Salivary defense factors in herpes simplex virus infection.

Saliva may contribute to a lowering of the infectious herpes simplex virus (HSV) dose during transmission and consequently abrogate infection or lead to decreased reactivation. To test this hypothesis, we assayed saliva for innate defense factors, immunoglobulin content, and the capacity to interfere with HSV infection. Serum or salivary anti-HSV IgG levels did not correlate with control of recurrent labial herpes (RLH) and were significantly higher in subjects with RLH compared with asymptomatic seropositive subjects. Although no differences in levels or output rate of innate defense factors between the groups were observed, the salivary neutralizing activity correlated with lactoferrin and hypothiocyanite concentrations in the asymptomatic seropositive group. Our results suggest that saliva contains factors, in addition to anti-HSV immunoglobulins, that neutralize HSV and may indirectly contribute to the control of RLH.

Cystatin and cystatin-derived peptides have antibacterial activity against the pathogen Porphyromonas gingivalis.

We investigated whether cystatins and cystatin-derived peptides, encompassing sequences of secondary structures of cystatin S and papain binding domains of cystatin C, display antimicrobial properties. Of the different microorganisms tested, only the growth of P. gingivalis was inhibited by chicken cystatin and cystatin C. Cystatin S, cystatin S:1-14, cystatin S:61-73 and cystatin S:108-121 also inhibited its growth, whereas cystatin S:21-38, cystatin S:39-55, cystatin S:81-95, cystatin S:94-109, and cystatin C: 9-12/55-60/106-107 did not. No inhibition of the cysteine proteinase activity of P. gingivalis was observed for all cystatin-derived peptides. On the other hand, leupeptin and antipain inhibited P. gingivalis proteinase activity, but had no effect on the growth. These data suggest that cystatins contain antibacterial sequences active against P. gingivalis and that the growth inhibition does not depend on the inhibition of P. gingivalis cysteine proteinases.

Cystatin A in gingival crevicular fluid of periodontal patients.

Cystatins are physiological inhibitors of cysteine proteinases which are widely distributed in human tissues and fluids. In the present study we analysed both the cystatin activity and the different cystatin isoforms in gingival crevicular fluid and saliva samples of nine periodontitis patients. All crevicular fluid samples, which were collected with filter paper points, showed cystatin activity ranging from 7-67 units/mg protein. The mean cystatin activity (24 units/mg protein) was significantly lower (p < 0.05) than that of the saliva samples (mean 93 units/mg protein). The cystatin isoforms in the crevicular fluid were further characterized by immunoblotting with specific antibodies against cystatin C, S, SN and A. While they were clearly present in saliva, cystatin C, cystatin S and cystatin SN could not be detected in any of the crevicular fluid samples. Remarkably, cystatin A was found in all the crevicular fluids as well as in the saliva samples. It is concluded that the cystatin activity found in crevicular fluid is caused, at least partially, by cystatin A. Furthermore, the gingival crevicular fluid is not a major contributor of cystatin C, S and SN activity in saliva.

The salivary lipocalin von Ebner's gland protein is a cysteine proteinase inhibitor.

The lipocalins make up a heterogeneous superfamily of proteins. Although showing almost no sequence homology, they share very similar secondary and tertiary structures. Their ability to bind hydrophobic ligands is well established, but the physiological function of most lipocalins remains unclear. The lipocalin from the human Von Ebner's Gland of the tongue (VEGh) contains three sequence motifs corresponding with the papain-binding domains of cystatins, a family of naturally occurring cysteine proteinase inhibitors. We found that VEGh inhibited papain activity to a similar extent as salivary cystatin S. Furthermore, synthetic peptides derived from VEGh and cystatin C, comprising these three motifs, inhibited papain, too. We conclude that VEGh is a physiological inhibitor of cysteine proteinases and therefore can play a role in the control of inflammatory processes in oral and ocular tissues.

Inhibition of the growth and cysteine proteinase activity of Porphyromonas gingivalis by human salivary cystatin S and chicken cystatin.

The mutual effects of P. gingivalis and several cystatin species has been investigated. After incubation with P. gingivalis culture supernatant, cystatin S, cystatin C and chicken cystatin were truncated from a 14 kDa protein into a polypeptide of approximately 13 kDa. Amino acid sequence analysis of the truncated cystatin S polypeptide revealed that cystatin S was cleaved after Arg-8. All three types of truncated cystatins fully retained their inhibitory activity toward papain. Cystatin S and chicken cystatin partially inhibited proteolytic activity in the culture supernatant of P. gingivalis. Furthermore, cystatin S and chicken cystatin inhibited the growth of P. gingivalis in culture to 50% at approximately 1 microM.