Specific histamine binding activity of a new lipocalin from Hyalomma asiaticum (Ixodidae) and therapeutic effects on allergic asthma in mice

Background: lipocalin proteins are secreted by tick salivary glands as an important strategy to interfere with the immune response of hosts. a large number of lipocalins are secreted,but the functions of most of these proteins are unclear. here,we report a new lipocalin protein with particular histamine binding capacity,which was isolated from the salivary glands of the tick hyalomma asiaticum. methods: the full length cdna of the ha24 gene was obtained by race,and ha24 gene was expressed in e. coli; after protein purification and mice immunizations,specific polyclonal antibodies (pcab) were created in response to the recombinant protein. reverse transcription pcr (rt-pcr),quantitative pcr (q-pcr),indirect immunofluorescence antibody (ifa) assay and western blot were used to detect the existence of native ha24 in ticks. to confirm the histamine-binding capacity of rha24,a histamine-binding assay was completed in vitro (elisa) and in vivo by inhibition of allergic asthma in mice. results: ha24 is coded by 681 bases,contains 227 amino acids,and has a molecular weight of 23.3 kda. abundant expression in the salivary glands of feeding ticks was confirmed by the identification of native ha24 in ticks. the results of a histamine binding assay both in vitro and in vivo demonstrated that rha24 binds specifically with histamine in a dose-dependent manner,and can provide relief from allergic asthma in mice. conclusions: ha24 is a new tick lipocalin with specific histamine binding activity that can provide relief from host inflammation response. © 2016 the author(s).