Developments of Anti-tick Vaccine and Bio-acaricides Using Recombinant Virus of Tick Bioactive Molecules

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The objective of this research is to develop bioacaricides and /or novel vaccines for tick control that do not pose environmental and health risks associated with chemical residues and can be used as an attractive alternative to chemical pesticides. In order to realize this approach, we must clarify tick bioactive molecules (TBMs) that are responsible for the blood-sucking and innate immunity in ticks and identify as the bioacaricide and/or vaccine candidates, because blood-sucking and innate immunity are important features of the hard ticks essential for survival, reproduction and pathogen transmission. Biochemical and functional analysis of these TBMs may therefore represent interesting target molecules to which novel and environmentally safety tick control could be directed.(1) During the period of this project, we could carry out about 50 novel TBMs the molecular identification and characterization researches on about 50 novel TBMs of the ixodid tick, Haemaphysalis longicornis.(2) We have tested a recombinant baculovirus expressing a chitinase gene from H. longicornis for its efficacy as a tick bioacaricide. A mixture of recombinant virus and chitinase was found to kill ticks faster than pure chitinase and recombinant virus alone.(3) We have examined the vaccine efficacy of two recombinant cement-like proteins, hlim2 and hlim3 against mice. The complementary effects of hlim2 on tick engorged body weight and hlim3 on tick attachment indicate the suitability of the 2 recombinant proteins for use in a cocktail vaccine.(4) We have immunized rabbits with a glycine-rich protein, RH50, from the tick Rhipicephalus haemaphysaloides and evaluated its vaccine potential against tick feeding. The results showed that the RH50 protein could be useful candidate for anti-tick vaccine because the low attachment rate both in the adult and nymphal ticks, and the high mortality of nymphal ticks feeding on recombinant RH50 immunized rabbits were found.