Human saliva contains a factor that blocks the AIDS virus from infecting cells, indicating the body may have a natural defense against the deadly disease, preliminary studies indicate.

"Fears about kissing, contact with eating implements and so on could be dispelled by this kind of evidence," said Enid Neidle, an assistant director of the Chicago-based American Dental Association, which reported the study in the May issue of its journal.

Isolating and understanding the inhibitory element in saliva may help researchers learn how to naturally prevent the transmission of the virus, said Philip Fox, head of clinical studies at the National Institute of Dental Research and senior investigator in the study.