Recombinant HcGAPDH Protein Expressed on Probiotic Spores Protects Sheep from Infection by Inducing both Humoral and Cell-Mediated Responses.

Probiotic are effective in controlling pathogens. Live probiotic bacteria improve the composition of the gastrointestinal microbiota, leading to a reduction in pathogen colonization. However, it remains largely unknown how probiotics regulate the host's immunologic responses and protect the host from parasitic infection. In this study, we addressed whether were effective against , a parasitic nematode that infects small ruminants worldwide. Using 16S rRNA sequencing, we found that were largely depleted in the abomasal microbiota of sheep infected with We constructed a recombinant named rBS that express the glyceraldehyde-3-phosphate dehydrogenase of (HcGAPDH) on its spore surface using the spore coat protein B (CotB) as a carrier. Mice receiving rBS orally showed strong Th1-dominated immune responses. More importantly, sheep administered BS showed increasing proliferation of the peripheral blood mononucleates, elevated anti-HcGAPDH IgG in sera, and higher anti-HcGAPDH sIgA in the intestinal mucus than the control sheep. The average weight gain of -infected sheep treated with rBS (Hc+rBS ) was 48.73% greater than that of unvaccinated sheep. Furthermore, these Hc+rBS sheep had fewer eggs per gram of feces by 84.1% and adult worms by 71.5%. They also demonstrated greatly lessened abomasal damage by with an abundance of probiotic species in the abomasal microbiota. Collectively, our data unequivocally demonstrate the protective roles of CotB-HcGAPDH-expressing spores in against infection and showed great potential of using probiotic-based strategy in controlling parasitic nematodes of socioeconomic importance in general. Initial analyses of the abomasal microbiota of sheep using 16S rRNA sequencing suggested that probiotic bacteria played a protective role in against infection. A recombinant expressing a fusion protein CotB-HcGAPDH on its spore's surface induced strong Th1 immune response in a murine model. The same probiotic recombinant, upon only one oral application, protected sheep against infection by reducing egg shedding and decreasing adult worm loads of the parasite and increasing body weight gain of infected sheep. Both Th1 and Th2 immune responses were evident in these immunized sheep.