Construction of Larval cDNA Expression Library and Immunological Identification of Positive Clones in Tick Haemaphysalis qinghaiensis

A primary cDNA expression library with a titer of 5.0 × 105 PFU mL-1 was constructed from mRNA extracted from larval Haemaphysalis qinghaiensis ticks in order to identify certain genes, which would then be used as candidate molecules for development of effective vaccines to control this parasite. Totally 11 positive clones, which designated as HqL01-11,were obtained by immunoscreening of the library using a polyclonal antibody generated in rabbit with larval tick protein extract. Results of sequence analysis from BLASTN searching revealed that 6 of them had no significant homology with the adult H. qinghaiensis ticks' known genes, 4 of them had no significant homology with all genes deposited in GenBank database. HqLO7, HqLO8, HqLO9, and HqL 11 were deposited to GenBank database, and accession numbers were EF605263,EF605264, EF605265, and EF605266, respectively. Subsequently, HqLO7 and HqLO9 were expressed in vitro and the molecular weights of the corresponding expressed products were 60 and 70 kDa, respectively. Western blot analyses showed that HqLO7 and HqLO9 had immunogenicity. This study laid the foundation for future production of genetically engineered vaccines for the immunological control of H. qinghaiensis.