Outer membrane protein A of bovine and ovine isolates of mannheimia haemolytica is surface exposed and contains host species-specific epitopes

Hounsome, J. D.A., Baillie, S., Noofeli, M., Riboldi-Tunnicliffe, A., Burchmore, R. J.S., Isaacs, N. W. and Davies, R. L. (2011) Outer membrane protein A of bovine and ovine isolates of mannheimia haemolytica is surface exposed and contains host species-specific epitopes. Infection and Immunity, 79(11), pp. 4332-4341. (doi:10.1128/IAI.05469-11)

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Abstract

Mannheimia haemolytica is the etiological agent of pneumonic pasteurellosis of cattle and sheep; two different OmpA subclasses, OmpA1 and OmpA2, are associated with bovine and ovine isolates, respectively. These proteins differ at the distal ends of four external loops, are involved in adherence, and are likely to play important roles in host adaptation. M. haemolytica is surrounded by a polysaccharide capsule, and the degree of OmpA surface exposure is unknown. To investigate surface exposure and immune specificity of OmpA among bovine and ovine M. haemolytica isolates, recombinant proteins representing the transmembrane domain of OmpA from a bovine serotype A1 isolate (rOmpA1) and an ovine serotype A2 isolate (rOmpA2) were overexpressed, purified, and used to generate anti-rOmpA1 and anti-rOmpA2 antibodies, respectively. Immunogold electron microscopy and immunofluorescence techniques demonstrated that OmpA1 and OmpA2 are surface exposed, and are not masked by the polysaccharide capsule, in a selection of M. haemolytica isolates of various serotypes and grown under different growth conditions. To explore epitope specificity, anti-rOmpA1 and anti-rOmpA2 antibodies were cross-absorbed with the heterologous isolate to remove cross-reacting antibodies. These cross-absorbed antibodies were highly specific and recognized only the OmpA protein of the homologous isolate in Western blot assays. A wider examination of the binding specificities of these antibodies for M. haemolytica isolates representing different OmpA subclasses revealed that cross-absorbed anti-rOmpA1 antibodies recognized OmpA1-type proteins but not OmpA2-type proteins; conversely, cross-absorbed anti-rOmpA2 antibodies recognized OmpA2-type proteins but not OmpA1-type proteins. Our results demonstrate that OmpA1 and OmpA2 are surface exposed and could potentially bind to different receptors in cattle and sheep.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Baillie, Mrs Susan and Riboldi-Tunnicliffe, Dr Alan and Davies, Dr Robert and Noofeli, Mr Mojtaba and Burchmore, Dr Richard and Isaacs, Professor Neil
Authors: Hounsome, J. D.A., Baillie, S., Noofeli, M., Riboldi-Tunnicliffe, A., Burchmore, R. J.S., Isaacs, N. W., and Davies, R. L.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
College of Science and Engineering > School of Chemistry
Journal Name:Infection and Immunity
Publisher:American Society for Microbiology
ISSN:0019-9567
ISSN (Online):1098-5522
Published Online:06 September 2011

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
418711Comparative adherence of bovine and ovine Mannheimia haemolytica strains to air-interface respiratory organ culture models from cattle and sheepRobert DaviesBiotechnology and Biological Sciences Research Council (BBSRC)BB/D018137/1Infection Immunity and Inflammation Life Sciences