Analysis of HIV type 1 subtype C full-length gag gene sequences from India: novel observations and plausible implications.

Twenty-four HIV-1 gag genes from patients in India were sequenced and analyzed. All measured 1476-1491 nucleotides with an average of 1483 nucleotides in length. Phylogenetic analysis revealed a homogeneous epidemic of HIV-1 subtype C. Intragenotypic divergence of up to 6.6% was present. Fourteen novel conserved signature pattern residues were delineated for HIV-1 subtype C strains. Each of the 15 nucleocapsid (NC) basic residues was highly conserved p6 gag LXSLFG and PT/SAPP motifs were highly conserved except for PTVPT in three and PTAPT in two strains. Zinc finger motifs were conserved in all. Documented HIV-1 subtype C gag immunodominant CTL epitopes were conserved. The evolving predominance and the change in nature of the epidemic from Thai B to that of subtype C in the Northeastern regions of India were observed. Tracking the evolution of the Indian epidemic has implications for developing a vaccine.