Browsing by Subject "Subtype C"

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    HIV type 1 subtype C gag and nef diversity in Southern Africa.
    (Mary Ann Liebert, 2007) Bredell, Helba; Martin, Darren P; Van Harmelen Joanne; Varsani, Arvind; Sheppard, Haynes W; Donovan, R; Gray, C; HIVNET028 Study Team; Williamson, C
    Several HIV-1 subtype C-specific gag- and/or nef-based vaccines are currently intended for clinical trial in southern Africa. Here we provide sequences of 64 gag and 45 nef genes sampled in Malawi, Zambia, Zimbabwe, and South Africa and assess the degree of southern African HIV-1 diversity that will confront these vaccines. Whereas reasonable phylogenetic evidence exists for geographical clustering of subtype C gag and nef sequences from various other parts of the world, there is little evidence of similar population founder effects in the southern African epidemic. The entire breadth of subtype C diversity is represented in the southern African genes suggesting there may be no advantage in producing region- or country-specific subtype C vaccines. We do not, however, find much evidence of intersubtype recombination in the Southern African genes, implying that the likelihood of vaccine failure due to the emergence of intersubtype recombinants is probably low.
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    The PTAP sequence duplication in HIV-1 subtype C Gag p6 in drug-naive subjects of India and South Africa
    (2017) Sharma, Shilpee; Aralaguppe, Shambhu G; Abrahams, Melissa-Rose; Williamson, Carolyn; Gray, Clive; Balakrishnan, Pachamuthu; Saravanan, Shanmugam; Murugavel, Kailapuri G; Solomon, Suniti; Ranga, Udaykumar
    Abstract Background HIV-1 subtype C demonstrates several biological properties distinct from other viral subtypes. One such variation is the duplication of PTAP motif in p6 Gag. PTAP motif is a key player in viral budding. Here, we studied the prevalence of PTAP motif duplication in subtype C viral strains in a longitudinal study. Methods In a prospective follow-up study, 65 HIV-1 seropositive drug-naive subjects were monitored in two different clinical cohorts of India for 2 years with repeated sampling at 6-month intervals. The viral RNA was extracted from plasma, the gag segment was amplified and sequenced. From a subset of viral isolates the sequences of pol, env and LTR were sequenced. Using HIV-1 gag amino acid sequences available from public databases and additional sequences derived from the Indian and South-African cohorts, we examined the nature of PTAP motif duplication in subtype C. Results In 16% (8 of 50) of the primary viral strains of India, we identified a sequence duplication of the PTAP motif in Gag p6. The length of the sequence duplication varied from 6 to 14 amino acids in the viral isolates but remained fixed within a subject over a period of 24–36 month follow-up. In the duplicated motif, the core PTAP motif was invariable, but the flanking residues were highly variable. In an acute phase clinical cohort of South Africa, in a subset of 75 subjects, we found the presence of the PTAP duplication at a frequency of 29.3%. An analysis of the gag sequences from the extant databases showed that unlike other subtypes of HIV-1, subtype C has a natural propensity to generate the PTAP motif duplication at a significantly higher frequency and of greater length. Additionally, the global prevalence of PTAP duplication in subtype C appears to be increasing progressively over the past 30 years. Conclusion We showed that in subtype C, the duplication of the PTAP motif in p6 Gag involves sequence stretches of greater length, and at a much higher frequency as compared to other HIV-1 subtypes. Given that subtype C naturally lacks the Alix binding motif, the acquisition of an additional PTAP motif may confer replication advantage on this HIV-1 subtype. Further investigation is warranted to examine the significance of PTAP motif duplication on the replicative fitness of HIV-1.