Prevalence of HIV-1 resistant strains in recent seroconverters

Twenty-nine HIV-1 recently infected subjects were retrospectively studied t o investigate both the prevalence of nucleoside reverse transcriptase inhib itors (NRTI)-related mutations at primary infection and the proportion of n aturally occurring mutations in protease inhibitor (PI)-naive patients. Nei ther HIV-1 plasma viremia nor CD4 absolute count at baseline could distingu ish patients with NRTI pre-existing mutations from those with wild-type vir us. An increasing proportion of ZDV-related mutations was observed over tim e with an overall frequency of 20.7% in the study period. Only 1 out of 6 p atients (16.7%) with ZDV-related mutations showed a phenotypically ZDV resi stant isolate. A striking proportion of polymorphic changes was present in the protease region of pol gene in newly infected individuals. As many as 8 0% of seroconverters presented at least one naturally occurring substitutio n. Some PI-associated substitutions, thought to be compensatory in protease enzymatic function, could confer intermediate to high PI-resistance. Their role following PI administration remains to be elucidated. Our data sugges t that the choice of drugs should be oriented by both genotypic and phenoty pic evaluations to tailor individual regimens in seroconverters.