Research Update

Mapping an HIV Vaccine Target

Researchers gain new insights into the potential power of broadly neutralizing antibodies 

Background 

Dr. Marit Van Gils

Dr. Marit Van Gils

There is currently no HIV vaccine capable of eliciting protective immunity. One promising area of vaccine research has focused on broadly neutralizing antibodies (bNAbs)—specialized antibodies capable of inactivating diverse types of HIV. Of interest to researchers are a small number of people living with HIV called “elite neutralizers” who naturally develop bNAbs, providing models for vaccine development. 

bNAbs obtained from such elite neutralizers are being studied for their possible use in HIV prevention, treatment, and cure interventions. While they have shown much potential—inactivating about half of all variants of HIV—there remain obstacles such as how to extend the duration of protection and how these antibodies can more effectively inactivate the virus.  

The Research Question 

Last year, researchers were able to protect monkeys against SIV—an HIV-like virus that causes disease similar to AIDS—through the infusion of bNAbs sourced from elite neutralizers. The study found that genetically modified bNAbs could provide long-term protection against the virus, and the modification did not affect the way they bound to the virus.  

Previous studies have demonstrated which region of the virus is vulnerable to bNAbs. In this study, amfAR-funded researchers asked: How do changes in the way binding at this region occurs aid recognition and neutralization of HIV? 

Findings 

Dr. Gabriel Ozorowski

Dr. Gabriel Ozorowski

Researchers studied the region of HIV recognized by a bNAb obtained from an elite neutralizer. They used highly sophisticated scanning procedures such as ultra-high resolution cryo-electron microscopy—which examines the topography of proteins—to capture the molecular interactions between the antibody and the participant’s own HIV. Scientists used these stop motion animation-like scanning procedures to locate points of contact between the antibody and the virus, and to piece together specific interactions that lead to the antibody’s potent ability to neutralize HIV. 

Researchers focused on interactions at the fusion peptide—a viral protein that folds back on itself to pull the bulk of the virus inside the cell. The fusion peptide is surrounded by a shield of sugar molecules that makes it largely inaccessible. Yet some antibodies have been known to penetrate the shield and neutralize the fusion peptide. The scanning techniques used by the researchers here revealed that this elite neutralizer’s bNAb could interact with the fusion peptide in an entirely new way. They also found that the fusion peptide is much more flexible than previously thought, making it amenable to targeting by this and perhaps other antibodies.   

Impact 

Knowledge of how the HIV fusion peptide can twist into multiple conformations, or shapes, illuminates antibody recognition strategies that can be used for HIV vaccine design.

 

amfAR’s Role 

Both Drs. Ozorowski and van Gils are funded by amfAR through the Mathilde Krim Fellowship program.

 

Original Article 

http://www.ncbi.nlm.nih.gov/pubmed/31194940

 

Dr. Laurence is amfAR’s senior scientific consultant.

Combination Treatment Cures Mice of HIV

Antiretroviral therapy (ART) has been extremely effective at reducing HIV in the blood to below levels of detection, but less able to stop viral activity in the tissues. Efforts to achieve a cure for HIV would therefore be aided by stopping this source of virus that continually feeds the HIV reservoir.

Dr. Howard Gendelman of the University of Nebraska Medical Center has developed LASER ART, a slow-release, long-acting nanomedicine version of ART that penetrates deep into tissues to effectively extinguish this source of viral activity. This powerful new technology raises the question: With a newly contained viral reservoir, could the right intervention have a chance to cure HIV?

In a July article in Nature Communications, Dr. Gendelman and Dr. Kamel Khalili, of the School of Medicine at Temple University, demonstrate that it may be possible.

Using humanized mice infected with HIV and treated with LASER ART, Dr. Khalili administered CRISPR, a protein that acts like a molecular scissor, to cut out HIV DNA from infected cells. Sequential treatment with LASER ART followed by CRISPR eliminated viral rebound in two of six mice when ART was stopped—a key measure to determine whether a cure has been achieved.

The research team went a step further, however, transferring cells from these two potentially cured mice into different, uninfected mice and confirming that no HIV infection was transmitted.

These encouraging results are a boon to the field of gene therapy, which is increasingly turning to various types of molecular scissors, including CRISPR, Brec1, and others to eliminate HIV from the body . amfAR’s is currently funding several such innovative gene therapy approaches through its ARCHE-GT collaborative grant initiative.

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

Could Gene Therapy Cure HIV?

Upcoming Advances in HIV Gene Therapy

In August, scientists will discuss their latest findings at the 5th Conference on Cell & Gene Therapy for HIV Cure in Seattle. amfAR’s research will feature prominently, including an update from ICISTEM, the amfAR-initiated and funded European consortium that reported a few months ago on the London patient. Several members of amfAR’s ARCHE-GT consortium will also report on their combination approach to cutting HIV DNA out of infected cells and boosting T cell and antibody responses against any remaining virus.

Background

Rowena Johnston, Ph.D.

Rowena Johnston, Ph.D.

The promise of gene therapy is beginning to make its way into the clinic. In 2017, the FDA approved two CAR T cell therapies for cancers of the immune system, and another gene therapy to correct a gene mutation that causes retinal dystrophy. And in May 2019, Zolgensma was approved as a one-time treatment for children under two years of age with spinal muscular atrophy.

The number of FDA-approved gene therapies appears set to grow in the coming years, with nearly 4,000 clinical trials underway to address illnesses ranging from rare inherited conditions to those that rank among the most common killers, including cancer, heart disease, Alzheimer’s disease, and diabetes.

The Research Opportunities

In some respects, HIV is a conceptually simple target because it exists as a strand of DNA—much like a gene—inserted into the normal DNA of human immune cells. Indeed, many research groups are exploring a range of tools that could cut this strand of HIV DNA out of infected cells and thus remove the virus from the body.

However, HIV is a complex virus that provides numerous other avenues of attack. For example, some research groups are exploring whether cutting out the gene for CCR5, and thus removing the CCR5 protein—the main doorway through which HIV enters cells—might cure HIV along similar lines to the Berlin patient’s cure. The HIV remission observed in the London and Düsseldorf patients—members of amfAR’s ICISTEM cohort—lends additional optimism to this approach.

The possibilities don’t end there. Protective genes could be inserted; new or improved immune function could be engineered; individual or multiple HIV genes could be turned off; and any or all of these approaches could be combined with other gene or traditional therapies.

Anticipated Conference Highlights

The conference will begin with a session on stem cell transplantation and gene editing, featuring a plenary talk delivered by ICISTEM researchers. Subsequent sessions will feature updates on CAR T cells and other T cell therapies, as well as lessons from cell and gene therapy in other diseases.

Day two of the conference will focus on in vivo delivery of gene therapy. Researchers from amfAR’s ARCHE-GT consortium will present their progress on using different methods to deliver gene-editing tools, for example via intravenous injection.

Impact

Although gene therapy approaches have shown much promise in various diseases including HIV, they are currently very expensive. Thus far, approved gene therapies cost up to $2 million, partly due to the complexity of preparing the gene therapy product. In vivo delivery could make gene therapy substantially less expensive and more easily deliverable to people around the world living with HIV.

amfAR’s Role

amfAR is currently supporting multiple gene therapy approaches to curing HIV and is providing support to the 2019 Conference on Cell & Gene Therapy for HIV Cure.

Conference Information

Researchers looking for more information about the conference, including registration and late-breaker abstract submission, should visit https://www.cgt4hivcure2019.org/

Dr. Johnston is an amfAR vice president and director of research.

Non-AIDS Defining Illnesses Impact Health in the Age of ART

Antiretroviral therapy (ART) has dramatically reduced mortality rates from both AIDS-related and non-AIDS related diseases of people living with HIV (PLWHIV). But there are important exceptions to this trend: Certain cancers and forms of heart and liver disease remain prominent among PLWHIV.

A Biomarker for the “Active” HIV Reservoir?

Background 

HIV persists in a small number of infected cells—the viral reservoir—that are not cleared from the body by antiretroviral therapy. A major goal of HIV cure research is to identify a molecule, or biomarker, that distinguishes these reservoir cells from healthy cells. Having such a biomarker would allow researchers to target these reservoir cells and clear them with precision.  

Co-leader of the study, Dr. Peter Hunt

Co-leader of the study, Dr. Peter Hunt

The Research Question 

In 2017, a team of researchers in France reported that they had found a potential biomarker of the reservoir in the blood—a protein called CD32. In their attempts to replicate the discovery, several other research teams found that CD32 may be a marker of HIV activity in blood cells rather than a specific marker of the latent reservoir. Scientists in this study ask: Could CD32 be a biomarker of HIV activity in the tissues, too? 

Findings 

Scientists examined gut biopsies from four study participants whose medication had reduced the HIV in their blood to undetectable levels. First, researchers noted that despite having undetectable virus in the blood, about four in every 100,000 cells in the tissue had jump-started activity of the provirus, meaning they had begun the first steps towards producing new viruses. These “actively” infected cells may be the first to re-seed viral infection in the blood if antiretroviral therapy is stopped. 

Next, the researchers explored whether CD32—the possible biomarker—was present in the actively infected cells, and to what degree. Using two separate techniques, the researchers found that those with undetectable virus in the blood had 100 times fewer actively infected cells in the tissue than those with detectable virus in the blood (viremia). But by one assay, between 60 and 100 percent of actively infected cells had CD32, compared to only 20 percent in those with viremia.  

Co-leader of this study, Dr. Timothy Henrich

Co-leader of this study, Dr. Timothy Henrich

Impact 

This study confirms the conclusion of other researchers that CD32 may not be a biomarker of the latent reservoir. However, CD32 may be a biomarker of what might be called the active reservoir—the persistent virus that is probably first to re-seed infection when antiretroviral therapy is stopped. Thinking on the nature of the reservoir is evolving to include not only latent, but also active reservoir, and both are major barriers to a cure. Finding a way to differentiate cells harboring active reservoir from healthy, uninfected cells would be an important advance. 

amfAR’s Role 

The co-lead scientists of this study, Drs. Timothy Henrich and Peter Hunt, are funded by amfAR and are members of the amfAR Institute for HIV Cure Research. 

Original Article 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6508427/

 

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

The Ability to Control HIV Without ART Runs in Families

Dr. Steven Deeks

Dr. Steven Deeks

In prior updates, we’ve focused on CCR5, the primary receptor enabling HIV to infect cells. CCR5 is known for its role in the cure of the “Berlin patient” following a bone marrow transplant with donor cells bearing a mutated, thus non-functional, CCR5 protein.

Reporting in the online journal eLIFE, Dr. Steven Deeks of the University of California, San Francisco, and colleagues, found another way that CCR5 is connected to the ability to control HIV without antiretroviral therapy (ART). Interestingly, they also found evidence that this ability is heritable.

Deeks and colleagues sought to define genetic factors enabling a small population of HIV-infected individuals called elite and viremic controllers to maintain viral loads less than 50 or 2000 copies, respectively, without ART. These are considered “functional cures” since the virus is not eradicated—the usual definition of “cure”—but the person does not develop immune problems over time.

The researchers studied 131 such individuals, about half elite and half viremic controllers, some of whom have been infected since 1980. Some had HLA types—cell protein markers—associated with elite control, but those protective genes account for only about 20% of the viral effect.

They discovered that control was related to a natural and partial resistance to infection in controllers and noncontrollers. Further analysis showed that controllers had less CCR5 present on their cells than noncontrollers, and their cells were less permissive to HIV infection. Furthermore, natural resistance to HIV was shown to be inherited, as multiple generations of family members, male and female, from one of the viremic controllers had a similar profile of lowered CCR5.

There have now been at least two instances related to CCR5 in which researchers identified partial or full resistance to HIV. The first is a rare mutation, CCR5-delta32—a defunct CCR5 protein—leading to the cures of the Berlin and London patients after stem cell transplants with cells containing this mutation. The second, in this new study by Deeks and colleagues, is the natural decrease in some elite and viremic controllers who make a normal CCR5 protein, but at much lower levels than people who cannot control HIV.

Studying how and under what circumstances these controllers make lower levels of CCR5 may lead to new discoveries that could inform interventions for a functional cure.

HIV Treatment Interruption: Lessons and Limitations

The recent case of the London patient—potentially the second known case of an HIV cure—highlights a challenge faced by the cure research field: How do you know when an intervention has resulted in a cure?  

To date, the field has used analytic treatment interruption (ATI)—stopping antiretroviral therapy (ART) under the guidance of a doctor—to monitor when, how high, and for how long the virus rebounds. If the virus rebounds, then the question of viral eradication has been answered and the participant can restart ART. But using ATI to determine whether post-treatment control (PTC)—the ability to keep the virus under control in the absence of ART—has been achieved, is a longer and more complex proposition. ATI presents challenges to participants, their partners, and to the researchers seeking to make sense of the data.

Dr. Sharon Lewin

Dr. Sharon Lewin

In the April issue of AIDS, amfAR-funded scientist Dr. Sharon Lewin of Monash University in Melbourne, Australia, documented nearly two decades of studies using ATI to chart achievements and lessons learned. Analyzing 159 ATI clinical trials conducted between 2000 and 2017, Dr. Lewin and colleagues noted a trend to restart ART as soon as virus was detected in plasma, especially after 2014, when the World Health Organization began recommending universal ART.

Prior to 2014, when CD4 count rather than plasma viral load was used as the main criterion to restart ART, researchers were more likely to delay restarting ART to determine whether an intervention had a post-treatment control effect. The trend toward restarting ART sooner alleviates the concern that a patient will unwittingly transmit HIV to a sexual partner and is generally agreed to be safest for the participant, but it comes at a cost to the researchers’ ability to discover effective interventions.

The challenge of when to restart ART was among the topics discussed by more than 40 scientists and clinicians who convened at the Ragon Institute of MGH, MIT and Harvard in July 2018, including amfAR grantee Dr. Dan Barouch and amfAR vice president and director of research, Dr. Rowena Johnston.

The attendees published their recommendations for researchers and clinicians planning ATI studies in The Lancet HIV, aiming to ensure that study designs maximize the knowledge gained and reduce the risk to trial participants. The group agreed that restarting ART should occur any time a participant requests it or if HIV-related conditions emerge.

However, mitigating the risk of transmitting the virus to a partner during a longer ATI to test for PTC was a more difficult challenge. Participants would require comprehensive counseling, including on the use of condoms or pre-exposure prophylaxis (PrEP), and researchers may need to exclude participants who engage in high-risk behavior. Some studies have begun to routinely test for sexually transmitted infections as one indicator of a participant’s use of condoms during ATI.

Until better predictors of curative success are found, or tests proving the absence of an HIV reservoir are developed, ATI will continue to be the gold standard in HIV cure research. By developing better standards and recommendations that guide current and future ATI studies, the field is ensuring that the progress made is safer for the participant and more valuable to the research community.

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

What Stem Cell Transplants Can Teach Us About Curing HIV

amfAR researchers unable to find HIV in London transplant patient

Stem cell transplants are used to treat cancers of the immune system, and are typically used in people for whom other cancer treatments have failed. The stem cells are taken from adult donors or from cord blood, and when transplanted into the recipient, those stem cells mature into a new and healthy immune system.

Sometimes people living with HIV (PLWHIV) develop one of these immune cancers, and they become candidates for stem cell transplants. Under these circumstances, we have an opportunity to learn a lot about how HIV persists even when it’s well controlled by antiretroviral therapy (ART), and how replacing the immune system affects the ability of HIV to persist.

amfAR set up and provided funding to the IciStem consortium so that we could learn some important lessons about curing HIV that could be applied to designing a cure that would work in anyone, whether or not they receive a stem cell transplant. The researchers in IciStem analyze the blood and tissues of HIV-positive transplant recipients. They can then compare the outcomes between people who received transplants that have fully functional CCR5—the main doorway that allows HIV to enter cells— and those whose transplanted cells contained the CCR5-delta32 genetic mutation. This is of particular interest because cells with the genetic mutation are highly resistant to HIV.

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.

What/Who are IciStem, the London patient, and the Düsseldorf patient?

IciStem is a large consortium of HIV researchers and transplant specialists who are currently studying HIV in a cohort of 45 patients who have already received, or will soon receive, stem cell transplants to treat their cancers. Two of these patients – the London patient and the Düsseldorf patient – received cells from donors who had the CCR5-delta32 genetic mutation. Both have stopped taking ART without any signs of HIV returning, but it’s important to note that while the London patient has been off ART for 18 months, the Düsseldorf patient stopped taking ART only four months ago. PLWHIV who stop taking ART typically experience HIV rebound in 2-4 weeks, but the Mississippi child took 28 months to rebound, so although we’re hopeful that the London and Düsseldorf patients are cured, it will take more time to know for sure.

What kinds of things can we learn from these transplant patients?

When Timothy Ray Brown, the Berlin patient, was cured of both his cancer and his HIV following a transplant of CCR5-delta32 cells, the scientific community was unable to determine how crucial the mutation was to his cure outcome. Timothy also received a myeloablative conditioning regimen, as well as total body irradiation, designed to destroy the great majority of his own immune cells, before ultimately receiving two stem cell transplants. IciStem researchers will be able to determine the relative importance of the myeloablation, irradiation, the CCR5-delta32 genetic mutation, and number of transplants by comparing many HIV-positive stem cell transplant recipients in their cohort, because each patient receives a different combination of these factors.

If we learn that the CCR5-delta32 mutation is a critical factor, this finding points a promising way forward for gene therapy. In fact, other researchers have been working on CCR5 gene therapy in HIV for many years, and interesting results are emerging concerning how many of the transplanted cells need to have the genetic mutation in order to make a difference in the clinical outcome. You can learn more here about additional gene therapy strategies currently under investigation by amfAR researchers.

If specific subsets of immune cells are especially effective at clearing small numbers of remaining HIV cells, we can turn that knowledge into a more broadly applicable intervention.We also have the opportunity to learn from the processes by which a stem cell transplant may clear out any remaining vestiges of HIV. If the conditioning regimen before a transplant does not completely clear the HIV-infected cells, we can learn which cells of the newly transplanted immune system finish the job, and how.

If specific subsets of immune cells are especially effective at clearing small numbers of remaining HIV cells, we can turn that knowledge into a more broadly applicable intervention.

By following transplant patients over time, and ultimately confirming they’re cured, we may be able to go back to samples collected earlier during the transplant and recovery process. Researchers could look at cells, proteins, and other substances in their blood to determine whether there are signs that could have predicted a cure, without having to wait years to know for sure. These biomarkers would then be valuable in assessing whether other more broadly applicable interventions have been effective in achieving a cure.

We can also compare the chemotherapy regimens the patients receive for their different cancers, and understand which regimens kill which subsets of cells. We may learn, for example, that some subsets of HIV-infected cells are the most important to target, and that others, even if they contain HIV, might be less important sources of rebounding virus and can be left alone.

And even transplant patients whose HIV we can still detect play an important role in our search for a cure. Because their remaining HIV reservoirs are so small, they may be ideal candidates to test early-generation immunotherapies for their ability to remove any remaining pockets of HIV.

Why do we need transplant patients to learn these things?

There are some things about curing HIV that you can only learn from people who have been cured. In the absence of other interventions so far that cure HIV, we need to learn those lessons from transplant patients.

For example, people living with HIV experience consequences of the persistence of the virus, such as damage to the architecture of their lymph nodes, that can hamper effective immune responses. If we remove the HIV, does their lymph node anatomy and function return to normal? If so, then we have learned that removing HIV may be sufficient for restoring lymph node health, without needing to devise additional interventions.

Similarly, PLWHIV have higher rates of atherosclerosis, a sign of possible heart disease and stroke. If those signs and symptoms return to normal after a stem cell transplant that removed HIV, then perhaps we’ve learned that no further interventions will be needed to deal with heart health after an HIV cure.

Dr. Johnston is an amfAR vice president and director of research.

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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Fishing for New Ways to Overcome HIV Latency

Dr. Satish Pillai

Dr. Satish Pillai

Over the past few months, we’ve reported on work by amfAR grantees charting the diversity of cell types capable of maintaining HIV in a latent state, protected from standard attack by the immune system. All such reservoirs, from T cell subsets to specialized cells in the vagina and brain, are potential impediments to achieving a cure for HIV.

In a new paper published in PLoS Pathogens, Dr. Satish Pillai of the amfAR Institute for HIV Cure Research, with colleagues from various institutions, describes how a component found in all cells contributes to establishing such latency, and how it appears to offer a specific new target for therapeutic intervention.

Pillai and colleagues began their study with the recognition that current drugs used to drive HIV from a dormant state—so-called latency reversing agents, or LRAs—are inadequate. Their potency is low, and they’ve had little impact on reducing the number of HIV-infected cells in clinical trials.

So Pillai began “fishing,” using sophisticated screening techniques based on CRISPR gene editing to search for unexpected processes that might be involved in the regulation of HIV in latently infected cells. They found one: the proteasome.

Proteasomes are structures found within normal cells that digest unneeded or damaged proteins. Several drugs that inhibit proteasomes have been approved by the FDA as cancer therapies. Two such drugs, bortezomib and carfilzomib, strongly enhanced the ability of existing LRAs to activate virus from the cellular reservoirs of HIV-infected individuals. They had the added benefit of limiting known side effects of LRAs such as activating the cells and expanding the reservoir by cellular division.

The researchers concluded that their findings provide “a new avenue to expose latent HIV,” and thus bring us one step closer to an ultimate cure for HIV.

Dr. Laurence is amfAR’s senior scientific consultant.

Why Are Some T Cells Especially Prone to HIV Infection?

Dr. Asier Sáez-Cirión

Dr. Asier Sáez-Cirión

Activated CD4+ T cells have been known for some time as especially susceptible to HIV infection, and that they form the largest reservoir of latently infected cells. But not all CD4+ T cells contribute equally to the pool of such dormant infected cells.

amfAR grantees Asier Sáez-Cirión from the Pasteur Institute in Paris, Nicolas Chomont of the University of Montreal, and other colleagues sought to determine if other features of subsets of T cells also contribute to their susceptibility to HIV infection and creation of a latent state.

Writing in the April issue of Cell Metabolism, they found that differences in susceptibility to HIV infection matched the level of metabolism of particular T cell subsets, and that this was true regardless of their activation profile. Cellular pathways linked to sugar metabolism and oxidation were particularly relevant. These metabolic distinctions were maintained in T cell subsets despite their state of activation.

Utilizing T cells from 6 HIV-positive donors who had maintained undetectable levels of virus after 3 to more than 16 years of antiretroviral therapy, the researchers showed that expression of certain genes important in cell metabolism correlated strongly with susceptibility to HIV infection. Moreover, partial inhibition of sugar metabolism in the test tube suppressed the susceptibility of these cells to HIV infection, and blocked amplification of the virus in cells from the HIV-infected individuals.

The authors concluded that their results “identify vulnerability in tackling HIV reservoirs.” These reservoirs are a major impediment to curing HIV, and such metabolic vulnerabilities may be targeted by new therapies.


Dr. Laurence is amfAR’s senior scientific consultant.

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.

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.