ObjectiveAn assessment of the impact of one year potent antiretroviral treatment initiated during primary HIV infection on the cell-associated viral burden.Design and methodsProviral HIV-1 DNA was quantified in serial peripheral blood mononuclear cell (PBMC) samples from 19 patients enrolled in the French prospective PRIMO Cohort for whom plasma HIV RNA was suppressed to undetectable levels after one year of triple therapy; that is, plasma HIV-1 RNA was maintained below 200 copies/ml. Results were compared with those observed in 19 patients with chronic HIV-1 infection presenting the same degree of virus suppression after 12 months of treatment.ResultsAt study entry, PRIMO subjects presented heterogeneous levels of proviral HIV-1 DNA: 2–3.92 log10copies/106PBMC and plasma HIV RNA: 2.3–6.5 log10copies/ml. One year of effective highly active antiretroviral therapy (HAART) resulted in a median diminution of proviral DNA of −0.78 log10/106PBMC in PRIMO subjects. The median decline in chronic-phase patients was −0.32 for those who were pre-treated and −0.52 for those previously naive of treatment.ConclusionThe decline in cell-associated HIV DNA observed throughout one year treatment indicated that HAART reduces the proviral HIV-DNA load more effectively when initiated during the primary rather than the chronic phase of HIV infection. These findings therefore tend to lend support to the early initiation of treatment. Nevertheless, heterogeneous baseline values observed for CD4 cell count, plasma HIV RNA and proviral HIV DNA in PRIMO subjects, raise the question of whether treatment should be delayed in some to spare early adverse effects of HAART.