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

HIV RNA expression inhibitors may restore immune function in HIV-infected individuals

Immune activation and inflammation persist in most treated HIV-infected individuals and is associated with excess risk of mortality and morbidity. A new study by Boston University School of Medicine (BUSM) researchers suggests that use of HIV RNA expression inhibitors as adjunct therapy might diminish atypical inflammation and restore immune function in HIV-infected individuals on combination antiretroviral therapy (cART).

HIV-1-infected individuals have excess risk of developing non-AIDS complications such as cardiovascular atherosclerosis, neurocognitive dysfunctions, non-AIDS cancers, osteoporosis, and renal disorders. Systemic chronic immune activation has been postulated to lead to these non-AIDS complications.

Despite long-term viral suppression by cART, it has remained unclear how chronic inflammation is induced in HIV-infected individuals. In this study, BUSM researchers identified a mechanism of HIV-1-induced chronic immune activation and T cell dysfunction. In studies performed with primary human macrophages and T cells, they found that persistent infection of macrophages with HIV-1 and expression of intron-containing HIV-1 RNA alone even in the absence of infectious virus production lead to induction of type I interferon (IFN-I)-dependent pro-inflammatory responses and immune exhaustion of co-cultured T cells. They believe that these findings might provide an explanation for the observed chronic inflammation-associated morbidities in HIV-infected individuals who are on cART.

"We hope our study will broaden knowledge of host-HIV interactions and might help to reduce inflammation-associated disorders caused by chronic viral infections," said Rahm Gummuluru, PhD, corresponding author and associate professor of microbiology.

Source: https://www.sciencedaily.com/releases/2018/08/180827102648.htm

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Study shows how HIV is shielded from Immune Attack

Scientists from UNSW Sydney and the UK have discovered that the human immunodeficiency virus (HIV) hijacks a small molecule from the host cell to protect itself from being destroyed by the host's immune system.

The finding, as well as details of the new strategy that enabled it, are published as back-to-back papers in eLife. They identify a new target for antiviral therapy against HIV and provide a method for testing and measuring new drugs designed to target the capsid.

UNSW Ph.D. student Chantal Márquez is involved in both studies and is the first author of the paper describing the new method.

HIV forms a protein shell—called a capsid—that shields its genetic material from host defence mechanisms as it enters the cell and makes its way to the nucleus to establish infection.

Using a new single-molecule microscopy technique—developed at UNSW's Single Molecule Science in the Faculty of Medicine—the research teams found that HIV specifically incorporates a small molecule from the host cell—inositol hexakisphosphate—to strengthen its capsid. The host inadvertently provides the key for the virus infecting it to lock down the protective shell, keeping the genetic cargo safe until it is released into the nucleus.

"The HIV capsid falls apart within minutes once it's isolated from the virus," said Associate Professor Till Böcking, who led the UNSW team involved in both studies.

"Our strategy lets us study exactly how a native capsid breaks apart in real-time without taking it out of the viral membrane."

With the help of Associate Professor Stuart Turville of the Kirby Institute, the team engineered viruses with fluorescent tags to monitor the viral capsid using fluorescence microscopy.

"We can now see the effect of different molecules on the capsid, and pinpoint precisely when it cracks open and begins to collapse," says Associate Professor Böcking.

"Capsids need to be much more stable inside a cell because the infection process takes hours, not minutes—so we wanted to find out what keeps it stable inside a cell," says Dr. David Jacques of Single Molecule Science, who is an author of both studies.

The researchers found that inositol hexakisphosphate, which is abundantly present inside mammalian cells, makes the capsid much stronger, stabilizing it for 10-20 hours.

"It's like a switch. When you bind this molecule, you stabilize the capsid, and release the molecule to open it up," explains Associate Professor Böcking.

"The HIV capsid has been intensively studied, but the question of how it can simultaneously be both stable and poised to 'uncoat' has been one of the great unanswered questions in HIV biology," says Dr. Leo James, leader of the research team at the Medical Research Council Laboratory of Molecular Biology in Cambridge, UK.

Most of the currently approved HIV therapies target enzymes needed at different stages of the virus' life cycle, but none of them are directed at the HIV capsid. New drug alternatives could improve the treatment of HIV with reduced toxic effects.

Source: https://medicalxpress.com/news/2018-07-hiv-shielded-immune.html

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New antibody attacks 99% of HIV strains

Scientists have engineered an antibody that attacks 99% of HIV strains and can prevent infection in primates.

 It is built to attack three critical parts of the virus - making it harder for HIV to resist its effects.

The work is a collaboration between the US National Institutes of Health and the pharmaceutical company Sanofi.

The International Aids Society said it was an "exciting breakthrough". Human trials will start in 2018 to see if it can prevent or treat infection.

Our bodies struggle to fight HIV because of the virus' incredible ability to mutate and change its appearance.

These varieties of HIV - or strains - in a single patient are comparable to those of influenza during a worldwide flu season.

So, the immune system finds itself in a fight against an insurmountable number of strains of HIV.

Super-antibodies

But after years of infection, a small number of patients develop powerful weapons called "broadly neutralising antibodies" that attack something fundamental to HIV and can kill large swathes of HIV strains.

Researchers have been trying to use broadly neutralising antibodies as a way to treat HIV or prevent infection in the first place.

The study, published in the journal Science, combines three such antibodies into an even more powerful "tri-specific antibody".

Dr Gary Nabel, the chief scientific officer at Sanofi and one of the report authors, told the BBC News website: "They are more potent and have greater breadth than any single naturally occurring antibody that's been discovered."

The best naturally occurring antibodies will target 90% of HIV strains.

"We're getting 99% coverage, and getting coverage at very low concentrations of the antibody," said Dr Nabel.

Experiments on 24 monkeys showed none of those given the tri-specific antibody developed an infection when they were later injected with the virus.

Dr Nabel said: "It was quite an impressive degree of protection."

The work included scientists at Harvard Medical School, The Scripps Research Institute, and the Massachusetts Institute of Technology.

'Exciting'

Clinical trials to test the antibody in people will start next year.

Prof Linda-Gail Bekker, the president of the International Aids Society, told the BBC: "This paper reports an exciting breakthrough.

"These super-engineered antibodies seem to go beyond the natural and could have more applications than we have imagined to date.

"It's early days yet, and as a scientist I look forward to seeing the first trials get off the ground in 2018.

"As a doctor in Africa, I feel the urgency to confirm these findings in humans as soon as possible."

Dr Anthony Fauci, the director of the US National Institute of Allergy and Infectious Diseases, said it was an intriguing approach.

He added: "Combinations of antibodies that each bind to a distinct site on HIV may best overcome the defences of the virus in the effort to achieve effective antibody-based treatment and prevention."

Source: https://www.bbc.com/news/health-41351159

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