From Wikipedia, the free encyclopedia HIV tropism
HIV tropism
HIV tropism refers to the cell type that the human im- CXCR4, for entry [1]. These strains are now called X4
munodeficiency virus (HIV) infects and replicates in. HIV viruses [2]. The alpha-chemokine, SDF-1, a ligand for
tropism of a patient’s virus is measured by the Trofile as- CXCR4, suppresses replication of T-tropic HIV-1 isolates.
say. It does this by down regulating the expression of CXCR4
HIV can infect a variety of cells such as CD4+ helper T- on the surface of these cells.
cells and macrophages that express the CD4 molecule on Viruses that use only the CCR5 receptor are termed
their surface. HIV-1 entry to macrophages and T helper R5, those that only use CXCR4 are termed X4, and those
cells is mediated not only through interaction of the viri- that use both, X4R5. However, the use of coreceptor
on envelope glycoproteins (gp120) with the CD4 molecule alone does not explain viral tropism, as not all R5 viruses
on the target cells but also with its chemokine corecep- are able to use CCR5 on macrophages for a productive in-
tors. fection.[1]
Macrophage (M-tropic) strains of HIV-1, or non-
syncitia-inducing strains (NSI) use the beta-chemokine
receptor CCR5 for entry and are thus able to replicate in
References
macrophages and CD4+ T-cells [1]. These strains are now [1] ^ Coakley, E., Petropoulos, C. J. and Whitcomb, J. M.
called R5 viruses [2]. The normal ligands for this receptor, (2005). "Assessing chemokine co-receptor usage in
RANTES, macrophage inflammatory protein (MIP)-1-beta HIV". Curr. Opin. Infect. Dis. 18 (1): 9–15. doi:10.1097/
and MIP-1-alpha, are able to suppress HIV-1 infection in 00001432-200502000-00003. PMID 15647694.
vitro. This CCR5 coreceptor is used by almost all primary [2] ^ Berger, EA; Doms, RW; Fenyö, EM; Korber, BT;
HIV-1 isolates regardless of viral genetic subtype. Littman, DR; Moore, JP; Sattentau, QJ;
T-tropic isolates, or syncitia-inducing (SI) strains Schuitemaker, H et al. (1998). "A new classification
replicate in primary CD4+ T-cells as well as in for HIV-1.". Nature 391 (6664): 240. doi:10.1038/
macrophages and use the alpha-chemokine receptor, 34571. PMID 9440686.
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