FIG. 3.

Foci of infection of HeLa-CD4/CCR5 cells by M-tropic HIV-1 clones or isolates. HIV-1 p24 antigen in infected cells was detected by indirect immunoperoxidase staining. p24-positive foci consisted of single or grouped multinucleated giant cells, with occasional adjacent mononuclear cells. (A) M-tropic HIV-1 clone 81A, containing the V1, V2, and V3 regions of the env gene of clone Ba-L in the background of clone NL4-3 (68). One small syncytium with four nuclei and three large syncytia containing greater than 20 nuclei are shown. (B) Field showing 10 typical foci of cells infected by M-tropic clone JR-CSF containing 1 to 10 nuclei each. (C) Numerous small foci of cells infected by an HIV-1 isolate obtained from a patient on day 7 of illness due to primary HIV-1 infection.