Abstract
Coccidiosis is a parasitic disease in the intestine caused by the genus Eimeria that poses a substantial economic threat to the broiler breeding industry. The misuse of chemoprophylaxis and live oocyst vaccines has a negative impact on chicken reproductivity. Therefore, there is a pressing need to develop safe, convenient, and effective vaccines. Lactic acid bacteria can be used as a means to deliver mucosal vaccines against intestinal pathogens, which is a promising strategy. In this study, a recombinant Lactobacillus plantarum (L. plantarum) with surface-expressed antigens constructed from the fusion of Eimeria tenella (E. tenella) antigen profilin and the Salmonella enterica serovar Typhimurium flagellin protein FliC was created. After oral immunization with the recombinant L. plantarum, T-cell differentiation was analyzed by flow cytometry, and specific antibody levels were determined via indirect ELISA. Oocyst shedding, body weight, and cecum lesions were assessed as measures of protective immunity after challenge with E. tenella. The results of this study demonstrate the effectiveness of recombinant L. plantarum as an immunization agent for chickens. Specific IgA titers in the intestine and specific IgG antibody titers in the serum were significantly higher in chickens immunized with recombinant L. plantarum (P < 0.001). Additionally, the levels of IL-2 (P < 0.05) and IFN-γ (P < 0.01) in the serum were markedly increased. Recombinant L. plantarum induced T-cell differentiation, resulting in a higher proportion of CD4+ and CD8+ T cells in splenocytes (P < 0.001). Fecal oocyst shedding in the immunized group was significantly reduced (P < 0.001). Additionally, recombinant L. plantarum significantly relieved pathological damage in the cecum, as evidenced by lesion scores (P < 0.01) and histopathological cecum sections. In conclusion, the present study provides evidence to support the possibility of using L. plantarum as a promising carrier for the delivery of protective antigens to effectively protect chickens against coccidiosis.