Introduction: This study aimed to evaluate the prevalence of resistance mutations in the protease gene of HIV-1 strains isolated from north Indian antiretroviral (ARV) treatment-naive patients and to assess the phylogenetic relatedness of these strains with known HIV-1 strains. Methodology: Fifty-four HIV-1 strains isolated from treatment-naive patients (n = 54) were included in this study. Resistance genotyping for the protease gene was performed using semi-nested PCR and DNA sequencing. The sequences were aligned (ClustalW) and a phylogenetic tree was built (MEGA 4 software). Drug resistance (DR) pattern was analyzed using the Stanford HIV-DR database and the IAS-USA mutation list. For subtyping purposes, all the nucleotide sequences were submitted to the REGA HIV-1 subtyping tool version 2.0l. Results: All the strains (100%) were found to belong to the C subtype and to harbor at least two secondary mutations in the protease gene. The most frequent mutations were H69K and I93L (52 of 52 strains), followed by I15V (80.7%), L19I (69.2%), M36I (67.3%), R41K (94.2%), L63P (61.5%), and L89M (82.7%). Conclusion: This study confirms that HIV-1 subtype C predominates in northern India. Protease secondary mutations associated with drug resistance to protease inhibitors (PIs) were present with high frequency in the HIV-1 C subtype strains isolated from north Indian ARV treatment-naive patients, but no primary resistance mutations were found in this region. We suggest that resistance testing in HIV-1 infected patients should ideally be performed before the initiation of therapy to tailor the treatment for the individual to achieve the optimal therapeutic outcome.
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