INHIBITION OF HERPES-SIMPLEX VIRUS TYPE-1, RESPIRATORY SYNCYTIAL VIRUS AND ECHOVIRUS TYPE-11 BY PEROXIDASE-GENERATED HYPOTHIOCYANITE

The human mouth is an important route of viral transmission and eviden ce exists that human saliva can neutralize some viruses, e.g. herpes s implex type 1 (HSV-1) and human immunodeficiency virus (HIV) in vitro. However, little is known of the actual antiviral agents in saliva. We have analyzed how hypothiocyanite (HOSCN/(OSCN)-O--) ions, present in human saliva and generated by salivary peroxidase systems, affect the viability of three different types of viruses: HSV-1 (capable of indu cing oral lesions), respiratory syncytial virus (RSV, respiratory infe ctions), and echovirus 11 (EV 11, enteric diseases). Viral suspensions were pretreated (30 min)with HOSCN/(OSCN)-O-- concentrations up to 18 0 mu M both at pH 6.0 and 7.1 and inoculated into human gingival fibro blasts. The cultures were incubated at 37 degrees C for 18-48 h, fixed and the infected cells were counted after immunoperoxidase staining. HSV-1 was most sensitive to HOSCN/(OSCN)-O-- with an IC50 of 8.5 mu M at pH 6.0 and an IC50 of 20 mu M at pH 7.1, respectively. RSV was inhi bited by HOSCN/(OSCN)-O-- only at pH 6.0 with an IC50 of 8.0 mu M. EV 11 was also resistant at neutral pH, but sensitive at pH 6.0 with an I C50 of 68 mu M. In Contrast to HSV-1 and RSV, the inhibition of EV 11 was not dependent on the concentration of HOSCN/(OSCN)-O--. The inhibi tion was in all cases stronger at pH 6.0 than at neutral pH. Our resul ts suggest that hypothiocyanite, a normal component of human whole sal iva, in physiological concentrations effectively inhibits HSV-1 and RS V at acidic pH, whereas EV 11 is more resistant in vitro.