Veterinary Science & Technology

Antimicrobial peptides are major components of host innate immunity, a well-conserved evolutionarily ancient defensive mechanism. Infectious disease-bearing vector ticks are thought to have evolved to produce specific defense peptides implicated in controlling the infection and transmission of various pathogens. Longicin, a defensin peptide identified from the hard tick, Haemaphysalis longicornis , is known to have a significant deadly effect against both Gram-negative and Gram-positive bacteria and other microorganisms. In this study, female H. longicornis ticks were experimentally injected with Toxoplasma gondii tachyzoite parasites, and the transcription profiles of longicin in ticks demonstrating the amplification of T. gondii B-1 gene fragments were examined to determine whether and how ticks may respond immunologically in controlling T. gondii infections. As a result, 10 days after parasite injection, ticks indicated the upregulation of the longicin gene, consistently with the presence of T. gondii . The effects of recombinant longicin on the morphology of T. gondii tachyzoites were also examined in vitro . Tachyzoite parasites incubated with recombinant longicin induced pathological changes in cell morphology followed by a marked reduction in the number of parasites. These findings suggested that recombinant longicin could impair parasite membranes, leading to the destruction of Toxoplasma parasites.