Immune response induced by ppGpp-defective Salmonella enterica serovar Gallinarum in chickens.
To protect chickens from typhoid caused by Salmonella enterica serovar Gallinarum (S. Gallinarum), the attenuated 9R strain has been used in the field as a vaccine. However, safety concerns have been raised because the mutations in 9R are undefined while its efficacy is still a question under debate. A global regulator, ppGpp, synthesized by RelA and SpoT, has been shown to induce various virulence genes in S. Gallinarum (Jeong et al., 2008). In this study, two mutant strains defective in ppGpp-synthesis were constructed in wild-type S. Gallinarum (ΔppGpp) and 9R strain (9R-ΔppGpp) backgrounds and tested as live vaccines in chickens. After oral inoculation, the LD(50) values of ΔppGpp and 9R-ΔppGpp were approximately 5×10(10) colony forming unit (CFU) similarly as 9R strain, which was ∼10(5)-fold higher than that of the wildtype S. Gallinarum strain. Immunological analyses revealed immunization with either of the two attenuated ppGpp-defective strains induced significant antibody responses, the production of antibody-secreting B cells in blood, proliferation of CD4+ and CD8+ T cells in the spleen, and splenic expression of proinflammatory cytokines, such as IFN-γ and TGF-β4, at levels comparable to the 9R strain. Chickens immunized with the mutants (1×10(8) CFU) were 80% protected against oral challenge with 1×10(9) wild-type virulent bacteria (4,000-fold LD(50) dose), similar to the level of protection achieved by 9R immunization. Based on these data, live attenuated ΔppGpp-defective strains may serve as novel vaccines to control fowl typhoid in chickens.
Bio-Therapy Human Resources Center, College of Veterinary Medicine, Gwangju 501-746, Republic of Korea.
Sang-Ik
SI
Park
Jae-Ho
JH
Jeong
Hyon E
HE
Choy
Joon Haeng
JH
Rhee
Hee-Sam
HS
Na
Tae-Hoon
TH
Lee
Moon
M
Her
Kyoung-Oh
KO
Cho
Yeongjin
Y
Hong
D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001402:B-Lymphocytes / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D049109:Cell Proliferation; D002645:Chickens; D016207:Cytokines / Q000096:biosynthesis; D017353:Gene Deletion; D020869:Gene Expression Profiling; D006159:Guanosine Tetraphosphate / Q000172:deficiency*; D007928:Lethal Dose 50; D011201:Poultry Diseases / Q000401:mortality / Q000517:prevention & control*; D012481:Salmonella Infections, Animal / Q000401:mortality / Q000517:prevention & control*; D022562:Salmonella Vaccines / Q000008:administration & dosage / Q000276:immunology*; D019779:Salmonella enterica / Q000235:genetics / Q000276:immunology* / Q000378:metabolism* / Q000472:pathogenicity; D013154:Spleen / Q000276:immunology; D016019:Survival Analysis; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology; D014774:Virulence
D000907:Antibodies, Bacterial; D016207:Cytokines; D022562:Salmonella Vaccines; D014613:Vaccines, Attenuated; D006159:Guanosine Tetraphosphate