The central role of endoconvertases and HIV-1 protease (HIV-1 PR) in the processing of HIV proproteins makes the design of specific inhibitors important in anti-HIV gene therapy. Accordingly, we tested native α1 antitrypsin (α1AT) delivered by a recombinant simian virus-40-based vector, SV(AT), as an inhibitor of HIV-1 proprotein maturation. Cell lines and primary human lymphocytes were transduced with SV(AT) without selection and detectable toxicity. Expression of α1AT was confirmed by Northern blotting, immunoprecipitation and immunostaining. SV(AT)-transduced cells showed no evidence of HIV-1-related cytopathic effects when challenged with high doses of HIV-1NL4-3. As measured by HIV-1 p24 assay, SV(AT)-transduced cells were protected from HIV-1NL4-3 at challenge dose of 40 000 TCID50 (MOI = 0.04). In addition, peripheral blood lymphocytes treated with SV(AT) were protected from HIV doses challenge up to 40 000 TCID50 (MOI = 0.04). By Western blot analyses, the delivered α1AT inhibited cellular processing of gp 160 to gp 120 and decreased HIV-1 virion gp 120. SV(AT) inhibited processing of p55Gag as well. Furthermore, high levels of uncleaved p55Gag protein were detected in HIV virus particles recovered from SV(AT)-transduced cells lines and primary lymphocytes. Thus, delivering α1AT using SV(AT) to human lymphocytes strongly inhibits replication of HIV-1, most likely by inhibiting the activities both of the cellular serine proteases involved in processing gp160 and of the aspartyl protease, HIV-1 PR, which cleaves p55gag, α1AT delivered by SV(AT) may represent a novel and effective strategy for gene therapy to interfere with HIV replication, by blocking a stage in the virus replicative cycle that has until now been inaccessible to gene therapeutic intervention.
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