R5 HIV-1 replication in unstimulated PBMCs from HTLV-2/HIV-1^MEU subjects. Dominant protective role of MIP-1α. (A) Kinetics of R5 BaL and X4 IIIB virus production in IL-2–stimulated PBMCs from a pool of 25 uninfected donors. Supernatants from PBMC cultures were harvested every 4 to 6 days and tested for HIV-1 p24 Gag Ag content. Results are representative of 5 independent experiments performed at 6-month intervals. (B) Kinetics of R5 and X4 virus production by primary cultures established from 3 HTLV-2/HIV-1^MEU persons. The neutralizing activity of antichemokine NmAbs (2 μg/mL each), added either individually or as cocktails, was determined. (C) Kinetics of virus production in PBMCs infected in the presence or absence of anti-CC chemokine NmAbs added individually (2 μg/mL each). Similar results were obtained with cells infected after 6 days of cultivation (see “HIV-1 envelope-restricted MIP-1α secretion in HTLV-2/HIV-1^MEU” of Document S2 and Figure S1).