Recombinant Salmonella gallinarum (S. gallinarum) Vaccine Candidate Expressing Avian Pathogenic Escherichia coli Type I Fimbriae Provides Protections against APEC O78 and O161 Serogroups and S. gallinarum Infection

Peng Dai; Hucong Wu; Guowei Ding; Juan Fan; Yuhe Li; Shoujun Li; Endong Bao; Yajie Li; Xiaolei Gao; Huifang Li; Chunhong Zhu; Guoqiang Zhu

doi:10.3390/vaccines11121778

Recombinant Salmonella gallinarum (S. gallinarum) Vaccine Candidate Expressing Avian Pathogenic Escherichia coli Type I Fimbriae Provides Protections against APEC O78 and O161 Serogroups and S. gallinarum Infection

Vaccines (Basel). 2023 Nov 28;11(12):1778. doi: 10.3390/vaccines11121778.

Authors

Peng Dai^{1

2

3}, Hucong Wu⁴, Guowei Ding³, Juan Fan³, Yuhe Li³, Shoujun Li⁵, Endong Bao⁵, Yajie Li⁵, Xiaolei Gao⁵, Huifang Li⁶, Chunhong Zhu⁶, Guoqiang Zhu^{1

2}

Affiliations

¹ Joint Laboratory of International Cooperation on Prevention and Control Technology of Important Animal Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou University, Yangzhou 225012, China.
² College of Veterinary Medicine, Yangzhou University, Yangzhou 225012, China.
³ Yangzhou Uni-Bio Pharmaceutical Co., Ltd., Yangzhou 225008, China.
⁴ Nei Monggol Animal Disease Control Center, Hohhot 010010, China.
⁵ Tianjin Ringpu Bio-Technology Co., Ltd., Tianjin 300308, China.
⁶ Jiangsu Institute of Poultry Sciences, Yangzhou 225125, China.

Abstract

Avian pathogenic Escherichia coli (APEC) is one of the leading pathogens that cause devastating economic losses to the poultry industry. Type I fimbriae are essential adhesion factors of APEC, which can be targeted and developed as a vaccine candidate against multiple APEC serogroups due to their excellent immunogenicity and high homology. In this study, the recombinant strain SG102 was developed by expressing the APEC type I fimbriae gene cluster (fim) on the cell surface of an avirulent Salmonella gallinarum (S. gallinarum) vector strain using a chromosome-plasmid-balanced lethal system. The expression of APEC type I fimbriae was verified by erythrocyte hemagglutination assays and antigen-antibody agglutination tests. In vitro, the level of the SG102 strain adhering to leghorn male hepatoma (LMH) cells was significantly higher than that of the empty plasmid control strain, SG101. At two weeks after oral immunization, the SG102 strain remained detectable in the livers, spleens, and ceca of SG102-immunized chickens, while the SG101 strain was eliminated in SG101-immunized chickens. At 14 days after the secondary immunization with 5 × 10⁹ CFU of the SG102 strain orally, highly antigen-specific humoral and mucosal immune responses against APEC type I fimbriae protein were detected in SG102-immunized chickens, with IgG and secretory IgA (sIgA) concentrations of 221.50 μg/mL and 1.68 μg/mL, respectively. The survival rates of SG102-immunized chickens were 65% (13/20) and 60% (12/20) after challenge with 50 LD₅₀ doses of APEC virulent strains O78 and O161 serogroups, respectively. By contrast, 95% (19/20) and 100% (20/20) of SG101-immunized chickens died in challenge studies involving APEC O78 and O161 infections, respectively. In addition, the SG102 strain effectively provided protection against lethal challenges from the virulent S. gallinarum strain. These results demonstrate that the SG102 strain, which expresses APEC type I fimbriae, is a promising vaccine candidate against APEC O78 and O161 serogroups as well as S. gallinarum infections.

Keywords: APEC; Salmonella vector; protective effect; safety; type I fimbriae.

Abstract

Grants and funding