The protective efficacy of pili from different strains of Moraxella bovis within the same serogroup against infectious bovine keratoconjunctivitis.
Three groups of ten calves were each immunised with a total of 400 micrograms pili prepared from three separate strains of Moraxella bovis in Alhydrogel-oil adjuvant as two divided, equal doses 21 days apart. Groups 1 and 2 each received a monovalent vaccine made from strain 4L and S276R respectively, which belonged to pili serogroup A. Group 3 received vaccine made from pili of strain Maff1, belonging to serogroup F. A further group of ten calves served as non-vaccinated controls. Calves in groups 1 and 2 had developed serogroup A-specific antibody and those in group 3 developed serogroup F-specific antibody, and some evidence of cross-reacting antibody was also detected when measured by an agglutination test using formalin-killed piliated cells of serogroup A strain 4L. Although antibody titres measured against purified pili by ELISA were highest with homologous serogroup antigens, cross-reactive titres to shared epitopes of M. bovis pili were also detected by this method. Ocular challenge of the 40 calves with virulent M. bovis of serogroup A strain S276R was carried out 14 days after the second vaccine dose. All non-vaccinated calves developed infectious bovine keratoconjunctivitis (IBK). The percentage protection in groups 1 (strain 4L) and 2 (strain S276R) was 60% and 80% respectively (P less than 0.05), with mean lesion scores of 0.7 and 0.3 out of a possible 6.0. The percentage protection of calves in group 3 (strain Maff1) was only 30%, with a mean lesion score of 1.4 compared with 2.2 for non-vaccinated controls. The present findings, together with other evidence indicating that immunity to IBK is serogroup-specific, suggest that inclusion of pili from one representative strain from each of the seven Australian and British serogroups in a polyvalent, subunit vaccine should effectively protect the majority of cattle against IBK caused by most field strains of M. bovis encountered in Australia and the United Kingdom.
Lepper
A W
AW
CSIRO Division of Animal Health, Animal Health Research Laboratory, Parkville, Vic., Australia.
Moore
L J
LJ
Atwell
J L
JL
Tennent
J M
JM
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001428:Bacterial Vaccines; D002417:Cattle; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D010861:Fimbriae, Bacterial / Q000276:immunology*; D007123:Immunoelectrophoresis, Two-Dimensional; D007639:Keratoconjunctivitis, Infectious / Q000517:prevention & control*; D008297:Male; D016955:Moraxella bovis / Q000145:classification / Q000276:immunology* / Q000648:ultrastructure; D016870:Neisseriaceae Infections / Q000517:prevention & control / Q000662:veterinary*; D012703:Serotyping; D014611:Vaccination / Q000662:veterinary
D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines