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immunology

Mopping up immune troublemakers after transplant

Emory scientists have identified a way to stop troublemaker cells that are linked to immune rejection after kidney transplant. The finding could eventually allow transplant patients to keep their new kidneys for as long as possible, without the side effects that come from some current options for controlling immune rejection.

The results are published in Journal of Clinical Investigation.

The standard drugs used for many years, calcineurin inhibitors, show side effects on cardiovascular health and can even damage the kidneys over time. A newer FDA-approved medication called belatacept, developed in part at Emory, avoids these harmful effects but is less effective at stopping acute rejection immediately after the transplant. Belatacept is a “costimulation blocker” – it interferes with a signal some immune cells (T cells) need to proliferate and become activated.

Researchers led by Emory transplant surgeon Andrew Adams, MD, PhD suspected that long-lasting memory CD8+ T cells were resistant to belatacept’s effects.

“Our previous work identified that memory CD8+ T cells may be elevated in animals and human patients who go on to reject their transplanted organs while taking belatacept,” says Dave Mathews, an MD/PhD student who worked with Adams and is the first author of the paper.

The researchers identified a certain marker, CD122, which was present on memory CD8+ T cells and important for their activity. On T cells, CD122 acts as a receiving dish for two other secreted molecules, IL-2 and IL-15, generally thought of as inflammatory cytokines, or protein messengers that can encourage graft rejection. Read more

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Probiotics for bone health study heads into clinic

Probiotic supplements can protect female mice from the loss of bone density that occurs after having their ovaries removed, researchers at Emory and Georgia State reported a couple years ago.

Roberto Pacifici, MD

This finding, published in Journal of Clinical Investigation, had clear implications for the treatment of osteoporosis in post-menopausal women. Prompted by external emails, Lab Land learned that the Emory investigators are now continuing their research in the clinic.

Endocrinologist/osteoimmunologist Roberto Pacifici and colleague Jessica Alvarez are conducting a double-blind study for women aged 50-65, using VSL3, a widely available and inexpensive dietary supplement. Participants would take the supplement or placebo for a year. More information is available here.

In mice, the loss of estrogen increases gut permeability, which allows bacterial products to activate immune cells in the intestine. In turn, immune cells release signals that break down bone. It appears that probiotics both tighten up the permeability of the gut and dampen inflammatory signals that drive the immune cells. Read more

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Less mucus, more neutrophils: alternative view of CF

A conventional view of cystic fibrosis (CF) and its effects on the lungs is that it’s all about mucus. The inherited disease leads to an accumulation of mucus in the lungs, which appears to be connected with inflammation, susceptibility to infection and loss of lung capacity.

Immunologist Rabin Tirouvanziam has an alternative view, centered on neutrophils. They are a type of immune cell that is very numerous, yet often overlooked, he says.

Rabindra Tirouvanziam, PhD

A new paper, published in Journal of Leukocyte Biology, substantiates his ideas about cystic fibrosis and harnesses them for future diagnostic and therapeutic advances. Tirouvanziam is an assistant professor of pediatrics at Emory University School of Medicine and Emory Children’s Center. He and his colleagues have developed a system for studying neutrophil behavior in a specialized culture, a model of a cell layer in the lung.

Neutrophils behave differently in the diseased lung environment, compared with when they are in the blood. The culture system makes the neutrophils pass through a layer of lung cells, under the influence of lung fluids obtained from CF patients. The culture system opens up the opportunity of testing fluids from patients to mark disease progression, as well as drug discovery: looking for compounds that could deprogram the neutrophils. Read more

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Exotic immune systems are big business

What timing! Just when our feature on Max Cooper and lamprey immunology was scheduled for publication, the Japan Prize Foundation announced it would honor Cooper and his achievements.

Cooper was one of the founders of modern immunology. We connect his early work with his lab’s more recent focus on lampreys, primitive parasites with surprisingly sophisticated immune systems.

Molecules from animals with exotic immune systems can be big business, as Andrew Joseph from STAT News points out. Pharmaceutical giant Sanofi recently bought a company focused on nanobodies, originally derived from camels, llamas and alpacas, for $4.8 billion.

Lampreys’ variable lymphocyte receptors (VLRs) are their version of antibodies, even though they look quite different in molecular terms. Research on VLRs and their origins may seem impractical. However, Cooper’s team has shown their utility as diagnostic tools, and his colleagues have been weaponizing them, possibly for use in cancer immunotherapy.

CAR-T cells have attracted attention for dramatic elimination of certain types of leukemias from the body and also for harsh side effects and staggering costs; see this opinion piece by Georgia Tech’s Aaron Levine. Now many research teams are scheming about how to apply the approach to other types of cancers. The provocative idea is: replace the standard CAR (chimeric antigen receptor) warhead with a lamprey VLR.

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Update on SIV remission studies

Tab Ansari’s research at Emory/Yerkes on how an antibody treatment can push monkeys infected with SIV into remission was published in Science last year. At that time, Ansari told Lab Land about follow-up experiments to probe which immune cells are needed for this effect, which surprised many HIV/AIDS experts.

Ansari’s partner on the project, NIAID director Anthony Fauci, described the follow-up work in July at the International AIDS Society Conference in Paris. We thank Treatment Action Group’s Richard Jefferys for taking notes and posting a summary:

The approach that the researchers took was to deplete different types of immune cells in the animals controlling SIV viral load, then assess whether this led to an increase in viral replication. The experiments compared:

*Antibodies to the CD8 receptor alpha chain, which deplete CD8 T cells, natural killer T cells (NKTs) and natural killer (NK) cells

*Antibodies to the CD8 receptor beta chain, which deplete CD8 T cells

*Antibodies to CD20, which deplete B cells

According to Fauci’s slides, which are available online, there was a transient rebound in viral load with the CD8 alpha antibody and to a small degree with the CD8 beta. This suggests NKTs and NK cells are making a contribution to the observed control of SIV replication, but a role for CD8 T cells cannot be ruled out.

For comparison, a study from Guido Silvestri and colleagues at Yerkes published in 2016 found that treating SIV-infected monkeys with anti-CD8 antibodies, without stopping antiretroviral drugs, resulted in a rebound in virus levels. [They used ultrasensitive assays to detect the rebound.] However, the Yerkes team only used antibodies to the CD8 receptor alpha chain.

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SIV remission follow-up

The surprising finding that an antibody treatment can push SIV-infected monkeys into prolonged remission, even after antiviral drugs are stopped, continues to rumble across the internet.

siv-a4b7-teaser-copy

Blue circles show how viral levels stayed low even after antiretroviral drugs were stopped.

The Science paper was featured on NIH director Francis Collins’ blog this week. NIAID director Anthony Fauci has been giving presentations on the research, which emerged from a collaboration from his lab and Tab Ansari’s at Emory. Fauci’s talk at the recent HIV prevention meeting in Chicago is viewable here.

At Lab Land, we were pleased to see that the watchdogs at Treatment Action Group had this to say:

“Media coverage of the paper has generally been accurate, but has had to wrestle with the uncertainty that exists among scientists regarding how ART-free control of viral load should be described.”

HIV pioneer Robert Gallo noted in an article accompanying the Science paper that the anti-integrin antibody treatment represents an emerging alternative to the vaunted “shock and kill” strategy, which he termed “soothe and snooze.” Note to reporters: the upcoming “Strategies for an HIV cure” conference at NIH in mid-November might be a good chance to compare the different strategies and put them in perspective.

Read more

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Dengue infection makes exhausted T cells?

An ongoing collaboration between the Emory Vaccine Center and the ICGEB (International Centre for Genetic Engineering and Biotechnology) in New Delh, investigating immune responses to dengue virus, is getting some attention.

A Journal of Virology paper published by the collaboration was highlighted by Nature Asia. In that paper, the researchers show that in dengue infection, the group of antiviral immune cells known as CD8+ T cells undergoes a massive expansion. That could be dangerous if all of the CD8 T cells were making inflammatory cytokines, but they do not. Only a small fraction are making cytokines.

The authors point out that this phenomenon is “somewhat reminiscent of T-cell exhaustion seen under the conditions of prolonged antigenic stimulus in chronic viral infections [which has been studied in detail by Rafi Ahmed and colleagues] or closely resembles the ‘stunned’ phenotype reported in febrile phase of other acute infections such as HIV and viral hepatitis… The IFN-γ unresponsiveness acquired during the massive antigen-driven clonal expansion is likely to ensure that these cells do not cause excessive inflammation at the time that their numbers are high during the febrile phase of dengue disease.” Read more

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Plasma cells, antibody factories

Immune cells that serve as antibody production factories, also known as plasma cells, are the focus of a recent Nature Immunology paper from Jeremy Boss and colleagues.

Plasma cells also appear in Ali Ellebedy and Rafi Ahmed’s recent paper on the precursors of memory B cells and Eun Lee’s work on long-lived antibody-producing cells. In addition, plasma cells appear prominently in Larry Boise’s studies of myeloma, because myeloma cancer cells are thought to come from plasma cells and have a similar biology.B cell methylation

The Boss lab’s paper focuses on patterns of methylation, modifications of DNA that usually help turn genes off. In comparison with resting B cells, plasma cells need to turn on lots of genes, so their DNA methylation level goes down when differentiation occurs (see graph). PC = plasma cells, PB = plasmablasts. DNAme indicates the extent of DNA methylation. Read more

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Are you experienced?

Are you experienced? Your immune system undoubtedly is. Because of vaccinations and infections, we accumulate memory T cells, which embody the ability of the immune system to respond quickly and effectively to bacteria or viruses it has seen before.

Not so with mice kept in clean laboratory facilities. Emory scientists think this difference could help explain why many treatments for sepsis that work well in mice haven’t in human clinical trials.

Screen Shot 2016-08-24 at 1.42.21 PM

Mandy Ford has teamed up with Craig Coopersmith to investigate sepsis, a relatively new field for her, and the collaboration has blossomed in several directions

“This is an issue we’ve been aware of in transplant immunology for a long time,” says Mandy Ford, scientific director of Emory Transplant Center. “Real life humans have more memory T cells than the mice that we usually study.”

Sepsis is like a storm moving through the immune system. Scientists studying sepsis think that it has a hyper-inflammatory phase, when the storm is coming through, and a period of impaired immune function afterwards. The ensuring paralysis leaves patients unable to fight off secondary infections.

In late-stage sepsis patients, dormant viruses that the immune system usually keeps under control, such as Epstein-Barr virus and cytomegalovirus, emerge from hiding. The situation looks a lot like that in kidney transplant patients, who are taking drugs to prevent immune rejection of their new organ, Ford says.

Ford’s team recently found that sepsis preferentially depletes some types of memory T cells in mice. Because T cells usually keep latent viruses in check, this may explain why the viruses are reactivated after sepsis, she says. Read more

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The cure word, as applied to HIV

HIV researchers are becoming increasingly bold about using the “cure” word in reference to HIV/AIDS, even though nobody has been cured besides the “Berlin patient,” Timothy Brown, who had a fortuitous combination of hematopoetic stem cell transplant from a genetically HIV-resistant donor. Sometimes researchers use the term “functional cure,” meaning under control without drugs, to be distinct from “sterilizing cure” or “eradication,” meaning the virus is gone from the body. A substantial obstacle is that HIV integrates into the DNA of some white blood cells.

HIV cure research is part of the $35.6 million, five-year grant recently awarded by the National Institutes of Health to Yerkes/Emory Vaccine Center/Emory Center for AIDS Research. Using the “shock and kill” approach during antiviral drug therapy, researchers will force HIV (or its stand-in in non-human primate research, SIV) to come out of hiding from its reservoirs in the body. The team plans to test novel “latency reversing agents” and then combine the best one with immunotherapeutic drugs, such as PD-1 blockers, and therapeutic vaccines.

The NIH also recently announced a cluster of six HIV cure-oriented grants, named for activist Martin Delaney, to teams led from George Washington University, University of California, San Francisco, Fred Hutchinson Cancer Research Center, Wistar Institute, Philadelphia, Beth Israel Deaconess Medical Center and University of North Carolina. Skimming through the other teams’ research plans, it’s interesting to see the varying degrees of emphasis on “shock and kill”/HIV latency, enhancing the immune response, hematopoetic stem cell transplant/adoptive transfer and gene editing weaponry vs HIV itself.

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