TSGP4 from Ornithodoros moubata: molecular cloning, phylogenetic analysis and vaccine efficacy of a new member of the lipocalin clade of cysteinyl leukotriene scavengers

•Novel O. moubata TSGP4 salivary lipocalin was cloned and characterized.•OmTSGP4 belongs to the clade of cysteinyl leukotrienes scavenger in soft ticks.•Native OmTSGP4 is not immunogenic by natural tick-host contact.•Vaccination with recombinant OmTSGP4 induces strong responses but low protection.•OmTSGP4 is a salivary silent antigen.

Recently obtained evidence indicated that an orthologue of the O. savignyi TSGP4 salivary lipocalin was present in the saliva of O. moubata. TSGP4 is known to act as a cysteinyl leukotrienes scavenger helping in the prevention of inflammation and oedema at the tick bite site. Since this function seems to be crucial for successful tick feeding, the novel O. moubata TSGP4 turned into a potential vaccine target. The purposes of the current work were: (i) to clone and characterize the O. moubata TSGP4 and, (ii) to produce it as recombinant to evaluate its protective efficacy as vaccine antigen. The results of these experiments indicated that the O. moubata TSGP4 shows high sequence and structural identity with the O. savignyi orthologue suggesting identical function in the physiology of the tick-host relationship. The mature native TSGP4 is not immunogenic when it is inoculated to host with tick saliva during feeding, but host vaccination with the recombinant protein TSGP4 in Freund's adjuvants induced strong humoral immune responses that recognized both the recombinant and native TSGP4 and protected the host with a 14.1% efficacy. So, the O. moubata TSGP4 can be considered a silent salivary antigen; however, in the light of the current results, its inclusion in the current repertory of protective antigens to be targeted by anti-tick vaccines could be controversial.

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