Significant contribution of subtype G to HIV-1 genetic complexity in Nigeria identified by a newly developed subtyping assay specific for subtype G and CRF02-AG

While abundant sequence information is available from human immunodeficiency virus type 1 (HIV-1) subtypes A, B, C and CRF01-AE for HIV-1 vaccine design, sequences from West Africa are less represented. We sought to augment our understanding of HIV-1 variants circulating in 6 Nigerian cities as a step to subsequent HIV-1 vaccine development. The G/CRF02-AG multi-region hybridization assay (MHA) was developed to differentiate subtype G, CRF02-AG and their recombinants from other subtypes based on 7 HIV-1 segments. Plasma from 224 HIV-1 infected volunteers enrolled in a cohort examining HIV-1 prevalence, risk factor, and subtype from Makurdi (30), Abuja (18), Enugu (11), Kaduna (12), Tafa (95), and Ojo/Lagos (58) was analyzed using MHA. HIV-1 genomes from 42 samples were sequenced to validate the MHA and fully explore the recombinant structure of G and CRF02-AG variants. The sensitivity and specificity of MHA varied between 73-100% and 90-100%, respectively. The subtype distribution as identified by MHA among 224 samples revealed 38% CRF02-AG, 28% G, and 26% G/CRF02-AG recombinants while 8% remained nontypeable strains. In envelope (env) gp120, 38.84% of the samples reacted to a G probe while 31.25% reacted to a CRF02 (subtype A) probe. Full genome characterization of 42 sequences revealed the complexity of Nigerian HIV-1 variants. CRF02-AG, subtype G, and their recombinants were the major circulating HIV-1 variants in 6 Nigerian cities. High proportions of samples reacted to a G probe in env gp120 confirms that subtype G infections are abundant and should be considered in strategies for global HIV-1 vaccine development.