Prokaryotic Expression And Functional Characterization Of EF Gene From Haemaphysalis Longicornis

Being a special group of arthropods, ticks are obligate ectoparasites of many terrestrial vertebrates. They are important vectors, which could carry a great variety of pathogens and cause many diseases, hence lead to serious damages to human health and livestock production. Ticks have an exceptional reproductive ability. Feeding plays a significant role in the life cycles of ticks, and is closely related to mating. Feeding, mating and their interactions can cause a series of profound physiological changes in ticks. Therefore, studies on feeding of ticks and its relationship with mating became a major topic in the physiological research of ticks. Here, we carried out a study on the characterization HLEFa, an important functional factor of Haemaphysalis longicornis, and investigated its potential value as vaccine, by prokaryotic expression and founctional characterization.We cloned the sequence of HLEFa form the cDNA library of engorged male H. longicornis using specific primers. The length of HLEFa (NCBI:HQ908090) is456bp. The ORF encodes a152-residue peptide, and the deduced mass of peptide is16.7kDa. The fragments were sub-cloned into an expression vector pET-32a, and a recombinational expression vector pET-32a-HLEFa was constructed. Then, the recombinant was expressed in E. coli BL21, and induced by IPTG. The MW of reHLEFa was approximate37kDa, including a carrier protein (-20kDa) and the target protein (-16.7kDa), which is consistent with the expectation. Virgin ticks fed beyond6days were injected with recombinant protein, and the feeding periods, engorgement rate, engorgement weight and ovary development of ticks were observed, and results indicated that, when compared with PBS control, the reHLEFa could stimulate the engorgement of females, and promote the development of ovary. When normal mated famales were put on a rabbit immunized against reHLEFa, a longer feeding period and a lower feeding rate was observed. Although there was no significant changes occurred on the amount of eggs laid, an obvious reduction on the weight of engorged females was observed. In conclusion, the above results suggest that the HLEFa have the potential to be a candidate vaccine, however, further researches should play on its characteristics and its preparation.