Researchers may have caught HIV becoming more virulent

Gus Cairns
Original Article:

A study from Cuba has generated wide media interest because researchers have identified a particular variety of the virus which is associated with rapid post-diagnosis falls in CD4 count and progression to AIDS. In the study, every member of the still relatively small minority of people who had this viral variant had progressed to clinically defined AIDS within three years of infection. It also seems to be becoming more common in Cuba and may partly explain what appears to be an increase in the proportion of people who progress rapidly to AIDS. However, it is not a drug-resistant strain and antiretroviral therapy (ART) works just as well against it as it does against any other strain of HIV.

This viral strain, dubbed CRF19_cpx, is a recombinant: this means that its genetic code is a patchwork of gene fragments that come from other varieties of HIV. In this case, the genes of CRF19_cpx come from subtypes A, D and G, which are mainly found in Africa. There, subtype D is associated with faster progression, and A/D recombinants even more so.

The researchers believe that the ultimate cause of CRF19_cpx’s unusual virulence is that its protease gene, which comes from HIV subtype D, produces an unusually potent protease enzyme that generates exceptional numbers of viral copies and rapidly alters the arms race between HIV and the immune response against it in favour of the virus.

So-called ‘circulating recombinant forms’ (CRFs) are not uncommon. In some countries they may even predominate, such as in Thailand, where CRF01_AE is so common it is often just called ‘subtype E’ (and has been associated with faster progression). CRF19_cpx has been found in Africa, but it is only in Cuba that it has been noted to be spreading.

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