Immunological evaluation of invasiveLactobacillus plantarumco-expressing EtMIC2 and chicken interleukin-18 againstEimeria tenella

Chicken coccidiosis is a protozoan parasitic disease that leads to considerable economic losses in the poultry industry. In this study, we used invasiveLactobacillus plantarum(L.P) expressing the FnBPA protein as a novel bacterial carrier for DNA delivery into epithelial cells to develop a live oral DNA vaccine. A fusion DNA vaccine co-expressing EtMIC2 and chicken IL-18 (chIL-18) was constructed and then delivered to the host by invasiveL.P. Its efficacy againstEimeria tenellachallenge was evaluated in chickens by examining the relative weight gain rate; caecal lesion score; OPG; anti-coccidial index (ACI); levels of EtMIC2 antibody, FnBPA, IL-4, IL-18, IFN-gamma and SIgA; and proliferation ability and percentages of CD4(+)and CD8(+)splenocytes. The experimental results showed that chickens immunized with invasiveL.Pcarrying the eukaryotic expression vector pValac-EtMIC2 (pValac-EtMIC2/pSIP409-FnBPA) had markedly improved immune protection against challenge compared with that of chickens immunized with non-invasiveL.P(pValac-EtMIC2/pSIP409). However, invasiveL.Pco-expressing EtMIC2 with the chIL-18 vector exhibited the highest protection efficiency againstE. tenella. These results indicate that invasiveLactobacillus-expressing FnBPA improved humoural and cellular immunity and enhanced resistance toE. tenella. The DNA vaccine delivered by invasiveLactobacillusprovides a new concept and method for the prevention ofE. tenella.