Detection of toxigenic Pasteurella multocida infections in swine herds by assaying antibodies in sow colostrum.

Toxigenic Pasteurella multocida is the causative agent of progressive atrophic rhinitis (PAR), a serious respiratory infection of swine. Diagnosis of the disease has hitherto been based on clinical signs, pathologic findings, and subsequent isolation of the agent. The best Finnish pig breeding herds participating in the Finnish Pig Health Scheme have been surveyed for PAR since 1963, and the disease has been eradicated from these herds. In this study, a total of 5,650 colostrum samples from 188 Finnish Pig Health Scheme herds were analyzed with a new serologic screening method: an enzyme-linked immunosorbent assay (ELISA) able to detect antibodies to the toxin of P. multocida (PMT). Although the herds had been continuously controlled for PAR, 1 herd with PMT antibodies was found. The positive reactions in the ELISA were confirmed by isolating the causative organism. The origin of the infection also appeared to be obvious. The serologic ELISA is a suitable method for the detection and screening of toxigenic P. multocida-infected pig herds.

Development of murine monoclonal antibodies for the immunohistochemical diagnosis of systemic bovine aspergillosis.

Murine monoclonal antibodies (MAbs) against water-soluble somatic antigens (WSSA) and the wall fraction (WF) from Aspergillus fumigatus were produced by fusion of splenocytes from immunized BALB/c mice with mouse myeloma X63-Ag 8.653 cells. The supernatants of in vitro cultured hybridomas were initially screened for reactivity with the WSSA and the WF from A. fumigatus and WSSA of other fungi in an enzyme-linked immunosorbent assay (ELISA). Supernatants reacting only with A. fumigatus antigens were subsequently screened for homologous and heterologous reactivity with immunohistochemical techniques using formalin-fixed, paraffin-embedded tissues from experimentally infected mice. Because of a high immunohistochemical reactivity with homologous fungi, 4 MAbs raised against A. fumigatus WSSA and WF were selected for a further evaluation of cross-reactivity (diagnostic specificity) in immunohistochemical and immunoblotting assays. In immunohistochemical assays, all MAbs raised against WSSA cross-reacted heavily with a number of other fungal species. All 4 MAbs (MAb-WF-AF-1-4) raised against the WF reacted strongly with hyphae of Aspergillus spp.; hyphae of Scedosporium apiospermum were also strongly labeled by MAb-WF-AF-3 and -4. The 2 specifically reacting MAbs (MAb-WF-AF-1 and -2) were of the IgM biotype and were precipitating, and in immunoblotting experiments both bound to a 106-kD antigen of the WF, whereas they did not bind to WSSA of A. fumigatus. One of the 2 aspergillosis-specific MAbs (MAb-WF-AF-1) was used to screen 145 mycotic lesions of cattle. The diagnoses on bovine lesions obtained by MAb-WF-AF-1 were compared with results based on reactivity with heterologously absorbed polyclonal antibodies and, for some lesions, to culture results. In the vast majority of lesions (n = 133), the MAb-WF-AF-1 and the polyclonal anti-Aspergillus antibodies reacted in a similar pattern, i.e., positively in 41 aspergillosis lesions and negatively in 92 zygomycotic lesions. Hyphae in 3 of 12 lesions that were not stained by the polyclonal antibodies reacted with the specific MAb-WF-AF-1; i.e., aspergillosis was diagnosed. The characteristics of the 2 MAbs (MAb-WF-AF-1 and -2) raised against the WF of A. fumigatus in ELISA and immunoblotting and immunohistochemical assays justify their application for the in situ diagnosis of systemic aspergillosis of cattle.

Protective immunity to Pasteurella multocida heat-labile toxin by intranasal immunization in rabbits.

Heat-labile Pasteurella multocida toxin (PMT) is an important virulence factor of some isolates from rabbits. To determine whether protective immunity to PMT could be induced in rabbits by intranasal immunization with heat-inactivated PMT, we immunized groups of rabbits intranasally at days 0, 7, 14, and 21 with inactivated PMT, with or without cholera toxin, an adjuvant for the mucosal immune system. Significant increases in anti-PMT IgA in nasal lavage samples and anti-PMT serum IgG, as determined by enzyme-linked immunosorbent assay, developed within 2 weeks after initial immunization. Coadministration of cholera toxin with inactivated PMT enhanced anti-PMT activity in the samples. Rabbits similarly immunized on days 0, 7, and 14 were challenged with PMT, and tissues were graded histologically on a numeric scale of lesion severity. Immunization conferred partial protection against development of pneumonia, pleuritis, hepatic necrosis, and testicular atrophy in rabbits challenged 16 days after initial immunization. Thus, immunization with inactivated PMT stimulates a protective response to PMT challenge in rabbits that is enhanced by coadministration of cholera toxin.

Pasteurella multocida toxin induces IL-6, but not IL-1 alpha or TNF alpha in fibroblasts.

Pasteurella multocida toxin (PMT) is the major virulence factor in Progressive Atrophic Rhinitis of swine. Other workers' previous findings that PMT was mitogenic for 3T3 fibroblasts, were confirmed in the present study. In addition, PMT stimulated 3T3 cells to release IL-6, but IL-1 alpha or TNF alpha were not detected in fibroblast supernatants sampled 24, 48, or 72 h after stimulation. In view of the role of IL-6 in osteoclastic bone resorption, these findings provide a new working hypothesis for investigations into the molecular pathogenesis of this important disease.

Enzyme immunohistochemistry with mono- and polyclonal antibodies in the pathological diagnosis of systemic bovine mycoses.

To improve the immunohistopathological diagnosis of systemic bovine mycoses, we have evaluated the utility of antifungal polyclonal and monoclonal antibodies, and peroxidase and alkaline phosphatase staining techniques. A rabbit polyclonal antibody to mannan from Candida albicans was specific for candidosis. The diagnosis of aspergillosis was accomplished using a rat monoclonal antibody to the galactofuran side chains of Aspergillus galactomannan. A murine monoclonal antibody reacting with weakly Con-A binding 41 and 46 kDa somatic antigens from Absidia corymbifera was used for immunostaining of zygomycetic hyphae. Peroxidase antiperoxidase (PAP) and alkaline phosphatase antialkaline phosphatase (APAAP) complexes were visualized using aminoethylcarbazole and fast red substrates. A green staining of PAP reactions with dioctyl sulfosuccinate sodium and 3,3',5,5'-tetramethylbenzidine (DONS/TMB) was effective for the demonstration of fungi in dual and triple infections. Tissue sections of experimentally infected mice were used to determine the sensitivity and specificity of the antibodies. Tissues obtained from 161 bovine mycotic lesions previously studied by indirect immunofluorescence staining were further evaluated using the three antibodies. In all of 45 lesions solely affected by aspergillosis and in three solely affected by candidosis the diagnoses were confirmed by the new evaluation. In 85 of 96 cases of single infections with zygomycetes the diagnosis was confirmed, while none of the antibodies reacted with fungal elements in the remaining 11 lesions. Aspergillus hyphae were detected in all three lesions with dual aspergillosis and zygomycosis, whereas zygomycetic material was confirmed in only two of these cases. A mixed infection of candidosis and zygomycosis in a lymph node was confirmed too. In 13 cases in which a diagnosis had not hitherto been obtained, aspergillosis and zygomycosis were recorded each in three cases.

Use of a dot enzyme-linked immunosorbent assay on absorbed sera for the diagnosis of bovine paratuberculosis.

This study describes the response of cattle to a dot enzyme-linked immunosorbent assay (ELISA) using sera absorbed with Mycobacterium phlei. Results obtained by visual observation are compared with those obtained using a densitometer. Infection status of cattle was determined by faecal culture. Cattle of different levels of exposure and disease manifestation were examined. A significantly higher dot ELISA response was observed (using both absorbed and non-absorbed sera) in animals with heavy shedding of M. paratuberculosis than in animals which tested negative by faecal culture or shed M. paratuberculosis at lower levels (P < 0.05). Paratuberculosis was diagnosed by visual determination of dot ELISA results using non-absorbed sera in 29 of 44 (65.9%) clinically-suspect animals giving positive results by faecal culture, and 85 of 93 (91.4%) cattle testing negative by faecal culture. With absorbed sera, the sensitivity of visual determination decreased to 15 of 44 (34.1%), while specificity increased to 91 of 93 (97.8%). Approximately 75% of cattle yielding positive results by dot ELISA were heavy bacterial shedders (> 1,500 colonies/g of faeces) at the time of serological testing. Comparison of the dot ELISA results determined visually with results obtained by objective densitometric measurement showed compatible specificity. Sensitivity of the dot ELISA was 65.9% for non-absorbed sera using visual evaluation and 87.5% using densitometric evaluation at a cut-off optical density value of 0.2. For absorbed sera, the values were 34.1% and 82.5%, respectively.

Experimental systemic bovine zygomycosis with reference to pathology and secretion of antigen into urine.

ELISA and immunoblotting were applied for the characterization of somatic antigens from Absidia corymbifera. Immunoblotting revealed major antigenic bands at 11 to 81 kDa. The ELISA showed some crossreactivity towards somatic antigens from other fungi. However, the crossreactivity was especially observed with somatic antigens from other fungi of the zygomycetes. The ELISA and immunoblotting assays were applied to urine samples from two groups of 3 calves each systemically infected with A. corymbifera and Aspergillus fumigatus, respectively. The immunoreactivity of the urine samples was similar by the two assays. Somatic antigens were demonstrated in the urine of all three calves infected with A.corymbifera, whereas only one of the calves with systemic aspergillosis was antigen positive. The level of antigen in the positive urine samples varied from 50 to 210 ng/ml.

Effect of Pasteurella multocida toxin on bone resorption in vitro.

Pasteurella multocida toxin (PMT), which is the primary etiologic factor in the pathogenesis of progressive atrophic rhinitis in pigs, was found to stimulate bone resorption in vitro. This stimulation was observed both in cultures of murine calvaria by measuring the release of calcium and of the lysosomal enzyme beta-glucuronidase and in murine long bone cultures by measuring the release of calcium. Both systems showed the same dose response curve, with the maximal effect at a concentration of 5 ng/ml. The effect on calvaria was studied in more detail. PMT increased bone resorption 24 h after its addition and always had to be present to express an effect. Calcitonin was able to inhibit this increase of resorption completely, and inhibitors of prostaglandin synthesis suppressed it partially. Although the data show an effect of PMT on bone tissue, the results do not exclude an action on cells in the nasal cavity, which could indirectly stimulate bone resorption.

Comparison of subjective and objective test evaluations for use of Mycobacterium phlei-adsorbed serum in a dot-enzyme-linked immunosorbent assay for diagnosis of paratuberculosis in cattle.

Use of a dot-ELISA with serum adsorbed with Mycobacterium phlei or with nonadsorbed serum was compared. In addition, results attained using visual observation were compared with those obtained using a densitometer. Infection status of cattle was determined by results of culture of feces from a number of cattle with various degrees of exposure (low prevalence and test-negative) and disease manifestation (clinical suspect vs subclinical infection). Two paratuberculosis-negative herds, fecal culture-confirmed clinically suspect cases of paratuberculosis, and cows from 2 paratuberculosis-infected herds with diagnosis confirmed on the farm (low infection rate) were tested. Significant (P less than 0.05) increase in the dot-ELISA response was found in cattle with heavy M paratuberculosis shedding when nonadsorbed and adsorbed sera were used, compared with the response in cattle that were fecal culture-negative or were shedding M paratuberculosis at lower amounts. Paratuberculosis was diagnosed by visual determination in 29 of 44 (65.9%) of fecal culture-positive, clinically suspect cattle when nonadsorbed serum was used. Results of the visual test were negative in 85 of 93 (91.4%) of the fecal culture-negative cattle when nonadsorbed serum was used. However, when using M phlei-adsorbed serum, the sensitivity of the visual determination decreased to 34.1% (15/44), and the specificity increased to 97.8% (91/93).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of toxin from different strains of Pasteurella multocida serotype A and D.

Chromosomal DNA from 13 different selected Pasteurella multocida spp. multocida strains of serotypes A and D were isolated and compared. All 10 toxigenic strains were recognized by a DNA probe which included the toxA gene coding for the Pasteurella multocida toxin (PMT). None of the three nontoxigenic strains reacted with the DNA probe. Toxin from the 10 toxigenic strains were isolated and compared. All were found to possess the biological characteristics previously described for the PMT isolated from P. multocida ssp. multocida NCTC 12178, including molecular mass of approx. 143 kDa and reactivity with a series of monoclonal antibodies. Toxin prepared from different toxigenic strains could not be differentiated immunologically by tandem crossed immunoelectrophoresis, Toxin, which was affinity purified from four of the strains and subsequently inactivated by formaldehyde, was cross-protective when used for vaccination of mice before challenge with PMT. It is concluded that the toxin from toxigenic strains of P. multocida ssp. multocida must be very similar, if not identical.

Peroxide chemistry of triaryl-substituted imidazoles. Fenflumizole, a non-steroidal, anti-inflammatory agent.

Fenflumizole, [2-(2,4-difluorophenyl)4,5-bis(4-methoxyphenyl)imidazole] is a nonsteroidal, anti-inflammatory analgesic. It reacts quantitatively with 1O2 forming 2-(2,4-difluorophenyl)-4-hydroperoxy-4,5-bis(4-methoxyphenyl)imidazole in a reversible reaction. In ethanol solution at ambient temperatures, the peroxide regenerates parent fenflumizole and 1O2 together with minor quantities of other products. The structures of those products point to the intermediacy of a 1,3-endoperoxide and a dioxetane. These observations may be relevant to the biological activity of fenflumizole.

Ultrastructural localization of the Pasteurella multocida toxin in a toxin-producing strain.

Toxigenic strains of Pasteurella multocida produce the 147 kDa protein Pasteurella multocida toxin (PMT) which is responsible for the osteoclastic bone resorption in progressive atrophic rhinitis in pigs and induces such resorption in all experimental animals tested so far. In the present study we have carried out immunocytochemistry on formaldehyde- and glutaraldehyde-fixed ultracryocut P. multocida using a pool of monoclonal antibodies against different epitopes on PMT as the first layer and affinity purified rabbit anti-mouse IgG as the second layer. Goat anti-rabbit IgG conjugated with 5 nm gold particles was used as marker. The gold particles were silver-enhanced prior to examination in the transmission electron microscope. Whole bacteria were also immunostained after fixation and critical point drying and examined by scanning transmission electron microscopy. The results showed that PMT was located in the cytoplasm of P. multocida. PMT could not be detected on intact, undamaged P. multocida by scanning electron microscopy. Neither pili nor flagella could be detected on the surface of the negatively stained P. multocida strains investigated. PMT has a series of characteristics encompassed in the definition of an exotoxin. However, that PMT was not secreted by living intact P. multocida is unexpected for an exotoxin.

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.