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.
Murphy
G L
GL
Department of Anatomy, Pathology and Pharmacology, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078-2007, USA.
Whitworth
L C
LC
Confer
A W
AW
Gaskins
J D
JD
Pandher
K
K
Dabo
S M
SM
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