Inhibition of HIV-1 IIIB and clinical isolates by human parotid, submandibular, sublingual and palatine saliva

Human saliva is known to possess components that decrease the HIV-1 infectivity in vitro. The mechanism of how these components inhibit the infectivity is still not clear on the molecular level. The purpose of this study was to discriminate between serous and mucous components with respect to inhibitory capacity and site of action. We have used total saliva and saliva from the major (sero)mucous glands: submandibular gland, sublingual glands, and glands in the palate, in comparison with the serous parotid glands. HIV-1 IIIB and primary variants were incubated with saliva, and inhibition of HIV-1-infection was determined by analysing the cytopathic effect on MT-2 cells. Mucous saliva, as well as serous saliva, contained high molecular weight components that reduced HIV-1-infectivity, at least partially by entrapment of the virus particles. Lower molecular weight components in all types of saliva possessed strong HIV-1 neutralizing capacity. Using pro-viral DNA synthesis by reverse transcription as a discrimination point in the replication cycle, the results indicated that part of the saliva samples acted before, but others after, this point. In conclusion, saliva inhibits HIV-1-infection by the action of high molecular weight components in combination with low molecular weight components from serous as well as mucous saliva, affecting different stages of the infection cycle.