This review summarizes the data on the anti-human immunodeficiency virus (HIV) activity associated with saliva and the possible routes of oral transmission of HIV. Saliva can be passed from an HIV-infected individual to an uninfected person via sexual or non-sexual activities. The relative risk of HIV transmission through saliva is a subject of continuing concern for dental practitioners. HIV-infected individuals frequently have oral lesions that can cause bleeding and release of the virus into the oral cavity. In addition, viral p24 and HIV-1 RNA were detected in tonsils and adenoids even in asymptomatic seropositive individuals. Nevertheless, the potential HIV-infectivity of saliva is low, although both infectious HIV-1 and HIV DNA have been detected in saliva. This observation has led to the suggestion that saliva may contain factors that inhibit HIV-1 infectivity. At least two anti-HIV activities have been partially characterized: (i) physical entrapment of HIV by high-molecular-weight molecules (e.g., mucins), and (ii) inhibition of viral infection by soluble proteins. Several studies have indicated that, of the salivary proteins evaluated, recombinant secretory leukocyte protease inhibitor (rSLPI) could inhibit HIV-1 infection in macrophages at physiological concentrations. The anti-HIV activity of the serine protease inhibitor rSLPI is most likely due to its interaction with a cell-surface molecule(s) other than the primary HIV-1 receptor, CD4, and may involve (i) inhibition of cell-surface serine protease(s), and/or (ii) interaction with other human-specific co-factors essential for viral entry.

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The binding of the trisaccharide, N,N',N'-triacet ylchitotriose, to Urtica dioica agglutinin (UDA) was investigated using ~H NMR spectroscopy. UDA is a small antiviral plant lectin containing two homologous 43-amino acid domains. Carbohydrate-induced perturbations occur in one domain of UDA at l risaccharide concentrations below equimolar. Residues in the • .econd domain are shifted at higher carbohydrate concentrations. Fhis data confirms the presence of two binding sites of nonidentical affinities per UDA monomer. Qualitative analysis of the 2D NOESY spectra indicates that UDA contains two short ~tretches of antiparallel/3-sheet. The ~H resonance assignments 10r both antiparallel/3-sheet sequences have been completed and there is one /]-stretch per domain. A number of these t-sheet residues are perturbed in the presence of carbohydrate. [4]. This antiviral effect is inked to its ability to recognize and bind a specific type of :arbohydrate. The present study was designed to characterize he UDA carbohydrate binding sites.Nuclear magnetic resonance (NMR) techniques were used to :xamine the complex between UDA and N,N',N"-triacetylchiotriose. Previous studies concluded that this trisaccharide is :omplementary to the binding site [5]. Because of the small size 89 amino acids) and monomeric nature of UDA, NMR has )rovided an excellent method for studying carbohydrate-intuced perturbations of specific lectin residues. Trisaccharidenduced shifts occur selectively for one set of UDA resonances a concentrations below equimolar and for a second group of • esonances at higher concentrations. These results are consisent with the presence of two binding sites of non-identical lffinities per monomer of UDA. The titration data were used o estimate the binding affinities at each site. A number of the ,'esonances perturbed in the presence of trisaccharide have been ;equentially assigned. We find that most of these perturbed "Corresponding author. Fax: (1) (415) 929 6654. 4bbreviations. UDA, Urtica dioica agglutinin; GlcNAc, N-acetylglu-,:osamine. residues reside in one of the two short stretches of antiparallel t-sheet located in UDA. Materials and methodsUDA was isolated and purified as described previously [6]. A single isolectin of UDA was obtained from reverse phase HPLC using a Vydac C-18 column (Hesperia, CA) and a 45 min linear gradient of 3.(~36% acetonitrile in 0.1% trifluoroacetic acid.The NMR samples were prepared by dissolving lyophilized lectin in either 90% H20/10% D20 or 99.996% D20. The samples prepared in D20 were lyophilized several times from 99.96% D20 prior to the final preparation. In order to maximize solubility, the pH was adjusted to 3.3 3.5 by adding small amounts of DC1. Initial studies monitoring the T~ relaxation of UDA at 35°C as a function of concentration indicated some aggregation of the protein at concentrations above 3 mM. Therefore, protein samples containing 3 mM UDA were used for the twodimensional studies.The NMR experiments were carried out either on the GN-500 or Omega 500 MHz...

Secretory leukocyte protease inhibitor (SLPI) has been proposed as a potential inhibitor of HIV-1 infection in human saliva. Although the ability of recombinant (r) SLPI to inhibit HIV-1 infection of macrophages and primary T-cells has been demonstrated by two independent laboratories, evidence to the contrary has also been reported. This study re-examines the anti-HIV effect of rSLPI and investigates the effects of repeated freeze-thawing and oxidation on the anti-HIV activity of rSLPI. rSLPI inhibited HIV-1BaL infection of human macrophages in a highly variable manner. HPLC and electrospray ionization mass spectrometry (ESI) analyses indicated that variability in our inhibition data could not be attributed to the degradation or oxidation of rSLPI. These results suggest that the variable anti-HIV effect of rSLPI may be due to differential expression of the cell-surface molecule(s) to which SLPI binds rather than to changes in the rSLPI molecule.

Lysyl-5-fluoro-L-tryptophyllysine and lysyl-5-fluoro-D-tryptophyllysine were synthesized, and their interactions with double-stranded DNA were investigated as a model for protein-nucleic acid interactions. The binding to DNA was studied by monitoring various 19F NMR parameters, the fluorescence, and the optical absorbance in thermal denaturation. The 19F resonance of the L-Trp peptide shifts upfield in the presence of DNA, and that of the D-Trp peptide shifts downfield with DNA present. The influence of ionic strength on the binding of each peptide to DNA and the fluorescence quenching titration of each with DNA indicate that electrostatic bonding (approximately 2 per peptide-DNA complex) dominates the binding in each case and accounts for the similar binding constants determined from the fluorescence quenching, i.e., 7.7 X 10(4) M-1 for the L-Trp complex and 6.2 X 10(-1) for the D-Trp complex. The 19F NMR chemical shift, line width, 19F[1H] nuclear Overhauser effect, and spin-lattice relaxation time (T1) changes all indicate that the aromatic moiety of the L-Trp complex, but not that of the D-Trp complex, is stacked between the bases of DNA. The relative increases in DNA melting temperature caused by binding of the tripeptide diastereomers are also consistent with stacking in the case of the L-Trp peptide. The magnitude of the changes and the susceptibility of the 19F NMR chemical shift to altering the solvent isotope (H2O vs. D2O) suggest that the L-Trp ring is not intercalated in the classical sense but is partially inserted between the bases of one strand of the double helix.