Characterization of a Pasteurella haemolytica A1 mutant deficient in production of three membrane lipoproteins.
OBJECTIVE
To determine whether a Pasteurella haemolytica A1 mutant that is unable to produce membrane lipoproteins has reduced susceptibility to complement-mediated killing, and to characterize the mutant strain.


METHODS
12 sera from cattle resistant to P haemolytica challenge exposure after vaccination with P haemolytica or its antigens, or after natural exposure.


METHODS
Complement-mediated killing assays were performed, using wild-type and mutant strains and, as antibody source, various immune sera from cattle that were resistant to P haemolytica challenge exposure. Antibody response to whole-cell antigens produced by mutant and wild-type strains, production of outer membrane proteins and iron-regulated outer membrane proteins by the 2 strains, and growth of the 2 strains in various media were analyzed.


RESULTS
Compared with wild-type P haemolytica, the lipoprotein mutant strain had increased susceptibility to bovine complement-mediated killing. Aside from the lipoproteins that are not produced by the mutant, immunoblot analysis did not reveal differences between immunoreactive antigens that are produced by the 2 strains. Some iron-regulated, outer membrane proteins, which usually are only produced by P haemolytica under iron-deficient conditions, were produced constitutively by the mutant. The mutant grew to a lower final cell density and at a lower rate under conditions likely to reflect those encountered in vivo.


CONCLUSIONS
Lack of 3 membrane lipoproteins resulted in enhanced susceptibility to bovine complement-mediated killing. Site-specific mutagenesis of genes encoding P haemolytica membrane lipoproteins alters production of iron-regulated outer membrane proteins by P haemolytica. Growth characteristics of the mutant suggested that it may have reduced capacity for survival in vivo.
Department of Anatomy, Pathology and Pharmacology, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078-2007, USA.
G L
GL
Murphy
L C
LC
Whitworth
A W
AW
Confer
J D
JD
Gaskins
K
K
Pandher
S M
SM
Dabo
D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis / Q000276:immunology; D000942:Antigens, Bacterial / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000517:prevention & control; D003165:Complement System Proteins / Q000276:immunology; D008074:Lipoproteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D016978:Mannheimia haemolytica / Q000235:genetics* / Q000254:growth & development / Q000276:immunology; D008565:Membrane Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D009154:Mutation; D010326:Pasteurella Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary; D014611:Vaccination / Q000662:veterinary
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D008074:Lipoproteins; D008565:Membrane Proteins; C083817:Plp1 protein, Pasteurella haemolytica; C083820:Plp3 protein, Mannheimia haemolytica; C083819:PlpB protein, Mannheimia haemolytica; D003165:Complement System Proteins