Ocular immune responses in steers following intranasal vaccination with recombinant Moraxella bovis cytotoxin adjuvanted with polyacrylic acid

Abstract

Infectious bovine keratoconjunctivitis (IBK) caused by Moraxella bovis is the most common eye disease of cattle. The pathogenesis of M. bovis requires 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 recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid. Beef steers were vaccinated with either 500 μg (n = 3) or 200 μg (n = 3) of recombinant M. bovis cytotoxin 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, in post hoc comparisons between individual group pairs at the tested time points, the differences were not significant. Our results suggest that i.n. vaccination of cattle with recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid effects changes in ocular antigen-specific IgA concentrations. The use of intranasally administered recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid could provide an alternative to parenteral vaccination of cattle for immunoprophylaxis against IBK.

FIG 1

Individual and group mean (+ standard error [SE]) values for changes in tear antigen-specific IgA ratios from day 0 to day 14 (D0-D14), day 0 to day 28 (D0-D28), day 0 to day 42 (D0-D42), and day 0 to day 55 (D0-D55) in steers that received primary and day-21 booster i.n. vaccination with 0 μg (control group, n = 2; black circles/white rectangles), 200 μg (n = 3; black squares/hatched rectangles), or 500 μg (n = 3; black triangles/gray rectangles) recombinant Moraxella bovis cytotoxin adjuvanted with polyacrylic acid. The tear IgA ratios were significantly different among the 3 groups (P = 0.0104) at the 4 tested time intervals. Post hoc comparisons between the individual treatment group pairs were not significantly different (P > 0.017).

FIG 2

Individual and group mean (+ SE) values for changes in tear antigen-specific IgG ratios from day 0 to day 14 (D0-D14), day 0 to day 28 (D0-D28), day 0 to day 42 (D0-D42), and day 0 to day 55 (D0-D55) in steers that received primary and day-21 booster i.n. vaccination with 0 μg (control group, n = 2; black circles/white rectangles), 200 μg (n = 3; black squares/hatched rectangles), or 500 μg (n = 3; black triangles/gray rectangles) recombinant Moraxella bovis cytotoxin adjuvanted with polyacrylic acid.

FIG 3

Individual and group mean (+ SE) fold changes in Moraxella bovis cytotoxin neutralization indices of tear samples from day 0 to day 14 (D0-D14), day 0 to day 28 (D0-D28), day 0 to day 42 (D0-D42), and day 0 to day 55 (D0-D55) in steers that received primary and day-21 booster i.n. vaccination with 0 μg (control group, n = 2; black circles/white rectangles), 200 μg (n = 3; black squares/hatched rectangles), or 500 μg (n = 3; black triangles/gray rectangles) recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid.

FIG 4

Individual and group mean (+ SE) fold changes in serum-neutralizing antibody titers to Moraxella bovis cytotoxin from day 0 to day 14 (D0-D14), day 0 to day 28 (D0-D28), day 0 to day 42 (D0-D42), and day 0 to day 55 (D0-D55) in steers that received primary and day-21 booster i.n. vaccination with 0 μg (control group, n = 2; black circles/white rectangles), 200 μg (n = 3; black squares/hatched rectangles), or 500 μg (n = 3; black triangles/gray rectangles) recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid.