Researchers at Cleveland's Case Western Reserve University and the Cleveland Clinic have discovered a way cells in the mouth may resist HIV infection. Reporting in the October 28 edition of the journal AIDS, the researchers wrote that because the lining of the mouth is constantly under attack by a barrage of bacteria and other pathogens, it has developed a defensive lining made up of peptides called human beta defensins 2 and 3 (hBD2 and hBD3) that prevent infection. These combinations of amino acids bind to and disable invading pathogens as well as promote rapid healing from food abrasions or accidental bites to the tongue and mouth. The research, which was prompted by the fact that so few people contract HIV through unprotected oral sex, suggests that the small peptides produced by cells lining the oral cavity bind to the viral particles directly and can even regulate important receptors the virus uses to infect human cells.
While human beta defensins, particularly hBD1, are found throughout the body's skin and epithelial cells, it was hBD2 and hBD3 in the normal lining of the mouth that responded directly to HIV. In the presence of the virus, the peptides even appear to be expressed in greater numbers on the surface of cells in the mouth. The researchers found in lab experiments that cellular hBD2 expression increased by almost 80-fold when HIV was introduced to the cells and that the heightened appearance of the defensive peptide remained for longer than 72 hours, far past the time any pathogen could survive in the mouth.
Information gained from the study, according to lead researcher Aaron Weinberg, director of research at the CWRU School of Dentistry, has the potential to be used as the foundation for new medical interventions to induce hBD2 and 3 expression in other sites of the body more susceptible to HIV infection. These products also could be used with medical instruments to prevent accidental infections in health care settings.