PASTEURELLA-HAEMOLYTICA LEUKOTOXIN - CHEMILUMINESCENT RESPONSES OF PERIPHERAL-BLOOD LEUKOCYTES FROM SEVERAL DIFFERENT MAMMALIAN-SPECIES TO LEUKOTOXIN-TREATED AND OPSONIN-TREATED LIVING AND KILLED PASTEURELLA-HAEMOLYTICA AND STAPHYLOCOCCUS-AUREUS

  • 1 January 1986
    • journal article
    • research article
    • Vol. 47  (1) , 67-74
Abstract
A luminol-dependent chemiluminescence (LDCL) assay was used to assess the response of polymorphonuclear leukocyte (PMN) preparations from 4 species of ruminants (ie, cattle, sheep, goats, and antelopes) and 6 species of nonruminants (ie, swine, dogs, cats, rabbits, horses, and persons) to both opsonized and nonopsonized preparations of living and heat-killed Pasteurella haemolytica and Staphylococcus aureus and to opsonized and nonopsonized heat-killed strains of each bacterium in the presence of sterile culture supernatant (leukotoxin) from P. haemolytica. The LDCL responses of PMN preparations from each of the species studied were greater for living than for heat-killed S. aureus. The most efficient LDCL emission was observed with reaction mixtures containing opsonized living S. aureus. Regardless whether they contained killed or living bacteria, the opsonized S. aureus preparations elicited LDCL emissions more efficiently than did the corresponding nonopsonized preparations. Living P. haemolytica cells and their sterile culture supernatant inhibited the LDCL emissions of phagocytically stimulated PMN preparations from ruminants, but not those from nonruminants. The LDCL response of ruminant PMN to nonopsonized living P. haemolytica was characterized by the development of a peak response at 10 minutes of incubation followed by a precipitous decrease and a subsequent complete cessation of chemiluminesence. The peak LDCL response was higher for opsonized living P. haemolytica than for nonopsonized living bacteria, and the increased response lasted longer. However, opsonization of living P. haemolytica with the serum samples tested only temporarily spared the ruminant PMN preparations from the detrimental effects of leukotoxin. Regardless whether P. haemolytica leukotoxin was presented with opsonized or nonopsonized heat-killed S. aureus or P. haemolytica, it was able to inhibit the LDCL response of PMN of ruminant sources, but not of nonruminants. Leukotoxin acted as a powerful phagocytic stimulus for nonruminant PMN yielding a marked increase in light emission over that observed in the same reaction mixtures without leukotoxin. It is suggested that P. haemolytica leukotoxin is a virulence factor involved in determining the species-associated occurrence of P. haemolytica-induced pneumonia and that its action on leukocytes may be a molecular pathogenetic mechanism of consequence in early stages of the disease. The potential value of adapting the LDCL assay as a tool to measure opsonizing antibody to P. haemolytica cells is considered.