No 'reservoir': Detectable HIV-1 in treated human liver cells found to be inert

Novel study suggests HIV-1 still detectable in human liver macrophages unlikely to stay infectious after long-term antiretroviral therapy. In a proof-of-principle study, researchers at Johns Hopkins report that a certain liver immune cell called a macrophage contains only defective or inert HIV-1 copies and aren't likely to restart infection on their own in HIV-1-infected people on long-term antiretroviral therapy (ART).

The study, the investigators say, strongly suggest that defective or inert HIV-1 can remain in the liver macrophages for up to ten years without functioning as an HIV-1 "reservoir" that can replicate the virus at high levels.

But the finding, they say, also suggests that HIV-1 treatment strategies that only or mostly focus on these macrophages in a search for a cure might need to shift more heavily to other cell types more likely to serve as active reservoirs of the virus.

A report of the findings was published online on Sept. 10 and in the Oct. issue of the Journal of Clinical Investigation.

"Our study was the first, to our knowledge, in which purified liver tissue macrophages from HIV-1 infected people taking ART directly tested the idea that tissue macrophages are a long-lived active HIV-1 reservoir," says Ashwin Balagopal, M.D., an associate professor in the Division of Infectious Diseases at the Johns Hopkins University School of Medicine.

According to the U.S. Centers for Disease Control and Prevention (CDC), 36.7 million people worldwide and 1.1 million people in the U.S. are infected with HIV-1. Commonly, ART is successfully used to suppress the replication of HIV-1 and stop or control the progression of acquired immunodeficiency syndrome (AIDS) in humans. The virus infects the body's immune system cells, commonly forming a persistent, and reservoir in humans in so-called resting memory CD4+ T white blood cells. Macrophages work with T cells normally to envelop and clear tissues of microbes and debris.

The inability to completely wipe out pools of infectious HIV-1 has for decades frustrated efforts to completely cure the infection. And it means that the interruption or discontinuation of ART at any time re-activates HIV-1 replication, spreading the virus to new cells.

As a result, Balagopal says, investigators are increasingly focused more specifically on the location and biology of these HIV-1 reservoirs.

To determine if liver macrophages were a true source of infection-capable HIV-1 reservoir after ART, liver tissue samples were taken from nine HIV-1 infected persons, seven of whom underwent liver transplantation at the Johns Hopkins Hospital and would have otherwise had their livers discarded. Eight of the nine persons were on ART for periods ranging from eight to 140 months.

The sample group included only adults whose demographic information is considered exempt from human subject research because all samples were obtained strictly for scientific reasons or post-mortem and would otherwise have been discarded. The Johns Hopkins School of Medicine institutional review approved this study protocol.

Using lab techniques that both measure HIV-1 containing T cells and separate out the liver macrophages, the researchers found HIV-1 to be present in the macrophages even after exposure to longstanding virus-suppressing ART.

However, Balagopal said that when his team tried to simulate virus "rebound" from the liver macrophages in the laboratory, they found only "fragments of HIV-1 in small quantities, without robust growth of full-length, infectious virus."

The researchers found that HIV-1 was in the liver macrophages of one subject who took ART for 11.7 years. They concluded that while liver macrophages might harbor HIV-1 for a long time, it's unlikely these viruses could continue an infection on their own, unlikely to function as a reservoir, because the viruses were not able to replicate.

Balagopal cautioned that their study results still affirm the need to address liver macrophage infection, because even if inert, these cells may be able to produce portions of viral proteins that can misdirect the immune system.

"These results contribute an important piece in our efforts to understand the role of non-T cells, such as macrophages, as HIV-1 cellular reservoirs in individuals on long-term ART, but also may help the research community focus on additional cure strategies," Abraham Kandathil, Ph.D., a research associate in the Division of Infectious Diseases at Johns Hopkins University School of Medicine who performed all of the key experiments.

In the future, Kandathil says, more research is needed to determine if the inert HIV-1 infected liver macrophages have any functional significance in people taking ART because expression of defective HIV-1 proteins can confuse the immune system and cause tissue inflammation.

"To find a comprehensive HIV-1 cure, it's important to identify all of the relevant HIV-1 reservoirs in the body, since it's possible that the virus hides in the DNA of numerous cell types and each may require different strategies to get a cure," says Balagopal.

Balagopal noted that their study was limited by the small number of liver macrophages and human samples studied, as well as the small number of CD4+ T cells in the liver cell cultures that may have prevented the researchers' ability to detect them.

Source: https://www.sciencedaily.com/releases/2018/10/181001110210.htm

Proof-of-concept HIV Immunotherapy study passes Phase 1 safety trial

Preliminary results from a phase I clinical trial have demonstrated the safety and tolerability of a cell therapy involving the ex vivo expansion of T cells and their subsequent infusion into HIV-infected individuals previously treated with antiretroviral therapy (ART). The study appears September 21st in the journal Molecular Therapy.

"This study is focused on finding a way to re-educate the body's immune system to better fight HIV infection," says co-senior study author David Margolis of the University of North Carolina (UNC) at Chapel Hill. "We found that this approach of re-educating the immune cells and reinfusing them was safe, which was the primary goal of the study. The data from this trial will continue to help us design improved immunotherapies against HIV."

A game changer for patients living with HIV, ART has turned what was once a death sentence into a chronically managed disease. But it is not a cure, and the virus continues to persist within a latent reservoir that remains hidden from the immune system. Approaches using pharmacological HIV-latency-reversal agents to induce latent virus to express viral protein could make this reservoir vulnerable to T cells. However, the existing HIV-specific immune response in ART-treated individuals is insufficient to clear persistent infection, even in the presence of latency-reversal agents that induce HIV expression.

One safe avenue for harnessing T cell responses to fight HIV is adoptive cellular therapy. This procedure involves collecting T cells from a patient, growing them in the laboratory to increase their numbers, and then giving them back to the patient to help the immune system fight disease. Earlier adoptive-T-cell-therapy approaches for HIV had limited efficacy as a result of multiple factors. Since these earlier attempts, the adoptive-T-cell-therapy field has made significant advances, largely in the oncology field, that could help to overcome some of the pitfalls encountered with earlier T-cell-therapy approaches for HIV. T cells generated by these sophisticated methods of expansion have been safe and well tolerated, as well as highly effective.

"Before we can combine this approach with treatments meant to bring HIV out from hiding so the improved immune response can clear it from the body, we need to first establish that this immunotherapy approach is safe on its own," says co-senior study author Catherine Bollard of the Children's National Health System. "We have long-standing experience treating patients with virus-specific T cells targeting latent viruses such as Epstein-Barr virus and cytomegalovirus. Therefore, we were extremely excited to work with the UNC team to adapt this virus-specific T-cell-therapy approach to the HIV setting."

In the small proof-of-concept study, Margolis, Bollard, and their collaborators produced ex vivo expanded HIV-specific T cells (HXTCs); their long-term goal was to use HXTCs as part of a strategy to clear persistent HIV infection. The researchers administered two infusions of HXTCs over a 2 week period to six HIV-infected participants whose viral load had been reduced to an undetectable level by ART.

This treatment was well tolerated and had few adverse events. Moreover, two patients exhibited a detectable increase in T-cell-mediated antiviral activity after the two infusions, although the clinical significance of this mild-to-modest impact is unknown. When evaluating participants in aggregate, the research team found no overall enhancement of the magnitude of the HIV-specific immune response. This could be due to the low dose of the two infusions and the lack of strategies to promote the expansion of the T cells once they are in the body.

There was also no decrease in the size of the latent reservoir, most likely because of the absence of therapies such as latency-reversal agents, which are designed to perturb the reservoir and induce recognizable expression of HIV proteins that trigger immune responses. In the future, a critical question will be whether HXTC therapy in combination with latency-reversal agents can deplete the HIV reservoir to an extent that is measurable by current gold-standard assays of HIV latency. A study of HXTC in combination with the latency-reversal agent vorinostat is currently undergoing evaluation in an ongoing clinical trial.

"This is a promising advancement for the field," says first author Julia Sung of UNC, although she also cautions people against over-interpreting the results. "The study did not cure HIV and should not be interpreted as doing so, but we also are very encouraged by the safety data, so it should not be considered discouraging either. This paves the way for the next step, which is to combine this immunotherapy approach with latency-reversal therapy in order to wake up the HIV out of its latent state, where it is invisible to the immune system, then clear it out with the immunotherapy."

Babies who dodge HIV may not be unscathed

Exposure to the virus, the mother's microbiome, and drugs each could cause harm.

Up to half of babies born to HIV-infected mothers become infected themselves either in utero, during labor, or through breastfeeding, unless the mothers and babies are treated with antiretroviral (ARV) drugs. But several studies suggest an additional burden for the many children in Nigeria who dodge transmission from their mothers, whether by luck or treatment: They may still suffer from growth retardation, immune abnormalities, and even an increased risk of mortality. “Exposed, uninfected children are a growing population, and they're neglected,” says virologist Nicaise Ndembi of the Institute of Human Virology, Nigeria (IHVN) in Abuja.

At the University of Benin Teaching Hospital in Benin City, Ndembi is a co–principal investigator (co-PI) of a study exploring what happens to those exposed, uninfected children and why. “There's a growing body of data that suggests they're very different from normal infants,” says another co-PI, epidemiologist Man Charurat of IHVN.

Theoretically, the harm could come from the mother's poor health, or from exposure to viral proteins or to the ARV drugs given to treat the mother and the baby to prevent transmission. “It's a really complicated picture,” says Claire Thorne, an epidemiologist at University College London who is trying to separate the effects of HIV exposure from exposure to ARV drugs.

The IHVN team is exploring whether an HIV-caused condition called “leaky gut” may transfer from mother to uninfected child. HIV preferentially destroys immune cells in the gut shortly after infection, leading to an overstimulated immune system, inflammation, and a permeable gut. That could alter the mother's microbiome, and she might pass the altered bacteria to her child during birth or breastfeeding. The Benin researchers suspect the child's altered microbiome then increases diarrhoea, impedes proper absorption of nutrients, and slows growth.

The IHVN study, which began in 2014 and will run through next year, compares 300 uninfected children, half of whom were exposed to HIV during their first 2 years of life. The researchers are analyzing stool samples from mothers and their children to see whether HIV alters the genera of bacteria that live in their guts. Researchers also are giving the children a dose of two sugars and then testing their urine to see whether their intestines have compromised permeability. “If we can identify problems, we can begin to look at interventions,” Ndembi says.

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Source: http://science.sciencemag.org/content/360/6394/1168.full

Latent HIV Reservoir

A latent HIV reservoir is a group of immune cells in the body that are infected with HIV but are not actively producing new HIV.

HIV attacks immune system cells in the body and uses the cells’ machinery to make copies of itself. After entering the body, HIV inserts its genetic blueprint into the DNA of an immune system cell, such as a CD4 cell. The infected cell starts producing HIV proteins that act as the building blocks for new HIV. To find out more about how HIV attacks cells, read the AIDSinfo HIV Life Cycle fact sheet.

Some HIV-infected cells, however, go into a resting (or latent) state. While in this resting state, the infected cells don’t produce new HIV.

When HIV infects cells in this way, it can hide out inside these cells for years, forming a latent HIV reservoir. At any time, cells in the latent reservoir can become active again and start making more HIV.

Latent HIV reservoirs can be found throughout the body, including in the brain, lymph nodes, blood, and digestive tract.

HIV medicines reduce the amount of HIV in the body (called the viral load) by preventing the virus from multiplying. Because the HIV-infected cells in a latent reservoir aren’t producing new copies of the virus, HIV medicines have no effect on them.

People with HIV must take a daily combination of HIV medicines (called an HIV regimen) to keep their viral loads low. If someone is not taking HIV medicines when the infected cells of the latent reservoir begin making HIV again, the viral load in the body will start to increase. That’s why it’s important to continue taking HIV medicines every day as prescribed, even when viral load levels are low.

Finding ways to target and destroy latent reservoirs is one of the major challenges facing HIV researchers. New studies are exploring different strategies for clearing out reservoirs, including:

·         Using gene therapy (which means manipulating genes to treat or prevent disease) to cut out certain HIV genes and inactivate the virus in HIV-infected immune cells.

·         Developing drugs or other methods that reactivate latent HIV reservoirs so that the immune system or new therapies can effectively eliminate them.

·         Developing approaches that enhance the immune system’s ability to recognize and clear reactivated latent HIV reservoirs.

Source: https://aidsinfo.nih.gov/understanding-hiv-aids/fact-sheets/19/93/what-is-a-latent-hiv-reservoir-

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