CXCR4 and infection: THP-1 macrophages and MDM were coinfected with an MTB strain (Rv, ΔpknE and CΔE) and a CCR5 (R5) or CXCR4 (X4)-tropic HIV strain to examine the effect of coreceptor modulation on HIV entry and infection, by measuring HIV-1 p24 antigen levels in infected culture supernatants.