Immunogenic Potency of Formalin and Heat Inactivated O157:H7 in Mouse Model Administered by Different Routes.

BACKGROUND

Enterohemorrhagic (EHEC) O157:H7 is a major foodborne pathogen causing severe disease in humans worldwide. Cattle are important reservoirs of O157:H7 and developing a specific immunity in animals would be invaluable. The administration of Whole Cell Vaccines (WCV) is a well-established method of vaccination against bacterial infections. Route of administration, inactivation and using suitable adjuvant have significant effects on the characteristics and efficacy of WCV.

METHODS

In the present study, an attempt was made to evaluate the immunogenic potency of heat and formalin inactivated cells administered orally and subcutaneously in mouse model by ELISA. Mice pretreated with streptomycin were used as a model to evaluate the efficacy of subcutaneous versus oral administration of the vaccine. Following immunization, mice were infected with O157:H7 and feces were monitored for shedding.

RESULTS

Both forms of inactivated cells induced immune response and hence protection against infectious diseases caused by O157:H7. However, formalin inactivated cells of O157:H7 showed superior antigenicity compared to heat inactivated cells. Subcutaneous immunization of mice with both heat and formalin inactivated O157:H7 induced significant specific levels of IgG antibodies but did not lead to significant antigen-specific IgA rise in feces, whereas oral immunization elicited significant levels of IgG antibodies with some animals developing antigen-specific IgA in feces.

CONCLUSION

Inactivated O157:H7 is highly immunogenic and can induce protective immune responses via oral immunization.