Selection of Vaccine Candidates for Fish Pasteurellosis Using Reverse Vaccinology and an In Vitro Screening Approach

The advent of new technologies in recent years has revolutionized the methods by which pathogens are studied and at the same time it has provided new tools to design vaccines against infections for which vaccine development has so far been unsuccessful. The availability of genomic data provides the basis for the reverse vaccinology approach, a biotechnological strategy that uses bioinformatics analysis of microbial genome data for the in silico selection of potential vaccine candidates for the development of protein-based vaccines. The antigens selected by reverse vaccinology can be produced as recombinant proteins and subjected to further in vitro screening assays before in vivo experiments to assess immunogenicity and protection. The reverse vaccinology approach has been applied to several pathogens affecting human health, but also to marine bacteria, including Photobacterium damselae subsp. piscicida causing significant harm in marine aquaculture.

Characterization of two lipoproteins in Pasteurella multocida

An in vivo expression technology (IVET) system was previously developed and used to identify Pasteurella multocida genes, which are upregulated during infection of the host. Of the many genes identified, two encoded products which showed similarity to the Haemophilus influenzae lipoproteins, protein D and PCP, which have been shown to stimulate heterologous immunity against infection with H. influenzae. Therefore, the lipoprotein homologues in P. multocida, designated GlpQ and PCP, were investigated. GlpQ and PCP were shown to be lipoproteins by demonstrating that post-translational processing of the proteins was inhibited by globomycin. The P. multocida GlpQ homologue showed glycerophosphodiester phosphodiesterase enzyme activity, indicating that it is a functional homologue of other characterized GlpQ enzymes. Using surface immunoprecipitation, PCP was found to be surface exposed, but GlpQ was not. Non-lipidated forms of GlpQ and PCP were expressed and purified from Escherichia coli and used to vaccinate mice. However, mice were not protected from challenge with live P. multocida. The lipoproteins were then expressed in E. coli in the lipidated form and used to vaccinate mice and chickens. Protection against challenge with live P. multocida was not observed.

Regulating effects of porcine interleukin-6 gene and CpG motifs on immune responses to porcine trivalent vaccines in mice

In order to develop novel immunoadjuvants to boost immune response of conventional vaccines, experiments were conducted to investigate the regulating effects of porcine interleukin-6 gene and CpG motifs as the molecular adjuvants on immune responses of mice that were co-inoculated with trivalent vaccines against Swine fever, the Pasteurellosis and Erysipelas suis. Synthetic oligodeoxynuleotides containing CpG motifs were ligated into pUC18, forming recombinant pUC18-CpG plasmid. Eukaryotic plasmid expressing porcine interleukin-6 (VPIL-6) were also constructed as molecular adjuvants in an attempt to enhance levels of immune responses of mice co-administered with the trivalent vaccines in this paper. The cellular and humoral immune responses of mice were systematically analysed, and the experimental results were observed that the number of white blood cells, monocytes, granuloytes and lymphocytes significantly increased, respectively, in the mice immunized with VPIL-6, compared with those of the control; the IgG content and titre of specific antibodies to the trivalent vaccine mounted remarkably in the sera from the VPIL-6 vaccinated mice; the proliferation of lymphocytes and induced IL-2 activities were significantly increased in the vaccinated groups. The above-mentioned immune responses of mice co-inoculated with pUC18-CpG plasmid were significantly stronger than those of co-inoculated with pUC18 plasmid, suggesting that the immunostimulatory effect of oligodeoxynuleotides CpG is closely connected with the number of CpG motifs. These results suggest that the porcine IL-6 gene and CpG motifs could be employed as effective immunoadjuvants to elevate immunity to conventional vaccines.

Detection and elimination of contaminating microorganisms in transplantable tumors and cell lines

As a quarantine of biological materials, we tested 96 transplantable tumors and cell lines for contamination with microorganisms in a mouse antibody production (MAP) test, enzymatic assay and microbiological culture. Contamination with lactic dehydrogenase elevating virus (LDV), mycoplasmas and Pasteurella pneumotropica was detected. A considerable difference in the contamination rate was observed between in vivo- and in vitro- propagated tumors. LDV in the tumors could be eliminated by both in vitro subculture and subpassage in nude rats. Mycoplasmas were eliminated by means of the mycoplasma-removal agent and P. pneumotropica by subpassage in mice. These results suggest that there is still a high risk of contamination in transplantable tumors and emphasizes the importance of adequate microbiological quality control.

Production and evaluation of a panel of monoclonal antibodies against Haemophilus paragallinarum

We report on the production and characterisation of monoclonal antibodies (MAbs) against Haemophilus paragallinarum, the causative agent of infectious coryza. A bank of 8 MAbs were produced by traditional techniques - four against the reference strain for Page serovar A (0083) and four against the reference strain for Page serovar C (Modesto). Seven of the eight MAbs were shown to be IgG(1) with one being nontypable. None of the MAbs had HI activity and none gave any detectable reaction when examined by Western blotting. None of the MAbs gave a positive reaction in the indirect ELISA with any of the eight type strains of Pasteurella species or sub-species. None of our 8 MAbs gave serovar specific reactions when used in an indirect ELISA format. There was a trend for the serovar A MAbs to give a higher titre with serovar A isolates/strains and a similar trend for the serovar C MAbs to give higher titres with the serovar C isolates/strains.

Dual infection with Pneumocystis carinii and Pasteurella pneumotropica in B cell-deficient mice: diagnosis and therapy

BACKGROUND AND PURPOSE

The clinical presentation, diagnosis, histopathologic findings, and elimination of dual respiratory tract infection with Pasteurella pneumotropica and Pneumocystis carinii were studied in 100 adult barrier-reared C.B17 and MRL- lpr mice homozygous for a targeted mutation of the JH region of the immunoglobulin heavy chain.

METHODS

Necropsy, aerobic bacteriologic culture of hematogenous and pulmonary tissues, histochemical staining of pulmonary tissues, polymerase chain reaction analysis of pulmonary tissues and feces, and viral serologic testing were performed on 19 clinically affected mice and 8 clinically normal mice, then later on antibiotic-treated and caesarian re-derived mice. Therapeutic strategies included sequential administration of trimethoprim/ sulfamethoxazole and enrofloxacin or enrofloxacin administration and caesarian rederivation.

RESULTS

Clinically affected mice had diffuse, nonsuppurative, interstitial pneumonia with superimposed pyogranulomatous lobar pneumonia that was detected microscopically. Affected lung tissue yielded pure culture of P. pneumotropica. Aged-matched, clinically normal mice of both genotypes had interstitial histiocytic pneumonia without lobar pneumonia, and P. pneumotropica was not isolated. Histochemical staining of lung tissues from normal and clinically affected mice revealed scattered cysts consistent with P. carinii, principally in the interstitium. Treatment with sulfamethoxazole/trimethoprim and enrofloxacin eliminated bacteriologic detection of P. pneumotropica, decreased mortality from 50% to 6%, and improved breeding performance.

CONCLUSION

A successful antibiotic therapy and rederivation approach, incorporating enrofloxacin, cesarian section, and isolator rearing, was developed for B cell-deficient mice with opportunistic infections.

A critical role of natural immunoglobulin M in immediate defense against systemic bacterial infection

To evaluate the role of natural immunoglobulin (Ig)M in the immediate response against microbial infection, we tested mutant mice that are deficient in secreted (s)IgM in an acute peritonitis model induced by cecal ligation and puncture (CLP). 20% of wild-type mice died within 32 h of CLP, whereas 70% of sIgM-deficient mice died within the same time period. The increased susceptibility was associated with a reduced level of tumor necrosis factor (TNF)-alpha, a decreased neutrophil recruitment and an increased bacterial load in the peritoneum, and elevated levels of endotoxin and proinflammatory cytokines in the circulation. Resistance to CLP by sIgM-deficient mice was restored by reconstitution with polyclonal IgM from normal mouse serum. Reconstitution with a monoclonal IgM specific to phosphatidylcholine, a conserved cell membrane component, has a modest effect but a monoclonal IgM specific to phosphocholine is not protective. These findings demonstrate a critical role of natural IgM in the immediate defense against severe bacterial infection.

Proliferative responses of peripheral blood leucocytes of sheep infected with Trypanosoma evansi

The effects of Trypanosoma evansi on the proliferative responses of ovine peripheral blood leucocytes (PBL) were examined in in vitro cell culture systems. Sheep were vaccinated against pneumonic pasteurellosis with a monovalent Pasteurella haemolytica vaccine and then infected with T. evansi TREU 2143. From 1 week post-infection (p.i.), the PBL were separated and stimulated in cultures with either Concanavalin A (Con A), bacterial lipopolysaccharide (LPS), pasteurella antigen (P.ag), or homologous trypanosome antigen (T.ag). The proliferative responses of the cells to Con A and LPS were significantly (P < 0.001) suppressed by the infection. This suppression was associated with active infection, as treatment of the sheep with a trypanocide restored the proliferative ability of the cells to both mitogens. Similarly, active infection significantly (P < 0.001) suppressed specific responses to P.ag and T.ag but although treatment resulted in full specific proliferative responsiveness to the homologous trypanosome antigen, the same was not true of P.ag, in which the responsiveness of cells from uninfected vaccinated sheep to it were still significantly higher (P < 0.001) than those of cells from infected sheep.

Divergent activity and function of superoxide dismutases in Pasteurella haemolytica serotypes A1 and A2 and Pasteurella trehalosi serotype T10

Representative strains of Pasteurella haemolytica serotypes A1 and A2 and Pasteurella trehalosi serotype T10 were examined for the presence of superoxide dismutase. Visualisation of superoxide dismutase enzyme activity on polyacrylamide gels, and specific inhibition with potassium cyanide verified a copper/zinc (Cu/Zn) superoxide dismutase only in serotype A2 whereas serotypes A1 and T10 showed other superoxide dismutase activity. Using a simple freeze-thaw method the cellular location of superoxide dismutase enzyme activity was determined in all three serotypes. In serotypes A1 and A2 but not T10 superoxide dismutases were located in the periplasm. The viability of serotypes A2 and T10 cells in the presence of exogenous superoxide was unchanged over a 30 min period, whereas serotype A1 cells declined in viability between 15 and 30 min. Purified immunoglobulin from sheep convalescent serum did not reduce superoxide dismutase activity in the serotypes in an in vitro assay. The presence of this enzyme within the pasteurellae suggests a supportive role in the virulence of this major pathogen of ruminants.

Immunization with bacterial antigens: pasteurellosis

Pasteurella piscicida is the aetiological agent of pasteurellosis or pseudotuberculosis, one of the most threatening diseases of wild and cultured marine fish. This bacterium has been reported from many geographical areas including USA, Japan, and the Mediterranean countries. In this review, the biochemical, serological, and molecular characteristics of the pathogen are described. In addition, its main virulence mechanisms, such as the presence of capsule, the iron uptake system, and the phospholipase activity, as well as their putative role in the pathogenicity of P. piscicida are also discussed. Finally, a detailed survey of the strategies for controlling the disease is performed, with a special emphasis on the vaccination programmes and the most effective protective antigens to be included in the vaccine formulations.

Phenotype and serotype of Pasteurella multocida isolates from diseases of dogs and cats in Zimbabwe

A variety of disease manifestations, comprising skin bite wounds, pyothorax, respiratory and genitourinary tract infections, in 202 dogs and cats presented to the University Clinic, were investigated for the presence of Pasteurella multocida. Of these, 25-42% of various cases (69) were found to be infected with P. multocida. P. multocida-associated respiratory tract infections were more common than bite wounds or genitourinary tract infections. The regimen of treatment consisted of those antibiotics, sensitivity to which had been confirmed in vitro. Following detailed characterization of the isolates of P. multocida, in order to assign them to the reclassified taxa of Pasteurella, a preponderance of P. multocida subspecies multocida and septica were recorded. There did not appear to be a correlation between the reclassified taxa and their serotypes. Certain strains of different species or subspecies belonged to a common serotype and vice versa. However, the strains which were serotyped belonged to capsular type A, except for a solitary isolate from a cat which was capsular type D. Type D is known to cause atrophic rhinitis and does not appear to have been isolated either from a dog or a cat. Two strains, one from a dog and another from a cat, were identified as group EF-4 bacteria. This group of organisms has been incriminated in human wounds resulting from dog/cat bites, and has so far not been reported in Africa. Three different species, P. stomatis, P. dagmatis and P. multocida subspecies multocida were simultaneously isolated from a case of chronic bronchitis in a dog. There was no evidence of any relationship between disease manifestation in a host and the isolation of a particular taxon of Pasteurella, except that P. canis and Pasteurella taxon 16 were only isolated from dogs.

Response of eosinophilic granule cells of gilthead seabream (Sparus aurata, Teleostei) to bacteria and bacterial products

Eosinophilic granule cells in the gills and peritoneal exudate of gilthead seabream (Sparus aurata L.) are characterized by the presence of prominent eosinophilic granules in their cytoplasm and are here described for the first time. The oval granules of these cells contain an electron-dense inclusion surrounded by a less dense filamentous matrix and are peroxidase- and acid phosphatase-negative. Unlike other granulocytes of gilthead seabream, eosinophilic granule cells do not ingest bacteria in vivo. The intraperitoneal injection of extracellular products of Pasteurella piscicida induces mobilization of eosinophilic granule cells to the blood and other tissues and causes changes in their structure. Shortly after injection, the granules of eosinophilic granule cells become swollen and some fuse with the cell membrane. From 7 h post-injection, many eosinophilic granule cells in the gills degenerate and are then phagocytosed by macrophages, which are especially abundant after 24 h. From 24 h to 72 h, eosinophilic granule cells from the gills contain abundant autolysosomes together with granules of a normal morphology.

Environment, incidence, aetiology, epizootiology and immunoprophylaxis of soil-borne diseases in north-east Mexico

Within the framework of an extensive research programme, the socio-economic and environmental conditions which influence the emergence of soil-borne diseases in north-eastern Mexico were analysed. Furthermore, specimens collected from carcasses in the field were bacteriologically examined and the causal organisms of soil-borne diseases differentiated by means of gas chromatographic analysis of their metabolic products and the long-chained fatty acids contained in the cell. With experimental clostridial vaccines prepared with the Goettingen Bioreactor Technique, trials to protect cattle and guinea-pigs against gas gangrene were carried out. It was found that the farm structure and the dry climate as well as the specific soil conditions and plant cover favour the emergence of soil-borne diseases. Causal organisms B. anthracis, C. perfringens, C. sordellii, C. haemolyticum, C. chauvoei/septicum, C. novyi A, C. botulinum and site-specific field strains of clostridia were detected. Experimental site-specific vaccines proved to be highly efficient in protecting cattle and guinea pigs.

Mycoplasma hyorhinis infection levels in lungs of piglets with porcine reproductive and respiratory syndrome (PRRS)

The infection levels of Mycoplasma hyorhinis, M. hyopneumoniae and M. hyosynoviae in the lung of piglets were examined in relation to porcine reproductive and respiratory syndrome (PRRS). These animals consisted of 43 PRRS piglets with PRRS, 2 piglets infected with PRRS virus but symptom-free, and 10 control piglets free of PRRS virus and its antibody. M. hyorhinis was isolated from 40 of the 43 PRRS piglets, from 1 of the 2 latent infected piglets and from 3 of the 10 control piglets. The number of M. hyorhinis isolated from the lungs of PRRS piglets was more than 10(5) CFU/g, but those isolated from the latent infected piglets and the control piglets were less than 10(3) CFU/g. In addition to this, Haemophilus parasuis and Pasteurella spp. were frequently isolated from the piglets with PRRS (51.2% and 25.6%, respectively). On the other hand, M. hyopneumoniae was isolated from only 4 of 55 piglets tested, and M. hyosynoviae was not isolated. M. hyorhinis was also detected directly in the lung emulsion samples from almost all the PRRS piglets using a polymerase chain reaction-based method.

Enzyme release by bovine neutrophils

Release of enzymes from cytoplasmic granules has been postulated to have a major role in neutrophil-mediated tissue injury. Secretion or release of primary granules, specific granules, and cytosolic enzymes by bovine neutrophils was examined by quantifying the release of beta-glucuronidase, B12-binding protein, and lactate dehydrogenase, respectively, in response to predetermined amounts of phorbol myristate acetate, calcium ionophore, and opsonized zymosan. These responses were compared with the enzyme release induced by exposure to live or dead, unopsonized or opsonized Pasteurella haemolytica. The greatest release of beta-glucuronidase, B12-binding protein, and lactate dehydrogenase was observed in neutrophils exposed to live organisms partially because of neutrophil lysis. Bovine neutrophils respond markedly to particulate agonists, live or dead, pathogenic or nonpathogenic, by a selective release of specific granules, an effect enhanced by opsonization. Particulate agonists induce minimal primary granule release other than that induced by cell death. Because bovine neutrophils contain quantitatively high numbers of specific granules, the high rate of secretion/release in response to P haemolytica organisms could have a major role in the tissue responses that characterize the lesions of pneumonic pasteurellosis.

An enzyme-linked immunosorbent assay (ELISA) for monitoring rodent colonies for Pasteurella pneumotropica antibodies

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of Pasteurella pneumotropica antibodies in the sera of rats, mice, hamsters and Mastomys. P. pneumotropica from mice and rats showed cross-reactivity. The ELISA using P. pneumotropica NCTC 8284 detected more infected animals than selective culture in groups of rodents from which P. pneumotropica, Haemophilus sp and/or Actinobacillus sp were cultured. Cross reactivity between P. pneumotropica NCTC 8284 and haemophilus and actinobacillus isolates were not studied.

An enzyme-linked immunosorbent assay (ELISA) for monitoring antibodies to SP group Pasteurellaceae in guineapigs

Cross-reactivity studies with Pasteurellaceae from guineapigs revealed 5 serologically distinct groups, comprising Pasteurella multocida, Sp group bacteria, SP-like bacteria, Pasteurella pneumotropica and an actinobacillus-like bacterium. Guineapig Pasteurellaceae differed serologically from mouse-derived P. pneumotropica NCTC 8284. An enzyme-linked immunosorbent assay (ELISA) using SP group antigen, developed to monitor 'natural' infections by SP group Pasteurellaceae in guineapigs, detected significantly more infection than did cultivation, and was found superior to an ELISA performed with P. pneumotropica NCTC 8284.

Capsular polysaccharide expressed by Pasteurella piscicida grown in vitro

Pasteurella piscicida grown in a glucose-rich medium produces a capsule that can be see under light and electron microscopy. The capsular polysaccharide was purified and characterized by chemical and HPLC analysis. The polymer has the composition glucose/mannose/N-acetylgalactosamine/galacturonic acid/acetic acid in the molar ratios of approximately 2.5:1.3:0.5:0.4:2.5. The polysaccharide was immunogenic in rabbits and did not cross-react with antibodies against the O-antigen lipopolysaccharide.

Interaction between immunity to Bordetella bronchiseptica and infection of pig herds by Bordetella bronchiseptica and Pasteurella multocida

The dynamics of toxigenic Bordetella bronchiseptica and Pasteurella multocida infection and the B. bronchiseptica specific antibody content of the blood and nasal secretion were studied in three Hungarian and three Dutch pig herds. In both countries, the studies involved young sows that had farrowed once or twice (YS), old sows that had farrowed more than four times (OS), and their piglets. The results indicate that Dutch sows are characterized by a lower prevalence of B. bronchiseptica and P. multocida infection than Hungarian sows. In Dutch sows and in their piglets, the rate of P. multocida infection was higher than that of B. bronchiseptica infection. The opposite was found for the Hungarian sows and their piglets. B. bronchiseptica infection commenced at 3 and 4 weeks of age in piglets of young and old Dutch sows, respectively, followed by the emergence of P. multocida infection at 5 (YS) and 6 weeks of age (OS). In Hungarian piglets, B. bronchiseptica infection was first demonstrable at 1 (YS) and 3 (OS) while P. multocida infection at 3 (YS) and 5 (OS) weeks of age. The serological tests demonstrated higher B. bronchiseptica specific antibody levels in the Dutch sows and piglets as compared to the Hungarian ones. According to the ELISA results, the levels of IgA and IgG in the serum and those of sIgA, IgA and IgG in the nasal secretion of Dutch sows were significantly (p < 0.001) higher in the Dutch than in the Hungarian piglets up to 3 and 4 weeks of age, respectively.

[Pasteurella anatipestifer: a controllable farm problem]

The performance of 13 flocks of ducks on a duck farm decreased markedly. Post-mortem and bacteriological examinations indicated that Pasteurella anatipestifer was a major cause, although Salmonella spp., Escherichia coli and Treponema spp. were also detected. Use of an autovaccine against Pasteurella anatipestifer markedly reduced the signs and symptoms in the second part of fattening period.

Outbreaks of Salmonella Dublin infection among calves on a dairy farm applying Salmonella bacterins in Zambia

In Zambia, a dairy farm keeping about 600 cows and self-contained calves had applied S. Dublin and S. Typhimurium bacterins to pregnant cows and calves in combination with all-in all-out pen system for rearing calves. Only relatively small scale outbreaks of S. Dublin infection occurred repeatedly in these years from 1989 to 1991 among fattening calves on the farm. The results obtained from the epizootiological study suggest that the preventive measures including the vaccination with Salmonella bacterins gave insufficient protection against S. Dublin infection to the calves, but they might have prevented large scale outbreak of the disease. This is the first report of the epizootiological study on outbreak of bovine S. Dublin infection on farm in Zambia.

[Results of experimental immunization of calves with different Pasteurella antigens]

Calves immunised with different Pasteurella antigens (inactivated whole cells, sodium chloride extract) where challenged two weeks after the second immunization with the homologous strain. The intracutaneous application of whole cells of P. haemolytica A1 and P. multocida A was effective. The incidence of pneumonia was reduced and the pneumonic lesions were less severe. The sodium chloride extract was not effective.

Release of tumor necrosis factor-alpha from bovine alveolar macrophages stimulated with bovine respiratory viruses and bacterial endotoxins

The release of tumor necrosis factor-alpha (TNF-alpha) from cultured bovine alveolar macrophages (BAM) was evaluated following stimulation of BAM with bovine herpesvirus-1 (BHV-1), parainfluenza-3 (PI-3) virus, bovine respiratory syncytial virus (BRSV), Escherichia coli 0111:B4 endotoxin, Pasteurella haemolytica type 1 endotoxin, Pasteurella multocida endotoxin, and virus/endotoxin combinations. A cytotoxic assay system using Georgia bovine kidney cells as targets was used to measure TNF-alpha activity. The cytotoxic activity was neutralized by an anti-human TNF-alpha monoclonal antibody. Stimulation of BAM with 1 median tissue culture infectious dose (TCID50) of live or ultraviolet (UV)-inactivated PI-3 virus/cell resulted in release of TNF-alpha in significantly (P less than 0.05) higher amounts than sham-induced BAM. The quantities of TNF-alpha released after live or UV-inactivated BHV-1 or BRSV induction were not significantly higher than sham-induced BAM. E. coli 0111:B4, P. haemolytica type 1 and P. multocida endotoxins stimulated TNF-alpha release in a dose-dependent manner. Sequential exposure of BAM to 1 TCID50 per cell of either live BHV-1, PI-3 virus or BRSV and then 5 micrograms ml-1 of either E. coli 0111:B4, P. haemolytica type 1 or P. multocida endotoxin caused a significant (P less than 0.05) reduction in detectable TNF-alpha in seven of nine virus/endotoxin combinations tested, when compared with 5 micrograms ml-1 of endotoxin alone. Parainfluenza-3 virus/endotoxin combinations stimulated higher TNF-alpha release when compared with other virus/endotoxin combinations. Five out of six test animals had serum-neutralizing antibodies to PI-3 virus, one out of six had serum-neutralizing antibodies to BHV-1, and two out of six had serum-neutralizing antibodies to BRSV, suggesting a possible relationship between serum neutralizing antibodies and TNF-alpha release from in vitro cultivated BAM.

Molecular studies of Ssa1, a serotype-specific antigen of Pasteurella haemolytica A1

A serotype-specific antigen of Pasteurella haemolytica A1 encoded on the recombinant plasmid pSSA1 is characterized. Nucleotide sequence analysis of the insert DNA in pSSA1 identified the gene ssaI, which codes for a protein of approximately 100 kDa. In vivo labeling of pSSA1-encoded protein in Escherichia coli maxicells showed the expression of a 100-kDa protein from the insert DNA on the recombinant plasmid. Northern blot and primer extension analyses were used to identify the mRNA transcript in P. haemolytica A1 and the putative promoter of ssaI. The antigen (designated Ssa1) could be localized to the outer membrane of P. haemolytica A1 and E. coli clones carrying pSSA1. A rabbit serum against Ssa1 was produced by using whole cells of E. coli expressing Ssa1 on the surface as the immunogen, demonstrating that Ssa1 is immunogenic in rabbits. The results from colony immunoblot analysis with calf serum from animals that were resistant to P. haemolytica A1-induced pneumonia suggest indirectly that Ssa1 is also immunogenic in the animals.

Differential induction of tumor necrosis factor alpha in ovine pulmonary alveolar macrophages following infection with Corynebacterium pseudotuberculosis, Pasteurella haemolytica, or lentiviruses

Soluble mediators such as tumor necrosis factor alpha (TNF-alpha) may be important in the pathogenesis of many chronic pulmonary infections. We examined the ability of Corynebacterium pseudotuberculosis, Pasteurella haemolytica, and ovine lentiviruses (OvLV) to induce TNF-alpha secretion by pulmonary alveolar macrophages (PAM). Bronchoalveolar lavage cells, composed of greater than 90% PAM, were obtained from normal sheep. Bronchoalveolar lavage cells were cultured for 2, 24, 48, 72, or 168 h in endotoxin-free RPMI medium (with 10% autologous serum) or in medium containing one of the following additives: lipopolysaccharide, 1-micron polystyrene beads, C. pseudotuberculosis, P. haemolytica, or one of two plaque-cloned OvLV, 85/28 or 85/34. Lipopolysaccharide, C. pseudotuberculosis, and P. haemolytica induced TNF-alpha activity in PAM cultures as early as 2 h after inoculation, as assessed by a colorimetric cytotoxicity assay. This activity could be blocked by rabbit anti-recombinant bovine TNF-alpha serum. In contrast, medium alone, polystyrene beads, and productive infection by OvLV did not induce TNF-alpha activity in PAM cultures. Bacterial pathogens which infect pulmonary macrophages may elicit the secretion of TNF-alpha within the lungs and lead to the cachectic state associated with chronic pneumonia.

Activation of bovine neutrophils by partially purified Pasteurella haemolytica leukotoxin

In this study we developed a new method for the partial purification of Pasteurella haemolytica leukotoxin by size-exclusion high-performance liquid chromatography. The partially purified leukotoxin had a molecular weight of 104,000, as estimated by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and reacted on an immunoblot with an antileukotoxin monoclonal antibody. As expected, high concentrations of the leukotoxin were inhibitory or lethal to bovine neutrophils. Incubation of bovine neutrophils with diluted leukotoxin, however, resulted in significant neutrophil activation that was comparable in magnitude to that obtained with standard activating agents such as opsonized zymosan or zymosan-activated serum. Dilute leukotoxin (1:128 to 1:8,192 dilutions) stimulated an oxidative burst (luminol-dependent chemiluminescence) by bovine neutrophils that was comparable in magnitude to that obtained with opsonized zymosan. Preincubation with leukotoxin did not significantly prime the neutrophils for an enhanced oxidative burst when they were then exposed to opsonized zymosan as a second stimulus. Dilute leukotoxin (1:100 to 1:1,000 dilutions) also stimulated cytoskeletal alterations in bovine neutrophils, as measured by a significant shape change response. Preferential release of secondary granule constituents (lactoferrin) occurred when neutrophils were incubated with 1:100 to 1:500 dilutions of leukotoxin. Significant release of primary granules, as measured by beta-glucosaminidase activity, was not observed except at low dilutions (1:20) of leukotoxin that resulted in significant release of cytosolic constituents (i.e., lactate dehydrogenase activity). The neutrophil-activating activity of the leukotoxin was heat labile, unaffected by polymyxin B, and abrogated by a leukotoxin-neutralizing monoclonal antibody. These data indicate that P. haemolytica leukotoxin, like the closely related Escherichia coli hemolysin, is a potent neutrophil-activating agent. Leukotoxin-stimulated release of neutrophil oxygen intermediates and granule constituents may contribute to the intense inflammation that characterizes bovine pulmonary pasteurellosis.

Rabies-specific production of interleukin-2 by peripheral blood lymphocytes from human rabies vaccinees

Cell-mediated immunity induced by rabies vaccination was studied in humans by the determination of specific interleukin-2 (IL-2) production in a large number of donors (postexposure immunized patients and pre-exposure immunized laboratory workers). Peripheral blood lymphocytes (PBL) from 35 donors were tested for IL-2 production after in vitro stimulation by different rabies and rabies-related viruses. IL-2 responses were compared to antibody recognition of these different virus serotypes by sera from the same individuals. IL-2 was produced by PBL from more than 85% of donors after stimulation with inactivated and purified rabies viruses (IPRV) prepared from either Pittman Moore (PM) or Pasteur Virus (PV) strains. IL-2 was also produced by 65 and 45% of donor PBL stimulated with IPRV from the European Bat Lyssavirus (EBL) and Mokola (Mok) rabies-related virus strains respectively. No correlation was found between the production of IL-2 by PBL and the levels of virus neutralizing antibody (VNAb). Moreover, 50, 25 and 35% of donors produced IL-2 after stimulation of their PBL with ribonucleoprotein (RNP) from PV-, EBL- and Mok-viruses, respectively. These results obtained with a large number of human rabies vaccinees and using an assay specific to T-cell activation confirm the significant cross-reactivity of T-cell responses directed against rabies and rabies-related viruses. This study shows that IL-2 production could be used for the study of cell-mediated immunity and T-cell memory induced in humans by rabies vaccination.

Detection and enumeration of toxin-producing Pasteurella multocida with a colony-blot assay

Colonies of toxin-producing Pasteurella multocida were detected with peroxidase-labeled monoclonal antibodies by a membrane assay. Examination of the specificity of the assay with 29 P. multocida cultures representing various geographic origins, hosts, and serotypes indicated that the test was specific for toxin-producing strains. No cross-reactions were observed with Bordetella species that can be associated with P. multocida in producing diseases in animals. A single membrane could be used to assay several isolated strains for toxin production or to enumerate toxin-producing colonies in mixed cultures. Toxin-producing P. multocida colonies were detected in primary cultures; hence, the assay appears to have good potential for widespread application with clinical samples.

Haemorrhagic septicaemia: correlation of vaccinal antibody responses in mice with protection against Pasteurella multocida strain M1404

This study examined the protection induced by oil adjuvant vaccine and broth bacterin in mice. Protective immunity was induced by both oil adjuvant and bacterin vaccination procedures. Oil adjuvant vaccination induced a 10(5)-fold increase for lethal challenge over control mice, while secondary vaccination induced a further 10-fold increase in resistance to lethal challenge. Broth bacterin induced a slightly weaker protective response with 10(4)- and 10(5)-fold increases in resistance to lethal challenge following primary and secondary vaccination, respectively. There was a significant relationship between IgG antibody levels and resistance to challenge (P = 0.026). Protection lasted for at least 20 weeks after a primary oil adjuvant vaccination. There was also a strong and significant relationship between IgG antibody levels and the passive protection afforded by serum transfer in each experiment within this study and the overall correlation was highly significant (P = 0.00001). There appeared to be a relationship between protection and the antibody response to major protein bands with the apparent molecular mass Mr. 94,000; 80,000; 67,000; 35,000 and 32,000 as well as to the bands in the region of the lipopolysaccharide components of P. multocida (approximately Mr, 14-15,000). Whether protection resulted from recognition of specific antigens or was a result of both antibody levels and antibody specificity remains to be defined.

Evidence of phenotypic dichotomy within an individual Pasteurella multocida type strain and among some haemorrhagic septicaemia-causing field isolates

Haemorrhagic septicaemia-causing strains of Pasteurella multocida were identified by a disease-specific ELISA. Some strains, however, were of the same serotype as those which cause haemorrhagic septicaemia (HS) but were negative when tested in the disease specific ELISA. The suspect false negative isolates were passaged in mice and retested in the HS ELISA with the same result. Immunoelectron microscopy was used to examine further these suspect HS-causing strains. Monoclonal antibodies and protein A-gold showed that the suspect negative organisms were a mixture of phenotypes with less than 10 per cent, and usually less than 2 per cent, of the population expressing HS-associated epitopes. The degree of staining on the organisms expressing the HS-epitopes was of the same intensity as the positive control organism. Expression of the HS-associated epitopes is presumably too low to allow detection in the current HS ELISA.

Proteins and antigens of Pasteurella multocida serotype 1 from fowl cholera

The protein profiles of Pasteurella multocida serotype 1 isolates and the response of chickens to serotype 1 antigens were investigated using SDS-PAGE. Patterns obtained with Coomassie blue staining of soluble protein extracts were similar. The major difference between isolates was the position of one of the major proteins in the 34-38 kDa region. When chickens were experimentally infected with a clinical isolate of P. multocida serotype 1 various proteins were recognised by immunoblotting, including one with a relative molecular weight of 34 kDa; however, no reactions were observed in the region where LPS is known to migrate. When these infection sera were used in an EIA with purified LPS obtained from Heddleston serotype 1 type strain (X-73) they reacted strongly. Serum used for serotyping isolates in the gel diffusion precipitin test recognised many antigens in common with sera from infected birds, but some antigens were specific to typing sera.

Vaccination against progressive atrophic rhinitis with a recombinant Pasteurella multocida toxin derivative

Vaccination against progressive atrophic rhinitis using a purified recombinant derivative of the Pasteurella multocida toxin (PMT), was carried out. Ten pregnant gilts were vaccinated twice with the nontoxic derivative (dO) which apart from a lack of 121 amino acids had an amino acid sequence identical to PMT, while seven gilts were vaccinated with a purified, formaldehyde treated, native PMT and ten gilts served as non-vaccinated controls. The resulting piglets were inoculated intranasally with Bordetella bronchiseptica and toxigenic P. multocida. Among piglets from the nonvaccinated gilts all except one developed clinical atrophic rhinitis and 90% developed severe turbinate atrophy while only a few pigs in the vaccinated groups developed clinical or pathological signs of disease. Gilt colostra from the two vaccinated groups had similar mean anti-PMT titers and the mean titers in the offspring's sera from these groups were nearly identical throughout the study. No pigs born from unvaccinated gilts were seropositive until 8 wk of age (7 wk post-challenge) but 23% became seropositive at slaughter. The infection rate with toxigenic P. multocida in piglets and the total number of P. multocida colonies cultured from nasal swabs were significantly reduced at 5 wk and 8 wk of age in the vaccinated groups, when compared to controls. There was a significantly improved weight gain (greater than 9%) from birth to slaughter in offspring from vaccinated gilts. No significant differences in feed conversion rate or % lean meat were observed among the groups. The study showed the excellent immunoprotective properties of the nontoxic derivative of the PMT molecule.

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

Rats were vaccinated with a toxoid (D-toxoid) prepared from purified heat-labile toxin (D-toxin) produced by Pasteurella multocida serogroup D. Vaccination of rats with D-toxoid prevented death and other effects of D-toxin (hepatic necrosis, development of elevated leukocyte counts, lymphopenia, neutrophilia, and elevated complement titers) that occurred in phosphate buffered saline (PBS)-vaccinated control rats.

Antibodies to outer membrane proteins but not to lipopolysaccharide inhibit pulmonary proliferation of Pasteurella multocida in mice

The role of rabbit antibodies against Pasteurella multocida outer membrane proteins and lipopolysaccharides (LPS) in resistance remains unknown. Pooled immune sera against P. multocida outer membranes were prepared from specific-pathogen-free rabbits immunized with sucrose gradient-purified P. multocida outer membranes. Western immunoblotting showed that purified outer membrane protein antibodies reacted strongly against the outer membrane proteins but not the purified LPS. Affinity-purified LPS antibodies exhibited strong reactivity against purified LPS and very little reactivity against outer membrane vesicles. Mice were inoculated intranasally with immune serum or normal rabbit serum, challenged intranasally with 10(6) CFU of P. multocida, and euthanatized 48 h later to determine the number of P. multocida organisms in the lungs. Mice inoculated with pooled immune serum had a 3,300-fold reduction (P less than 0.001) in the numbers of P. multocida in the lungs as compared with the controls. Similarly, mice inoculated with purified outer membrane protein antibodies had a 201-fold reduction (P less than 0.001) in the numbers of P. multocida. Conversely, mice inoculated with affinity-purified LPS antibodies had a 1.1-fold reduction (P greater than 0.50) in the numbers of P. multocida. These results show that antibodies against the outer membrane proteins but not the LPS are the components of rabbit immune sera which inhibit P. multocida proliferation in mouse lungs.

Comparison of live avirulent M-9, Minnesota, and CU fowl cholera vaccines

The M-9 and Minnesota (MN) avirulent Pasteurella multocida vaccines were evaluated and compared with the Clemson University (CU) vaccine, which had been shown to be highly effective in preventing fowl cholera in turkeys. Neither the M-9 nor the MN vaccine given in the drinking water was as effective as the CU vaccine in protecting turkeys against challenge with virulent P. multocida. When grown in brain-heart infusion (BHI) agar as recommended, the M-9 was not as efficacious as when it was grown in BHI broth. The M-9 was as effective as the CU vaccine only when grown in BHI broth and given at 10 times the standard dosage. Injection of the M-9 vaccine into the air spaces of the head at a site near the caudal rim of the ear after one vaccination in the drinking water was not as effective for hyperimmunizing potential breeders as was the CU vaccine injected at the same site. A microtiter agglutination test demonstrated a significant (P less than 0.05) correlation between the level of anti-P. multocida antibody found 1 week after vaccination and survival after challenge with virulent P. multocida.

In vivo antigen expression by Pasteurella multocida

Pasteurella multocida was purified from the blood of turkeys affected with acute fowl cholera, and membrane preparations from those bacteria were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized on immunoblots. Antigens were detected in the membranes of these in vivo-propagated bacteria that were not detected in membrane preparations of the same P. multocida strain grown in vitro. The unique antigens were detected in the detergent-insoluble phase and were enriched to various degrees by different detergents.

Recombinant derivatives of Pasteurella multocida toxin: candidates for a vaccine against progressive atrophic rhinitis

Potential vaccine components for protection against atrophic rhinitis in pigs were developed. This was achieved by deletion mutagenesis of the gene encoding the Pasteurella multocida toxin. Four purified toxin derivatives lacking different and widely separated regions in the amino acid sequence were characterized by a lack of toxic activity. One such component was shown to induce efficient protection of vaccinated female mice and their offspring against challenge with purified P. multocida toxin.

Crossed immunoelectrophoresis applied to representative strains from 11 different Pasteurella species under taxonomic aspects

Crossed immunoelectrophoresis evaluated on a numerical basis revealed a close antigenic relationship between species of the genus Pasteurella. By cluster analysis, 4 groups on similarity levels between 87% and 72% S could be separated which were connected by a minimum level of 69.5% S. One subgroup included all biovars or subspecies consisting of strains with mucoid growth. Another feature governing the antigenic relationship seemed to be the host range of Pasteurella species. Despite a considerable number of cross-reacting antigens, representative strains of the genera Haemophilus and Actinobacillus were clearly separated from Pasteurella. Similarly, "Pasteurella" haemolytica and Taxon 16 strains tested did not belong to this genus. An Escherichia coli strain showed a higher number of cross-reacting antigens, confirming known antigenic relationship among Gram-negative bacterial species.

Pasteurella haemolytica A1 purified capsular polysaccharide does not stimulate interleukin-1 and tumor necrosis factor release by bovine monocytes and alveolar macrophages

Purified capsular polysaccharide (CPS) stimulated significant release of interleukin-1 (IL-1) activity from bovine blood monocytes but not alveolar macrophages in vitro. The ability of CPS to induce IL-1 release was resistant to boiling and inhibited by the addition of polymyxin beta. Thus, it is likely that the IL-1 release stimulated by CPS resulted from the small amount of contaminating lipopolysaccharide (LPS) that was present (an estimated 5 pg LPS per microgram CPS) rather than to a direct effect of CPS. Tumor necrosis factor activity was not detected in the culture supernatants of bovine monocytes incubated with purified CPS for 1-18 h in vitro.

Development of pneumonia in desert bighorn sheep after exposure to a flock of exotic wild and domestic sheep

From 1986 to 1989, 5 desert bighorn sheep (3 Ovis canadensis mexicana and 2 O c nelsoni), ranging in age from 2 to 3 years, were exposed to a flock of exotic wild and domestic sheep to potentially achieve naturally acquired pneumonia. Pasteurella multocida was isolated from nasal samples from 4 of 6 sheep randomly sampled from the flock. Bighorn sheep were exposed individually and each exposure period was a trial. Treatment before and after exposure varied and included combinations of alpha interferon, antibiotics, anti-inflammatory drugs, and vaccines. Treatments were chosen on the basis of recommendations of others for treating pneumonia in desert bighorn sheep as well as our own experience in sheep and cattle. Regardless of treatment used, bighorn sheep in trials 1 to 4 developed signs of pneumonia within 10 to 14 days of exposure. Bighorn sheep in trials 1 to 3 died within 11 to 17 days of initial exposure. In trial 4, the bighorn sheep was isolated from the carrier sheep for treatment of pneumonia on day 14 and died on day 30. Pasteurella multocida was isolated from lung tissue in 3 of the 4 bighorn sheep. On the basis of results of trials 1 to 4, a more in depth clinical study was conducted in trial 5. Nasal and blood specimens were collected prior to and during trial 5 for bacteriologic culturing and serologic testing for bovine viral diarrhea virus, infectious bovine rhinotracheitis, parainfluenza-3 virus, and respiratory syncytial virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and expression of a 30 kDa surface antigen of Pasteurella haemolytica

Pasteurella haemolytica biotype A serotype 1 is the principal etiologic agent of bovine pneumonic pasteurellosis. A clear understanding of the pathogenesis of this disease and the mechanisms of resistance to it has been limited by a lack of information on the important antigens of the organisms. Using recombinant DNA techniques we have cloned a segment of DNA from P. haemolytica A1 that encodes three proteins of 28, 30, and 32 kDa. Two of these proteins, 30 and 28 kDa, react strongly on a Western blot with a bovine serum raised against live cells of P. haemolytica A1. The gene for the 30 kDa protein was localized to a 3.1 kbp EcoRI fragment, and expression of the 30 kDa protein was found to be independent of an E. coli promoter. The 30 kDa protein comigrated with a 30 kDa P. haemolytica protein that was susceptible to radioiodination and presumably exposed on the bacterial cell surface. The other principal radiolabeled P. haemolytica proteins were 100, 45, and 15 kDa. Antibodies against the 30 kDa protein, isolated from E. coli carrying the recombinant plasmid, recognized 30 kDa and 15 kDa proteins in P. haemolytica serotypes 1-15 and caused agglutination of whole P. haemolytica A1 cells. Cattle vaccinated with live P. haemolytica, P. haemolytica outer membrane proteins, or the cloned 30 kDa protein developed antibodies to the cloned 30 kDa protein as detected by Western blotting and densitometry. Sera were obtained from cattle vaccinated with live or killed P. haemolytica or saline and challenged with P. haemolytica. Those sera were evaluated for antibody responses to the cloned 30 kDa protein. High antibody responses to the 30 kDa protein significantly correlated (P less than 0.01) with resistance to challenge. From these studies it is concluded that the 30 kDa protein represents a surface antigen of P. haemolytica A1 that may be important in inducing immunity to P. haemolytica.

Interaction of bovine alveolar macrophages with Pasteurella haemolytica A1 in vitro: modulation by purified capsular polysaccharide

Preincubation of bovine alveolar macrophages with Pasteurella haemolytica A1 purified capsular polysaccharide markedly reduced the phagocytosis of P. haemolytica A1 in vitro in a dose-dependent manner. Both the percentage of macrophages with intracellular P. haemolytica and the mean number of bacteria per ingesting macrophage were decreased by treatment with capsular polysaccharide. Untreated bovine alveolar macrophages had little ability to kill P. haemolytica A1 in vitro at bacteria to macrophages ratios of 1 to 1 or greater; at lower ratios of bacteria to macrophages (1 to 3 or less) modest killing was observed. Preincubation with capsular polysaccharide impaired phagocytosis and killing of P. haemolytica A1 by alveolar macrophages even when the macrophages outnumbered the bacteria. These data indicate that P. haemolytica capsular polysaccharide inhibits the ability of alveolar macrophages to defend against P. haemolytica, as has been reported previously for bovine neutrophils.

Opsonic monoclonal antibodies against lipopolysaccharide (LPS) antigens of Pasteurella multocida and the role of LPS in immunity

A panel of six monoclonal antibodies (MAbs) produced from mice immunized with Pasteurella multocida (M1404) (Heddleston serotype 2) reacted with homologous lipopolysaccharide, as indicated by enzyme immunoassay and immunoblotting. All six MAbs reacted with serotypes 2 and 5 of the 16 Heddleston serotypes. The reactive epitopes were localized on the bacterial cell surface by immunogold labelling. The antibodies could agglutinate P. multocida only if cells were first treated with 1 N HCl. All six MAbs opsonized P. multocida for phagocytosis by mouse macrophages but were not bactericidal in the presence of complement. They afforded only partial protection against infection in mice. The results, together with those of active immunization experiments with LPS, suggest a subordinate role for LPS in protection from experimental infection in mice.

Interaction of bovine neutrophils in Pasteurella haemolytica mediated damage to pulmonary endothelial cells

The purpose of these studies was to determine mechanisms of pulmonary tissue damage mediated by Pasteurella haemolytica and interaction with bovine neutrophils. Bovine pulmonary artery endothelial cell monolayers were treated with various combinations of P. haemolytica factors including bacterial culture supernatant (CS) and purified LPS, with and without bovine neutrophils. Damage to endothelial cells was monitored by 51Cr release, cell detachment rate, and morphological changes. At 5 h post-treatment (PT) bacterial factors produced very little toxic change in cells, however, by 22 h PT both crude leukotoxin and LPS caused high levels of cytotoxicity and detachment. Neutrophils did not augment toxicity mediated by LPS, but actually protected endothelial cells from low levels of LPS. When the LPS component of CS was neutralized with polymyxin B, leukotoxin mediated neutrophil killing resulted in extensive endothelial cell damage. These results suggest that LPS may directly injure endothelial cells and this toxic effect may be reduced by neutrophils. However, neutrophil killing by leukotoxin may also contribute to endothelial cell damage in the absence of LPS.

Vaccine containing iron-regulated proteins of Pasteurella haemolytica A2 enhances protection against experimental pasteurellosis in lambs

A vaccine containing sodium salicylate extract (SSE) of Pasteurella haemolytica A2 cells grown in a medium chemically depleted of available iron by the addition of alpha alpha dipyridyl to induce iron-regulated proteins (IRPs) conferred protection to specific pathogen-free (SPF) lambs exposed to an aerosol of P. haemolytica A2. The disease score in these lambs was significantly lower (p less than 0.005) than those in unvaccinated lambs or in lambs immunized with SSE prepared from cells grown in iron-replete medium. Immunoblotting of sera from these SPF lambs against whole cell antigens of P. haemolytica A2 grown under iron-restricted conditions demonstrated that antibodies to IRPs were present only in the sera of animals immunized with SSE-IRP. The antibody profile of sera from the SSE-IRP group was similar to that obtained with serum from a lamb which had recovered from P. haemolytica A2 disease produced experimentally. Negligible levels of cytotoxin-neutralizing and bactericidal antibodies were detectable in the SSE-IRP group and therefore appear not to be involved in the protection observed in this experiment.

Vaccination of turkeys with cell-free culture filtrate of Pasteurella multocida

Turkeys given cell-free culture filtrate (CCF) of Pasteurella multocida strain R44/6 orally, via air sacs, or subcutaneously mixed 1:1 with incomplete Freund's adjuvant (IFA) at 6 and 9.5 weeks of age were compared with negative controls given bacteriologic medium and positive controls vaccinated with a commercial bacterin. At 13 weeks of age, serum antibody titers to P. multocida were detectable only in turkeys given CCF in IFA (low titers) and positive control turkeys (high titers), at which time turkeys were challenged orally with either the homologous strain or strain P-1059. Protection against challenge with strain R44/6 was provided by the commercial bacterin, CCF in IFA, and CCF given via air sacs. When turkeys were challenged with strain P-1059, protection was superior in turkeys given CCF via air sacs, intermediate in turkeys given commercial bacterin or CCF in IFA, and absent in negative control turkeys and turkeys given CCF orally. These results indicate CCF is an effective immunogen when administered via the lower respiratory tract for protecting turkeys against pasteurellosis.