Detection of the protease codon 35 amino acid insertion in sequences from treatment-naïve HIV-1 subtype C infected individuals in the Central Region of Portugal

Abstract Background Amino acids insertions in the protease (PR) coding region have been reported in protease inhibitors (PIs) treatment-naïve and experienced HIV-1 infected individuals ranging from 0.1% to 4.55% and have been rarely found in non-B HIV-1 subtype strains. Objectives To investigate the presence of amino acid insertions in the PR coding region in sequences from treatment-naïve HIV-1 infected individuals in the Central Region of Portugal. Study design Sequences of the pol gene from 260 treatment-naïve HIV-1 infected individuals between 2000 and 2008 were analyzed and phylogenetic analysis was performed. Results A threonine insertion (E35E_T) was detected in 2.69% ( n = 7) of the sequences analyzed and all the sequences that possessed this insertion were identified as subtype C. All the seven inserted sequences clustered in the same lineage of the phylogenetic tree. Heterosexual and intravenous drug use were found to be the routes of infection. No major mutations in the PR coding region associated with resistance to PIs were detected. Conclusions It was found the highest prevalence of PR codon 35 insertion among treatment-naïve HIV-1 infected individuals ever reported in the western countries. Epidemiological data and Phylogenetic analysis indicated the possibility of transmission of this insertion. The results suggested that these inserted strains have normal susceptibility to PIs containing regimens. This study demonstrated the spreading epidemic of PR codon 35 inserted strains from subtype C in the Central Region of Portugal, during the past eight years.