Macrophage tropic strains of HIV use ?

Ans. is 'a' i.e., CCR5 Receptors for HIV The receptor for the virus is CD4 antigen, and therefore the virus may infect any cell bearing the CD4 antigen on the surface this is primarily the CD4 + (Helper) T Lymphocyte Specific binding of virus to CD4 receptor is by the envelope glycoprotein gp-I 20. However, for infection to take place, cell fusion is essential, which is brought about by the transmembrane gp41. Entry of virus into the cells also requires coreceptor molecule :- T cell CXCR4 Macrophage CCR5