Immunogold detection of HIV on ultrathin cryosections.

(A) In platelets incubated with the supernatant of HIV-infected cultured PBMCs, immunogold labeling for the HIV core protein p24 can specifically and sensitively identify a virionlike particle (vi) that has been internalized in the platelet. This allows its definite identification as an HIV particle. Virtually no background labeling is observed. Original magnification, × 40 250; inset original magnification, × 86 250. (B) Immunogold labeling for p24 was applied on the supernatant of HIV-infected cultured PBMCs: viral particles (arrows) are rare and are scattered among abundant cellular debris. Original magnification, × 46 200.