Human Immunodeficiency Virus -1 subtypes : Couldgenetic diversity translate to differential pathogenesis?

Abstract

Human Immunodeficiency Virus (HIV) exhibits extremely high degree of variation at genetic level. This extensive genetic variation is a consequence of two factors. Firstly, there have been multiple introductions of genetically diverse simian retroviruses into the human populations. Secondly, following introduction, the viruses diversify rapidly with time, generating heterogeneous viral strains. Based on the genetic relatedness, HIV-1 and HIV-2 are classified into several distinct subtypes. Distribution of the viral subtypes across the globe is nonuniform. Additionally, epidemic outbreaks due to recombinant forms of the viruses are also becoming a serious problem in several geographical regions. Whether the various genetic subtypes and recombinant forms of HIV-1 have biological differences, for instance with respect to transmissibility and the course of disease progression, is controversial. The extent of genetic divergence among subtypes is probably more than sufficient to cause such differences. However, adequately controlled data from in vivo studies are yet to emerge. This article presents an overview of what is known on the genetic variation of the viral subtypes and its practical implication for viral pathogenesis and efficient engineering of intervention strategies.