering RNA (siRNA), namely the deletion of a defined protein function in situ, is restricted to those very cells it has entered. siRNA cannot act in cells that are not directly accessed owing to biological barriers such as non-fenestrated capillaries. In tissues with endothelial fenestration, siRNA may reach a few tissue layers adjacent to capillaries. Plasmid DNA (pDNA) is only incorporated and active in those cells undergoing mitosis at the time of exposure. This impairs its use for tissues with non-fenestrated capillaries and restricts the number of transfectable cells in tissues with endothelial fenestration to those undergoing mitosis at the time of exposure. In contrast to pDNA, mRNA enters and acts in endothelial cells of non-fenestrated tissues, and in fenestrated tissues it reaches both mitotic and non-mitotic cells in cell layers adjacent to the capillaries 233. Non-target cells, such as vascular endothelial cells transfected with mRNA or pDNA, can express pharmacologically active proteins and, via paracrine secretion, can reach target cells that are located behind the mRNA delivery barriers 234 (obviously siRNA cannot rely on such a function). Proteins produced in transfected cells are able to diffuse after secretion into the target tissue and mediate the intended biological effects via paracrine activity on adjacent cell populations. Such paracrine activity may be of particular value in tissues that have non-fenestrated capillaries.

In vitro transcribed (IVT) mRNA is recognized by various endosomal innate immune receptors (Toll-like receptor 3 (TLR3), TLR7 and TLR8) and cytoplasmic innate immune receptors (protein kinase RNA-activated (PKR), retinoic acid-inducible gene I protein (RIG-I), melanoma differentiation-associated protein 5 (MDA5) and 2′–5′-oligoadenylate synthase (OAS)). Signalling through these different pathways results in inflammation associated with type 1 interferon (IFN), tumour necrosis factor (TNF), interleukin-6 (IL-6), IL-12 and the activation of cascades of transcriptional programmes. Overall, these create a pro-inflammatory microenvironment poised for inducing specific immune responses. Moreover, downstream effects such as slow-down of translation by eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, enhanced RNA degradation by ribonuclease L (RNASEL) overexpression and inhibition of replication of self-amplifying mRNA are of relevance for the pharmacokinetics and pharmacodynamics of the IVT mRNA. IRF, interferon regulatory factor; ISRE7, interferon-stimulated response element; MAVS, mitochondrial antiviral signalling protein; MDA5, melanoma differentiation-associated protein 5; MYD88, myeloid differentiation primary response protein 88; MX1, myxovirus (influenza) resistance 1; NF-κB, nuclear factor-κB; TRIF, Toll-IL-1 receptor domain-containing adapter protein inducing IFNβ.

Figure 6: Potential therapeutic applications of IVT mRNA.

The therapeutic applications of in vitro transcribed (IVT) mRNA are summarized in detail in Table 1. The solid arrows pointing in the right hand column denote applications that are in the clinic, whereas stippled arrows refer to preclinical applications. Cas9, CRISPR-associated protein 9; CRISPR, clustered regularly interspaced short palindromic repeat; EPO, erythropoietin; FOXP3, forkhead box P3; IL-10, interleukin-10; MSC, mesenchymal stem cell; RSV, respiratory syncytial virus; SPB, surfactant protein B; TALEN, transcription activator-like effector nuclease; VEGFA, vascular endothelial growth factor A; ZNF, zinc finger nuclease.

Title: mRNA-based therapeutics — developing a new class of drugs

Author: Ugur Sahin, Katalin Karikó & Özlem Türeci 

Publication: Nature Reviews Drug Discovery | Review 

Publisher: Nature Publishing Group 

Date:19 September 2014 

Copyright © 2014, Rights Managed by Nature Publishing Group

 

Read More