RESUMO
Enterotoxigenic Escherichia coli (ETEC) causes severe diarrhea in piglets. The current primary approach for ETEC prevention and control relies on antibiotics, as few effective vaccines are available. Consequently, an urgent clinical demand exists for developing an effective vaccine to combat this disease. Here, we utilized food-grade Lactococcus lactis NZ3900 and expression plasmid pNZ8149 as live vectors, together with the secreted expression peptide Usp45 and the cell wall non-covalent linking motif LysM, to effectively present the mutant LTA subunit, the LTB subunit of heat-labile enterotoxin, and the FaeG of F4 pilus on the surface of recombinant lactic acid bacteria (LAB). Combining three recombinant LAB as a live vector oral vaccine, we assessed its efficacy in preventing F4+ ETEC infection. The results demonstrate that oral immunization conferred effective protection against F4+ ETEC infection in mice and piglets lacking maternal antibodies during weaning. Sow immunization during late pregnancy generated significantly elevated antibodies in colostrum, which protected piglets against F4+ ETEC infection during lactation. Moreover, booster immunization on piglets during lactation significantly enhanced their resistance to F4+ ETEC infection during the weaning stage. This study highlights the efficacy of an oral LAB vaccine in preventing F4+ ETEC infection in piglets by combining the sow immunization and booster immunization of piglets, providing a promising vaccination strategy for future prevention and control of ETEC-induced diarrhea in piglets.
RESUMO
Salmonella is an important zoonotic pathogen that not only endangers food safety and human health, but also causes considerable economic losses to the poultry industry. Therefore, it is essential to establish a rapid, sensitive, and specific diagnostic method for the early detection of Salmonella infection in poultry. In this study, we developed a novel enzyme-linked immunosorbent assay (ELISA) for the detection of anti-Salmonella antibodies using a recombinant SifA protein. Amino acid sequence comparison revealed that SifA is a relatively conserved secretory protein across Salmonella serotypes. Therefore, we hypothesized that SifA can serve as a detection antigen for diagnostic testing. The SifA protein was expressed in Escherichia coli and used as a coating antigen to establish an SifA-ELISA. Control sera from specific-pathogen-free (SPF) chickens infected with Salmonella or several other non-Salmonella pathogens were then tested using the SifA-ELISA. Specificity testing demonstrated that the SifA-ELISA could detect antibodies against 3 different serotypes of Salmonella, whereas antibodies against other non-Salmonella pathogens could not be detected. Compared to the SifA-ELISA, the Salmonella plate agglutination test (PAT) failed to detect antibodies in serum samples from chickens infected with Salmonella Typhimurium. This result suggests that our SifA-ELISA may be better than PAT at detecting Salmonella infection. Comparing clinical sera, we observed a similar rate of Salmonella positivity between SifA-ELISA and PAT (92.6%). In addition, anti-SifA antibodies were continuously detected during Salmonella infection of SPF chickens, demonstrating that SifA-ELISA could consistently detect high levels of antibodies for at least 8 wk. Furthermore, the intra-assay and interassay coefficients of variation (CV) of the SifA-ELISA were below 10%, which is considered acceptable. In summary, the SifA-ELISA established here is a promising and reliable method for detection of anti-Salmonella antibodies in poultry and may contribute to the early diagnosis of Salmonella infection.