Antimicrobial peptides are major components of host innate immunity, a well-conserved, evolutionarily ancient defensive mechanism. Infectious disease-bearing vector ticks are thought to possess specific evolutionarily acquired molecules that provide a defense against the pathogens they transmit. We found a parasiticidal peptide in the tick Haemaphysalis longicornis that may have evolved from a common ancestral peptide resembling spider and scorpion toxins. H. longicornis is the primary vector for animal Babesia parasites in Japan. This novel protein, longicin, also displayed bactericidal and fungicidal properties that resemble those of defensin homologues from invertebrates and vertebrates. Longicin's babesiacidal effect occurs through specific adherence to the parasite membrane, as demonstrated in vitro and in vivo. Moreover, RNA interference data demonstrate that endogenous longicin is able to directly kill Babesia, thus, it may play a role in regulating the vectorial capacity in the vector tick H. longicornis. Theoretically, longicin may serve as a model for development of chemotherapeutic compounds against tick-born disease organisms.
(Research Team for Zoonosis, TEL +81-29-838-7708)
Reference:
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- Tsuji N. et al. (2007) Infect. Immune. 75 : 3633-3640.
