Identification and Sequence Analysis of Five p36 Immunosuppressant Protein Homologs from Haemaphysalis qinghaiensis

Ticks secrete immunosuppressant proteins that modulate the host's immune system during blood feeding. Five putative genes encoding similar p36 immunosuppressant proteins from other tick species were cloned by sequencing randomly picked plaques from a complementary DNA library constructed from salivary glands of partially engorged Haemaphysalis qinghaiensis. The genes were designated Hq-p36-1, Hq-p36-2, Hq-p36-3, Hq-p36-4, and Hq-p36-5. By doing a Multiple Em for Motif Elicitation (MEME) tool search, 3 potential common motifs, which coincided with 3 conserved regions, were found among the 8 aligned tick p36 homologs. Antigenicity analysis suggested that most of these homologs might be satisfactory antigen candidates, and 2 common antigenic determinants were predicted from each of the 5 proteins, and they overlapped with 2 common motifs. Four out of the 5 Hq-p36 proteins might share a similar 3-dimensional model with an exposed big loop overlapped by the motif MEME-1 and a conserved antigenic region. The finding of the 5 H. qinghaiensis p36 protein homologs could expand our knowledge of tick immunosuppressant proteins and lay ground for future studies to determine their exact role in tick feeding process.