Immune Mechanisms of Viral Control in HIV-2 Infection

Human immunodeficiency virus 2 (HIV-2) infection is a zoonosis in which simian immunodeficiency virus from a West African monkey species; the sooty mangabey is thought to have entered the human population on at least eight separate occasions. This has given rise to eight distinct HIV-2 groups, of which only groups A and B have continued to spread among humans; the other clades appear only to have led to single-person infections. Viral control in HIV-2 infection is associated with several distinct features-a high-magnitude cellular immune response directed toward conserved Gag epitopes, an earlier-differentiated CD8 + T cell phenotype with increased polyfunctionality and exceptionally high functional avidity, supported by polyfunctional virus-specific CD4 + T cells, against a background of substantially less extensive immune activation than is seen in human immunodeficiency virus 1 (HIV-1) infection. Emerging as one of the most striking differences from HIV-1 infection is the slower evolution and a possible lower frequency of adaptive immune escape in asymptomatic HIV-2-infected individuals. © 2012 Elsevier Inc. All rights reserved.