leukotoxin and Swine-Diseases

Topics: Animals; Exotoxins; Fusobacterium Infections; Fusobacterium necrophorum; Host-Pathogen Interactions; Lameness, Animal; Swine; Swine Diseases

Haemophilus paragallinarum is the causal agent of infectious coryza, an economically important disease for the poultry industry. This bacterium secreted proteins of 25-110 kDa during its growth in brain heart infusion, tryptic soy broth, or Luria-Bertani glucose phosphate media, all lacking serum. Some of these proteins were recognized by sera from chickens experimentally infected with H. paragallinarum. A 110-kDa protein was recognized by a serum pool from convalescent-phase pigs naturally infected with Actinobacillus pleuropneumoniae, and also by a rabbit polyclonal serum against Apx I as well as a rabbit serum against Mannheimia haemolytica leukotoxin, suggesting the presence of an RTX-like protein in H. paragallinarum. H. paragallinarum secreted proteins could be important immunogens in the control of infectious coryza.

Topics: Actinobacillus Infections; Actinobacillus pleuropneumoniae; Animals; Antibodies, Bacterial; Antigens, Bacterial; Bacterial Proteins; Blotting, Western; Chickens; Cross Reactions; Culture Media; Exotoxins; Haemophilus Infections; Haemophilus paragallinarum; Mannheimia haemolytica; Molecular Weight; Pasteurellaceae Infections; Poultry Diseases; Rabbits; Swine; Swine Diseases

Pasteurella haemolytica-like (PHL) strains isolated from diarrheic pigs are known to produce a leukotoxin that is lethal to ruminant leukocytes. In the present study, 12 PHL strains were screened for leukotoxin production using a tetrazolium dye-reduction assay. Sterile culture supernatant from strain 6213A, the maximum leukotoxin producer, was used as the crude leukotoxin for characterization studies. The leukotoxin was inactivated by heat at 60 degrees C and by trypsin, protease, and amylase. Toxicity was retained over a pH range of 3.0-11.0. The leukotoxin was lethal to polymorphoneutrophils (PMNs) of cattle, sheep, goat, and swine. Chromosomal DNA of all 12 PHL strains hybridized with a 3.9 kb Pasteurella haemolytica A1 leukotoxin probe, indicating similarities between the leukotoxin genes of P. haemolytica and PHL strains.

Topics: Animals; Bacterial Toxins; Cattle; Diarrhea; DNA, Bacterial; Enteritis; Exotoxins; In Vitro Techniques; Kinetics; Mannheimia haemolytica; Neutrophils; Pasteurella Infections; Species Specificity; Swine; Swine Diseases

A Pasteurella haemolytica-like organism, a new species of bacterium isolated from piglets with diarrhea, secretes a leukotoxin into the culture media. Western blot (immunoblot) analysis indicated that this leukotoxin cross-reacted with antileukotoxin antibody derived from cattle immunized with P. haemolytica. Five overlapping recombinant bacteriophages carrying the gene for this 105-kDa polypeptide were identified with a DNA probe containing sequences from the P. haemolytica lktCA genes from a P. haemolytica-like organism strain 5943 genomic library. Sequence analysis of a region of the cloned DNA revealed two open reading frames encoding proteins with predicted masses of 19.4 and 101.6 kDa. These genes, which we designate pllktC (P. haemolytica-like organism leukotoxin C gene) and pllktA (A gene), respectively, are similar in sequence to the RTX (repeat of toxin) toxin family. The structure of the 101.6-kDa protein derived from the DNA sequence shows three transmembrane domains in the N-terminal part of the protein, 13 glycine-rich repeat domains in the second half of the protein, and a hydrophobic C-terminal part. pllktC and pllktA are strongly homologous to P. haemolytica lktC and lktA genes. However, this leukotoxin kills both BL-3 and pig leukocytes and is not hemolytic.

Topics: Amino Acid Sequence; Animals; Base Sequence; Blotting, Western; Cloning, Molecular; Cytotoxins; Diarrhea; DNA, Bacterial; Exotoxins; Genes, Bacterial; Molecular Sequence Data; Pasteurella; Recombinant Proteins; Sequence Alignment; Swine; Swine Diseases