cDNA cloning, characterization and vaccine effect analysis of Haemaphysalis longicornis tick saliva proteins

Immunological control of ticks is currently the only sustainable and practi cal alternative method to the current use of acaricides which has serious l imitations. The success of this method is dependent upon identification and cloning of potential tick vaccine antigens. We used a combination of immun o-screening of an adult tick cDNA library as well as the 3 and 5 rapid ampl ification of cDNA ends to clone two cDNAs, encoding tick saliva proteins fr om Haemaphysicalis longicornis. The two cDNAs herein named HL 34 and 35 are 1000 by each and encode polypeptides with 292 and 321 amino acid residues respectively. Northern blotting analysis of total RNA from ticks at differe nt feeding stages revealed that expression of both HL 34 and HL35 mRNAs is induced during the slow feeding phase. We speculate that the functions of b oth genes are closely associated with blood feeding. Expression analysis by RT-PCR showed that both genes are expressed in other tick organs in additi on to salivary glands. Recombinant HL 34 was successfully expressed in Esch erichia coli and its suitability as a tick vaccine antigen was analyzed in rabbits. We propose that rHL34 could be a useful component of a cocktail ti ck vaccine. (C) 2001 Elsevier Science Ltd. All rights reserved.