Ndawula et al.
Constituting a glutathione S-transferase-cocktail vaccine against tick infestation
Vaccine 2019, in press, doi.org/10.1016/j.vaccine.2019.02.039

The development of vaccines to reduce tick infestation is one way to reduce the burden of disease in the veterinary field. A potential target for a vaccine with a broad spectrum against ticks includes the glutathione S-transferase (GST). GST comprises a family of enzymes which can catalyze the conjugation of the reduced form of glutathione to endogenous and xenobiotic substrates in order to detoxify them. GST enzymes are ubiquitous in ticks. Brazilian scientists have cloned and expressed in E. coli the GSTs of some tick species of economic interest: Amblyomma variegatum, Rhipicephalus appendiculatus, R. decloratus, R. microplus and Haemaphysalis longicornus. The recombinant GSTs had different immunogenicity and induced antibodies with different cross-reactivity. The authors have tested various cocktails of different GSTs and finally decided for a bivalent combination using the GSTs of A. variegatum and R. decloratus, because this combination showed the broadest cross-reactivity of induced antibodies in rabbits. When rabbits immunized with this bivalent vaccine were infested with R. sanguineus ticks these female ticks fed on vaccinated animals were smaller than those fed on a control group and the number of ticks that finished engorgement was significantly lower (37.3% reduction). In addition, vaccinated animals were more susceptible to lower concentrations of acaricides. These results show that a vaccine cocktail of recombinant tick GSTs may be able to reduce the size of tick population on hosts.

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