Faculty Bibliography

An oral fluid-based test for antibodies to human immunodeficiency virus (HIV), equivalent to serum in its accuracy but safer and easier to use, is now available in the United States. The development of the oral test involved overcoming technical obstacles to the use of oral fluid as a testing medium, including low immunoglobulin G (IgG) titers, suboptimal assay performance, protease degradation of IgG, high viscosity, and lack of a standardized method of specimen collection, all of which contribute to suboptimal assay performance. The currently available oral HIV test utilizes a collection device to isolate a mucosal transudate component of oral fluid rich in IgG. A vial containing a preservative solution facilitates the transport of stable, low-viscosity specimens to the laboratory for testing with an ELISA and confirmatory Western blot assay, specifically designed for use with oral fluid. Non-HIV medical conditions and oral pathologies do not appear to affect oral test results. Hopefully, the availability of a more patient-friendly, portable diagnostic test for antibodies to HIV will facilitate identification of greater numbers of infected individuals with the ultimate goals of early identification, early treatment, and prevention of disease transmission.

OBJECTIVE: Human saliva is known to decrease HIV infectivity in vitro. The purpose of this study was to extend these findings and to focus on the mechanism of action of these salivary factor(s). DESIGN: A number of viruses and several assay systems have been utilized to determine if the effect of submandibular saliva is directly on the virus, on the host cell, or on the virus-cell interaction. MATERIALS AND METHODS: Submandibular saliva from seronegative donors was incubated with HIV-1, other retroviruses, or unrelated viruses. Viral infectivity was monitored either by determining p24 antigen levels in peripheral blood mononuclear cells or Sup T1 cells, or using HeLa cells expressing CD4 and an HIV derived long terminal repeat linked to the beta-galactosidase gene. RESULTS: The inhibition of viral infectivity by submandibular saliva is specific for HIV-1. While inhibition increases with time of incubation of saliva with virus, pretreatment of cells with saliva does not inhibit HIV production, and saliva has only modest inhibitory effects when added to HIV-infected cells. CONCLUSIONS: It appears that the effect of submandibular saliva on decreasing the infectivity of HIV-1 is directly on the virus, rather than on the host cell

The broad-spectrum anti-microbial agent, C31G, containing an equimolar mixture of n-dodecyl-dimethylamine-N-oxide (C12-N-O) and N-(n-dodecyl), N-dimethyl-glycine (C12-betaine), was tested for spermicidal activity in comparison with the currently used spermicide, nonoxynol-9 (N-9). The rate of sperm cell permeabilization by the spermicides, as assayed with the fluorescent probe, TO-PRO-1, increased as the cube of the C31G concentration, while the rate increase was linear with N-9 concentration. At 0.04%, the rate of sperm cell permeabilization with both spermicides is at the limit of rapid measurement. C31G diffuses through cervical mucus at a more rapid rate than does N-9. C31G has long been known to aid wound healing and reduce inflammation, whereas N-9 has been reported to induce vaginal irritation. C31G would, thus, seem to have the spermicidal efficacy, the broad range of anti-microbial activity, and the lack of inflammatory activity that is sought in the ideal vaginal spermicide.

Interbacterial binding is considered an important colonization mechanism many of the organisms that inhabit dental plaque. Porphyromonas gingivalis, a periodontal pathogen, can adhere to species that comprise early plaque, such as Streptococcus gordonii. In this study, the molecules of S. gordonii G9B that mediate binding to P. gingivalis were investigated. Biotinylated surface molecules of S. gordonii were extracted and mixed with P. gingivalis cells. Interactive streptococcal components were identified by SDS-PAGE of the P. gingivalis cells followed by electroblotting, and visualization of the adsorbed streptococcal molecules with streptavidin-alkaline phosphatase. S. gordonii molecules of 45 kDa and a doublet of 62/60 kDa were observed to bind to P. gingivalis. Polyclonal antibodies raised to the 62/60 kDa proteins inhibited the binding interaction. These antibodies demonstrated an antigenic relationship between the 62/60 kDa molecules and the 45 kDa protein. Both molecules were also antigenically related to, and may be breakdown products of, a larger molecule of 170 kDa which is antigenically related to the P1 antigen of S. mutans. Cloning and expression in Enterococcus faecalis of the gene for the P1-like molecule from S. gordonii M5 resulted in a phenotype that expressed the 62/60 kDa and 45 kDa antigens and was capable of binding to P. gingivalis. These results suggest that a P1-like molecule in S. gordonii is involved in adherence to P. gingivalis. Processing of the P1-like molecule into smaller fragments of 62/60 kDa and 45 kDa may be required for binding activity.

We previously observed that when human immunodeficiency virus (HIV)-infected T lymphocytes are added to epithelial cells, they adhere, polarize, and secrete virions unidirectionally onto the epithelium. Epithelial cells subsequently take up virus and become productively infected. We report here that colchicine treatment of T-lymphocyte suspensions induced lymphocyte polarization, redistribution of F-actin into a pseudopod, and secretion of HIV from the pseudopod. Immobilization of T lymphocytes on negatively charged plastic also caused redistribution of F-actin and unidirectional secretion of HIV onto the plastic. As neither colchicine nor adhesion caused an increase in HIV secretion, they apparently act by focusing secretion to the tip of the pseudopod. We speculate that adhesion-induced polar secretion of HIV, from activated mononuclear cells onto epithelia, is a cytoskeleton-mediated process which may be involved in HIV transmission in vivo.

Streptococcus gordonii M5 expresses a lectin on its surface (SSP-5) which binds to human salivary agglutinin (SAG). This interaction requires sialic acid residues of SAG and divalent cations and may mediate the colonization of oral tissues by this organism. In this report, we show that the binding of SAG to SSP-5 requires calcium and that SSP-5 is a high-affinity calcium-binding protein. SAG-mediated aggregation of S. gordonii M5 was inhibited by 1 mM EDTA, and the restoration of aggregation occurred only upon the readdition of calcium. To ascertain the level at which calcium exerts its effects, the calcium-binding properties of SSP-5 were evaluated by using a 45Ca binding assay. In addition, a kinetic analysis of calcium binding was carried out by using fura2, a fluorescent calcium-binding dye. These analyses showed that SSP-5 is a high-affinity calcium-binding protein that binds 1 mol of calcium per mol of protein and has a dissociation constant of 0.45 +/- 0.2 microM. The calcium-binding capacity of SSP-5 was also calculated independently to be 1.0 +/- 0.2 mol of Ca per mol of SSP-5 by column chromatography on Sephadex G-25 equilibrated with 10 microM 45Ca. To localize the calcium binding site of SSP-5, a series of C-terminal deletion mutants were expressed in Escherichia coli and evaluated for calcium-binding activity. Deletion of the 250 C-terminal residues of SSP-5 had little effect on calcium binding. However, deletion of residues 1168 to 1250 resulted in the loss of calcium-binding activity, suggesting that this region is important for calcium binding by SSP-5.