Comparative Protective Antigenicity of 37 Kda Major Outer Membrane Protein (Omp) and 61 Kda whole Cell Extracted Protein of Edwardsiella tarda in Rohu (Labeo rohita)

Edwardsiella septicemia is an economically important fish disease, caused by a bacterium Edwardsiella tarda having zoonotic potential. It affects many fish species and various animal groups including reptiles, birds and mammals. The whole cell antigenic proteins and outer membrane proteins (OMP) of E.tarda were extracted from different isolates and assessed their reactivity with anti E. trada rohu and anti E. trada rabbit serum via Western blot. The strongly reacted proteins were considered as immunogenic proteins. The 61 kDa whole cell proteins and 37 kDa OMP were extracted from SDS PAGE gelsto evaluate their vaccine potential in rohu fish. Fish were vaccinated 10µg of individual proteins intraperitoneally as immunogen with Freund's incomplete adjuvant (FIA). The boosters were given on the 10th day of immunization with PBS. The blood was drawn from vena caudalis at every 7th day for hematological and immunological studies. Fish were challenged on 35th day with 1× 106 cfu E. tarda field isolate ET-1. The cumulative mortality (CM) was recorded over one week and relative percentage survival (RPS) was calculated. The 61 kDa and 37 kDa proteins had significantly higher (p ≤ 0.05) nonspecific and specific parameters and relative percentage survival (RPS) over control group. The non specific immune parameters were more active in first four weeks of vaccination. Specific antibody production for E. tarda in both proteins was not significantly different at the end of experiment. However, the significantly higher RPS of 61 kDa (63%) over 37 kDa (53%) reflect the against E.tarda and a better vaccine can did ate over 37 kDa to control E. tarda in rohu. The presence of 61 kDa in all isolates indicated it could use as an antigen in indirect ELISA for the sero-monitoring and surveillance of edwardsiellosis.