Phenotypic Susceptibility to Antiretrovirals Among Clades C, F, and B/F Recombinant Antiretroviral-Naive HIV Type 1 Strains

Abstract

To evaluate antiretroviral phenotypic susceptibility of wild-type HIV-1 strains circulating in Brazil, samples from antiretroviral-naïve individuals infected with subtypes C (n=16), F (n=9), or B/F (n=7), where reverse transcriptase is B and protease is F, were phenotyped using the AntivirogramTM Assay (Virco, Mechelen, Belgium). Reduced susceptibility to protease inhibitors (PIs) was observed in one C and three F isolates. None of these samples had any known PI resistance mutations. The Phenotypic Fold Change to one PI was above the biologic cut-off in 3 of 96 (3.1%) of clade F phenotypic determinations and 1 of 96 (1.0%) of C. Phenotypic resistance to at least one nucleoside reverse transcriptase inhibitor (NRTI) was found for two B/F, four C, and three F isolates. The Phenotypic Fold Change in susceptibility to NRTIs was above the cut-off value in 9 of 111 (8.1%) of clade C determinations, as compared to 3 of 63 (4.8%) for clade F and 2 of 49 (4.1%) for clade B. The Phenotypic Fold Change to non-NRTI (NNRTI) was above the cut-off in 7 of 32 (21.9%) of C isolates determinations, whereas none of the F isolates had decrease of susceptibility. Only two of the sixteen C samples had a known NNRTI resistance mutation. The NNRTI Fold Change was above the cut-off value in 3 of 14 (21.4%) of phenotypic determination of Brazilian B/F recombinants, representing clade B reverse transcriptase. NNRTI susceptibility should be better investigated in clade C and B/F recombinants.