SIV Pathogenic and Nonpathogenic Infections
Thaidra Gaufin Ivona Pandrea and Cristian Apetrei
from: Lentiviruses and Macrophages: Molecular and Cellular Interactions (Edited by: Moira Desport). Caister Academic Press, U.K. (2010)
Simian immunodeficiency viruses (SIVs) naturally infect African nonhuman primates. Cross-species transmissions of SIVs from naturally infected chimpanzees/gorillas and sooty mangabeys are at the origin of HIV-1 and HIV-2, respectively. Experimental or accidental transmission of SIVsmm to different species of macaques resulted in the development of AIDS animal models. Differently from humans and macaques which, upon infection, invariably progress to AIDS, natural SIV hosts are generally spared of disease progression. Pathogenic and nonpathogenic SIV infections share some major features, such as a very active viral replication during both acute and chronic infection, a significant acute depletion of CD4+ T cells, which is more prominent at mucosal sites, and a partial control of the virus by both adaptive and innate immune responses. Although SIVs have the potential to infect macrophages, the bulk of viral replication in vivo is supported by CD4+ T cells in both pathogenic and nonpathogenic infections. The major differences between the two models are: maintainance of CD4+ T cell homeostasis in natural hosts, with rebounds to near preinfection levels of peripheral CD4+ T cells and significant recovery in the intestine; normal levels of T cell immune activation, cell proliferation and apoptosis in natural infection, while increases in these three parameters are associated with disease progression in pathogenic infection. A better understanding of the mechanisms underlying the lack of disease in natural hosts for SIV infection will likely provide important clues as to the pathogenesis of AIDS in HIV-infected individuals read more ...