HIV integrase variability and genetic barrier in antiretroviral naive and experienced patients

Background: HIV-1 integrase (IN) variability in treatment naive patients with different HIV-1 subtypes is a major issue. In fact, the effect of previous exposure to antiretrovirals other than IN inhibitors (INI) on IN variability has not been satisfactorily defined. In addition, the genetic barrier for specific INI resistance mutations remains to be calculated. Methods: IN variability was analyzed and compared with reverse transcriptase (RT) and protease (PR) variability in 41 treatment naive and 54 RT inhibitor (RTI) and protease inhibitor (PRI) experienced patients from subjects infected with subtype B and non-B strains. In addition, four HIV-2 strains were analyzed in parallel. Frequency and distribution of IN mutations were compared between HAART naive and RTI/PI experienced patients; the genetic barrier for 27 amino acid positions related to INI susceptibility was calculated as well. Results: Primary mutations associated with resistance to INI were not detected in patients not previously treated with this class of drug. However, some secondary mutations which have been shown to contribute to INI resistance were found. Only limited differences in codon usage distribution between patient groups were found. HIV-2 strains from INI naive patients showed the presence of both primary and secondary resistance mutations. Conclusion: Exposure to antivirals other than INI does not seem to significantly influence the emergence of mutations implicated in INI resistance. HIV-2 strain might have reduced susceptibility to INI.