HIV-1-induced cytopathogenicity in cell culture despite very decreased amounts of fusion-competent viral glycoprotein

Disinfection of cell-associated and extracellular HIV-1 by PUVA treatment

To inactivate cell-associated and extracellular HIV-1 while preserving cellular surface antigens, a procedure was used based on PUVA treatment, i.e. addition of psoralen to cell suspensions followed by irradiation with UVA light. T-lymphoid MT-4 cells were infected with HIV-1 strain NL4-3, 4'-aminomethyl-4,5',8-trimethylpsoralen was added, and the cell suspension was irradiated with 20 mW/cm2 UVA light for 3, 4 and 5 min. To evaluate virus inactivation, cells and supernatants were diluted serially and cocultured with uninfected MT-4 cells. Infectious HIV-1 was detected by cytopathic effects, immunofluorescence and p24 antigen ELISA. UVA irradiation at 3.6 J/cm2 (3 min 20 mW/cm2) reduced the amounts of both cell-associated and extracellular infectious HIV-1 by more than five orders of magnitude. Even at more stringent conditions of PUVA treatment (10 min 20 mW/cm2 UVA irradiation), conformational cellular surface epitopes remained detectable by flow cytometry.

Generation of lymphocyte cell lines coexpressing CD4 and wild-type or mutant HIV type 1 glycoproteins: implications for HIV type 1 Env-induced cell lysis

To gain more insight into the processes leading to HIV-1 Env-induced cell death, we aim to coexpress stably wild-type and relevant mutant variants of both HIV-1 Env and human CD4 in lymphocyte cell lines. Here we report on the generation and characterization of several cell lines inducibly or constitutively expressing wild-type or cleavage-defective HIV-1 glycoproteins and human CD4 either singly or in combination. Coexpression of CD4 and wild-type Env led to the formation of multinucleated syncytia, to growth arrest and cell death, effects that all could be prevented by cultivation in the presence of monoclonal antibodies that inhibit cell surface membrane fusion. Cell lines coexpressing CD4 and mutated, noncleavable Env, detectable at the cell surface and still retaining CD4-binding capacity, were not retarded in their growth and cytolysis did not occur. These results indicate that cell lysis requires cell surface interaction of CD4 and gp120/41 and cleavage of gp160 to gp120 and gp41.