Objective: Resistance to antiretroviral drugs has been associated with characteristic mutations in the genes that encode enzymes which are the target of anti-retroviral therapy. In this paper we evaluate the different mutations revealed by molecular typing of viruses from different patients who were referred to be genotyped at the Instituto de Referencia Andino in Bogotá for therapeutic purposes.

Design: A total number of 1064 mutations in viruses from 16 HIV infected unrelated patients were initially genotyped for the analysis of sensitivity to antiretrovirals. Afterwards, we proceeded to the tabulation of the mutations found in four main categories: a- resistance mutations, b- silent mutations, c-genetic polymorphisms outside of sites associated with resistance, and d- mutations at sites not yet associated with resistance. 

Materials and methods: Sixteen EDTA blood samples drawn from patients with HIV genotyping application for analysis of sensitivity to antiretroviral drugs were selected in strict order of arrival. Viral RNA was extracted from each sample by the QIAamp® method, and we then proceeded to its amplification by reverse transcriptase PCR (RT-PCR). Once the viral nucleic acid was successfully amplified, we proceeded to molecular typing in the sequencer LongRead-Tower-Opengene®, using the Trugene® HIV-1 kit. The sequences obtained were transcribed to an Excel® spreadsheet, to calculate the frequencies of mutations by direct counting. 

Results: We revealed 1064 viral mutations among which only 164 (15,4%) were associated with resistance to antiretroviral drugs (68 in the retrotranscriptase or reverse transcriptase gene and 96 in the protease). The remaining 84,5% corresponds to polymorphisms (n=301), silent mutations (n=564), and other mutations (n=35) that have not been associated with resistance so far, but can be a source of recurring failures on antiretroviral treatment. We also found three identical viral genotypes in 3 unrelated patients coming from different geographic areas in the country. This finding implies that viral genotyping can be a useful indicator for epidemiological tracking of this viral disease. 

We also report the molecular mapping of the 1064 mutations identified in all 16 patients studied, which show which codons mutate more frequently. Among these, the codon 63 of the protease, with 18 mutations, and codon 184 of the retrotranscriptase, with 14 mutations, housed the higher number of variants in the viruses that were sequenced in this preliminary study.

Conclusions: Genetic typing of HIV can be the basis of molecular epidemiological investigations, beyond their obvious utility in the study of resistance to antiretroviral drugs for which these tests are used exclusively today.