A CATIONIC ANTIMICROBIAL PEPTIDE ENHANCES THE INFECTIVITY OF COXIELLA-BURNETII

Purified Coxiella burnetii (Nine Mile, phase I) ricketssiae were expos ed to a synthetic peptide (CAP37(20-44)) based on the amino acid seque nce of CAP37 - a 37 K human neutrophil granule-associated cationic ant imicrobial protein - and their capacity to infect L929 mouse fibroblas t cells was assessed during a 10-day post-exposure period. Because the parasite thrives within the acidic phagolysosome we anticipated that CAP37(20-44) would have no adverse effect on the organism. This was bo rne out by the experiments; however, to our surprise, treated C. burne tii had a much greater capacity to infect L cells than the non-treated counterpart. We speculate that the peptide exhibits opsonin-like prop erties, enhancing attachment of the rickettsia to the host cell surfac e and subsequent entry.