Tag Archives: HIV

Antiviral Drugs, Epidemics, Immunology, Molecular Virology

Luring HIV out of its latency may be the secret to developing an effective HIV cure

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Contributed by guest blogger: Steven Chan ‘12

The emergence of highly active antiretroviral therapy (HAART) in the treatment of HIV-infected individuals has certainly changed the outlook of an HIV diagnosis today, compared to what such an outlook looked like in the earliest years of the epidemic. Such a treatment regimen, if strictly adhered to, has the potential to suppress the levels of active circulating HIV in the infected individual to a level that is manageable, essentially halting the progression of the disease. It soon became clear however, that these treatments could not effectively clear the body of all HIV particles—the virus manages to stow itself away within the cellular genome of the memory CD4+ T-cells, and remain transcriptionally silent indefinitely. These latent reservoirs of HIV-infected cells prove to be undetectable for these antiretroviral therapies, since antiretroviral drugs can only target HIV-infected cells when they are replicating. And so, memory cells, which replicate infrequently, cannot be effectively targeted, making it impossible to clear HIV-infected bodies of all HIV-particles. “We’re never going to cure anybody unless we go for this latent pool,” says Robert Siliciano, the researcher at Johns Hopkins University that first identified the latent HIV memory-T cells.

A great deal of HIV-therapy research over the past decade has focused on finding a way to coax these infected cells out of their latency to make them detectable by antiretroviral drugs. The problem that has been persistently hounding researchers has been the difficulty in luring these cells out of their latency without triggering the immune system in an inflammation response that would end up doing more harm than good. David Margolis, MD, and his research team at UNC Chapel Hill, who have been working on this problem for a while now, have found success with a set of histone deacetylase inhibitors called Zolinza (vorinostat), a chemotherapeutic cancer drug that has been found to stimulate gene expression within the latent HIV-infected cells without inducing an overwhelming immune response. HDAC inhibitors accomplish this by inhibiting the activity of histone deacetylase, which removes the acetyl groups from the lysine residues in the core histones, resulting in the formation of a condensed and transcriptionally silenced chromatin. By inhibiting this activity, the core histones become less compact, and the chromatin becomes more transcriptionally active. After initial success with in vitro tests in cell cultures and in blood tissues, six HIV-positive men were recruited in a clinical trial pairing this treatment alongside consistent antiretroviral therapy. Each of the study volunteers had already been taking part in a robust antiviral regimen for an average of four years, and displayed undetectable viral loads and stable CD4+ T-cell counts. Post-exposure to Zolinza, HIV-RNA levels—a marker of viral activity—in these patients increased by an average of 4.8 times, ranging from a 1.5-fold increase in one patient to a 10.0-fold increase in another. The drug took effect in as little as 8 hours, inducing a two-fold increase in cellular and chromatin-bound histone acetylation within that time span. Increased expression made these cells susceptible to detection and eradication by the antiretroviral drugs, which proceeds just as efficiently as usual.

Margolis addresses the significance of this advancement, “This study provides first proof of concept, demonstrating disruption of latency, a significant step toward eradication.” Just how effective this drug is in teasing out the latent cells still remains to be seen—with nearly a ten-fold difference in one trial participant compared to the other, the efficacy of such a drug remains questionable. The limited sample size in this initial trial also doesn’t give us too much to go on. There are also concerns that the drug could induce some serious side effects such as blood clots in the legs and lungs, diabetes, fewer platelets and RBC count, as well as dehydration from nausea and vomiting, but at least in this trial, there were only mild adverse effects at worst. Little is known about the potential adverse effects of long-term use of the drug. Margolis et al.’s study design made use of a single dose of Vorinostat, but it is likely that repeated intermittent doses would yield the most optimal effects. “Vorinostat may not be the magic bullet, but this success shows us a new way to test drugs to target latency and suggests that we can build a path that may lead to a cure,” says Margolis. Further studies to assess Vorinostat’s safety and effectiveness, and the way it interacts with other HAART treatments, would certainly be crucial before it can be deployed as a component in future HIV treatment regimen.

 

Links:

Archin N, Liberty A, Kashuba A, Choudhary S, Kuruc J, Hudgens M, Kearney M, Eron J, Hazuda D, and Margolis D. “Administration of Vorinostat Disrupts HIV-1 Latency in Patients on ART,” HIV Persistence, Latency, and Eradication at 19th Conference on Retroviruses and Opportunistic Infections, March 8, 2012,              http://www.retroconference.org/2012b/Abstracts/45315.htm

Contreras X, Schwenwker M, Chen CS, McCune JM, Deeks SG, Martin J, Peterlin BM. Suberoylanilide Hydroxamic Acid Reactivates HIV from Latently Infected Cells, J. Biol. Chem., January 9, 2009, http://www.jbc.org/content/284/11/6782.full

Horn T. “Pathway to a Cure: Cancer Drug Helps Purge HIV From Resting Cells,”  AidsMeds, March 9, 2012, http://www.aidsmeds.com/articles/hiv_vorinostat_ cure_1667_22059.shtml

“Lymphoma Drug Wakes Up Dormant HIV,” AidsMeds, March 17, 2009,     http://www.aidsmeds.com/articles/hiv_zolinza_latent_1667_16307.shtml

Steven Chan is a senior at Vassar College, majoring in Science, Technology, and Society

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Antiviral Drugs, Epidemics

Highly Active Antiretroviral Therapy and Tenofovir: Lowering HIV Viral Loads, Raising the Risk of Renal Failure

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Contributed by guest blogger: Michael McManus ‘12

People undergoing anti-retroviral therapies, which target and interrupt the replicative processes of HIV, are living longer due to the relative success of treatments. Those with HIV are using these drug cocktails for longer periods of time, an important characteristic with results that could not be observed in short-term clinical studies.

Mortality for patients with HIV who are able to undergo highly active antiretroviral therapy (HAART) has shifted from higher rates, during the initial HIV scare, to relatively lower rates. HAART has been incredibly successful, increasing the quality of life for those who have access to it. For some, however, the effects of an HAART regimen, which combines up to four medications, can lead to renal failure within two weeks of regimen administration due to the toxic nature of some of the medications.

Renal failure, or loss of kidney function, can lead to organ failure and eventually death. The kidneys are normally responsible for filtering the blood. They maintain homeostasis by regulating electrolytes, regulating blood pressure, maintaining pH balances, and by removing and diverting waste from the blood into the urinary bladder, producing urine. The kidneys filter many things from the blood in order to retain them in the body, ranging from proteins to glucose. When the kidneys fail, proteins, glucose, and even blood become detectable in the urine. Glycosuria, proteinuria, and hematuria are all biological indicators of a lack of reabsorption and therefore renal failure.

In a recently published paper, Juliette Pavie et al. describe a case of renal failure in an HIV-positive patient after only two weeks of tenofovir therapy. Tenofovir is a nucleotide reverse transcriptase inhibitor associated with low risk of severe renal adverse events in clinical trials. However, tenofovir is in the same class of drugs such as adefovir and cidofovir, which have well-documented nephrotoxicity1,2.

The patient followed was a 46-year-old homosexual male of Scottish descent. His weight, CD4 cell count, plasma HIV RNA level, serum creatine, and urea levels were all taken before HAART regimen, which consisted of tenofovir, emtricitabine, atazanavir, and ritonavir, was started. During treatment, the patient did not take any nonsteroidal anti-inflammatory drugs (NSAIDs), which are known to lead to kidney dysfunction.

Fifteen days after treatment began levels were tested again: serum creatine and urea had increased 3-fold and 2.5-fold respectively. Five days later, the patient became unable to pass urine and levels were immediately measured again: serum creatine showed a 15-fold increase from the original amount, and urea a 12-fold increase. Urinalysis showed glycosuria and proteinuria, indicating loss of kidney function. Renal biopsy indicated necrosis of the kidneys and other abnormalities. After these observations, HAART was halted and hemodialysis was started to rescue lost kidney function. After three months of hemodialysis, HAART was resumed, but tenofovir was excluded from the treatment.

After one year of treatment, the patient showed signs of recovery. CD4 cell count increased to relatively normal levels, and serum creatine and plasma HIV RNA levels dropped. To this day, the patient is still undergoing the same HAART, with serum creatine and plasma HIV RNA levels remaining stable. However, the patient still suffers from moderate glycosuria and proteinuria, indicating that kidney function has not fully recovered.

Although this case only followed one individual undergoing a HAART regimen containing tenofovir, the observations and results are still crucial to studying renal failure resulting from HAART. The novel form of nephrotoxicity observed may serve as a model for other forms of nephrotoxicity caused by reverse transcriptase inhibitors. Although the nephrotoxicity studies1,2 only reported findings in one individual each, their findings should not be discredited, as this is the nature HIV symptom studies. For example, the emergence of Kaposi’s sarcoma as a symptom of HIV began with isolated incidents. The nature of HIV and its rapid mutation also obfuscates the relationship between HAART effectiveness and strain type. From this observation, one question out of many must be addressed: Did the combination of drugs used in the patient’s HAART regimen have an effect on nephrotoxicity?

Despite the emergence of renal failure as a threat, great strides have been made in the fight against HIV. The quality of life for those who are suffering from HIV and who have access to HAART is drastically improved compared to those who are unable to undergo HAART. However, now that HIV patients are living longer, research must switch from just targeting HIV to focusing on HIV and the complications created by decreased mortality. Nephropathy, or disease of the kidney, and subsequent nephrectomy, removal of a kidney, now contribute to the decrease in quality of life associated with the aging HIV population. When developing future treatments, scientists and doctors must analyze the nephrotoxicity of the products they are synthesizing, as renal failure is a clear and present danger for those undergoing HAART.

Article Links:

http://online.liebertpub.com/doi/abs/10.1089/apc.2011.0056

1Tanji, N., Tanji, K., Kambham, N., Markowitz, G. S., Bell, A., and D’Agati, V. D. (2001) Adefovir nephrotoxicity: Possible role of mitochondrial DNA depletion. Human Pathology. 32, 732-740.

2 Meier, P., Dautheville-Guibal, S., Ronco, P. M., and Rossert, P. (2001) Cidofovir-induced end-stage renal failure. Nephrology Dialysis Transplantation. 17, 148-149.

Michael McManus is a senior at Vassar College, majoring in Biochemistry

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Epidemics, Immunology

HIV Microbicides and the Risks of Clinical Trials

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Contributed by guest blogger: Julia Ding ’12

Once preliminary studies suggest that a drug is safe for human use, clinical trials are conducted in order to further investigate the effects and possible adverse reactions of the drug. The example of HIV microbicides has shown that caution and careful scrutiny is highly important for these trials. HIV microbicides are chemical entities which, when applied before vaginal or rectal intercourse, prevent the transmission of the virus. Of the potential microbicide agents that have been studied, two compounds classified as polyanions were thought to be promising for inhibiting HIV-1 transmission: carrageenan and cellulose sulfate (CS). However, these compounds were deemed in phase III clinical trials to be ineffective as microbicides.

In addition to that discovery, the more surprising and disturbing result of these trials was that the HIV microbicides appeared to actually enhance the rates of HIV infection. Pirrone and colleagues examined the validity of this claim in a study reassessing the in vitro activities of the compounds. Cells were infected with different strains of HIV-1 in the presence of three different polyanions: CS, λ-carrageenan (LC), and destran sulfate (DS). Resulting assays showed that all of these compounds exhibited antiviral activity against both R5 and X4 HIV-1 strains. However, further experiments also discovered that application and removal of polyanion microbicides prior to HIV exposure enhanced and increased the rates of HIV-1 infection. The compounds were added to cell cultures and washed out prior to HIV-1 infection to simulate the natural loss of the compound after vaginal application. In both HIV-susceptible cells and regular human cells, the results indicated an increase in the percentage of cells infected, unrelated to any change in cell viability. The level of enhancement was found to be dependent on the target cell, its co-receptor phenotype, the compound identity and concentration, and the timing of the viral challenge. While the mechanism through which HIV-1 transmission increased in the in vitro experiments is still unclear, these factors suggest that the nature of the host cell also plays a role in polyanion-dependent HIV-1 infection.  This data provides a discouraging outlook on the use of these compounds as effective microbicides, while introducing new questions about its mechanisms of action.

This study provides us with many valuable insights about not only the microbicide technology itself, but also the risks and complications associated with clinical trials. The data suggested a significant increase in HIV-1 infection after the application and removal of the two microbicides. Furthermore, it emphasized the need for intense scrutiny of compounds prior to clinical trials, considering the dangers they may pose on human subjects. While previous studies supported the use of polyanion microbicides as a safe and possibly effective means of preventing HIV-1 transmission in women, the effects of the leakage and loss of the product over time was not taken into consideration, and significantly more women on the drug were found to have contracted HIV than if they had not taken it. The study also provides us with an example of the vital role clinical trials play in the testing of a drug, and how certain adverse effects may be missed through in vitro studies that only become apparent when applied to real world uses.

Links:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3295645/

http://www.nejm.org/doi/full/10.1056/NEJMoa0707957#t=abstract

 

Julia Ding is a senior at Vassar College, with a major in Science, Technology and Society.

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Epidemics, Guest Blogger, Immunology, Vaccines

A possible new HIV vaccine target?

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Contributed by guest blogger: Lydia Mendoza ’11

In 2009, it was estimated that 33.3 million people in the world were living with HIV/AIDS. Since the discovery of HIV, more than two decades ago, money has poured into research in the hopes that an effective vaccine might be developed. As of yet a vaccine remains elusive. One reason why it is so difficult to create a vaccine is because HIV is highly mutable and genetically diverse subtypes, or clades, have evolved. A vaccine needs to be able to offer protection from a range of HIV clades.

Normally viral vaccines are based upon neutralizing antibodies, which prevent infection of the host cell. The first attempts to develop neutralizing antibodies against HIV targeted gp120, which is known to play a role in HIV’s ability to enter and infect CD4 t-cells. These attempts have not been successful as of yet because of the gene’s high rate of mutations. However a recent paper has shown that the V3 loop of gp120 is a potential vaccine target.

The strand of protein known as the V3 loop was never thought to be an attractive vaccine target because it is not highly conserved. However, it appears to have conserved structural elements that are involved in interactions with coreceptors. To study whether V3 was a viable vaccine target, a human monoclonal antibody, HGN194 was used. HGN194 was isolated from memory B cells of a person infected with HIV-1 clade AG circulating recombianant form (CRF). HGN194 targets the V3 loop and has been previously shown to neutralize a broad range of neutralization-sensitive and resistant strains of HIV.

The study evaluated whether HGN194 was able to protect rhesus monkeys from an HIV model system. One group of monkeys was injected with HGN194 then they were challenged with a high dose of a clade C SHIV, which is a chimeric simian-human imunodeficiency virus encoding HIV envelope genes in a SIV backbone. The second group of monkeys was also given a high dose of SHIV but was not given the HGN194. The monkeys given the antibody were protected from SHIV infection, and those not given the antibody were infected. The researchers concluded that HGN194, isolated from an HIV-positive individual harboring a clade AG CFR, was able to confer complete cross-clade protection against clade C SHIV.

The antibody apparently latches onto the virus’s V3 loop and prevents the virus from invading cells. This does not mean that this antibody treatment technique is a vaccine for HIV. It does not create long-term protection because the antibodies do not remain active in the body for very long. This is only a first step. A vaccine target has been identified but now scientists must create an antigen that induces formation of an antibody similar in structure to HGN194. There is a lot of work left to be done but this finding hopefully brings researchers much closer to the development of a vaccine.

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Antiviral Drugs, Guest Blogger, Molecular Virology

A different alphabet, a different treatment?

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Contributed by Guest Blogger: Sean Koerner ’11

It’s easy to think of viruses as alien or lifeless – after all, they can’t reproduce on their own, eat anything, or even move around without assistance. However, viruses have evolved to use the same toolbox that human cells use, right down to the way their genes and proteins are encoded. One of the most problematic viruses for humans, HIV, works by putting its own information into our cells’ genomes, turning host cells into viral factories. This information is formed from two types of alphabets: strung-together sequences of deoxyribonucleotides, which exist intracellularly as deoxyribonucleotide triphosphate (dNTP) monomers in our own cells and ribonucletides, which form the HIV genome as well as existing independently as ribonucleotide triphosphate (rNTP) monomers within our own cells. In order to infect our cells, HIV uses a protein known as reverse transcriptase to generate the DNA that our cells are used to reading from the viral RNA genome. This reverse transcription of RNA to DNA has long been a target of anti-HIV drugs, since without this step, HIV cannot successfully infect our cells.

Recently, a team at the University of Rochester discovered a previously unknown characteristic of this process. Two of the cells most commonly infected by HIV, CD4+ lymphocytes and macrophages, displayed different levels of dNTPs and rNTPs after being infected by HIV, with the lymphocytes containing much less rNTPs and more dNTPs than the macrophages. After a biochemical analysis of the cells, the research team discovered that HIV’s reverse transcriptase is capable of using cellular rNTPs to generate RNA based upon the HIV genome, which is then reverse transcribed into cellular DNA while in the macrophage environment. This allows HIV to use the higher concentrations of rNTPs in macrophages to continue replicating efficiently, despite the relative dearth of dNTPs as compared to lymphocytes. Since HIV uses one method (dNTPs) in lymphocytes and one method (rNTPs) in macrophages, it may be possible to target HIV replication in macrophages specifically. Why care about the difference between the two cell types? Well, macrophages travel the body much more rapidly than lymphocytes; if we can stop HIV infecting them, we may be able to slow the progression of HIV infection throughout the body.

How could we do that? In short, by targeting the synthesis of rNTP strands with new drugs. Although we would likely experience side effects, they could be negligible compared with the repression of HIV. The research team at Rochester have already demonstrated that rNTP string inhibitors slow HIV’s infection of macrophages, so specific drugs targeted for this process might be able to halt it altogether.

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Guest Blogger

Using HIV to treat HCV

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Contributed by Guest Blogger: R. Trenchard ’14

Traditionally, the go-to method used to treat patients with hepatitis C virus has been to administer a combination of antiviral agents called pegylated interferon-a (PEG-IFN) and ribavirin. These agents combat the virus particles that cause HCV, and regulate the immune system. Clinical studies of this type of treatment however, show that the mixture of these two agents achieves the desired sustained virological response (SVR) for only 36%-46% of HCV patients. This sad statistic has led to recent research that has proposed a more advanced treatment method that includes specifically targeted antiviral therapy for HCV (STAT-C). This treatment would work like HIV therapy and involve the inclusion of protease and polymerase inhibitors to the standard HCV antiviral concoction. It is expected to improve treatment outcomes, because every stage of the HCV life cycle could be a target for STAT-C agents.
The STAT-C agents mentioned above have worked in trials because they target enzymes that are essential for viral replication. Currently they have been used in addition to PEG-IFN and ribavirin, but once there are a sufficient amount of STAT-C agents licensed they can be used alone as a combination therapy used to act at distinct stages of viral replication and to create a barrier to resistance. Like HIV therapy however, these drug combinations increase the risk for drug-drug interactions (DDI) in patients. Some of these drug reactions include anaemia, haematological adverse events, and mitochondrial toxicity. Aside from this some patients for whom the treatment works for can suffer from side effects ranging from flu-like symptoms to anemia and cardiovascular problems.
This evokes a number of questions. With such dangerous risks involved, is the treatment worthwhile? What characteristics of HIV and HCV allow them both to be treated with protease and polymerase inhibitors? Can this type of treatment be used on other viruses as well?

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Guest Blogger

Social Spread of HIV

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Contributed by Guest Blogger: T. McKinnon ’14

In the mid-1980’s, businesspeople were crossing the Tanzania/Uganda border, and caught a disease. This disease spread through all of Tanzania after 2 years, and this is the birth of the HIV/AIDS epidemic. The question that was being asked in this research is how rampant HIV is in two differing economic classes, the “rich” and the “poor,” and in which is it more prevalent. The model created by studying the transmission of this disease through differing socio-economic classes is to see the impact HIV/AIDS has on one economic class versus another, and whether transmission is easier, harder, faster, etc. in different social classes.
The experiment conducted worked like this: a total population of individual is accounted for, divided into susceptibles, infectives (infectious), pre-AIDS and AIDS patients. These people are then divided into pre-AIDS hospitalized patients and AIDS patients seeking no hospitalization, because this is common in lower economic classes. From then, the spread and rate of infection of HIV and the spread of AIDS is measured among these separate groups, whether it is initial infection or development into full blown AIDS.
Through extensive experimentation, HIV/AIDS was found to be more prevalent among wealthier populations, but it spreads faster among the lower classes. I find it very interesting that this disease is not more prevalent and spreads faster in the lower classes. In the upper class, people can more readily afford the treatments and medications than people living in lower classes with less money.
The researchers acknowledged that this experiment was by no means exhaustive. I would like this experiment to expand to how race and sexuality interact with social class in the spread and prevalence of HIV/AIDS or if race has anything to do with it, both separately and together. I also would like to know how level of sexual activity among social class propagates HIV spread, and if the members of the upper class were more or less sexually active, or participated in more unsafe sexual practices than those of the lower class, or if it was the other way around.

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Guest Blogger

Creating Synthetic HIV Vaccines

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Contributed by Guest Blogger: A. Lee ’14

HIV is particularly virulent due to its specific attack of host immune cells and disruption of their normal function. The human body needs helper T-lymphocytes (HTL), which coordinate and activate other immune cells, and cytotoxic T-lymphocytes (CTL), which attack infected cells, to work cooperatively to defeat illness. HIV attacks HTL and through its high sequence mutation rate evades the body’s attempts to identify a parts of it for counterattack, called epitopes; these constant, minute changes in the virus also makes vaccine development difficult. However, recent technological advances have allowed immunologists to circumvent this problem through study of HIV’s amino acid sequence, or its structural makeup.
Researchers have identified key epitopes of major HIV subtypes, recognizable by HTL and CTL, and combined them into two vaccines, a synthetic protein structure to activate HTL (called EP-1043) and a plasmid (DNA segment, EP HIV-1090) to activate CTL. EP-1043 was created by cutting the DNA sequence of the 18 epitopes into overlapping sequences, fusing that with insect and viral sequences to ensure viability in a bacterium, and using this sequence in a non-deadly virus to force a bacteria to create the protein. The EP-1090 DNA sequence was created using a similar process of combining epitopes into overlapping sequences and replicating them using a process called PCR (no similar process exists for replicating proteins). Importantly, EP-1043’s protein epitopes are joined by weak bonds, meant to break and spread the epitopes through the body. Because the protein aggregates (becomes useless) at blood pH, it is packaged in aluminum hydroxide (Alhydrogel) and aluminum phosphate gels, which dissolve later.
Effectiveness of the virus was measured 39-42 days after infection by measuring cytokine (cytokines are secretions of infected cells causing immune reaction) and by measuring reproduction of splenocytes (spleen immune cells). Though EP-1090 was ineffective, EP-1043 was significantly effective in causing immune. Despite the low toxicology of the vaccine, and the fact that a true vaccine for HIV would require CTL and HTL epitope response from singular cells, this is an important step towards combating HIV.
One wonders, then, what more complex methods can be used to amalgamate epitopes for vaccines, and what method immunologists will use to create true HIV vaccines, if at all possible. This method can be used for other, less complex viruses, but does this relatively non-specific, general epitope flood lessen the necessary specific response? Can the body handle such a large, sudden appearance of viral material?

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