Efficacy of outer membrane protein vaccine against avian pathogenic E. coli in broiler chicks

In present study an experiment has been carried out to assess the immunological response of E. coli outer membrane proteins (OMPs) with the use of cytokines as adjuvant and its protective efficacy has been evaluated after challenge study in immunized birds with homologous and heterologous virulent strains of E.coli in broiler chicks. The OMP vaccines were made from the isolate 078 and the cytokines which was used as adjuvant were prepared from mononuclear cells from adult bird's spleen previously immunized with E.coli organism (05) per os. The one-week-old chicks were immunized with single dose of OMPs vaccine with or without adjuvants subcutaneously with 50 |ig protein in 500ul of cytokine preparation. Indirect ELISA was carried out to detect humoral immune response and CMI response was measured by MTT colorimetric assay. In OMP vaccinated chicks the ELISA antibody titers started rising at 1st wpv and reached the peak at 5th wpv which declined slowly after 5th wpv. The ELISA titres were found to be significantly correlated with protection index. The ELISA titre of 7.4 and above was found to be 100% protective. The CMI response as measured by MTT colorimetric assay was also significantly higher among the birds vaccinated with OMPs vaccine alongwith cytokines which indicates the superiority of the cytokines as adjuvant in these vaccines. In conclusion, it is evident that OMPs with cytokine as an adjutant can induce a high and long lasting immunity to broiler-chicks against E.coli infection even to heterologous strains.