[Immunological modulation of chickens by recombinant Lactococcus lactis expressing ferric enterobactin receptor CfrA...

The purpose of this study is to reduce the colonization level of Campylobacter jejuni in chicken intestine by oral immunization of recombinant Lactococcus lactis expressing the ferric enterobactin receptor CfrA of C. jejuni.

The whole cfrA gene and its N-terminal fragments were amplified by PCR, inserted into the expression vector pNZ8149 and transformed into L. lactis NZ3900. Based on the expression of CfrA in recombinant L. lactis by Western blot, the expression level was optimized by screening nisin concentration, induction temperature and time. Then the recombinant L. lactis strains were used to orally immunize specific-pathogen-free chickens. After oral immunization, the duration of recombinant L. lactis in chickens was determined by PCR, and the antibody levels of anti-CfrA serum IgG and intestinal mucosal sIgA were measured by ELISA. Finally, the immunized chickens were orally inoculated with C. jejuni to evaluate the inhibitory effect of recombinant L. lactis on colonization of C. jejuni.

Western blot results determined that the whole cfrA gene and its N-terminal fragments were both expressed in recombinant L. lactis in soluble forms whereas no secreted CfrA protein was detected outside bacterial cells. The optimal conditions for inducing the expression were grown at 37℃ for 1 h with nisin concentration of 25 ng/mL. Detection of chicken cloacal swabs showed that the duration of oral L. lactis was less than 10 days in chicken. The immunized groups produced higher antibody titers of anti-CfrA specific serum IgG and mucosal sIgA than the control groups. Moreover, the colonization rate of C. jejuni in the immunized groups was significantly lower than that in the control groups.

Oral immunization of chickens with recombinant L. lactis expressing CfrA inhibited the colonization of C. jejuni. Our findings can be useful to develop oral vaccines with recombinant Lactobacillus for control of C. jejuni infection in chickens.