Research Update

A New Way to Overcome HIV Latency

Dr. Nicolas Chomont

Dr. Nicolas Chomont

Last month we reviewed the proteasome, a cell structure rarely discussed in the context of HIV but, according to researchers at amfAR’s Institute for HIV Cure Research, one that may offer a novel target in attempts to disrupt viral latency. The proteasome is potentially amenable to attack by two currently used anti-cancer drugs.

This month we highlight the work of amfAR-funded researcher Dr. Nicolas Chomont of the University of Montreal, who is studying another component of normal cells that is also a target of certain cancer therapies and has promise in multi-pronged HIV eradication strategies.

Writing in the journal Nature Communications, Chomont and colleagues examined PD-1, a protein found in higher than expected amounts on the surface of T cells latently infected with HIV. They showed that PD-1 inhibited the ability of certain types of immune stimulation to drive HIV out of its dormant state.

Using T cells from HIV-infected individuals on long-term antiretroviral therapy, the investigators found that blocking PD-1 with pembrolizumab (Keytruda)—a drug currently used in the treatment of many formerly untreatable types of cancer—enabled a second drug, known as a latency reversing agent, to induce HIV escape from latency. Forcing HIV out of latency is a key component of the proposed “shock and kill” approach to curing HIV.

In support of these test-tube studies, Chomont and associates studied an HIV-infected individual who was treated with pembrolizumab in an attempt to cure the person’s malignant melanoma. Markers consistent with latent HIV were decreased by this treatment.

The authors caution that it remains to be determined whether pembrolizumab or other anti-PD-1 cancer drugs, collectively known as immune checkpoint inhibitors, can activate HIV in all the cell types currently thought to contribute to the latent state. But they look forward to pursuing this line of research in the quest for an HIV cure.

Dr. Laurence is amfAR’s senior scientific consultant.

amfAR RESEARCHERS UNABLE TO FIND HIV IN LONDON TRANSPLANT PATIENT

Second patient from Düsseldorf shows similar profile

SEATTLE, WA, March 5, 2019 – Researchers have reported that a stem cell transplant patient from London has not experienced a rebound of his HIV during the past 18 months off antiretroviral therapy (ART). His is the longest duration of ART-free undetectable virus in an adult since the Berlin patient, who is believed to have been cured by a similar procedure. The case was reported at the Conference on Retroviruses and Opportunistic Infections (CROI) in Seattle.

The patient is part of amfAR’s ICISTEM research consortium, which has so far enrolled 45 patients with cancer and HIV who have received or soon will receive stem cell transplants.

What does this mean for people living with HIV today?

Another ICISTEM patient was also reported on at CROI—a man from Düsseldorf, Germany, who shows no evidence of viral rebound after a similar transplant procedure, though he has been off treatment only since November. Researchers will follow both patients closely to look for any signs of resurgent HIV.

Lead investigator in the London case, Dr. Ravi Gupta of the University of Cambridge, UK, reported that the HIV-positive man was diagnosed with cancer in 2013 and received a stem cell transplant in 2016. Like the Berlin patient—Timothy Ray Brown—he received donor cells with a genetic mutation (CCR5-delta 32) rendering them resistant to HIV infection. Since discontinuing ART in late 2017, the London patient has shown no trace of the virus.

Comprehensive reservoir analyses were conducted by the ICISTEM consortium, which is co-led by the University Medical Center Utrecht in the Netherlands and the IrsiCaixa AIDS Research Institute in Barcelona, Spain. It includes cure researchers who systematically assess changes in the HIV reservoir resulting from stem cell transplantation, and who provide treatment and monitoring guidance to the collaborating transplant doctors. The researchers are now able to compare changes in the HIV reservoir across the patient cohort.

What does this mean for the future of HIV research?

The ICISTEM group has screened over two million stem cell donors to identify those with the CCR5-delta32 mutation, increasing the chance that new candidate transplant recipients may receive donor cells with this rare genetic mutation. With additional patients in the cohort about to stop ART in what is known as an analytic treatment interruption, researchers are cautiously optimistic that there may soon be additional cases of sustained undetectable virus in the absence of therapy.

“While we fully understand that stem cell transplantation is not a practical way of curing large numbers of people, we can learn a tremendous amount from these cases” said amfAR Chief Executive Officer Kevin Robert Frost. “And we can apply that new knowledge to the development of strategies aimed at a more widely applicable cure.”

Because the London and Düsseldorf patients received an intervention similar in many respects to the case of the Berlin patient, researchers can begin to compare and contrast the procedures. Mr. Brown, for example, underwent two stem cell transplants, whereas the London and Düsseldorf patients received just one. While Brown had intensive chemotherapy and irradiation to prep for the transplant, the London patient had low intensity conditioning and no irradiation, and the Düsseldorf patient received myeloablative conditioning but no irradiation.   

What would it take to call this a cure?

A key question that has vexed researchers is whether or not the CCR5-delta32 mutation was necessary to achieve Mr. Brown’s cure. Since it was present in the cells transplanted into both Mr. Brown and the London and Düsseldorf patients, it will be important to follow them over time.

“Although it’s too early to say for sure, we’re certainly hopeful that the London patient is cured,” said Dr. Rowena Johnston, amfAR vice president and director of research. “amfAR’s  investments in innovative and forward-thinking projects like ICISTEM give us the opportunity to learn which factors will form the scientific basis of a cure for HIV.”

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New amfAR Grants Address Critical HIV Cure Research Questions

FOR IMMEDIATE RELEASE

Media Contact:
Mary Pavlu, Program Communications Manager
(212) 806-1602
mary.pavlu@amfar.org

New amfAR Grants Address Critical HIV Cure Research Questions

More than $800,000 awarded to researchers studying post-treatment control and differences in the HIV reservoir 

NEW YORK, Jan. 8, 2019 --- amfAR, The Foundation for AIDS Research, has awarded a new round of funding totaling $828,000 to advance two critical areas of HIV cure research.

Five grants will support a range of efforts to understand the mechanisms and predictors of post-treatment control, whereby a small number of individuals are able to control their HIV after stopping treatment. Three additional grantees will study HIV-positive populations in low- and middle-income countries to look for differences in how the persistent viral reservoir - the principal barrier to a cure - forms and changes over time.

"Post-treatment controllers may hold the key to understanding how the immune system naturally controls the virus, so it's essential that we achieve a fuller understanding of what mediates post-treatment control," said amfAR Chief Executive Officer Kevin Robert Frost. "It's also vital that we improve our knowledge of the crucial differences in the viral reservoir that may exist in those hit hardest by the epidemic."  

Dr. Jonathan Li of Brigham and Women's Hospital in Boston has assembled an impressive cohort of post-treatment controllers from one of the largest HIV clinical trial networks in the world. Using next-generation genomic sequencing, he is investigating whether characteristics of the virus or immunologic responses can predict post-treatment control. Understanding the combination of factors that contribute to post-treatment control could help scientists design interventions to enable control of the virus after stopping ART.

Another grantee, Dr. Godwin Nchinda, a researcher in Yaounde, Cameroon, has identified a cohort of women who received ART during pregnancy and continue to control their virus despite discontinuing treatment after giving birth. He aims to study this group to determine the causes of their viral control. 

The majority of what is known about HIV comes from research done in high-income countries, where HIV subtype B predominates. However, subtype B accounts for just 12% of global HIV infections. Dr. Edward Kankaka of the Rakai Health Sciences Program in Kampala, Uganda, has shown that non-B HIV-positive Ugandans had a smaller reservoir of persistent virus compared to people infected with subtype B.

Dr. Kankaka will expand these studies to determine whether formation and maintenance of the reservoir differ in these populations. His findings will add to our understanding of the potential effectiveness of curative interventions in people infected with HIV subtypes other than B.

In Durban, South Africa, Dr. Alex Sigal will examine the influence of tuberculosis-a common co-infection in low- and middle-income countries-on the HIV reservoir. He will explore whether the immune response to TB itself alters HIV reactivation-a key component of the "shock and kill" approach to curing HIV.

The remaining grantees are Dr. Mohamed Abdel-Mohsen of the Wistar Institute, Philadelphia, PA; Dr. John Frater of Oxford University, UK; Dr. Reena Rajasuriar of the University of Malaya, Kuala Lumpur, Malaysia; and Dr. Rui Wang of Harvard Pilgrim Healthcare Institute, Wellesley, MA.

 

"This group of grantees brings diversity to our efforts in their approaches, goals and geographic focus," said Dr. Rowena Johnston, amfAR Vice President and Director of Research. "Our efforts must support every promising approach that gets us closer to our goal of a cure for every person living with HIV." 

For a full list of grantees and descriptions of their research projects, click here.

 

About amfAR

 

amfAR, The Foundation for AIDS Research, is one of the world's leading nonprofit organizations dedicated to the support of AIDS research, HIV prevention, treatment education, and advocacy.  Since 1985, amfAR has invested more than $517 million in its programs and has awarded more than 3,300 grants to research teams worldwide.

Gut vs. Blood: Deeper States of HIV Latency

Dr. Steve Yukl

Dr. Steve Yukl

Earlier this year, we presented research by amfAR grantees investigating HIV latency in cells apart from CD4+ T cells of the blood. These reports included studies of specialized cells in the brain and vagina that may represent unrecognized reservoirs for latent HIV, and thus additional impediments to an HIV cure.

Writing in the November issue of PLoS Pathogens, amfAR-funded scientists Steve Yukl and colleagues from the amfAR Institute for HIV Cure Research continue this work, exploring latency in cells of the intestine vs. the blood.

A technique known as “transcription profiling” was used to examine the initial steps of the viral life cycle in infected CD4+ T cells from the blood and cells extracted from rectal biopsies. Sixteen HIV-infected individuals were included; all but one were male. They were followed as part of two long-term studies, and all individuals had complete suppression of virus with ART—as assessed by blood tests—for a range of 2 to 10 years.

Yukl and colleagues found that CD4+ T cells from the rectum may be more vulnerable to latent infection compared with T cells isolated from the blood. This “deeper state of latency” in the gut suggests that it is maintained by different processes than in the blood. One such mechanism, a block in transcriptional initiation—the first step in the viral life cycle of infected cells—was particularly prominent in the gut. Whether this difference is due to special features of HIV viruses that infect gut tissues, or conditions peculiar to the gut, is being explored.

The authors conclude that “infected cells in the rectum may be less susceptible to agents designed to reverse latency. [Our studies] could help inform new therapies aimed at HIV cure.”

Dr. Laurence is amfAR’s senior scientific consultant.

amfAR Announces 2018 Mathilde Krim Fellowship Recipient

Krim Fellowships continue to identify and support new scientific
talent with fresh approaches to HIV/AIDS research

NEW YORK, Dec. 11 2018 --- amfAR, The Foundation for AIDS Research, has announced the 2018 recipient of the Mathilde Krim Fellowship in Basic Biomedical Research. Named in honor of amfAR Founding Chairman Dr. Mathilde Krim, the Krim Fellowship program supports promising young scientists pursuing innovative solutions to HIV/AIDS. The Fellowship was awarded to Yen-Ting Lai, Ph.D., of the Vaccine Research Center/National Institutes of Health, Bethesda, MD, who will receive $150,000 over two years.

Working under the mentorship of Dr. Peter Kwong, Dr. Lai is applying his expertise in structural biology to understand how resistance arises to a drug in the entry inhibitor class called temsavir, which is now in phase III clinical trials. Currently, there are only two FDA-approved drugs in this class, which targets the earliest stage of the HIV life cycle, when the virus enters the cell. Understanding the cause of resistance to temsavir, which has been observed in some studies to date, could help in the development of a new and improved generation of the drug.

Dr. Lai began to contribute to the structural biology field while at UCLA, where he earned his third master’s degree, and later received a PhD in bioengineering. The Pittsburgh Diffraction Society recently awarded Dr. Lai the prestigious Sidhu Award in recognition of his significant contribution to the science of crystallography—a tool central to the field of structural biology.

The Krim Fellowship coincides with a new issue of the journal AIDS Research and Human Retroviruses, published in honor of Dr. Krim, who died in January 2018. It features tributes from amfAR CEO Kevin Robert Frost and Director and Associate Director of Research Drs. Rowena Johnston and Marcella Flores, respectively. It also features new research findings published by former Krim fellows.

“What we remember most about Dr. Krim is her passionate and unrelenting advocacy of science and the implementation of evidence-based policies,” wrote Dr. Johnston. “In 2014, I had the good fortune to co-author an article with Dr. Krim for this journal. In it, we discussed our vision for ending AIDS. We can think of no more fitting tribute than to imagine a role for amfAR's Krim Fellows and their research findings in realizing this vision.”

The Krim Fellowships have committed more than $7.8 million since 2008 to support the development of outstanding young researchers who have demonstrated a commitment to preventing, treating, and curing HIV/AIDS.

About amfAR
amfAR, The Foundation for AIDS Research, is one of the world’s leading nonprofit organizations dedicated to the support of AIDS research, HIV prevention, treatment education, and advocacy.  Since 1985, amfAR has invested more than $517 million in its programs and has awarded more than 3,300 grants to research teams worldwide.

amfAR Awards New Funding for Gene Therapy Study Aimed at Curing HIV

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Grant supports next phase of three-pronged approach to gene therapy-based cure

NEW YORK, Nov. 6, 2018 --- amfAR, The Foundation for AIDS Research, has awarded $800,000 in new funding to researchers developing an ambitious gene therapy-based approach to curing HIV. The award launches a critical new phase in a study initiated in 2017 with $2.3 million in grants awarded to seven teams of researchers. Six of the teams will move forward with the next phase of the project.

amfAR has forged a unique collaboration among world leaders in gene therapy that began with a think tank in 2016. The amfAR-led meeting gave rise to a plan to create the first combination intervention that will simultaneously address the main barriers to a cure. In a three-pronged attack on the HIV reservoir, the researchers will employ broadly neutralizing antibodies, CAR stem cells—cells genetically reprogrammed to recognize and attack disease cells—and molecular scissors targeting the virus.  

“This is an ambitious and complex project with very exciting potential,” said amfAR Chief Executive Officer Kevin Robert Frost. “It’s a carefully constructed strategy that involves some of the most talented and innovative scientists in the field. We think it holds great promise for developing the scientific basis of a cure by the end of 2020, which is the aim of our Countdown to a Cure for AIDS initiative.”

The researchers will test an approach that combines CAR stem cells that secrete broadly neutralizing antibodies, together with an enzyme (Brec1) that targets HIV DNA in the cell it has infected (while leaving other DNA intact), and long-term secretion of a broadly neutralizing antibody from the liver. The goal is to 1) induce CAR stem cells to kill reservoir cells; 2) to express two different antibodies to neutralize virions (virus that exists outside of cells) in the blood and tissues, and; 3) to use Brec1 to remove the provirus (virus that has been integrated into a cell’s DNA) from infected cells.

The investigators are: Hildegard Büning, Ph.D. (co-principal investigator, molecular biologist, Hannover Medical School, Hannover, Germany), who was recently named president of the European Society of Gene and Cell Therapy;  Keith Jerome, M.D., Ph.D. (co-principal investigator, virologist, University of Washington, Seattle); Hans-Peter Kiem, M.D., Ph.D. (transplantation biologist, Fred Hutchinson Cancer Research Center, Seattle); Scott Kitchen, Ph.D. (molecular biologist, UCLA, Los Angeles); Drew Weissman, M.D., Ph.D. (Immunologist, University of Pennsylvania, Philadelphia); and Richard Wyatt, Ph.D. (immunologist, The Scripps Research Institute, La Jolla).

Timothy Brown (the "Berlin patient") remains the only person known to have been cured of HIV. Brown received a stem cell transplant from a donor with a rare genetic mutation known as CCR5-delta 32, which conferred resistance to HIV infection. Ten years later, he remains free of the virus. 

“While Timothy Brown’s cure was the result of a very different gene therapy intervention, it nonetheless points to the enormous potential of gene therapy as a means of eliminating HIV,” said Dr. Rowena Johnston, amfAR Vice President and Director of Research. “We realize that delivering a gene therapy intervention to HIV-infected people around the world will be a considerable challenge. Part of the mandate of this group of researchers is to design a combination gene therapy intervention that could be effectively delivered by a single injection.”

The grant was supported in part by the Bill and Melinda Gates Foundation.

 About amfAR

amfAR, The Foundation for AIDS Research, is one of the world’s leading nonprofit organizations dedicated to the support of AIDS research, HIV prevention, treatment education, and advocacy.  Since 1985, amfAR has invested more than $517 million in its programs and has awarded more than 3,300 grants to research teams worldwide.

A Novel “Kick and Kill” Strategy to Eliminate HIV

These updates often focus on HIV cure strategies based on methods to eliminate latent reservoirs of HIV infection, the main barrier to a cure. amfAR-funded scientist Dan Barouch of Harvard University, with colleagues from the Ragon Institute, Gilead Sciences, and the University of Massachusetts, now present the results of a study using a novel combination of an immune activator and an HIV neutralizing antibody. The pairing delayed and, in some animals may have eliminated, viral rebound in their monkey model.

Dr. Dan Barouch

Dr. Dan Barouch

Writing in the October issue of the prestigious journal Nature, Barouch and associates report on 44 monkeys infected with a strain of HIV. This hybrid strain, known as SHIV, contained components of both human and simian immune deficiency viruses.

Beginning on day 7 after infection, all animals received daily antiretroviral therapy (ART) for 96 weeks. They were then divided into four groups: one received nothing; one an antibody (PGT121) capable of neutralizing HIV; one an immune stimulant, vesatolimod (also known as GS-9620), which activates CD4+ T cells and other immune cells including monocytes and natural killer (NK) cells, via a protein known as TLR7; and a final group received both the antibody and the immune stimulant.

ART was continued for another 34 weeks, then stopped. The hope was that vesatolimod would “kick,” or activate, latently infected T cells, rendering them more susceptible to binding by the antibody, and also stimulate monocytes and NK cells to help “kill” infected T cells.

The results were striking.

In all the treated monkeys, the combination of stimulant and antibody delayed time to reappearance of virus after ART was stopped. In those monkeys showing no viral rebound, intensive investigations found no evidence of virus for more than 6 months of follow up.

Given that viral rebound can occur in humans long after stopping ART, the authors cautioned that they “cannot exclude the possibility that exceedingly low levels of virus may still exist in these monkeys.” In addition, ART was begun rapidly—only one week after infection—which is unlikely in the real world of HIV infection. But despite these caveats, the investigators concluded that their experiments provide proof of concept for combining neutralizing antibodies with immune activators in the design of a potential HIV cure.

Dr. Laurence is amfAR’s senior scientific consultant.

Training a Person’s Own T Cells to More Effectively Kill HIV

Dr. Clio Rooney

Dr. Clio Rooney

CD8+ killer T cells are known to play a critical role in controlling the growth of HIV. But those cells, as produced during the course of an infection, are insufficiently potent to eliminate a persistent HIV infection, regardless of the use of antiretroviral therapy and strategies to induce—or “shock”—HIV from a dormant to an active state.

amfAR-funded scientists Clio Rooney, Cynthia Gay, Catherine Bollard, and David Margolis, working at the University of North Carolina at Chapel Hill and the Children’s National Health System in Washington, DC, along with colleagues from Baylor University, started a clinical trial aimed at overcoming obstacles to T cell-mediated clearance of HIV in ART-treated individuals.

Writing in the October issue of the journal Molecular Therapy, these investigators borrowed a page from the immunotherapy of cancer and certain viral infections. They removed T cells from HIV-infected individuals taking ART, and grew them to very large numbers in the presence of small pieces of HIV protein, immune hormones, and anti-HIV drugs (to prohibit the simultaneous growth of HIV). They then re-infused these “educated” cells—predominantly CD8+ killer T cells and so-called natural killer cells—into their original hosts on two occasions, two weeks apart.

Six subjects ranging in age from 35 to 65, on effective ART for 1 to 9.5 years, underwent this procedure known as adoptive T cell therapy. This first phase of the experiment was structured to evaluate the safety of the procedure. The infusions were well tolerated. As expected based on the study design, there was no change in the size of the latent HIV reservoir. The next step is to combine these infusions with a drug serving as a “latency-reversing agent” capable of inducing HIV growth from latent reservoirs. Such a clinical trial is already underway.

Dr. Laurence is amfAR’s senior scientific consultant.

The Mathilde Krim Effect

Photo: Annie Leibovitz

Photo: Annie Leibovitz

The September issue of the journal AIDS Research and Human Retroviruses pays tribute to the life and legacy of Dr. Mathilde Krim, amfAR’s Founding Chairman, who died in January. It focuses on amfAR’s Mathilde Krim Fellowships in Basic Biomedical Research, awarded each year to advance the careers of promising young investigators and to invigorate the field of AIDS research, and features new research findings by several recent Krim Fellows.

“On January 15, 2018, the world lost Dr. Mathilde Krim, a woman who changed the life of every person who has ever worked in HIV research,” write Drs. Rowena Johnston and Marcella Flores, amfAR’s Director and Associate Director of Research, respectively, in an introductory essay. The authors go on to describe the extraordinary impact of the Krim Fellowships, now in their tenth year: “What is clear is that the Krim Fellowship program has been a highly successful propagator of exceptional talent.”  

“The Krim Fellowship program has been a highly
successful propagator of exceptional talent.”

amfAR’s Chief Executive Officer Kevin Robert Frost writes: “The cause of human rights was the thread that bound the fabric of Dr. Krim's life, a life defined by an unwavering commitment to the principle that every life was of equal value. She had neither the patience for, nor the interest in, moralizing or philosophizing on the human condition. Dr. Krim celebrated life in all its beautiful diversity, for she loved a colorful world.”

Former Krim Fellow Dr. Nuria Izquierdo-Useros describes Dr. Krim’s unrivaled legacy in advancing the role of women in science. She writes: “The Matilda effect illustrates how the contributions of women to science have been historically attributed to their male colleagues in some circumstances. As a way to overcome the Matilda effect I propose to embrace the Mathilde Krim effect, and commemorate how the will of a woman had such a profound impact on the fight against HIV and AIDS.”

AIDS Research and Human Retroviruses can be found at www.liebertpub.com/toc/aid/34/9

The CHAMP Study: Clues to Natural Control of HIV Infection

In the search for an HIV cure--complete eradication of virus in the absence of ongoing antiretroviral therapy (ART)--one interim strategy involves identification of treatments that can induce sustained suppression of the virus, even if it remains present at very low levels.

Dr. Steven Deeks

Dr. Steven Deeks

The feasibility of such an approach is greatly strengthened by the existence of a small number of individuals known as post-treatment controllers, who maintain control of HIV growth after discontinuing ART. Writing in The Journal of Infectious Diseases, amfAR-funded scientist Dr. Steven Deeks from the University of California, San Francisco, with colleagues from eight AIDS Clinical Trials Groups (ACTG), identified such individuals and provided insights into their viral control.

In the CHAMP (Control of HIV after Antiretroviral Medication Pause) study, Deeks and colleagues sought to define the frequency of these post-treatment controllers. Reviewing participants in 14 ACTG studies enrolling over 700 individuals, they identified 67 people, of whom 38 were treated during early HIV infection and 25 during its chronic phase. These individuals maintained viral loads less than or equal to 400 copies at least two-thirds of the time after stopping ART, for a minimum of six months of follow-up.

Post-treatment controllers were over three times more prevalent among those who had started ART early in the course of their infection. But most impressive was the durability of HIV control. After one year, 75% still controlled their virus off ART. After five years, 22% still did. Deeks and colleagues also found that the level of virus at which participants in ART interruption trials restarted ART had a dramatic effect on the frequency of post-treatment controllers. Restarting ART at a threshold of 1000 viral copies would have failed to identify about half of those individuals.

The investigators also noted an unusual pattern: one of the 14 ACTG studies reported a surprisingly high number of post-treatment controllers. That study included cycles of ART treatment interruption, suggesting that the concept of “autovaccination,” by which bursts of virus following ART interruption stimulate effective immune responses, should be explored further in HIV cure research.

The authors concluded that “The presence of individuals who can maintain HIV suppression after discontinuing ART provides hope that the goal of sustained HIV remission is possible.”

Dr. Laurence is amfAR’s senior scientific consultant.

Potential New Targets to Block HIV Latency

Dr. Sharon Lewin

Dr. Sharon Lewin

It’s been known for over two decades that HIV establishes a dormant, or latent, state in CD4+ T cells, in which virus is impervious to the effects of currently available antiretroviral therapies (ART). Multiple subtypes of these T cells can similarly harbor HIV, but it had been assumed that HIV latency occurred when these cells reverted from an activated state to a resting state. Infection of actively growing, proliferating cells was thought to favor productive over latent viral states.

But in a recent issue of the Journal of Immunology, amfAR-funded scientist Sharon Lewin and her colleagues demonstrate that HIV latency can indeed be maintained in actively growing cells. The researchers suggest that this finding may open new avenues to abolish latency.

Lewin and associates used a novel test-tube model, which the team developed, to study the establishment of the HIV reservoir in active and resting CD4+ T cells, simultaneously. The team found that latency was established in both types of T cells but by distinct mechanisms. HIV latency preferentially occurred in a portion of resting T cells through a prolonged interaction with a second cell, the myeloid dendritic cell (mDC). 

Unexpectedly, they found a greater frequency of latent infection in active rather than resting T cells. The active cells bore large amounts of PD-1, a so-called immune checkpoint protein. Blocking its activity is the focus of several new “miracle” anti-cancer drugs, which work for some patients when chemotherapy has failed.

The authors conclude that the means by which HIV induces latency in T cells, and thus evades current cure strategies, may be dependent on interactions with other immune cells such as mDC and immune checkpoint proteins. Overcoming latency therefore “may require targeted therapeutic strategies.”

Dr. Laurence is amfAR’s senior scientific consultant.

 

Sex and the HIV Reservoir

New research points to the powerful effect of estrogen

A newly published study reveals that the female hormone estrogen has a significant effect on the persistent HIV reservoir. It suggests that women may respond differently than men to some curative interventions that are currently under investigation or, perhaps, that an effective cure for women could differ from a cure for men.

Dr. Jonathan Karn (Photo: Marcus Rose/IAS)

Dr. Jonathan Karn (Photo: Marcus Rose/IAS)

The reservoir of HIV that is impervious to antiretroviral therapy remains the principal barrier to a cure. Following a cohort of 26 men and 26 women, the researchers, led by Dr. Jonathan Karn of Case Western Reserve University, found that women have a smaller “inducible” reservoir than men. In other words, while the total size of the reservoir appears to be the same for both sexes, women have a smaller amount of reservoir virus that can be coaxed out of hiding by so-called latency-reversing agents (LRAs).

The finding has several important implications. First, one of the main cure strategies being pursued by researchers is “shock and kill” (or “kick and kill”). The intent is to shock HIV out of the reservoir so that it can be killed by the immune system or some other killing agent. Given their smaller inducible reservoir, would such a strategy be less effective in women?

Second, since reactivation of the reservoir is inhibited by estrogen, the researchers suggest that “studies of the impact of hormonal contraception on reservoir establishment and its long-term maintenance should be undertaken.”

And, given the small size and exploratory nature of cure-focused clinical studies to date, the inclusion of women in small clinical trials may lead to skewed results if hormone exposure is not considered.

The study concludes that further investigations into sex differences in latency reversal and HIV persistence “are mandatory to extend the benefits of the HIV cure effort to all men and women impacted by the global epidemic.”

Published in the Proceedings of the National Academy of Sciences, these findings are the most recent outgrowth of a multi-year amfAR investigation into sex differences in HIV. “We’ve long known that women and men differ in immune system function and response to antiretroviral therapy, but few researchers have followed up on these leads in cure research,” said amfAR Vice President and Director of Research Dr. Rowena Johnston, a co-author of the study. “It is imperative that we develop a cure that works for everyone.”

In 2012 Dr. Johnston was invited to give a talk on sex differences in HIV cure research at a conference. She soon realized, however, that there were very little available data on the topic. So she teamed up with Dr. Mary Heitzeg of the University of Michigan to undertake a systematic review of more than 150 published HIV cure research studies.

“It is imperative that we develop a cure that works for everyone.” —Dr. Rowena Johnston

The study, published in 2015, found that while there was a strong possibility that the efficacy of a potential cure could vary by demographic variables, only 8% of the studies reported conducting efficacy analyses by sex. They concluded that, “More data are needed to determine associations between demographic characteristics and safety/efficacy of curative interventions.”

Responding to this need, in 2016 amfAR awarded a grant to two teams of researchers led by Dr. Karn and Dr. Eileen Scully of Massachusetts General Hospital to explore how sex-based differences might affect the HIV reservoir and, by extension, a potential cure. The researchers were tasked with comparing the key differences in latent virus in men and women, and exploring the immune profile, activation levels and distribution of latent viral reservoirs in men versus women.

Their first set of findings, detailed in the PNAS paper, lay the groundwork for a preliminary trial to evaluate the effectiveness of the drug tamoxifen combined with the latency-reversing agent vorinostat in reactivating latent HIV in women.  Supported by the National Institutes of Health’s AIDS Clinical Trials Group, the study is expected to conclude in September 2019.  

The CD8 T Cell in HIV: New Insights from Tissue vs. Blood

For obvious reasons, physicians rely on peripheral blood samples to describe the state of the immune system in an HIV-infected individual, and follow the impact of antiretroviral therapies on activity of the virus and immune function. But new data from a large international collaboration that included amfAR-funded scientist Dr. Steven Deeks, suggest that most prior studies, all involving blood, failed to consider a major component of the body’s attack against HIV: the resident memory CD8 T cell, or CD8 TRM.

Dr. Steven Deeks

Dr. Steven Deeks

Writing in the June issue of Science Immunology, Dr. Deeks, from the University of California, San Francisco, and colleagues* emphasize that the CD8+ killer T cell is required for effective immune control of HIV. However, this type of immune cell exists in three forms. Only two, the central memory and effector memory T cells, circulate in blood. The third form, TRM, resides in lymphoid and non-lymphoid tissues. Yet these TRM cells establish a front line of defense to eliminate invading viruses and bacteria, and do so largely without involvement of circulating CD8 T cells.

Deeks and associates demonstrate that TRM cells dominate the CD8+ killer T cell response against HIV in lymph nodes and other lymph tissue throughout the body. They obtained tissue samples from HIV-infected individuals in the acute and early stages of infection. The highest frequency of these cells was found in “elite controllers,” individuals who maintain very low levels of HIV in the absence of ART.

This discovery has several implications. Importantly, it is known that the potency of certain experimental vaccines against SIV, the simian form of HIV, in monkeys can be predicted from the magnitude of virus-specific CD8 T cells in the lymph tissue of these animals. Expanding knowledge of the activity of the CD8 TRM cells in these tissues should, as the authors conclude, inform “new approaches to the development of vaccines or immunotherapeutic strategies designed to eliminate the viral reservoir in established HIV infection.” In other words, help us reach a cure.

*From the University of Pennsylvania, the Karolinska Institute in Stockholm, the Instituto Nacional de Enfermedades Respiratorias in Mexico City, the National Institutes of Health, the University of Minnesota, Emory University, Case Western Reserve, and Cardiff University in Wales.

Dr. Laurence is amfAR’s senior scientific consultant.

A New Source of Latent HIV?

amfAR-funded researchers continue to study cells other than CD4+ T cells that may harbor latent HIV. Such cells may pose additional obstacles to an HIV cure. Last month’s update featured amfAR grantee Dr. Paula Cannon and her work on specialized cells in the brain. In a study published online in May in The Journal of Clinical Investigation, amfAR grantee Dr. Luis Agosto and colleagues from Boston University look at possible HIV reservoir cells in the vagina.

Dr. Luis Agosto

Dr. Luis Agosto

Agosto and associates obtained vaginal biopsies from five HIV-negative women and two women with HIV who were receiving antiretroviral therapy. First, they documented that a special type of immune cell, known as a vaginal epithelial dendritic cell (VEDC), could be infected with HIV in the test tube. VEDCs are recognized by their shape, a characteristic internal structure on electron microscopy, and specific cell surface proteins.

But their research went further, showing that these cells were much more susceptible to infection by those strains of HIV that utilize a certain cell surface protein—known as CCR5—to enter a cell, rather than an alternative protein receptor, CXCR4. Based on their findings, the authors suggest that VEDCs may be strict “gatekeepers” for infection, selecting which strains of HIV will establish an infection in a woman.

The researchers also examined the possibility that VEDCs could establish a reservoir of latent virus. They found evidence that this may indeed be a possibility by identifying proviral HIV DNA in VEDCs obtained from the two HIV-positive women. By sequencing the DNA, they established that the VEDCs harbored “ancestral” fragments of HIV (the founder virus that established infection) in the women.

The number of such proviruses per VEDC was four- to eight-fold lower than those found in the women’s blood cells, but the amount was still highly significant. 

More work needs to be done to definitively conclude that vaginal cells are part of the latent HIV reservoir. It is possible that the VEDCs simply scavenged pieces of latent virus from T cells and could not produce infectious viruses when stimulated—the test of a true latent reservoir.

Dr. Laurence is amfAR’s senior scientific consultant.

Neutrophils: A Deadly, if Delicate, Killer

Dr. Amy Chung

Dr. Amy Chung

Researchers have long focused on natural killer (NK) cells as the principal cells of the immune system that receive a signal via antibodies to kill HIV-infected cells. In the May issue of the Journal of Immunological Methods, amfAR Krim Fellow Dr. Amy Chung and colleagues shed new light on this topic by highlighting the role of neutrophils, a more numerous and much more difficult cell to study, and their less well studied role in killing infected cells via antibodies.

Unlike NK cells, which can persist for years, neutrophils live less than a week inside the body. Outside of the body, they die easily within a few hours and react so quickly to their new environment that, in a petri dish, they no longer resemble the cells the researchers set out to study. While it is known that neutrophils use antibodies to direct their killing ability towards HIV-infected cells, the mechanisms through which they do so remain a mystery.

A neutrophil

To spur this research, Dr. Chung developed a tool to study how antibodies in a patient’s blood might team up with neutrophils. To get around studying the fragile neutrophils in healthy blood, Dr. Chung developed the tool using cells from a cancer patient who donated her cells to science. It was Robert Gallo, one of three scientists credited with discovering that HIV causes AIDS, who archived the cells in 1977. In a petri dish, these cancerous cells can live indefinitely and maintain many of the same characteristics as fresh neutrophils.

Using this tool, Dr. Chung found, surprisingly, that neutrophils were six times better able than NK cells to kill HIV-infected cells when antibodies were present. The authors note that “neutrophil-mediated effector responses should be investigated in future HIV vaccine trials.”

Given what the field is learning about the diverse activities of antibodies (see here and here, for example), there is real potential for neutrophil function to also play an important role in an HIV cure.

Dr. Flores is amfAR’s associate director of research.

HIV in the Brain

Dr. Paula Cannon

Dr. Paula Cannon

Most studies of the latent HIV reservoir, the primary impediment to a cure, focus on T cells. But amfAR grantee Dr. Paula Cannon, working at the University of Southern California with colleagues there and at Case Western Reserve University, has taken a different approach. She notes that the brain also contains distinct populations of three specialized cells infected with HIV: microglia, astrocytes, and macrophages. She sought to develop a mouse model to study these cells and their role in HIV latency.

Writing in the April issue of the Journal of Neurovirology, Cannon and associates emphasize the difficulty of studying brain cells from HIV-infected humans. In addition, the differences between simian immune deficiency virus and HIV make the monkey a less-than-ideal model for studying HIV in the brain. Instead, she used “humanized mice”—immune deficient animals transplanted with human blood-forming cells. When such cells enter the brain, they transform into just the types of cells thought to harbor the HIV reservoir.

The researchers also focused on a drug, phenelzine (Nardil), currently used to treat depression that doesn’t respond to other medications and able to enter the brain. Phenelzine stimulated HIV production from human microglial cells recovered from the brains of the HIV-infected humanized mice.

The authors felt that their model, and this new form of LRA, or latency reversing agent, shows “great promise as a model system for the development of strategies aimed at defining and reducing the central nervous system [brain] reservoir.”

Dr. Laurence is amfAR’s senior scientific consultant.

Gutting HIV

Very soon after an initial HIV infection, regardless of how it was acquired, HIV homes in on T cells in the gut. It establishes a latent HIV reservoir and, within days, disrupts the normal barrier between intestinal bacteria and the blood. These changes promote a state of chronic inflammation, which in turn fosters HIV growth and spread, and may accelerate disorders associated with aging of the heart, kidney and bone. Antiretroviral therapy (ART) may diminish, but does not stop, these processes.

Dr. Peter Hunt and Dr. Steven Deeks

Dr. Peter Hunt and Dr. Steven Deeks

Writing in the March issue of the online journal PLoS Pathogens, Drs. Steven Deeks, Peter Hunt and associates from the amfAR Institute for HIV Cure Research at the University of California, San Francisco, and The Wistar Institute in Philadelphia, discovered a new link in this chain of events that may hold the key to promoting intestinal recovery in such individuals.

Using gut biopsies obtained from infected people taking ART, Deeks, Hunt and colleagues found higher levels of A20, a protein associated with reduced inflammation. In the gut biopsies of people not taking ART, on the other hand, A20 levels were reduced. The increase in A20 in those on ART was associated with an increase in three intestinal proteins that support healthy barrier functions of the gut.

But the link between A20 and gut integrity proved to be complex. Using a mouse model of the intestines—an “intestinoid” grown from gut cells in the test tube—they showed that A20 is critical for survival of those cells. But during untreated infection, A20 is suppressed by one element of the immune system’s response to the virus, namely interferon-alpha. The research team confirmed the link between interferon-alpha and A20 by studying the blood cells of HIV-infected individuals on ART who received additional treatment with interferon-alpha.  

Simply put, HIV infection increases the activity of interferon-alpha, which decreases A20 and thus causes harm. Conversely, antiretroviral therapy increases levels of A20, preventing the damage that would otherwise be done to cells in the gut.

The researchers concluded that “variation in A20 expression during the course of HIV infection could underlie both the development of [intestinal] epithelial dysfunction before the initiation of ART and the recovery of intestinal epithelial integrity thereafter…. Further studies are warranted.” Clearly they are, as this may be yet another part of the search for an HIV cure.

 

Dr. Laurence is amfAR’s senior scientific consultant.

 

Can "the Berlin Patient’s" Cure Be Replicated?

amfAR-funded European research consortium aims to find out

When the scientific community learned in a 2009 article in The New England Journal of Medicine that a man known as “the Berlin patient” had been cured of HIV, the news ushered in a new era of HIV research, one underpinned by the knowledge that curing HIV is possible.

But a single person represents an anecdote, and many questions remained unanswered. What are the best ways to measure a vanishingly small amount of virus to confirm that none remains? What were the key elements of his treatment that led to the cure? And most importantly, could this case be replicated?

Co-Principal Investigators Drs. Javier Martinez-Picado (front right) and Annemarie Wensing (center right), pictured with ICISTEM members including Dr. Gero Hütter, “the Berlin patient’s” physician, and Dr. Maria Salgado. Also pictured are Dr. Rowena Johnston (front, second from right) and Dr. Jeffrey Laurence (back row, right) of amfAR. 

Co-Principal Investigators Drs. Javier Martinez-Picado (front right) and Annemarie Wensing (center right), pictured with ICISTEM members including Dr. Gero Hütter, “the Berlin patient’s” physician, and Dr. Maria Salgado. Also pictured are Dr. Rowena Johnston (front, second from right) and Dr. Jeffrey Laurence (back row, right) of amfAR. 

amfAR addressed the first question by bringing together a team of researchers to intensively study the blood and tissues of Timothy Brown, the Berlin patient, who has been remarkably generous with his body and his time in the service of science. We also brought together another team of researchers to compare every available assay that could quantify low levels of persistent viral reservoir.

amfAR subsequently funded three separate teams to more closely interrogate the circumstances and procedures that led to Timothy Brown’s cure. One of those researchers, Dr. Timothy Henrich, followed the two so-called “Boston patients,” who, after unusually long delays, experienced viral rebound, confirming that their transplants did not cure their HIV infection.

The groundbreaking work conducted by amfAR’s ICISTEM consortium has been recognized by two prestigious awards. Dr. Maria Salgado, a researcher from the IrsiCaixa AIDS Research Institute in Barcelona, Spain, was presented with the inaugural Dominique Dormont Award during the International ADIS Society Conference on HIV Science in Paris in July 2017. And Dr. Jon Badiola of the Virgen de las Nieves University Hospital in Granada, Spain, was presented with a Best Young Abstract Award at the Annual Meeting of the European Society for Blood and Marrow Transplantation in March 2018.

As ever in science, even disappointing results are an opportunity to learn new facts. Scientific findings were increasingly suggesting that the genetic mutation in the donor stem cells that Timothy Brown received were a vital, perhaps even foundational, element of his cure. Another grantee, Dr. Jonah Sacha, concluded that the rejection reaction of the transplanted cells against the recipient’s immune system (known as graft versus host disease) plays a central role in success against cancer and probably also HIV.

In 2012, amfAR began discussions with a group of European researchers with the goal of establishing a research consortium, now known as ICISTEM (www.icistem.org), that could take these questions even further. We chose Europe because it has the highest proportion of people living with the CCR5-delta32 genetic mutation that appears to have been central to Timothy Brown’s cure. The consortium is co-led by the IrsiCaixa AIDS Research Institute in Barcelona, Spain, and the University Medical Center Utrecht in the Netherlands. It includes HIV cure researchers, cancer transplant doctors, and doctors working to register stem cell donors and test their cells for the genetic mutation.

In January, amfAR met with the ICISTEM team in Berlin for an annual progress update and planning session. They have so far enrolled more than 30 patients with cancer and HIV who have received or soon will receive stem cell transplants. And they have identified over two million potential stem cell donors with the CCR5-delta32 mutation.

Most exciting, the group has conducted exhaustive testing for persistent reservoir in many of the transplanted participants and in several cases are unable to find evidence that any HIV remains. They are preparing to embark on the next phase of this scientific journey, the definitive test of a cure, namely the withdrawal of antiretroviral therapy. Results will take at least a year, and while we cannot promise that any of these people will be shown to be cured, we can promise that amfAR is pursuing every promising avenue to discover what it will take to finally cure HIV.

Dr. Johnston is an amfAR Vice President and Director of Research.