Tuesday, 5 May 2020

Virologists detect new potential reservoir of latent HIV

Scientists have described a class of cells that preferentially support latent infection by HIV. These cells are characterized by a surface protein called CD127 and are found in tissues such as lymph nodes, which are thought to harbor a larger share of the HIV reservoir than blood does.

Scientists have long known that even in the face of antiretroviral therapy, some HIV virus remains in infected individuals forever, hiding in small reservoirs of cells of the immune system. When these individuals discontinue the therapy, the virus almost always rebounds rapidly from the reservoirs, causing deadly symptoms to re-emerge.

These reservoirs remain the main obstacle to curing HIV/AIDS. But there is at present no easy way of targeting reservoir cells for elimination. Nor can scientists efficiently extract reservoir cells from patients to study them, and, ultimately, find ways to control them.

The reason is that the virus in these cells is silent. As a result, the cells do not carry on their surfaces the viral proteins that would make them easy to find.

Scientists have therefore been looking for other means to pinpoint reservoir cells. HIV targets immune cells, known as T cells, that reside primarily in lymphoid tissues, such as lymph nodes and tonsils. Yet HIV infection studies have largely focused on T cells circulating in the blood, which are relatively easy to gain access to -- volunteers are more likely to submit to a blood draw than a tissue biopsy.

But focusing on T cells present in the blood is probably giving scientists a skewed view of the reservoir composition.

Instead, virologists have been studying HIV infection using tissue specimens. In previous work, her team exposed tonsil cells to HIV in the lab to see which ones were most susceptible to infection. Using a variety of experimental approaches, the team found that tonsil cells with the surface protein CD127 efficiently took up the HIV virus but only rarely let it replicate. By contrast, another type of tonsil cells, carrying CD57 on their surface, readily supported a productive infection.

See: Tissue memory CD4 T cells expressing IL-7 receptor-alpha (CD127) preferentially support latent HIV-1 infection. PLOS Pathogens, 2020; 16 (4): e1008450 DOI: 10.1371/journal.ppat.1008450

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)

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