Abstract
BackgroundRhipicephalus appendiculatus is the primary vector of Theileria parva, the etiological agent of East Coast fever (ECF), a devastating disease of cattle in sub-Saharan Africa. We hypothesized that a vaccine targeting tick proteins that are involved in attachment and feeding might affect feeding success and possibly reduce tick-borne transmission of T. parva. Here we report the evaluation of a multivalent vaccine cocktail of tick antigens for their ability to reduce R. appendiculatus feeding success and possibly reduce tick-transmission of T. parva in a natural host-tick-parasite challenge model.MethodsCattle were inoculated with a multivalent antigen cocktail containing recombinant tick protective antigen subolesin as well as two additional R. appendiculatus saliva antigens: the cement protein TRP64, and three different histamine binding proteins. The cocktail also contained the T. parva sporozoite antigen p67C. The effect of vaccination on the feeding success of nymphal and adult R. appendiculatus ticks was evaluated together with the effect on transmission of T. parva using a tick challenge model.ResultsTo our knowledge, this is the first evaluation of the anti-tick effects of these antigens in the natural host-tick-parasite combination. In spite of evidence of strong immune responses to all of the antigens in the cocktail, vaccination with this combination of tick and parasite antigens did not appear to effect tick feeding success or reduce transmission of T. parva.ConclusionThe results of this study highlight the importance of early evaluation of anti-tick vaccine candidates in biologically relevant challenge systems using the natural tick-host-parasite combination.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1774-0) contains supplementary material, which is available to authorized users.
Highlights
Rhipicephalus appendiculatus is the primary vector of Theileria parva, the etiological agent of East Coast fever (ECF), a devastating disease of cattle in sub-Saharan Africa
Interference with saliva components that inhibit itch and inflammation and aid attachment may make the feeding ticks more subject to being groomed off. Either of these mechanisms may result in tick mortality, reduction in tick feeding success and/or reduced reproductive capacity, which may in turn reduce transmission of tick-borne disease [6,7,8,9]
High antibody titres were generated against subolesin but lower titres were observed against p67 C-terminal (p67C) with average endpoint titres of only 1:8,500
Summary
Rhipicephalus appendiculatus is the primary vector of Theileria parva, the etiological agent of East Coast fever (ECF), a devastating disease of cattle in sub-Saharan Africa. Repeated host exposure to tick feeding has been shown to result in the development of resistance against future infestations, most likely through development of an adaptive immune response targeting the saliva proteins [1,2,3,4,5] This natural ability to develop resistance to ticks forms the conceptual basis for development of vaccines targeting tick feeding. Interference with saliva components that inhibit itch and inflammation and aid attachment may make the feeding ticks more subject to being groomed off Either of these mechanisms may result in tick mortality, reduction in tick feeding success and/or reduced reproductive capacity, which may in turn reduce transmission of tick-borne disease [6,7,8,9]
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