Evaluation of Salmonella Gallinarum ghost formulated with Montanide™ ISA 70 VG adjuvant as a vaccine against fowl typhoid

Abstract

Escherichia coli heat-labile enterotoxin B subunit (LTB) protein is a potent adjuvant. Salmonella Gallinarum ghosts carrying LTB (S. Gallinarum-LTB ghosts) were genetically constructed using a plasmid, pJHL187-LTB, designed for the co-expression of the LTB and E lysis proteins. This study evaluates the immunopotentiating effects of Montanide™ ISA 70 VG on S. Gallinarum-LTB ghost vaccination against fowl typhoid. Five-week-old layer chickens were injected intramuscularly with sterile PBS (non-immunised control, Group A), S. Gallinarum-LTB ghost (Group B) or S. Gallinarum-LTB ghost emulsified with Montanide™ ISA 70 VG adjuvant (Group C). Chickens from both Groups B and C showed significant induction of antigen-specific systemic IgG response compared to controls; in addition, Group C showed enhanced induction of systemic IgG response compared to Group B. We observed significant induction of antigen-specific lymphocyte proliferative response and increased mRNA levels of Th1 cytokines (IFN-γ and IL2) in both Groups B and C. Furthermore, in the challenge experiment with a virulent strain of S. Gallinarum, Group C showed higher survival rates compared with other groups. These results indicate that vaccination with the S. Gallinarum-LTB ghost in combination with Montanide™ ISA 70 VG may enhance the protective immunity against fowl typhoid.