The molecular adjuvant mC3d enhances the immunogenicity of FimA from type I fimbriae of Salmonella enterica serovar Enteritidis.
BACKGROUND
The fimbriae of Salmonella enterica serovar Enteritidis are used for colonization and invasion into host cells, and have drawn considerable interest because fimbriae can serve as potential immunogens against many pathogenic bacteria that colonize on epithelial surfaces. The purpose of the study is to use a molecular adjuvant, C3d, to enhance the immunogenicity of FimA proteins against Salmonella enterica serovar Enteritidis.


METHODS
FimA of type I fimbriae from Salmonella enteritidis and FimA with one copy of mC3d, two copies of mC3d2 and three copies of mC3d3 were cloned into the expression vector pCold-TF. Soluble fusion proteins of FimA with different copy of mC3d were induced by IPTG and expressed into Escherichia coli BL21 (DE3). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the recombinant proteins from pCold-TF-fimA, TF-fimA-mC3d, TF-fimA-mC3d2, TF-fimA-mC3d3 were 70 kDa, 100 kDa, 130 kDa and 160 kDa, respectively. The fusion protein was recognized by rabbit anti-fimbriae polyclonal antibodies, and then visualized by goat anti-rabbit polyclonal antibodies with a chrome appearance by enzyme-subtract interaction. The recombinant proteins were purified by Ni-TED (tris-carboxymethyl ethylene diamine), immobilized metal ion affinity chromatography (IMAC). Balb/c mice were subcutaneously immunized with the purified proteins and the immune response was monitored by an enzyme-linked immunosorbent assay (ELISA) for FimA-specific antibody. The immunized mice were challenged with a 10-fold LD50 dose (i.e., 100 CFU) of Salmonella enterica serovar Enteritidis standard strain (SD-2) 1 week after the second immunization.


RESULTS
The immunized mice with the fusion proteins FimA-mC3d2 and FimA-mC3d3 had increased levels of ELISA titer of antibody that were 2 and 4 logs, respectively, more immunogenic than the TF-FimA protein alone. The challenge results showed that immune protection rate in the mice immunized with 10 μg of FimA, FimA-mC3d2, and FimA-mC3d3 were 50%, 75% and 100%, respectively.


CONCLUSIONS
We conclude that mC3d can be expressed in a prokaryotic vector and enhance the immune response of the recombinant protein. FimA-mC3d3 is potentially a subunit vaccine against S. enterica serovar Enteritidis infection.
College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Faculty of Veterinary Science, University of Nyala, Sudan. Electronic address: hassan_hm30@yahoo.com.
Hassan-Hussein
HH
Musa
College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Wei-Juan
WJ
Zhang
College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Jing
J
Lv
College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Xiao-Li
XL
Duan
College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Yang
Y
Yang
College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Jiangsu Institute of Poultry Science, Yangzhou 225003, China.
Chun-Hong
CH
Zhu
Jiangsu Institute of Poultry Science, Yangzhou 225003, China.
Hui-Fang
HF
Li
Jiangsu Institute of Poultry Science, Yangzhou 225003, China.
Kuan-Wei
KW
Chen
College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
Xia
X
Meng
College of Veterinary Medicine, Yangzhou University, Yangzhou, China. Electronic address: yzgqzhu@hotmail.com.
Guo-Qiang
GQ
Zhu
D000276:Adjuvants, Immunologic / Q000008:administration & dosage* / Q000235:genetics; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000235:genetics / Q000276:immunology*; D015933:Complement C3d / Q000008:administration & dosage* / Q000235:genetics; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D036781:Fimbriae Proteins / Q000235:genetics / Q000276:immunology*; D007279:Injections, Subcutaneous; D051379:Mice; D008807:Mice, Inbred BALB C; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D012481:Salmonella Infections, Animal / Q000276:immunology / Q000517:prevention & control*; D022562:Salmonella Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D012477:Salmonella enteritidis / Q000276:immunology*; D014611:Vaccination / Q000379:methods*; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology
D000276:Adjuvants, Immunologic; D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D011993:Recombinant Fusion Proteins; C110675:SEF21 protein, Salmonella enteritidis; D022562:Salmonella Vaccines; D014614:Vaccines, Synthetic; D036781:Fimbriae Proteins; D015933:Complement C3d
FimA; Salmonella enterica serovar Enteritidis; mC3d; recombinant protein