P. Lutwyche et al., A CONSERVED AEROMONAS-SALMONICIDA PORIN PROVIDES PROTECTIVE IMMUNITY TO RAINBOW-TROUT, Infection and immunity, 63(8), 1995, pp. 3137-3142
A protein with an apparent M(r) of 28,000 was isolated from outer memb
rane preparations of Aeromonas salmonicida A440. The protein was teste
d for the ability to form pores, using a planar lipid bilayer model me
mbrane system. The protein appeared to be a monomer with a single-chan
nel conductance in 1.0 M KCl of 1.96 nS and a cation/anion permeabilit
y ratio of 2.91 +/- 0.68. These data show that the porin channel is co
mparable in size to OmpC and OmpF of Escherichia coli and is relativel
y nonselective, having some preference for cations over anions. The po
rin was purified by preparative sodium dodecyl sulfate-polyacrylamide
gel electrophoresis, and a polyclonal antibody was raised. Immunoblot
analysis showed that an immunologically cross-reactive protein was pre
sent in other Aeromonas strains but not in strains of Vibrio or Yersin
ia. The N-terminal amino acid sequence of the porin was determined and
was found to show some homology to an Aeromonas hydrophila outer memb
rane protein. This is the second porin species of A. salmonicida to be
described, and it differs from the other in subunit molecular weight,
aggregation properties, peptidoglycan association, pore size, and ant
igenicity. Rainbow trout (Oncorhynchus mykiss) immunized intraperitone
ally with the purified porin protein were significantly protected from
experimental A. salmonicida challenge. This is the first report of su
ccessful vaccination against A. salmonicida with a purified outer memb
rane component.