Multifaceted immune responses and protective efficacy elicited by a recombinant autolyzed Salmonella expressing FliC flagellar antigen of F18+Escherichia coli.
Porcine edema disease (ED) caused by F18+Shiga toxin 2e-producing Escherichia coli (STEC) has imposed significant economic losses in the swine industry worldwide, resulting in sudden deaths in post-weaned piglets. The flagellin protein of F18+STEC, a structural component of the flagellar filament, is a known virulence factor that mediates adhesion and invasion to porcine epithelial cells. In this study, Salmonella inactivated by the E lysis gene and expressing the flagellin (fliC) antigen was genetically engineered utilizing a plasmid (pMMP184) carrying an efficient heterologous antigen delivery system. The resulting strain JOL1485 producing FliC was successfully inactivated by the E lysis gene cassette. Following the lysis procedure, FliC secretion and production of JOL1485 was validated by immunoblot analysis. To evaluate protective immunogenicity elicited by the constructed strain, BALB/c mice were injected with 1×108lysed cells via the intramuscular route. The markedly elevated titers of FliC-specific IgG, IgG1 and sIgA antibodies were observed, indicating a robust Th2-associated humoral immune response was raised in the immunized mice. The proportion of CD3+CD4+splenic T cells and proliferative activity were also elevated in in vivo and in vitro stimulated mice splenocytes. Further, JOL1485 successfully elicited upregulated gene expression of cytokines IL-6, IL-8, IL17, IL-21, IFN-γ and TNF-α in naïve porcine peripheral blood mononuclear cells (PBMCs). The overall immune response elicited by JOL1485 conferred a significant rise of protection against a lethal virulent F18+STEC challenge whereas all non-immunized mice died following the challenge. Our results demonstrate that fliC efficiently expressed in the genetically inactivated Salmonella strain has immunostimulatory and protective effects against a F18+STEC lethal challenge, and may be promising as a potential vaccine candidate against ED infection.
College of Veterinary Medicine, Chonbuk National University, Iksan Campus, Gobong-ro 79, Iksan 54596, Republic of Korea.
Gayeon
G
Won
College of Veterinary Medicine, Chonbuk National University, Iksan Campus, Gobong-ro 79, Iksan 54596, Republic of Korea. Electronic address: johnhlee@jbnu.ac.kr.
John Hwa
JH
Lee
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D049109:Cell Proliferation; D016207:Cytokines / Q000096:biosynthesis; D004195:Disease Models, Animal; D004337:Drug Carriers; D004488:Edema Disease of Swine / Q000517:prevention & control*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000276:immunology*; D022361:Escherichia coli Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D005260:Female; D005408:Flagellin / Q000235:genetics / Q000276:immunology*; D005822:Genetic Vectors; D007071:Immunoglobulin A, Secretory / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007273:Injections, Intramuscular; D008807:Mice, Inbred BALB C; D012475:Salmonella / Q000235:genetics*; D016019:Survival Analysis; D013552:Swine; D014614:Vaccines, Synthetic / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology
D000907:Antibodies, Bacterial; D016207:Cytokines; D004337:Drug Carriers; D029968:Escherichia coli Proteins; D022361:Escherichia coli Vaccines; C516095:FliC protein, E coli; D007071:Immunoglobulin A, Secretory; D007074:Immunoglobulin G; D014614:Vaccines, Synthetic; D005408:Flagellin
Delivery system; Edema disease; F18(+) STEC; Flagellin; Salmonella ghost