Protective efficacy of a single-domain ASP-based vaccine against the bovine intestinal nematode Cooperia oncophora

Gastrointestinal nematode infections are a common burden in farm animals. As the prevalence of anthelmintic resistance is rising, vaccination is considered a promising alternative for preventive anthelmintic treatments. In search of a vaccine candidate against the bovine small-intestinal helminth Cooperia oncophora, a mid-molecular weight protein fraction (MMW) was isolated from C. oncophora excretory-secretory (ES) material and was protective in a vaccination-infection model. Consequently, the most abundant MMW protein, i.e. a single domain activation-associated secreted protein (Co-sdASP), was purified and evaluated in two vaccine trials, first in a three-dose (initial dose + two repeats) and subsequently in a two-dose (initial dose + one repeat) regimen. The three-dose regimen with native Co-sdASP resulted in 86% reduction in parasite egg output and 63% reduction in worm burden following challenge infection, while the two-dose regimen reduced egg output by 64% but did not significantly affect worm burden. Analyses of immune responses in both vaccination regimens showed that CD4 + T cells and B cells of vaccinated animals exhibited significantly higher proliferation in response to ex vivo restimulation with vaccine antigen, compared to cells from the control groups. In conclusion, Co-sdASP is a promising antigen for vaccinating cattle against C. oncophora infections.