Attachment of Moraxella bovis to calf corneal cells and inhibition by antiserum

An in vitro assay was developed using calf corneal cells to assess the importance of fimbriae in the colonisation of the bovine ocular surface by Moraxella bovis, and the role of fimbrial antibodies in the bovine immune response and resistance to infectious bovine keratoconjunctivitis (IBK). Fimbriae promoted adherence of M. bovis to calf corneal cells in culture; 15 fimbriate isolates, representative of 6 fimbrial serogroups of M. bovis, adhered to the cells whereas 4 non-fimbriate isolates failed to do so. Fimbrial antibodies in hyperimmune rabbit serum inhibited attachment of all fimbriate strains of the homologous fimbrial serogroup but not those of 5 heterologous serogroups. The relevance of these results to the use of a polyvalent fimbrial vaccine in the control of IBK is discussed.