Antigenic characterization of outer membrane protein of Aeromonas sobria isolated from goldfish (Carassius auratus L.)

Aeromonas sobria, along with A. hydrophila, has frequently been reported as a causative agent of motile aeromonas septicemia (MAS) in fish and other aquatic organisms. Currently, there are no precise tools to diagnose or vaccinate against this disease. The aim of the present study was to fractionate and characterize the outer membrane protein (OMP) antigen of A. sobria by serological and cellular techniques so as to identify immunoreactive molecules that might be useful in preparing immunodiagnostic and/or immunoprophylactic tools against A. sobria infection in goldfish. Eight fractions were isolated from the crude OMP antigen using sephacryl S-200 and DEAE-cellulose chromatography. The highest seroreactivity was observed in the gel-permeated protein G, which had an optical density (OD) of 0.72 nm, higher even than that of the crude OMP antigen, 0.63 nm. The serodiagnostic potential of G(1) was assessed by using dip-stick ELISA. The in vitro goldfish lympho-proliferation ability of the fractionated antigen, G(1)A(3), was higher than of all the other fractionated antigens and the crude OMP. Therefore, fractionated antigen G, (molecular wt 42-67 kDa) and G(1)A(3) (molecular wt 45-47 kDa) should be further studied in immunodiagnostic and/or immunoprophylactic preparations for A. sobria infection.