Ocular Immune Responses in Steers following Intranasal Vaccination with Recombinant Moraxella bovis Cytotoxin Adjuvanted with Polyacrylic Acid

Abstract

ABSTRACTInfectious bovine keratoconjunctivitis (IBK) caused byMoraxella bovisis the most common eye disease of cattle. The pathogenesis ofM. bovisrequires the expression of pili that enable the organism to attach to the ocular surface and an RTX (repeats in the structural toxin) toxin (cytotoxin or hemolysin), which is cytotoxic to corneal epithelial cells. In this pilot study, ocular mucosal immune responses of steers were measured following intranasal (i.n.) vaccination with a recombinantM. boviscytotoxin adjuvanted with polyacrylic acid. Beef steers were vaccinated with either 500 μg (n= 3) or 200 μg (n= 3) of recombinantM. boviscytotoxin plus adjuvant. Control group steers (n= 2) were vaccinated with adjuvant alone, and all steers were given a booster on day 21. Antigen-specific tear IgA and tear IgG, tear cytotoxin-neutralizing antibody responses, and serum cytotoxin-neutralizing antibody responses were determined in samples collected prevaccination and on days 14, 28, 42, and 55. Changes in tear antigen-specific IgA levels from day 0 to days 28, 42, and 55 were significantly different between groups; however, inpost hoccomparisons between individual group pairs at the tested time points, the differences were not significant. Our results suggest that i.n. vaccination of cattle with recombinantM. boviscytotoxin adjuvanted with polyacrylic acid effects changes in ocular antigen-specific IgA concentrations. The use of intranasally administered recombinantM. boviscytotoxin adjuvanted with polyacrylic acid could provide an alternative to parenteral vaccination of cattle for immunoprophylaxis against IBK.