Ribonuclease is partly responsible for the HIV-1 inhibitory effect activated by HLA alloantigen recognition

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Abstract
Objective: This study was performed to determine whether ribonucleases (RNases) contribute to the soluble HIV-1 inhibitory activity that results from the recognition of HLA alloantigens. Design and methods: Supernatants from mixed lymphocyte reactions of peripheral blood mononuclear cells from healthy HLA-discordant individuals exhibited HIV-1 inhibitory activity (alloantigen-stimulated factors; ASF). These supernatants were tested for their sensitivity to heating (90°C for 3 min), and for the presence of three RNases belonging to the RNase A superfamily: eosinophil-derived neurotoxin (EDN); RNase A; and angiogenin. Polyclonal antibodies specific for these RNases were used for Western blot analysis of the ASF, as well as for blocking the HIV-1 inhibitory activity of ASF. In addition, an RNase inhibitor (RI) was used to determine whether the anti-viral activity of ASF was due to RNase activity. Results: HIV-1 inhibitory activity of ASF was: (i) resistant to heat treatment; (ii) blocked by 58% with an antibody specific for EDN, but not with antibodies against RNase A or angiogenin; and (iii) blocked by 65–100% with an RI. Moreover, Western blot analysis with an anti-EDN antibody detected EDN in the ASF. Conclusion: These findings indicate that the majority of the soluble HIV-1 inhibitory activity contained in the supernatants of mixed lymphocyte reactions is due to EDN or a closely related RNase.