In vitro anti-HIV and immunomodulatory potentials of Azadirachta indica (Meliaceae) leaf extract

Abstract

Azadirachta indica (neem) is attributed to have many ethnopharmacological properties and has been postulated to have a significant effect on CD4 counts in HIV/AIDS subjects, however, the precise anti-retroviral mechanism is not yet known. In this study, a hydroacetone extract of A. indica leaves was investigated for its anti-retroviral and immunomodulatory potentials. The effect of the neem leaf extract on acute HIV infectivity and fusion was measured by the syncytia formation assay on HIV-1-infected C8166 CD4+ cells. The inhibitory effect of the extract on reverse transcriptase (RT) polymerase activity and HIV p24 antigen expression were evaluated in the culture supernatant. The extract was also assessed for its ability to decrease the phenotypic expression of the immune activation markers CD38 and CD69. Results from a syncytium formation assay indicated that the extract blocked HIV-1 envelope-mediated membrane fusion. The extract inhibited HIV-1 replication in C8166 CD4+ cells in vitro by inhibiting the biochemical activity of HIV-1 reverse transcriptase, the result being a subsequent decrease in HIV p24 antigen concentration. In the effective dose range, no cytotoxicity was detected on uninfected target cells. Ex vivo the extract exhibited a dose dependent reduction in the levels of the immune activation marker CD38 and CD69 on phytohemagglutinin A (PHA)-stimulated human peripheral blood mononuclear cells (PBMC). The observed anti-HIV activity and immunomodulatory potentials of the extract shows that neem could impart health benefits to HIV/AIDS patients possibly by acting as fusion or reverse transcriptase inhibitors and also down-regulate hyperimmune activation. © 2011 Academic Journals.