Vesicles released by bacteria may protect against HIV infection in human tissues

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Researchers at the National Institutes of Health (MD, USA) and the University of Bologna (Italy) have discovered that nano-sized vesicles released by lactobacilli in the vagina may protect against HIV infection. The study, led by Leonid Margolis (National Institutes of Health) and published in Nature Communications, outlines the possible mechanisms used by the vesicles to suppress the spread of HIV.

Lactobacillus species are already known to play a key role in preventing HIV-1 transmission. However, less is known about how this protective effect is mediated.

In order to determine whether extracellular vesicles (EVs) interfere with the ability of HIV to infect cells, researchers conducted a series of experiments using cervico-vaginal and tonsillar tissues ex vivo, which were infected with HIV-1 and treated with EVs released by lactobacilli from healthy women.

One experiment involved adding EVs to cultures of T lymphocytes infected with HIV-1. The team observed a lower rate of HIV infection in cultures that were treated with the EVs from L. crispatus BC3 and L. gasseri BC12, compared with the untreated cells. Further, when increasing the quantity of EVs, they observed an even lower rate of infection.

When conducting further experiments, the researchers discovered this protection to be associated with decreased viral attachment to target cells and viral entry due to diminished exposure of the viral envelope gene env, which mediates virus-cell interactions, essential for viral infection.

Additionally, researchers observed a reduction in the number of surface molecules on HIV-1, indicating a suppressive mechanism used by the EVs to directly prevent the virus from binding to the host cell surface.

The results of this study demonstrate that EVs contribute to the anti-HIV effect of Lactobacillus species. If confirmed in vivo, these findings may pave the way to new strategies and treatments to prevent male-to-female sexual HIV-1 transmission.

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Sources: Laomino RAN, Vanopuille C, Laghi L et al. Extracellular vesicles from symbiotic vaginal lactobacilli inhibit HIV-1 infection of human tissues. Nat. Commun. 10, 5656 (2019); www.eurekalert.org/emb_releases/2019-12/nksn-vrb121019.php

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