Figure 7.
The accessory protein Vpu is required for an efficient spreading infection in macrophages but not for maintenance and viral dissemination in trans of cell-associated virus. (A) Requirement for Vpu in a spreading viral infection of macrophages. Macrophages were infected with R5-tropic HIV-1ADA variants comprising intact (ADAWT) or mutated (ADAΔVpu) vpu genes. Viral replication in macrophages was assessed by measurement of RT activity in culture supernatants. (B) Role of Vpu in the maintenance of cell-associated virus was examined using the same strategy as in Figure 6. Macrophages were infected with VSV-pseudotyped X4-tropic HIV-1 variants containing functional or inactive vpu genes. IVS was then added 4 days post infection to inhibit virus production. At 4 and 6 weeks post infection, the presence of processed gag p24 in culture supernatants and in cell lysates was determined by ELISA (C). (D) Infectivity of cell-associated virus at 4 and 6 weeks post infection was determined following addition of PBLs and measurement of infectivity in trans. 2-LTR cDNAs were quantitated in two aliquots (0.1 and 0.5) of infected PBL lysates. (E) The presence of infectious virus in cytoplasmic macrophage lysates was directly assessed by titration on MAGI cells. 2-LTR cDNA products were quantitated in two aliquots (0.1 and 0.5) of MAGI cell extracts. Data shown are representative of two independent experiments.