Poly (D, L-lactide-co-glycolide) delivery system improve the protective efficacy of recombinant antigen TA4 against Eimeria tenella infection

Abstract Eimeria tenella is a protozoan parasite endemic in chickens and is one of the causative agents of avian coccidiosis. The aim of this research was to determine if Poly (D, L-lactide-co-glycolide, PLGA) nanoparticles carrying recombinant TA4 protein of Eimeria tenella (rEtTA4) could improve the level of protective immunity against E. tenella challenge. Recombinant TA4 protein was expressed and purified. PLGA loaded with rEtTA4 (PLGA-rEtTA4) nanoparticles was prepared and was delivered to two-week old layer chickens via intramuscular inoculation. Chickens injected with PBS and PLGA nanoparticles were served as control groups. The rEtTA4 and PLGA-rEtTA4 nanoparticles induced changes of serum cytokines, IgY levels, T lymphocytes subpopulation and the protective efficacy against E. tenella challenge were evaluated. Results showed that both rEtTA4 and PLGA-rEtTA4 vaccination groups induced significantly higher levels of specific-EtTA4 IgY antibody, interleukin-17 and higher proportion of CD8+ T lymphocytes. However, no significant differences were observed in the proportion of CD4+ T lymphocytes compared to the PBS control. Chickens immunized with rEtTA4 and PLGA-rEtTA4 prominently increased the body weight gains and decreased oocyst output compared to chickens immunized with PBS and PLGA after oral challenge with Eimeria tenella. PLGA encapsulated rEtTA4 nanoparticles immunized chickens significantly induced higher levels of IFN-γ, IL-6, IL-17 and a little bit higher proportion of CD8+ T lymphocytes compared to rEtTA4 subunit vaccine immunized chickens. Thus, PLGA encapsulated rEtTA4 nanoparticles appeared to have great potential to enhance the immune response and improved the protective efficacy against Eimeria tenella infection. Our results provided available protective subunit vaccine rEtTA4 and PLGA loaded with rEtTA4 nanoparticles against coccidiosis, and suggested that PLGA nanoparticles could be an effective adjuvant to enhance the protective efficacy of rEtTA4 subunit vaccine.