a Faculty of Veterinary Medicine , Chiang Mai University , Chiang Mai 50100 Thailand.
b Nippon Veterinary and Life Science University , Tokyo 180-8602 Japan.
A previous study demonstrated that a recombinant outer membrane protein H (rOmpH)-based intranasal fowl cholera vaccine elicited efficient homologous protection against Pasteurella multocida strain X-73 (A:1) in chickens. The present study aimed to determine the cross protectivity against heterologous P. multocida strains. The rOmpH was purified via electroelution and formulated with two kinds of adjuvants. The vaccine formulations in a total volume of 100 µl were 100 µg rOmpH with 3 µg of Escherichia coli enterotoxin B (LTB) or 10 µg of CpG ODN2007. Chickens were assigned into three experimental groups depending on bacterial strain challenge-exposure as well as three control groups. The chickens were intranasally immunized three times at three week intervals. Challenge exposures were conducted by inoculation with homologous strain X-73 or heterologous strains P-1059 (A:3) or P-1662 (A:4) at four weeks after the final immunization. The specific antibody against rOmpH was produced in vaccinated birds. Sera IgY and secretory IgA antibody titers were significantly increased (P < 0.05) post immunization. The stimulation index values of the vaccinated groups were significantly different from stimulation index (SI) values of the non-vaccinated groups (P < 0.05). Chicken survival rates after exposure to avian P. multocida strains ranged from 70-100%. There was no significant difference in protection between two kinds of adjuvants in vaccine formulations. Statistical analysis indicated no significant differences in protection among avian P. multocida strains challenge exposure. We conclude that an in-house rOmpH-based intranasal fowl cholera vaccine produced efficient cross-protectivity against heterologous strains of P. multocida.
Pasteurella multocida; chicken; cross protection; intranasal fowl cholera vaccine; recombinant outer membrane protein H