The role of crude saliva and purified salivary mucins in the inhibition of the Human Immunodeficiency Virus type 1

BACKGROUND: Sub-Saharan Africa is the world’s worst HIV-AIDS affected region. More interventions to manage this pandemic are urgently required. Transmission of the virus through an exchange of saliva is rarely known to occur. This project sought to verify statistically previous findings in our laboratory, that crude saliva from uninfected individuals together with its purified mucin components inhibited HIV-1, whilst mucins from infected saliva did not show this inhibition, in an in vitro assay. METHODS: Saliva was extracted in 4 M guanidinium hydrochloride and proteolytic inhibitors at pH 6.5, followed by the isolation of MUC5B and MUC7 by Sepharose 4B gel filtration and further purification of these mucins by density-gradient ultra-centrifugation in caesium chloride. Agarose gel electrophoresis, Western blotting and amino acid compositional analysis determined the size, purity and identity of the mucins. The inhibitory activity of crude saliva and purified MUC5B and MUC7, from HIV negative (n=20) and HIV positive (n=20) donors, was tested by their incubation with subtype C HIV-1 and subsequent infection of peripheral blood mononuclear cells (PBMCs). PCR was done on tandem repeat regions of MUC5B and MUC7 DNA to investigate whether any association existed between gene polymorphism and susceptibility to infection. RESULTS: There was an inter-individual variation in the amounts of MUC5B and MUC7 in saliva. In contrast to previous studies, crude saliva and purified mucins from both HIV negative and HIV positive individuals inhibited the infection of HIV-1 in an in vitro assay. DNA analysis of the tandem repeat regions of MUC5B and MUC7 revealed no difference between groups. CONCLUSIONS: Crude saliva and its mucins, MUC5B and MUC7, from both uninfected controls and HIV positive individuals inhibited HIV-1 in an in vitro assay.