A peptide was isolated from the hemolymph of ticks, Dermacentor variabilis. Following challenge with Borrelia burgdorferi, the protein was purified, its molecular weight determined by MALDI-TOF and an N-terminal amino acid sequence was obtained. The molecular weight was found to be 4.2 kDa. A BLAST P search showed that the protein had an 83% similarity with the defensin found in a scorpion. Based on these findings, the peptide was identified as a defensin, hereafter named varisin. This is the first defensin from a hard tick (Family Ixodidae). Two defensin isoforms also were reported from the midgut of a soft tick, Ornithodoros moubata by Nakajima et al. (2001). Studies to identify the defensin gene of D. variabilis, its sites of activity and expression in response to microbial challenge are in progress using reverse transcriptase-polymerase chain reaction (RT-PCR), cloning and DNA sequence analysis.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA