Assessing the success of any proposed HIV cure currently requires withdrawing combined antiretroviral therapy (cART) under carefully monitored conditions, commonly referred to as an analytic treatment interruption (ATI).
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.
Innovation Grants: July 2017
PI: Andrew Badley, MD
Mayo Clinic College of Medicine, Rochester, MN
Ixazomib to reduce HIV reservoir size: Cells have a recycling mechanism that disposes of or reuses old proteins—the proteasome. If the proteasome is disrupted, these damaged proteins persist, clogging up the cell and eventually leading to cell death. Ixazomib is a drug that is currently used in multiple myeloma, a form of blood cancer. Dr. Andrew Badley proposes to conduct a clinical study to test the ability of the drug to reduce the viral reservoir, the main barrier to a cure.
PI: Benjamin Burwitz, PhD
Oregon Health and Science University, Portland, OR
Creation of CCR5 knockout Mauritian cynomolgus macaques for stem cell transplants:
The Berlin patient, the first and only patient so far to have been cured of HIV, received a stem cell transplant from a donor who was genetically resistant to HIV because the donor lacked a key HIV receptor, the protein CCR5. The Berlin patient’s difficult medical history and complications have made it difficult to determine exactly what led to his cure: was it the stem cell transplant, the complications presented by his new immune system attacking HIV-infected cells as part of a transplant complication known as graft vs. host disease, the chemotherapy and radiation used in the transplant, or some combination of these? Dr. Benjamin Burwitz proposes to answer these questions by generating a monkey model lacking CCR5, enabling him to test the multiple hypotheses concerning the Berlin patient’s cure.
PI: Andrew Henderson, PhD
Boston University School of Medicine, Boston, MA
Disabling HIV provirus by promoting chromatinization: CRISPR/Cas9, a protein complex recently discovered in bacteria, has revolutionized biology because of the flexibility and ease with which scientists can use it to target and edit DNA, cutting out unwanted pieces, including the DNA form of HIV. Dr. Andrew Henderson is proposing to use this protein complex to silence the HIV DNA in a so-called “Block & Lock” approach. Unlike “Shock & Kill”, which requires the cell to wake up from latency- a formidable challenge - “Block & Lock” would permanently silence HIV and prevent the emergence of virus when ART is stopped.
PI: Brad Jones, PhD
The George Washington University, Washington, DC
HLA-E specific TCR-like Antibodies for the Universal Targeting of Persistent HIV Reservoirs: Broadly neutralizing antibodies that target the viral protein Env—the only viral protein expressed on the surface of infected cells - must circumvent the high mutation rate of Env in order to be effective. On the other hand, viral proteins present inside the cell are much less subject to mutation but are poorly accessible to our body’s antibody making machinery. Because of a newly discovered immune mechanism, scientists have now found that the internal viral proteins may be digested and displayed on the surface of cells in a molecule called HLA-E. Dr. Brad Jones proposes to engineer antibodies that will recognize the digested protein/HLA-E complex and make the cell susceptible to death by Natural Killer cells.
PI: Fabio Romerio, PhD
University of Maryland, Baltimore, MD
Permanent Silencing of HIV-1 Expression through the Polycomb Repressor Complex 2 epigenetic pathway: Dr. Fabio Romerio has uncovered a unique mechanism through which HIV drives its own latency, namely by making a molecule called Ast. He proposes that Ast participates in actively preventing the viral DNA from making virus. Dr. Romerio aims to determine how Ast asserts its effect and whether it can be delivered to all HIV infected cells to permanently and specifically block viral DNA. In contrast to the curative approach “Shock & Kill”, this “Block & Lock” approach aims to silence HIV and prevent the emergence of virus when ART is stopped.
PI: Joshua Schiffer, MD
Fred Hutchinson Cancer Research Center, Seattle, WA
Anti-proliferative therapy for eradication of the HIV reservoir: Antiretroviral therapy (ART) controls viral load because the virus is prevented from infecting new cells. However, the reservoir persists even under ART through mechanisms that are still being uncovered. One possibility is that normal cell division of latent HIV infected cells maintains the reservoir even in the absence of viral replication. Dr. Joshua Schiffer aims to determine if CellCept, a drug that reduces cell replication – normally used to prevent organ transplant rejection - can also eliminate the persistence of the reservoir. His clinical trial will span 2 years, after which participants will discontinue their ART and determine whether the curative intervention worked.
Last month we highlighted the work of scientists from the amfAR Institute for HIV Cure Research at the University of California, San Francisco, and their identification of a new pathway to induce HIV out of its latent state. Such activation renders the virus vulnerable to attack by the immune system. Unfortunately, many of the drugs currently being studied as such latency reversing agents work much better in the test tube than in patients.
Writing in the June issue of the journal Clinical Infectious Diseases, amfAR-funded scientist Dr. Ole Søgaard of Aarhus University in Denmark, with colleagues from there and the University of Copenhagen, joining an international team from Barcelona, Berlin, Belgium, Boston, San Francisco, and Philadelphia, report on an experimental drug with the capacity not only to activate latent HIV, but also to enhance the patient’s innate immune defenses against the activated virus.
Lefitolimod, also known as MGN1703, activates a protein known as TLR9, found on the surface of many types of immune cells. It belongs to a class of agents known as “immune surveillance reactivators,” which induce production of immune hormones, such as interferon-alpha, and enhance the function of dendritic cells, B cells, and natural killer cells. All of these cell types form part of our innate defense against HIV. Lefitolimod is currently in advanced stages of testing in colon cancer patients.
Based on promising studies in the test tube with cells from HIV-infected patients, Søgaard and associates sought to test the drug’s effects in patients themselves.
Fifteen adults taking effective antiretroviral therapy (ART) for at least one year were enrolled in the study. Lefitolimod was injected under the skin twice a week for four weeks. In 40% of the participants, HIV levels dramatically increased, from undetectable (less than 20 copies) to over 1500 copies, consistent with the role of a latency reversing agent. In addition, the researchers observed an enhancement of all immune responses evaluated.
The authors noted that the use of another drug to enhance TLR7, a related immune surveillance reactivator, in monkeys infected with the simian form of HIV also showed promising results, but only when combined with a therapeutic vaccine.
They concluded that their research is “the first clinical trial using a single drug in HIV-1-infected individuals on ART with the aim of both enhancing innate immunity and activating the HIV-1 reservoir.”
Further studies are underway in this promising area of cure research.
Dr. Laurence is amfAR’s senior scientific consultant.
Researchers at Temple University and the University of Pittsburgh have been able to cut a fraction of HIV out of infected mice using CRISPR gene-editing technology, according to a new study in Molecular Therapy. The study builds upon previous findings by the research team, including one where CRISPR was used to cut HIV out of transgenic mice (genetically modified mice with HIV DNA inserted into their genomes—as opposed to having been infected with HIV).
In this study, researchers reduced HIV RNA (a measure of HIV) in transgenic mice by 60−95%. They were able to achieve a 96% reduction when they used the method in mice with EcoHIV, a mouse equivalent of HIV, during acute infection.
Employing a more widely used humanized BLT (bone marrow, liver, and thymus) mouse model, the researchers found that CRISPR was able to cut a fraction of HIV out of latently infected cells in some organs.
“It’s a good step forward,” said Dr. Marcella Flores, amfAR’s associate director of research. “It would be important to repeat the studies in monkeys and ensure that CRISPR is able to excise HIV from reservoir cells.”
Read more about the study here: http://bit.ly/gene-editing-tool
A major part of amfAR’s “Countdown to a Cure for AIDS” initiative, which is aimed at developing the scientific foundations for a cure by 2020, is to determine the best method to detect and measure latently infected cells from individuals on antiretroviral therapy (ART).
This is critical to assessing the outcome of a cure intervention. Writing in the April issue of the journal Virology, amfAR-funded scientist Dr. Ramesh Akkina and colleagues at Colorado State University, along with researchers from the amfAR Institute for HIV Cure Research and Harvard University, reported a very novel approach.
The current “gold standard” for detecting persistent HIV is a test-tube technique known as qVOA (quantitative viral outgrowth assay). It is cumbersome and involves chemicals and antibodies in an attempt to activate virus in latently infected cells. One of its greatest drawbacks, however, is its inability to detect every virus that is capable of growing out of infected cells, estimated at approximately 60 per million cells. Akkina and colleagues sought a living alternative, using mice with human immune systems.
To “humanize” the mice and thus enable HIV to grow in these animals, the researchers used genetically immune-deficient mice transplanted with human stem cells or with bone marrow, liver, and thymus gland cells. They injected these animals with varying numbers of CD4+ T cells—from 100,000 to 20 million cells per mouse—obtained from 11 HIV-positive donors, all on ART. Five of these donors had undetectable viral loads by the standard qVOA.
The injected mice were followed for eight weeks. At weekly intervals blood was obtained in an attempt to detect, by a very sensitive molecular test known as RT-PCR, virus that wasn’t detectable using qVOA. Of the five qVOA-negative samples, four proved positive in the mice. The one sample that failed to produce virus was said to be of “poor quality”—donor samples had been frozen and don’t always thaw out well.
The authors concluded that the higher sensitivity of their humanized mouse models over qVOA and other types of mice used in similar experiments may ultimately lead to avoiding ART interruption as the only means to definitively assess the effectiveness of a potential HIV cure.
Let the mice do the work.
Dr. Laurence is amfAR’s senior scientific consultant.
Lab Mice Photo By Maggie Bartlett, NHGRI. - http://www.genome.gov/pressDisplay.cfm?photoID=5006, Public Domain, https://commons.wikimedia.org/w/index.php?curid=19805359
Scientists at The Scripps Research Institute (TSRI) have discovered a way of creating HIV- resistant cells by using antibodies to block HIV directly on the cell surface. Interestingly, in lab experiments, the resistant cells largely replaced the susceptible cells, potentially leading to long-term HIV protection.