Immunity induced in rats vaccinated with toxoid prepared from heat-labile toxin produced by Pasteurella multocida serogroup D

Development of immunization trials against Pasteurella multocida

Pasteurellosis is one of the most important respiratory diseases facing economically valuable farm animals such as poultry, rabbit, cattle, goats and pigs. It causes severe economic loss due to its symptoms that range from primary local infection to fatal septicemia. Pasteurella multocida is the responsible pathogen for this contagious disease. Chemotherapeutic treatment of Pasteurella is expensive, lengthy, and ineffective due to the increasing antibiotics resistance of the bacterium, as well as its toxicity to human consumers. Though, biosecurity measures played a role in diminishing the spread of the pathogen, the immunization methods were always the most potent preventive measures. Since the early 1950s, several trials for constructing and formulating effective vaccines were followed. This up-to-date review classifies and documents such trials. A section is devoted to discussing each group benefits and defects.

Cellular and molecular action of the mitogenic protein-deamidating toxin from Pasteurella multocida

The mitogenic toxin from Pasteurella multocida (PMT) is a member of the dermonecrotic toxin family, which includes toxins from Bordetella, Escherichia coli and Yersinia. Members of the dermonecrotic toxin family modulate G-protein targets in host cells through selective deamidation and/or transglutamination of a critical active site Gln residue in the G-protein target, which results in the activation of intrinsic GTPase activity. Structural and biochemical data point to the uniqueness of PMT among these toxins in its structure and action. Whereas the other dermonecrotic toxins act on small Rho GTPases, PMT acts on the α subunits of heterotrimeric G(q) -, G(i) - and G(12/13) -protein families. To date, experimental evidence supports a model in which PMT potently stimulates various mitogenic and survival pathways through the activation of G(q) and G(12/13) signaling, ultimately leading to cellular proliferation, whilst strongly inhibiting pathways involved in cellular differentiation through the activation of G(i) signaling. The resulting cellular outcomes account for the global physiological effects observed during infection with toxinogenic P. multocida, and hint at potential long-term sequelae that may result from PMT exposure.

Cloning, sequencing, expression, and protective capacity of the oma87 gene encoding the Pasteurella multocida 87-kilodalton outer membrane antigen

Membrane proteins of Pasteurella multocida have been shown previously to elicit protective immunity. We have identified an 87-kDa outer membrane antigen, Oma87, which is present in all 16 serotypes of P. multocida. The gene encoding this protein was cloned and sequenced and found to have significant similarity to the D15 protective surface antigen of Haemophilus influenzae. Oma87 was localized to the outer membrane of the cell, and proteinase K treatment suggested that the protein is surface exposed. Native and recombinant Oma87 were strongly immunostained by convalescent-phase antiserum, indicating that the protein is expressed in vivo. Specific Oma87 antiserum protected mice against homologous, lethal P. multocida challenge. These results suggest that Oma87 is a protective outer membrane antigen of P. multocida.

Reduced physeal area and chondrocyte proliferation in Pasteurella multocida toxin-treated rats

Pasteurella multocida toxin depresses weight gain in rats and pigs. It also affects tissues with rapidly dividing cells. In the present study, we investigated the role of this protein toxin on chondrocyte growth in vivo. Rats were divided into a single- or multiple-dose group and were given, respectively, either a single injection (0.15 or 0.6 micrograms/kg toxin subcutaneously) or multiple injections (0.01-0.2 micrograms/kg subcutaneously) of toxin. Bone (humerus) and other selected tissues were stained for bromodeoxyuridine immunoreactivity (BrDU-IR) in order to gauge cell proliferation. Physeal area was measured in rats from the multiple-dose group. Serum from single- and multiple-dose groups were tested for tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) activity using a bioassay system. Decreased weight gain, feed intake, and feed efficiency were observed in single- and multiple-dose groups of rats. Decreased BrDU-IR indices were present in the resting and proliferative zone chondrocytes of the humeral physis in rats from the multiple-dose group, as was decreased physeal area. Increased serum IL-6 bioactivity was present in rats after 24 hours, and no changes in TNF-alpha bioactivity were seen in any group. No alterations in BrDU-IR were seen in rats fed restricted (80% of control) diets. These studies show that sublethal doses of toxin decrease weight gain and affect growth of long bones through suppression of chondrocyte proliferation. These effects may be mediated by direct binding of the toxin to target cells or IL-6 but are not associated with altered feed intake or TNF-induced cachexia.

Immunogens of Pasteurella

The family Pasteurellaceae Pohl contains Gram-negative, facultatively anaerobic and fermentative bacteria of the genera Pasteurella, Haemophilus, and Actinobacillus. Approximately 20 different species of the genus Pasteurella have been identified using phenotypic and genetic analyses. Of these species, P. multocida and P. haemolytica are the most prominent pathogens in domestic animals causing severe diseases and major economic losses in the cattle, swine, sheep, and poultry industries. Mechanisms of immunity to these bacteria have been difficult to determine, and efficacious vaccines have been a challenge to develop and evaluate. Pasteurella multocida of serogroups A and D are mainly responsible for disease in North American poultry and pigs and to a lesser extent in cattle. Fowl cholera in chickens and turkeys is caused by various serotypes of P. multocida serogroup A and characterized by acute septicemia and fibrinous pneumonia or chronic fibrinopurulent inflammation of various tissues. Current biologicals in use are live P. multocida vaccines and bacterins. Potency tests for avian P. multocida biologicals are a bacterial colony count for vaccines and vaccination and challenge of birds for bacterins. Somatic antigens, particularly lipopolysaccharide (LPS), appear to be of major importance in immunity. In North American cattle, P. multocida serogroup A is associated mainly with bronchopneumonia (enzootic pneumonia) in young calves; however, it is occasionally isolated from fibrinous pleuropneumonia of feedlot cattle (shipping fever). Biologicals currently available are modified-live vaccines and bacterins. The potency test for vaccines is bacterial colony counts. The test for bacterin potency is vaccination and challenge of mice. Important immunogens have not been well characterized for P. multocida infection in cattle. In swine, P. multocida infection is sometimes associated with pneumonia; however, its major importance is in atrophic rhinitis. A protein toxin (dermonecrotic toxin), produced by toxigenic strains of P. multocida types A and D, and concurrent infection with Bordetella bronchiseptica appear to be the major factors in development of atrophic rhinitis. Currently available biologicals are bacterins and inactivated toxins (toxoids). The toxin appears to be the major immunogen for preventing atrophic rhinitis. There are, however, no standardized requirements for potency testing of P. multocida type D toxoid. Various serotypes of P. haemolytica biotype A are responsible for severe fibrinous pleuropneumonia of cattle and sheep, occasionally septicemia of lambs, and mastitis in ewes. Several serotypes of P. haemolytica biotype T are isolated from acute septicemia of lambs. The currently available P. haemolytica biologicals are modified-live vaccines, bacterins, bacterial surface extracts, and culture supernates that contain an exotoxin (leukotoxin).(ABSTRACT TRUNCATED AT 400 WORDS)

Use of rats to compare atrophic rhinitis vaccines for protection against effects of heat-labile protein toxin produced by Pasteurella multocida serogroup D

Four bacterin-toxoid and three bacterin commercial vaccines against atrophic rhinitis were tested in rats for their capacity to immunize against the lethal and systemic effects of purified heat-labile protein toxin (D-toxin) produced by Pasteurella multocida serogroup D. Only one bacterin-toxoid vaccine stimulated sufficient immunity to prevent the death of all rats challenged with D-toxin. None of the vaccines prevented weight loss, leukocytosis or increases in serum complement titers in rats challenged with D-toxin. Rats provide an inexpensive animal model for testing the capacity of vaccines to generate antitoxic immunity against the lethal and systemic effects of D-toxin.

Experimental model of atrophic rhinitis in gnotobiotic pigs

To study the pathogenesis of atrophic rhinitis, gnotobiotic pigs (n = 6) were inoculated intranasally with a sterile sonicate of a toxigenic strain of Bordetella bronchiseptica (0.16 mg of protein per ml) at 5 days of age, and they were then inoculated intranasally with 1 ml (5,250 CFU/ml) of a live, toxigenic strain of Pasteurella multocida at 7 days of age. Pigs were necropsied at 2, 5, 9, 14, 21, and 28 days postinoculation; those pigs necropsied after 5 days had developed turbinate atrophy. Other gnotobiotic pigs received the following inoculation protocols: (i) a sterile sonicate of a nontoxigenic strain of B. bronchiseptica (0.2 mg of protein per ml), followed by toxigenic P. multocida (n = 4); (ii) toxigenic P. multocida alone (n = 7); (iii) diluent (sterile tryptose broth) (n = 2); (iv) the sterile sonicate of toxigenic B. bronchiseptica alone (n = 2); or (v) the sterile sonicate of a nontoxigenic strain of B. bronchiseptica alone (n = 2). Turbinate atrophy did not occur in the latter groups except for one pig inoculated with only toxigenic P. multocida. These studies show that turbinate atrophy occurs in pigs given the toxigenic B. bronchiseptica sonicate and then given live, toxigenic P. multocida. This experimental regimen is a useful model for (i) studying the pathogenesis of atrophic rhinitis and (ii) testing vaccine strategies.