leukotoxin and Pneumonia

Pasteurella haemolytica is represented by two biotypes (A and T), 15 serotypes, and numerous untypable strains. Specific biotypes and serotypes are associated with fibrinous pleuropneumonia (pneumonic pasteurellosis) in cattle, sheep, and goats, septicemic pasteurellosis in lambs, and mastitis in ewes. Four virulence factors have been associated with P. haemolytica: fimbriae, a polysaccharide capsule, endotoxin [lipopolysaccharide (LPS)], and leukotoxin (LKT). The interactions of these virulence factors with components of the pulmonary alveolus are discussed as a model for the pathogenesis of pasteurellosis. Fimbriae on P. haemolytica may enhance colonization of the upper respiratory tract. The capsule of P. haemolytica varies in composition among serotypes. It inhibits complement-mediated serum killing as well as phagocytosis and intracellular killing of P. haemolytica. The capsule enhances neutrophil directed migration and adhesion of P. haemolytica to alveolar epithelium. Pasteurella haemolytica LPS can alter bovine leukocyte functions, by dose-dependent inhibition or augmentation; it is directly toxic to bovine endothelium; it modifies cardiopulmonary hemodynamics; and it elevates circulatory prostanoids, serotonin, cAMP, and cGMP. Leukotoxin is produced by all known serotypes and many untypable strains. Leukotoxin is a poreforming cytolysin that affects ruminant leukocytes and platelets by altering function at low levels but causing lysis at high levels.

Topics: Animals; Bacterial Toxins; Exotoxins; Fimbriae, Bacterial; Lipopolysaccharides; Pasteurella; Pasteurella Infections; Pneumonia; Polysaccharides, Bacterial; Virulence

Mannheimia haemolytica consistently causes fatal bronchopneumonia in bighorn sheep (BHS; Ovis canadensis) under natural and experimental conditions. Leukotoxin is the primary virulence factor of this organism. BHS are more susceptible to developing fatal pneumonia than the related species Ovis aries (domestic sheep [DS]). In BHS herds affected by pneumonia, lamb recruitment is severely impaired for years subsequent to an outbreak. We hypothesized that a lack of maternally derived antibodies (Abs) against M. haemolytica provides an immunologic basis for enhanced susceptibility of BH lambs to population-limiting pneumonia. Therefore, the objective of this study was to determine the titers of Abs directed against M. haemolytica in the sera of BH and domestic lambs at birth through 12 weeks of age. Results revealed that BH lambs had approximately 18-fold lower titers of Ab against surface antigens of M. haemolytica and approximately 20-fold lower titers of leukotoxin-neutralizing Abs than domestic lambs. The titers of leukotoxin-neutralizing Abs in the serum and colostrum samples of BH ewes were approximately 157- and 50-fold lower than those for domestic ewes, respectively. Comparatively, the higher titers of parainfluenza 3 virus-neutralizing Abs in the BH lambs ruled out the possibility that these BHS had an impaired ability to passively transfer Abs to their lambs. These results suggest that lower levels of leukotoxin-neutralizing Abs in the sera of BH ewes, and resultant low Ab titers in their lambs, may be a critical factor in the poor lamb recruitment in herds affected by pneumonia.

Topics: Age Factors; Animals; Animals, Newborn; Antibodies, Bacterial; Disease Susceptibility; Exotoxins; Female; Immunization, Passive; Mannheimia haemolytica; Maternal-Fetal Exchange; Pneumonia; Pregnancy; Sheep; Sheep Diseases; Sheep, Bighorn; Sheep, Domestic

Six, 5- to 10-week-old male Holstein calves were inoculated intratracheally with 5 x 10(9) logarithmic growth phase Pasteurella haemolytica biotype A serotype 1 (A1). Immunohistochemical techniques in conjunction with the use of monoclonal antibodies directed against P. haemolytica A1-derived lipopolysaccharide (LPS), capsular polysaccharide, and a polyclonal rabbit anti-leukotoxin antibody were used to localize their respective antigens in tissue sections of pneumonic lung at the light and electron microscopic levels. We found the following: 1) LPS, capsular polysaccharide, and leukotoxin were released into the inflammatory exudate; 2) LPS was found within the cytoplasm of neutrophils (located in the alveolus and alveolar wall), alveolar macrophages, endothelial cells, pulmonary intravascular macrophages, and on epithelial cell surfaces; 3) capsular polysaccharide was found in the alveolus and alveolar macrophages but not in cells of the alveolar wall; and 4) leukotoxin was associated with cell membranes of degenerating inflammatory cells located in the alveolus. This is the first study that demonstrates the presence of leukotoxin in the pulmonary inflammatory lesions caused by P. haemolytica A1 and implicates endotoxin as an important factor in the genesis of the pulmonary lesions.

Topics: Animals; Antibodies, Monoclonal; Blotting, Western; Cattle; Cattle Diseases; Electrophoresis, Polyacrylamide Gel; Endotoxins; Exotoxins; Immunoenzyme Techniques; Lung; Male; Mice; Pasteurella; Pasteurella Infections; Pneumonia; Polysaccharides, Bacterial; Rabbits

The induction of pulmonary antibodies to a bacterial antigen following intraduodenal (D) stimulation of the gut-associated lymphatic tissue (GALT) was investigated. Six calves were divided into two groups of three calves each. The GALT-primed calves received an ID dose of live Pasteurella haemolytica A1 followed by a subcutaneous (SC) dose of killed P. haemolytica. The sham-primed calves received an ID dose of phosphate-buffered saline solution (PBSS) followed by a SC dose of killed bacteria. Serum and pulmonary lavage fluids were collected weekly from each calf and assayed for titers of leukotoxin neutralizing antibodies (LNA), as well as IgG and IgA (lavage fluids only) to P. haemolytica. The GALT-primed calves responded to the ID stimulation by bacteria with increased serum IgG. The sham-primed calves had no change in antibody titers following ID stimulation. The GALT-primed calves had increased serum IgG, lavage IgG and IgA and increased LNA titers in both lavage fluids and serum following the SC dose of killed bacteria. The sham-primed calves demonstrated only an increase in serum IgG following the SC inoculation. A challenge study to evaluate if antibodies induced by GALT stimulation could reduce pulmonary lesions was performed using six calves divided into two groups. One group received an ID dose of P. haemolytica followed two weeks later by a SC dose of killed P. haemolytica. The sham vaccinated calves received an ID dose of PBSS followed in two weeks by a SC dose of killed bacterin. Calves were challenged by an intrapulmonary dose of live P. haemolytica A1 eleven days after the SC inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antibodies, Bacterial; Bacterial Toxins; Cattle; Cattle Diseases; Exotoxins; Immunoglobulin A; Immunoglobulin G; Intestinal Mucosa; Lung; Lymphoid Tissue; Pasteurella; Pasteurella Infections; Pneumonia

In this study we examined the direct effects of bovine herpesvirus-1 on the interaction of bovine blood neutrophils with Pasteurella haemolytica A1. Preincubation of neutrophils for approximately 2 h in vitro with BHV-1 at a multiplicity of infection of 5:1 had no effect on neutrophil random migration and directed migration to zymosan-activated bovine serum. Neutrophils also were unimpaired in their ability to ingest and kill P. haemolytica A1. Preincubation of neutrophils with BHV-1 did not elicit an oxidative burst, as measured by luminol-enhanced chemiluminescence, nor did it alter neutrophil chemiluminescence in response to opsonized P. haemolytica A1. Prolonged preincubation with BHV-1 for 18-24 h similarly did not affect neutrophil chemiluminescence in response to opsonized P. haemolytica A1. The susceptibility of neutrophils to the lethal effects of crude P. haemolytica cytotoxin also was unaltered by preincubation with BHV-1. We observed no evidence of BHV-1 replication in bovine neutrophils as determined by indirect immunofluorescence and electron microscopy. Previous reports have indicated that active BHV-1 infection alters certain neutrophil functions and results in hypersusceptibility to pulmonary pasteurellosis. Our results suggest that these effects are unlikely to be mediated directly by BHV-1, but instead may reflect the action of endogenous mediators that are released during active BHV-1 infection.

Topics: Animals; Cattle; Cattle Diseases; Chemotaxis, Leukocyte; Exotoxins; Herpesvirus 1, Bovine; In Vitro Techniques; Infectious Bovine Rhinotracheitis; Luminescent Measurements; Neutrophils; Pasteurella; Pasteurella Infections; Phagocytosis; Pneumonia