The purpose of this investigation was to adapt an MT-2 cell syncytium-forming assay for measuring anti-infectivity activity of salivary secretions toward HIV and to determine the distribution of this activity in a population of healthy adult subjects. Whole saliva samples were collected from 27 volunteers, who reported that they did not belong to any group at high risk for HIV infection, and tested for anti-infectivity activity using the syncytium-forming assay. Nine of these subjects were subsequently retested on one or more occasions to assess the variability in appearance of this activity. Parotid and extraparotid salivas of six subjects were also tested. Samples were frozen immediately after collection and submitted in blinded fashion for quantitation of their anti-HIV activity using a syncytia-forming MT-2 cell assay or the p24 antigen ELISA. Nine out of the 27 subjects showed detectable anti-HIV infectivity activity. One parotid sample and one extraparotid sample out of four from subjects with positive whole salivas were positive and none of the parotid or extraparotid samples from two subjects with negative whole salivas were positive. The inhibitory activity ranged from 0.5 to 1 log 10 TCID50 /ml and could not be correlated with total protein content in saliva or any specific electrophoretic component. Filtration of the saliva through an Amicon 10 filter before incubation with the virus abolished the activity. Similar studies using two other biological fluids, urine and cerebrospinal fluid, revealed no anti-HIV infectivity activity. These findings confirm the presence in saliva of inhibitory activity directed toward HIV.

The B1-immunoreactive proteins of type in cells of the perinatal rat submandibular gland are immunologically cross-reactive with proteins of both the sublingual and parotid glands; in particular, protein SMG-A appears similar to a major parotid protein. We isolated SMG-A and the parotid protein (known as M1 or leucine-rich protein), prepared polyclonal antibodies to them, and compared their biochemical properties and immunological reactivities. They were identical in their molecular weight on SDS-PAGE (23.5 kDa), tenacious binding to Affi-gel Blue, isoelectric point (pH 4.53), and proteolysis to a 14 kDa peptide: Antibodies to SMG-A showed reactivity with protein SMG-C, a product of the neonatal type I cells, as well as with proteins SMG-B1 and SMG-B2, contrasted with the absence of reactivity of anti-M1 IgG with these proteins. Anti-M1 reacted with the "parotid secretory protein" (PSP) of the mouse, and M1 appears to be the homologue, in the rat, of mouse PSP.

Changes in the rat parotid gland and its secretion, brought about by chronic isoproterenol administration, were studied. In addition to the expected enlargement, morphological and biochemical analyses of the glands showed evidence of changes in the secretory components. Chromatographic and electrophoretic experiments revealed both qualitative and quantitative changes in the secretory proteins.

No abstract

G proteins were identified in rat parotid plasma membrane-enriched fractions and in two populations of isolated secretory granule membrane fractions. Both [32P]ADP-ribosylation analysis with bacterial toxins and immunoblot analysis with crude and affinity-purified antisera specific for alpha subunits of G proteins were utilized. Pertussis toxin catalysed the ADP-ribosylation of a 41 kDa substrate in the plasma membrane fraction and both secretory granule membrane fractions. Cholera toxin catalysed the ADP-ribosylation of two substrates with molecular masses of 44 kDa and 48 kDa in the plasma membrane fraction but not in the secretory granule fractions. However, these substrates were detected in the secretory granule fractions when recombinant ADP-ribosylating factor was present in the assay medium. Immunoblot analysis of rat parotid membrane fractions using both affinity-purified and crude antisera revealed strong immunoreactivity of these membranes with anti-Gs alpha, -Gi alpha 1/alpha 2 and -Gi alpha 3 sera. In contrast Gs alpha was the major substrate found in both of the secretory granule fractions. Granule membrane fractions also reacted moderately with anti-Gi alpha 3 antiserum, and weakly with anti-Gi alpha 1/alpha 2 and -G(o) alpha sera. The results demonstrate that the parotid gland membranes express a number of G proteins. The presence of G proteins in secretory granule membranes suggests that they may play a direct role in regulating exocytosis in exocrine glands.