Candidiasis: New Peptide Derived From Protein in Saliva May Be Promising Antifungal Agent

Oral biologists at the University at Buffalo have developed a peptide that appears to be a good candidate for treating candidiasis, a fungal condition that affects HIV patients and other people with compromised immune systems. "We wanted to develop an antifungal agent that would have fewer side effects than current treatments," said Libuse Bobek, Ph.D., professor of oral biology in the University at Buffalo School of Dental Medicine and senior author of the study. "We found that a peptide called MUC7 12-mer-D, a small piece of the parent human salivary protein mucin, killed 92 percent of the fungal agent Candida albicans in saliva in vitro," she said. The researchers presented their findings at the International Association of Dental Research meeting in Hawaii.

Peptides are susceptible to enzyme degradation in saliva, which renders them inactive or less active, but that is not the case with MUC7 12-mer-D, according to Bobek. "This peptide, in which D-amino acid derivatives are substituted for natural L-amino acids (producing a mirror image of the original), is not recognized and thus not broken down by protein-degrading enzymes in saliva," she said.

Bobek tested the peptide's activity in saliva and salt solutions containing C. albicans, and compared its fungicidal activity with MUC 12-mer, natural L form, the normal configuration of the peptide, which is active against C. albicans, but susceptible to enzyme degradation.

Results showed that in saliva at 100 micromolar concentration, the D peptide killed 95 percent of the organisms, while the L peptide killed only 56 percent. In the salt solution, at much lower concentration (25 micromolar), the D peptide killed 85 percent of the fungal agent, while the L form killed less than 20 percent. The D peptide was much less toxic than current treatments. Bobek noted that even at the relatively high concentration of 100 micromolar, the D peptide showed little red-blood-cell destruction, a standard toxicity measure. Next, Bobek will test the peptide in a mouse model of oral candidiasis.