Red blood cells new sensitive markers for HIV disease progression?

Erythrocytes are an important extracellular reservoir of HIV-1 and quantification of this viral pool may help judge suppression of HIV-1 replication in patients with undetectable plasma viral loads, say researchers in The Lancet.

Failure of current antiretroviral therapies to completely suppress viral replication presents a major obstacle to eradication of the HIV-1 virus. This barrier remains in place, despite reduction of HIV-1 plasma RNA concentrations to levels below the limit of currently available detection systems in many patients. A number of different cell types are known to act as reservoirs or carriers for the virus, prompting calls for the design of targeted drugs.

Reports that erythrocytes bind HIV-1 immune complexes in vitro prompted Christopher Hess, of University Hospital Basel and colleagues to look for a circulating pool of virus associated with red blood cells in people with HIV-1 infection. They tested the plasma, white cells and erythrocytes from 82 chronically HIV-infected individuals using RT-PCR, and found that the HIV-1 virus was associated with erythrocytes in 80 of these patients.

In 23 of the patients tested, erythrocyte-associated HIV-1 was detected despite the fact that plasma HIV-1 RNA had previously been undetectable by standard methods (< 20 copies/ml) for up to 32 months. Up to 82 878 HIV-1 RNA copies were detected per ml of blood in the corresponding erythrocyte samples.

Confirmation of the association between HIV-1 and this group of cells could lead to a new method for judging the suppression of HIV-1 replication in individuals with low virus levels, the authors suggest. The finding that higher numbers of HIV-1-associated erythrocytes correlated with a history of advanced clinical stages of the infection suggests that quantification of this viral pool could be used as a sensitive method for monitoring disease progression.