Elevated tumor necrosis factor-α activation of human immunodeficiency virus type 1 subtype C in southern Africa is associated with an NF-κB enhancer gain-of-function

The human immunodeficiency virus type 1 (HIV-1) epidemic within southern Africa is predominantly associated with the HIV-1C subtype, Functional analysis of the enhancer region within the long terminal repeat (LTR) indicates that HIV-1C isolates have greater than or equal to 3 NF-kappa B binding sites, unlike other subtypes, which have only 1 or 2 sites. A correlation was shown between NF-kappa B enhancer configuration and responsiveness to the proinflammatory cytokine tumor necrosis factor (TNF)-alpha within the context of naturally occurring subtype LTRs, subtype-specific NF-kappa B enhancer regions cloned upstream of an isogenic HXB2 core promoter or a heterologous SV40 minimal promoter, and full-genome subtype clones, In all cases, TNF-alpha alpha activation was correlated with the subtype configuration of the NF-kappa B enhancer. Whether the naturally occurring gain-of-function in the NF-kappa B enhancer of HIV-1C observed in this study can provide a selective advantage for the virus in vivo remains to be determined and warrants further study.