The lymphocyte HIV reservoir in patients on long-term HAART is a memory of virus evolution

To investigate the dynamics of the lymphocyte HIV reservoir in patients on prolonged and effective highly active antiretroviral therapy (HAART).

Nine HAART-treated patients were selected on the basis of long-term infection and long-term undetectable plasma viral RNA. Five patients had received antiretroviral therapy before HAART. We compared a polymorphic region of the env gene (C2V4), and the part of the pol gene encoding the reverse transcriptase in pre-HAART plasma and in the reservoir lymphocytes during HAART; the first plasma sample taken after structured treatment interruption was also studied in three patients.

Both regions of interest were amplified from plasma HIV RNA and cellular proviral DNA, then cloned, sequenced and subjected to phylogenetic analysis.

Diversity of the lymphocyte reservoir was found in six of nine patients. Archiving of pre-HAART plasma clones was observed in six of nine patients. 'Wild-type' and zidovudine-resistant strains co-existed in reservoir T cells of two pre-HAART treated patients. In three patients, no resistant virus was found in the T-cell reservoir despite the detection of resistant virus in pre-HAART plasmas. However, virus archiving was documented in two of these three patients on the basis of C2V4 analysis. Latently infected T cells only partly accounted for the plasma viral load rebound after structured treatment interruption.

The HIV lymphocyte reservoir is dynamic. Its diversity results mainly from successive archiving of circulating plasma viruses during the course of HIV infection. Archiving of resistant virus must be taken into account in therapeutic decisions.