CXCR4 and infection: Although in current and other studies5,15,53,55,56 there were no significant differences between patients with RHI harbouring non-R5 and R5 viruses with regard to the baseline CD4+ T-cell count and viral load, longitudinal observations indicated that the presence of CXCR4-utilizing strains at the beginning of infection was associated with faster disease progression characterised by accelerated CD4+ T-cell count decline below 350 cells/μl5,53.