amfAR, The Foundation for AIDS Research, today announced a pair of research grants that renew its support for innovative approaches to HIV cure research. Totaling nearly $1 million, the Investment grants will allow two collaborative teams of HIV researchers and bioengineers to embark on a second phase of projects initiated with amfAR funding awarded in February 2017.
A team of French doctors observed a “drastic and persistent decrease” of the HIV reservoir in a lung cancer patient given a drug commonly used to treat several cancers in their advanced stages.
The reservoir is the collection of HIV-infected cells that persists despite antiretroviral drugs and hides under the radar of the immune system. It is the wellspring of HIV that quickly rebounds when treatment is stopped.
“This is the first case of such a drastic decrease of the HIV reservoir,” said Dr. Jean-Philippe Spano, head of the medical oncology department at Pitié-Salpêtrière Hospital in Paris where the patient was treated. But, he cautioned, “we must remain careful, especially because this is only one case.” Spano and his colleagues detailed the case last month in a letter published in Annals of Oncology.
The 51-year-old man was given nivolumab (marketed as Opdivo) once every two weeks starting in December 2016 after he relapsed following surgery and chemotherapy for his tumor. Nivolumab has been shown to be effective in treating melanoma, non-small cell lung cancer, and kidney cancer.
When the patient started treatment, his viral load was undetectable. It steadily climbed until day 45 before falling again. During that time, the activity of his T cells also increased. By day 120, he had experienced "a drastic and persistent decrease" in HIV reservoir levels, the researchers said.
Doctors believe the cancer drug may have enhanced the “killing” of HIV-infected cells by releasing the brakes the immune system deploys for safety. However, they noted that another HIV-infected patient given the same treatment did not experience a reduction in the reservoir.
Still, the findings “could have implications for HIV patients, both with and without cancer, as it can work on HIV reservoirs and tumor cells independently," Spano said. “The absence of side effects in this patient is also good news and suggests this could be an optimum treatment for HIV-infected patients with cancer."
Commenting on the study for HealthDay, Dr. Marcella Flores, amfAR’s associate director of research, called the case “interesting and hopeful.” However, she noted that while the drug caused a substantial decrease of the HIV reservoir, it did not completely eradicate the virus.
She told the news service that more work needs to be done to better understand this particular patient's experience and to figure out how it might help others.
Killing HIV reservoir cells—cells that are persistently infected with the virus—would potentially eradicate HIV from the body. In three journal articles published in December, amfAR-funded scientists discuss recent advances in understanding how immune system cells use antibodies to kill HIV-infected cells via antibody-dependent cellular cytotoxicity (ADCC). ADCC is an immune response in which antibodies act as homing devices to recruit immune cells that target and kill infected cells.
These advances include: developing tools to better understand antibody functionality; identifying which antibodies are most suited to ADCC; and examining their protective role against infection.
The goal: to learn how antibodies can cure HIV.
A new tool to examine antibody function
In a study published in the journal Retrovirology, amfAR-funded scientists Drs. Amy Chung of the University of Melbourne in Australia and Galit Alter of the Ragon Institute of MGH, MIT and Harvard University in Cambridge, MA, write about a platform of techniques called systems serology, which they developed to explore the functionality of antibodies. Through this approach, which uses machine learning algorithms to analyze data on the biophysical and functional properties of antibodies, Chung and Alter can identify features of HIV-specific antibodies that are better able to engage in ADCC. They hope that by using systems serology in primate vaccine studies, they can better understand how vaccines skew immune responses to protect against infection or how to improve the ADCC response in humans.
Antibodies protect non-HIV infected partners
Supported by an amfAR Mathilde Krim Fellowship, Chung is studying the mechanisms of interaction between vaccines that produce IgA, a type of antibody present only in mucosal tissues, and IgG, an antibody present in the blood, to provide partial protection against HIV. Writing in the journal EBioMedicine, she comments on a study carried out by researchers at the University of Buenos Aires in Argentina that supports her observations: the ratio of IgG to IgA correlates with the killing action of antibodies, most likely through ADCC. Furthermore, HIV-infected persons with high ratios of IgG to IgA are much less likely to transmit the virus to their HIV-free partners. She concludes that even people not infected with HIV benefit from their HIV-positive partners’ effective antibody responses.
A narrow window for antibody susceptibility in HIV-infected cells
And in a third study published in the journal Virology, amfAR-funded scientist Dr. Andrés Finzi of the Centre de Recherche du CHUM in Montreal, reports on the susceptibility of the viral protein Env—present on the surface of actively infected cells—to antibodies. Finzi shows that Env exists in three different states: open, partially open, and closed. It had previously been thought that Env was only vulnerable to antibody attack in the open position. However, by altering the protein to lock it into a partially open position, Finzi found that it, too, was subject to antibody binding. Through this finding, Finzi has increased the options researchers have for designing antibodies to target Env and eventually eliminate HIV-infected cells through ADCC.
In conclusion, all three of these studies will provide us with the tools and knowledge we need to manipulate immune responses to harness the killing power of antibodies and cure HIV.
Dr. Flores is amfAR’s associate director of research.
The first FDA-approved gene therapy treatment for cancer patients has shown promise in suppressing HIV infection long term in lab monkeys, according to a study partially funded by amfAR.
Researchers genetically engineered stem cells to express chimeric antigen receptors (CAR) that can detect and destroy SHIV (a combination of HIV and SIV—the monkey form of the virus). The cells were then tested in four male juvenile SHIV-infected macaques.
Not only did the engineered cells decrease the viral load, they persisted for more than two years in the monkeys without any adverse effects. Furthermore, the cells were widely distributed throughout the lymph nodes and gastrointestinal tract, where viral replication and persistence are concentrated.
“The advantage of the stem cell-based approach is that once these cells are grafted into the body, they continuously produce new T cells that have this gene in them that can target HIV cells,” said amfAR grantee Dr. Scott Kitchen of the University of California, Los Angeles.
The FDA approved the gene therapy treatment Kymriah in August 2017 for young people up to age 25 with a form of acute lymphoblastic leukemia, a blood cancer. The therapy involves modifying a patient’s own T cells and genetically engineering them with CAR cells that can recognize and kill tumors.
Its approval coincided with the announcement of two amfAR grants exploring a similar strategy to curing HIV.
Commenting on the study for HealthDay, Dr. Marcella Flores, amfAR’s associate director of research, said she was cautiously optimistic about the potential of gene therapy to eradicate the virus. “CAR therapy is already leading to impressive results in cancer,” she said.
However, she noted that the study was performed in monkeys. Results in humans may be quite different.
Kitchen said human trials could begin within two to three years. While it is unlikely that the CAR strategy will work completely on its own, he said it could be used with antiretroviral therapy to engineer an immune response to target and kill HIV.
“Theoretically the goal is to provide lifelong immunity to HIV,” he said. “We’re aiming for a cure, and we know that to cure HIV you need an effective immune response.”
The study was published in the December 28 issue of PLOS Pathogens.
In a summer update, we highlighted research from the amfAR Institute for HIV Cure Research at the University of California, San Francisco, involving a drug developed to fight cancer in a “shock and kill” approach to curing HIV. The authors concluded that findings from such a line of research underscore “the emerging ties between cancer and HIV treatment through shared drug targets.”
Now in an article in the December 2017 issue of PLoS Pathogens, amfAR-funded scientists Drs. Cheryl Cameron from Case Western Reserve University in Cleveland and Franck Dupuy from McGill University in Montreal, with colleagues from both institutions, Emory University in Atlanta—including amfAR board member Dr. Raymond Schinazi—and the University of Montreal, explore using other drugs approved to treat other diseases to eradicate HIV.
The investigators studied two FDA-approved drugs, ruxolitinib, used to treat a bone marrow disorder known as myelofibrosis and some cases of lymphoma, and tofacitinib, used to treat rheumatoid arthritis and inflammatory bowel disease. These agents share a mechanism of action: inhibition of a normal cell protein known as Jak, a key promoter of inflammation.
In test tube studies, the researchers used concentrations of the two drugs that are typically found in the blood of the patients taking them. They were able to block HIV production from infected T cells, inhibit activation of the virus from latently infected cells, and reduce the number of latently infected cells in HIV-infected individuals on antiretroviral therapy. This was accomplished without suppressing immune function.
The authors concluded: “Jak inhibitors represent a potential therapeutic modality that addresses a clinical need which traditional direct-acting antiviral agents that interfere with steps in the viral replication cycle have not been successful.”
Indeed, the role of ruxolitinib in reducing inflammation associated with HIV infection is currently being evaluated in a National Institutes of Health-funded clinical trial. Inflammation is believed to contribute to the persistent HIV reservoir, the primary barrier to a cure.
Dr. Laurence is amfAR’s senior scientific consultant.
The vast majority of these updates have described methods for eliminating the primary barrier to a cure: the latent reservoir of HIV that persists in infected individuals despite receiving antiretroviral therapy. Now an international team of researchers reports a major new finding on how this reservoir is actually formed, and what it implies for cure strategies.
The research was reported in the October issue of the journal Immunity by Dr. Liang Shan, an amfAR Mathilde Krim Fellow working in the laboratory of Dr. Robert Siliciano at Johns Hopkins University in Baltimore, along with colleagues from Yale University in New Haven, CT, Sun Yat-sen and Guangzhou Medical Universities in China, National Taiwan University Hospital in Taipei, North Carolina State University in Raleigh, and Washington University in St. Louis.
Shan and colleagues note that in untreated patients, HIV replicates continuously, avoiding immune responses through rapid evolution in a process known as viral escape. But then why should HIV bother to establish reservoirs, given this ability to evolve and evade? Based on their data, the researchers argue that latency is simply an “unfortunate consequence” of CD4+ T cell infection within a narrow time frame after T cells are activated.
They report that during the natural process of T cell transition from one functional state to another—referred to as EMT, or effector-to-memory transition—T cells temporarily increase the expression of CCR5, a critical receptor for HIV, and decrease the function of certain normal cell genes necessary for HIV growth. So the virus gets into the cells more easily via the abundant CCR5, but then is rendered dormant because of dampened gene activity.
Shan and associates didn’t stop there. They found that this process of viral latency could be interrupted by HIV-specific CD8+ killer T cells and concluded that their finding has “implications for elimination of latent HIV-1 infection by T cell-based vaccines.”
Dr. Laurence is amfAR’s senior scientific consultant.
Scientists from the Westmead Institute for Medical Research in Australia have identified the specific immune cells in the body that harbor most of the HIV reservoir, the main barrier to a cure.
The study, which was partially funded by amfAR and published in the October 17 issue of Cell Reports, found that genetically intact and presumably replication-competent HIV hides in effector memory T cells, where it avoids detection by the immune system. These are the same white blood cells that “remember” previous infections and provide lifelong immunity to diseases such as chickenpox or measles. Replication-competent HIV DNA produces infectious particles.
“HIV is really very clever,” said amfAR-funded scientist Dr. Sarah Palmer, an associate professor at the University of Sydney and deputy director of the Centre for Virus Research at the Westmead Institute. “Essentially it is hiding in the exact same cells within the immune system that are meant to attack it.”
Palmer and her colleagues developed a next-generation genetic sequencing assay known as FLIPS (Full-Length Individual Proviral Sequencing) to determine where and how much replication-competent virus remained in six HIV-infected individuals on long-term antiretroviral therapy (ART). The assay measures intact HIV proviruses to deduce the amount of replication-competent virus in the body. Using the efficient, high-throughput technology, they discovered that about 70% of presumably replication-competent virus hides in specific subsets of CD4+ T cells.
Interestingly, the researchers found that only 5% of all HIV DNA present in these participants was genetically intact. (The other 95% was defective, i.e., noninfectious.) However, this small proportion hides in the effector memory T cells and is the likely source of viral rebound after ART cessation.
“This virus inserts its genome into the body's memory cells and sits there quietly avoiding detection by the immune system,” Palmer said. "These infected cells go into a resting state and stop producing HIV, but these latent cells can wake up and start making infectious HIV.”
Palmer said if a person stops taking ART, the virus that is hidden in effector memory T cells can return and start producing more HIV. The virus will spread throughout the body within weeks of stopping ART, she said.
She concluded: “Now that we’ve identified where the replication-competent virus is hiding, we can start work towards targeting these cells with new therapies aimed at fully eliminating HIV from the body.”
Use of combinations of antiretroviral drugs in “cocktails” to attack different parts of the HIV life cycle is the reason why most HIV-positive people maintaining undetectable viral loads can anticipate a normal lifespan. But the key obstacle to curing HIV remains the latent reservoir of virus, which is impervious to standard anti-HIV drugs. It has been a target of numerous research teams, many centered on a “kick and kill” approach by which dormant, HIV-infected cells are activated, rendering them susceptible to drug- and immune-based attack.
Such a strategy demands a robust shock to the latent state, but so far no single pharmacologic approach—using classes of drugs known as latency-reversing agents (LRAs)—has come close to the required potency. amfAR-funded scientist Dr. Robert Siliciano and colleagues at Johns Hopkins, Columbia, and Harvard Universities, writing in the May issue of The Journal of Clinical Investigation, have now put numbers on the amount of viral production an LRA needs to induce to be effective. Using the level of T cell activation required for maximum reactivation of dormant HIV in the test tube as the benchmark, the most potent drug tested thus far, bryostatin-1, could only get us 4% of the way.
A possible solution? Returning to lessons learned in designing antiretroviral therapy cocktails, Siliciano and associates explored two-drug combinations of mechanistically distinct LRAs. Using resting CD4+ T cells from HIV-positive individuals as targets, they found that certain LRA combinations acted synergistically to induce HIV growth. Equally important, this occurred without the release of proinflammatory immune hormones or cytokines, which can have deleterious side effects. They also developed a quantitative assay that uses the information gained from their test-tube studies to predict how effective the drug combinations might be in patients.
Dr. Laurence is amfAR’s senior scientific consultant.
A combination of broadly neutralizing antibodies protected monkeys from infection with an HIV-like virus better than single antibodies in two recent, separate studies.
The results offer further evidence that a combination strategy may be the key to preventing HIV infection. Previous studies have found that individual antibodies do not provide sufficient protection from the virus.
“The virus is just so good at mutating away from any single thing we throw at it,” said amfAR Vice President and Director of Research Dr. Rowena Johnston in an interview with HealthDay. “When we treat HIV, you can’t give a single antiretroviral drug. You have to give a combination of at least two and optimally three. They are now also looking at this idea for antibodies.”
In one study, an amfAR-funded research team injected monkeys with a cocktail of two HIV-blocking antibodies and then exposed them to two different strains of SHIV (a combination of HIV and SIV—the simian version of HIV). Each strain was vulnerable to one of the antibodies.
The monkeys that received one of the antibodies individually became infected with the strain that was not sensitive to the one antibody; however, when they received the two-antibody cocktail, they were protected against both.
In the other study, scientists from the National Institutes of Health (NIH) and the Paris-based pharmaceutical company Sanofi created a three-pronged antibody based on three individual antibodies, each of which neutralizes many strains of the virus. The “trispecific” antibody binds to three different vulnerable sites on the virus.
None of the monkeys given the three-pronged antibody became infected after being exposed to two strains of SHIV.
Plans are underway to begin clinical trials of both the trispecific antibody and the two-antibody cocktail in the hope of eventually using the strategies for both HIV prevention and treatment.
However, as Johnston noted to HealthDay, all antibodies die off quickly. That means, “if you were going to use these in clinical practice to prevent HIV infection, you would have to repeatedly administer them,” perhaps as often as every several weeks, she said.
Read a press release on the NIH study here.
On August 30, 2017, the U.S. Food and Drug Administration approved Kymriah as the first gene therapy for patients with a drug-resistant form of acute leukemia. The chimeric antigen receptor (CAR) therapy involves modifying a patient’s own T cells to seek and destroy cancer cells. It is a one-time treatment, and for many people, a lifesaving one. The approval of this therapy received worldwide publicity. But what may come as a surprise to many is the critical role HIV research played in the development of Kymriah, and how this proof-of-concept treatment for cancer relates to progress toward an HIV cure.
Writing in the September issue of the journal Translational Research, amfAR-funded scientist Dr. Scott Kitchen and colleagues from the University of California, Los Angeles note that most investigators believe that enhancing a person’s natural immune response will be key in eliminating HIV-infected cells. Indeed, HIV-specific CD8+ killer T cells can be engineered to inhibit HIV growth and reduce the size of the HIV reservoir in the test tube. But this strategy has numerous drawbacks, including the need to alter HIV killer cells based on an individual’s HLA tissue type. CARs are based on engineering CD4+ T cells, which don’t have that requirement. Almost all HIV-infected patients can be treated with the therapy, regardless of genetic makeup.
The researchers explain that the first CAR T cells to be used in clinical trials were actually designed and tested for the treatment of HIV—not cancer. In addition, in order to enable those cells to recognize infected cells, a self-inactivating lentivirus—a modified form of HIV—was used to introduce the necessary genes. However, pilot trials showed less than satisfactory results, as unlike cancer, HIV can attack the very CAR T cells administered to fight the infection. With this in mind, Kitchen and associates discuss several novel approaches to enhance the activity of anti-HIV CAR T cells and to protect them against infection.
These strategies include removing, through genetic engineering, the primary HIV co-receptor CCR5. (The “Berlin patient” became the first person to be cured of HIV after receiving a stem cell transplant from a donor with a CCR5 mutation.) The scientists also propose a combination approach to kill infected cells and eliminate latent HIV reservoirs.
The authors conclude: “CAR-based therapy for HIV infection is becoming a promising approach to provide lifelong immune surveillance and viral suppression without the use of antiretroviral therapy … a closer step toward a functional cure for HIV.”
Dr. Laurence is amfAR’s senior scientific consultant.
While the role of antibodies in preventing infection is clear, a growing number of researchers are enlisting antibodies to help cure HIV. One of the most promising avenues to achieve this is passive immunization, in which antibodies are injected directly into the patient.
In the August issue of the Journal of Virology, amfAR-funded scientist Dr. Dan Barouch of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, with colleagues from the Ragon Institute of MGH, MIT, and Harvard in Cambridge, MA, the National Institutes of Health in Bethesda, MD, and Leidos Biomedical Research and Frederick National Laboratory Center for Cancer Research in Frederick, MD, uses a passive immunization approach to explore the potential role of antibodies in curing HIV infection.
Barouch and associates tested two antibodies, PGT121 and N6, in 18 monkeys infected with SHIV, a combination of HIV and SIV (the simian form of the virus). Both PGT121 and N6 are known to be active against HIV. The monkeys were treated with either PGT121 or N6, a combination of both, or a placebo. The antibodies reduced the viral load in the monkeys.
The researchers then measured SHIV DNA in the blood and lymph nodes to see if the antibodies had any effect on infected cells. They found significantly reduced levels of SHIV DNA in the blood two weeks after the antibodies were administered; in the lymph nodes, SHIV DNA dropped markedly after 10 weeks. The authors note that the monkeys’ naturally occurring antibodies and immune responses to SHIV were not enhanced as a result of the PGT121 or N6 infusions, arguing against their contribution to the observed viral effects.
These results suggest that passive immunization using these antibodies might, under the right conditions, kill cells of the persistent viral reservoir and thus play a role in curing HIV.
The strongest proof that HIV can be cured comes from the case of Timothy Brown, the “Berlin patient.” That triumph was predicated on physicians taking advantage of nature’s own experiment: the existence of a genetic mutation in a normal cell protein, CCR5, the main co-receptor that HIV uses to gain entry into a cell.