Comparative Genetic Variability in HIV-1 Subtype C vpu Gene in Early Age Groups of Infants

Identifying the genetic variability in vertically transmitted viruses in early infancy is important to understand the disease progression. Being important in HIV-1 disease pathogenesis, vpu gene, isolated from young infants was investigated to understand the viral characteristics.

Blood samples were obtained from 80 HIV-1 positive infants, categorized in two age groups; acute (<6 months) and early (>6-18 months). A total of 77 PCR positive samples, amplified for vpu gene, were sequenced and analyzed.

73 isolates belonged to subtype C. Analysis of heterogeneity of amino acid sequences in infant groups showed that in the sequences of acute age group both insertions and deletions were present while in the early age group only deletions were present. In the acute age group, a deletion of 3 residues (RAE) in the first alfa helix in one sequence and insertions of 1-2 residues (DM, GH, G and H) in the second alfa helix in 4 sequences were observed. In the early age group, deletion of 2 residues (VN) in the cytoplasmic tail region in 2 sequences was observed. Length of the amino terminal was observed to be gradually increasing with the increasing age of the infants. Protein Variation Effect Analyzer software showed that deleterious mutations were more in the acute than the early age group. Entropy analysis revealed that heterogeneity of the residues was comparatively higher in the sequences of acute than the early age group.

Mutations observed in the helixes may affect the conformation and lose the ability to degrade CD4 receptors. Heterogeneity was decreasing with the increasing ages of the infants, indicating positive selection for robust virion survival.