HqHBP, a histamine-binding protein derived from the hard tick Haemaphysalis qinghaiensis, alleviates xylene-induced mice skin edema

As one of the most important blood-sucking parasites, ticks can secrete various biological molecules to counteract responses such as hemostasis and inflammation in their host during the blood-feeding process. A cDNA clone named as Hq018 was identified from a salivary gland cDNA expression library of Haemaphysalis qinghaiensis. A protein consisting of 217 amino acids with a molecular mass of 24.4 kDa was encoded by the tick cDNA. Homology analysis using database comparisons revealed that Hq018 protein is a homology of a histamine-binding protein identified in a female Rhipicephalus appendiculatus. Recombinantly produced protein by Hq018 cDNA in Escherichia coli could dose-dependently bind to histamine in an enzyme-linked immunosorbent assay (ELISA)-based histamine-binding test. We designated this H. qinghaiensis orignated histamine-binding protein as HqHBP. HqHBP could significantly inhibit xylene-induced mice ear edema and the accompanied vascular dilation, mucus secretion and increase of mast cells, reduce the amount of histamine and the expression levels of some inflammatory factors in mice skin. These results suggest that HqHBP exhibits potent antihistamine activity. HqHBP might be a good candidate for the development of pharmaceutical products aimed at preventing and treating anaphylactic reactions.