The receptor through which M - tropic HIV strains bind?

Ans. is 'a' i.e., CCR5(Ref: Chemokines in Disease, 4th/e, p. 136)* Macrophage (M - tropic) strains of HIV - 1, or non - synctia inducing strains (NSI) use the beta chemokine receptor CCR5 for entry and are thus able to replicate in macrophages and CD4+ T - cells. These strains are now called R5 viruses.* The normal ligands for this receptor, RANTES, macrophage inflammatory protein (MIP) - l - beta and MIP-1- alpha, are able to suppress HIV - 1 infection in vitro. This CCR5 coreceptor is used by almost all primary HIV - 1 isolates of viral genetic subtype.* T - tropic isolates or synctia inducing (SI) strains replicate in primary CD4+ T cells as well as in macrophages and use the alpha - chemokine receptor, CXCR4, for entry.