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Objective: 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., Methods: 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., Results: 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., Conclusion: 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.

Objective: To explore the improved immunological responses induced by an amino acid ABC transporter, permease protein PEB1 DNA vaccine primer-protein boost immunization method against Campylobacter jejuni., Methods: The DNA vaccine pcDNA3.1(-)-PEB1 and protein vaccine were prepared, respectively. The female BALB/c mice were intranasally immunized with the vaccines. PBS and pcDNA3.1(-) were used as controls. The humoral and cellular immunological responses were detected in female BALB/c mice that were challenged by Campylobacter jejuni at 28 days after the final immunization., Results: In the DNA primer-protein boost group at day 56, the stimulation index (SI) of lymphocytes was 2.625±0.275, serum IgG was (2.507±0.124) μg/mL, IL-4 in spleen supernatant was (377.47±14.560) pg/mL, IFN-γ in spleen supernatant was (258.920±13.472) pg/mL, and sIgA in genital tract was (80.351±5.769) ng/mL. All of them were significantly higher than those in controls (P<0.05). The DNA primer-protein boost vaccines induced the strongest levels of protection to BALB/c mice (91.53%)., Conclusion: The DNA primer-protein boost immunization could induce significant protective immunity against Campylobacter jejuni challenge. It could significantly enhance both humoral and cellular immunologic responses in BALB/c mice, compared with DNA vaccine or protein vaccine immunization alone.

Objective: According to risk assessment results of the Campylobacter jejuni in chicken of Chinese residents' dietary, from the point of the standard management, establish the feasible measures to reduce the risk., Methods: Half-quantity risk assessment of Risk Ranger was used., Results: Campylobacter jejuni usually could not reproduce in the processing environment or in the processed products of chicken. Currently, the risk of the likelihood that the urban people of our country have Campylobacter jejuni infections due to eating chicken was six times as that of the rural people., Conclusion: There is no need to set a limit level for Campylobacter jejuni in the standard of chicken products. Control in the feeding, processing and preparation before eating of chicken are the important measures in reducing the Campylobacter jejuni infections caused by chicken.

Objective: The immunogenicity and protective efficacy of an experimental Campylobacter jejuni (C. jejuni) chitosan-DNA vaccines were evaluated in mice., Methods: The chitosan-DNA vaccines were prepared by embedding pcDNA3.1(+)-cadF and pcDNA3.1(+)-peblA with chitosan respectively. BALB/c mice were intranasally immunized in a four-dose primary series (7 d intervals) at doses of 60 microg chitosan-DNA vaccines each time. The comparative immunogenicities of nine formulations were assessed on the basis of the generation of antigen-specific antibodies in serum and intestinal secretions. Mice were attacked repeatedly through intragastric administration of C. jejuni HS:19 at the 8th week after the immunization and protective efficacy was determined by detecting the degrees of protection afforded against C. jejuni invaded., Results: The mice immunized with chitosan-DNA vaccines have generated high levels of IgA and IgG from the sera and IgA from the intestinal secretions and the P/N value went up to 20.58, 30.13 and 6.87 respectively. Meanwhile, the expression of intestinal SIgA increased correspondingly. Moreover the chitosan-DNA vaccines induced strongest level of protection in BALB/c mice against challenge with C. jejuni HS:19 strain and the protective efficacies was 93.70., Conclusion: The results of this study indicate that the chitosan-DNA vaccines could induce significant protective immunity against C. jejuni challenge in the mice model.