A monoclonal antibody against a Pasteurella multocida outer membrane protein protects rabbits and mice against pasteurellosis

Efficiency of NHEJ-CRISPR/Cas9 and Cre-LoxP Engineered Recombinant Turkey Herpesvirus Expressing Pasteurella multocida OmpH Protein for Fowl Cholera Prevention in Ducks

Fowl cholera is caused by the bacterium Pasteurella multocida, a highly transmissible avian ailment with significant global implications, leading to substantial economic repercussions. The control of fowl cholera outbreaks primarily relies on vaccination using traditional vaccines that are still in use today despite their many limitations. In this research, we describe the development of a genetically engineered herpesvirus of turkeys (HVT) that carries the OmpH gene from P. multocida integrated into UL 45/46 intergenic region using CRISPR/Cas9-NHEJ and Cre-Lox system editing. The integration and expression of the foreign cassettes were confirmed using polymerase chain reaction (PCR), indirect immunofluorescence assays, and Western blot assays. The novel recombinant virus (rHVT-OmpH) demonstrated stable integration of the OmpH gene even after 15 consecutive in vitro passages, along with similar in vitro growth kinetics as the parent HVT virus. The protective efficacy of the rHVT-OmpH vaccine was evaluated in vaccinated ducks by examining the levels of P. multocida OmpH-specific antibodies in serum samples using ELISA. Groups of ducks that received the rHVT-OmpH vaccine or the rOmpH protein with Montanide™ (SEPPIC, Paris, France) adjuvant exhibited high levels of antibodies, in contrast to the negative control groups that received the parental HVT or PBS. The recombinant rHVT-OmpH vaccine also provided complete protection against exposure to virulent P. multocida X-73 seven days post-vaccination. This outcome not only demonstrates that the HVT vector possesses many characteristics of an ideal recombinant viral vaccine vector for protecting non-chicken hosts, such as ducks, but also represents significant research progress in identifying a modern, effective vaccine candidate for combatting ancient infectious diseases.

Genome-wide association studies of immune, disease and production traits in indigenous chicken ecotypes

Background

The majority of chickens in sub-Saharan Africa are indigenous ecotypes, well adapted to the local environment and raised in scavenging production systems. Although they are generally resilient to disease challenge, routine vaccination and biosecurity measures are rarely applied and infectious diseases remain a major cause of mortality and reduced productivity. Management and genetic improvement programmes are hampered by lack of routine data recording. Selective breeding based on genomic technologies may provide the means to enhance sustainability. In this study, we investigated the genetic architecture of antibody response to four major infectious diseases [infectious bursal disease (IBDV), Marek’s disease (MDV), fowl typhoid (SG), fowl cholera (PM)] and resistance to Eimeria and cestode parasitism, along with two production traits [body weight and body condition score (BCS)] in two distinct indigenous Ethiopian chicken ecotypes. We conducted variance component analyses, genome-wide association studies, and pathway and selective sweep analyses.

Results

The large majority of birds was found to have antibody titres for all pathogens and were infected with both parasites, suggesting almost universal exposure. We derived significant moderate to high heritabilities for IBDV, MDV and PM antibody titres, cestodes infestation, body weight and BCS. We identified single nucleotide polymorphisms (SNPs) with genome-wide significance for each trait. Based on these associations, we identified for each trait, pathways, networks and functional gene clusters that include plausible candidate genes. Selective sweep analyses revealed a locus on chromosome 18 associated with viral antibody titres and resistance to Eimeria parasitism that is within a positive selection signal. We found no significant genetic correlations between production, immune and disease traits, implying that selection for altered antibody response and/or disease resistance will not affect production.

Conclusions

We confirmed the presence of genetic variability and identified SNPs significantly associated with immune, disease and production traits in indigenous village chickens. Results underpin the feasibility of concomitant genetic improvement for enhanced antibody response, resistance to parasitism and productivity within and across indigenous chicken ecotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-016-0252-7) contains supplementary material, which is available to authorized users.

Development of OMP based indirect ELISA to gauge the antibody titers in bovines against Pasteurella multocida

Pasteurella multocida (P. multocida) is an important pathogen of various domestic animals. The outer membrane proteins (OMPs) play a major role in pathogenesis and immunogenicity of P. multocida. The aim of the study was to develop indirect enzyme linked immuno sorbant assay (ELISA) based on OMPs to ascertain the antibody titers in animals post-infection or to gauge the potency of vaccine. The OMPs were extracted and purified from P. multocida P:52 (vaccine strain) and P. multocida B:2 isolated from natural outbreak of Haemorrhagic septicaemia (HS) and analyzed on SDS PAGE and through western blot. The OMPs profile of the vaccine strain and the isolate from the natural outbreak of HS were found to be similar. Optimization of various components viz. coating antigens, anti-species conjugate, etc. were carried out against both anti-P. multocida hyper immune and pre immune serum. Validation of OMP based indirect ELISA assay to measure immune response against P. multocida in bovine revealed 91% diagnostic sensitivity (DSN) and about 100% diagnostic specificity (DSP) at 25% cut off. OMP based indirect ELISA was found to be more specific, but less sensitive as compared to WCL based assay.

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.

Immune responses and protective efficacy of a novel DNA vaccine encoding outer membrane protein of avian Pasteurella multocida

Avian Pasteurella multocida is a causative agent of fowl cholera. Two proteins OmpH and OmpA are the major immunogenic antigens of avian P. multocida, which play an important role in inducing immune responses that confer resistance against infections. In the present study, we used pcDNA3.1(+) as a vector and constructed DNA vaccines with the genes encoding the two antigens mentioned above. These DNA vaccines include monovalent (pcDNA-OMPH, pOMPH and pcDNA-OMPA, pOMPA), divalent combination (pcDNA-OMPH+pcDNA-OMPA, pOMPH+pOMPA) and fusion of two gene vaccines (pcDNA-OMPH/OMPA, pOMPHA). The immune responses to these DNA vaccines were evaluated by serum antibody titers, lymphocyte proliferation assay and titers of a cytokines, IFN-γ. The protective efficacy after challenging with a virulent avian P. multocida strain, CVCC474, was evaluated by survival rate. A significant increase in serum antibody levels was observed in chickens vaccinated with divalent combination and fusion DNA vaccines. Additionally, the lymphocyte proliferation (SI value) and the levels of IFN-γ were both higher in chickens immunized with divalent combination and fusion DNA vaccines than in those vaccinated with monovalent DNA vaccines (P<0.05). Furthermore, the protection provided by divalent combination and fusion DNA vaccines was superior to that provided by monovalent DNA vaccines after challenging with the avian P. multocida strain CVCC474. And the protective efficacy in chickens immunized three times with the fusion DNA vaccine was equivalent to the protective efficacy in chickens vaccinated once with the attenuated live vaccine. This suggests that divalent combination and fusion DNA vaccines represent a promising approach for the prevention of fowl cholera.

Pasteurella multocida pathogenesis: 125 years after Pasteur

Pasteurella multocida was first shown to be the causative agent of fowl cholera by Louis Pasteur in 1881. Since then, this Gram-negative bacterium has been identified as the causative agent of many other economically important diseases in a wide range of hosts. The mechanisms by which these bacteria can invade the mucosa, evade innate immunity and cause systemic disease are slowly being elucidated. Key virulence factors identified to date include capsule and lipopolysaccharide. The capsule is clearly involved in bacterial avoidance of phagocytosis and resistance to complement, while complete lipopolysaccharide is critical for bacterial survival in the host. A number of other virulence factors have been identified by both directed and random mutagenesis, including Pasteurella multocida toxin (PMT), putative surface adhesins and iron acquisition proteins. However, it is likely that many key virulence factors are yet to be identified, including those required for initial attachment and invasion of host cells and for persistence in a relatively nutrient poor and hostile environment.

Lipid composition-dependent incorporation of multiple membrane proteins into liposomes

Membrane proteins from bacteria Pasteurella multocida were used as a model for studying its incorporation into liposomes. An important step to achieve efficient high yield protein incorporation in proteoliposomes is the study of the more suitable lipid composition. To this end, we compared the amount of total protein, reconstituted by co-solubilization methods, into liposomes of phospholipids with different polar head groups and acyl chain lengths. The liposomes and proteoliposomes were characterised by isopycnic centrifugation in sucrose gradient and by dynamic light scattering. Experimental and theoretical results were compared considering the effects exerted through the hydrocarbon chain length, volume, and optimal cross-sectional area of the phospholipid (combined in the geometrical critical packing parameter, lipid-protein matching), critical spontaneous radius of curvature of the bilayer vesicle, phase transition temperature of the lipid and ratio of lipid-protein molecules present in the vesicles. The highest incorporation of multiple proteins was found with dipalmitoylphosphatidylcholine (DPPC), reaching a yield of 93% compared to the lower relative amounts incorporated in proteoliposomes of the other lipids. The incorporation of multiple proteins induces a proportional enhancement of vesicular dimension, since DPPC-proteoliposomes have an average diameter of 1850A, compared to the 1430A for pure DPPC vesicles.

Characterization of, and immune responses of mice to, the purified OmpA-equivalent outer membrane protein of Pasteurella multocida serotype A:3 (Omp28)

Pasteurella multocida A:3 is a major cause of bovine pneumonia. A major antigenic heat-modifiable 28kDa outer membrane protein (Omp28) was previously identified. The purpose of this study was to purify and characterize Omp28 immunologically and structurally. Omp28 was extracted from N-lauroylsarcosine-insoluble protein preparations by a combination of detergent fractionation with Zwittergent 3-14 and chromatography. Partial N-terminal amino acid sequence confirmed Omp28 as a member of the OmpA-porin family. However, porin activity could not be demonstrated in a lipid-bilayer assay. Heat modifiability of purified Omp28 was demonstrated, and Omp28 was found in outer membrane fraction of P. multocida. Surface exposure of Omp28 was demonstrated by partial protease digestion of intact bacteria, by binding of anti-Omp28 polyclonal ascites fluid to the bacterial surface, and by partial inhibition of anti-outer membrane antiserum binding by previous incubation of the bacteria with anti-Omp28 serum. CD-1 mice vaccinated with purified Omp28 developed a significant antibody titer (P<0.05) compared to the control treatment group but were not protected from a homologous intraperitoneal bacterial challenge. By contrast, treatment groups vaccinated with P. multocida outer membrane, formalin-killed P. multocida or a commercial vaccine were significantly protected from challenge. In vitro complement-mediated killing of P. multocida was observed in post-vaccination sera of outer membrane, formalin-killed P. multocida, and commercial vaccine-treatment groups, but not with sera from the Omp28-treatment group. In conclusion, although Omp28 is surface exposed and antigenic, it may not be a desirable immunogen for stimulating immunity to P. multocida.

Intranasal vaccination of rabbits with Pasteurella multocida A:3 outer membranes that express iron-regulated proteins

OBJECTIVE

To determine efficacy of intranasal vaccination of rabbits with Pasteurella multocida A:3 outer membrane proteins (OMP) expressing iron-regulated OMP (IROMP) in conferring protection against experimental challenge exposure.

ANIMALS

52 male New Zealand White rabbits.

PROCEDURE

Rabbits were vaccinated intranasally on days 0, 7, and 14; some vaccines included cholera toxin (CT) as an adjuvant. Concentrations of intranasal IgA and serum IgG antibodies against P multocida OMP were determined. In experiment A, rabbits were vaccinated with either phospate-buffered saline solution (PBSS), PBSS-CT, OMP-CT, or IROMP-CT, challenge-exposed intranasally on day 16, and euthanatized and necropsied on day 28. Rabbits were also vaccinated with OMP or IROMP without CT and were not challenge-exposed. In experiment B, rabbits were vaccinated with PBSS, PBSS-CT, IROMP, or IROMP-CT. On day 17, rabbits were challenge-exposed intranasally. Nasal bacteria and antibodies were determined on day 24.

RESULTS

In experiment A, OMP-CT vaccination stimulated mucosal and systemic antibody responses to the bacterium and enhanced resistance against challenge exposure. Intranasal bacterial counts were not significantly reduced. Vaccination with IROMP-CT stimulated mucosal and systemic antibodies, enhanced resistance to challenge exposure, and significantly reduced nasal bacterial counts. In experiment B, natural infection was detected in several rabbits at challenge exposure; however, IROMP-CT-vaccinated rabbits had significantly higher serum and nasal antibody responses, compared with other rabbits IROMP-CT-vaccinated rabbits had significantly lower nasal bacterial counts compared to control rabbits.

CONCLUSIONS AND CLINICAL RELEVANCE

Intranasal vaccination of rabbits with P multocida outer membranes containing IROMP and CT stimulated immunity against experimental pneumonic pasteurellosis.

Respiratory diseases of rabbits

Respiratory diseases are second only to gastroenteric diseases in importance in rabbits. Pasteurellosis is the primary respiratory disease affecting domestic rabbits, but other bacteria (e.g., Bordetella broniseptica and Staphylococcus spp) are significant opportunistic pathogens. The primary manifestations are upper respiratory disease (e.g., rhinitis, sinusitis, conjunctivitis, and dacryocystitis). Various antimicrobials are effective for treatment.

Identification of protective outer membrane antigens of Brucella ovis by passive immunization of mice with monoclonal antibodies

Outer membrane proteins (OMPs) and rough lipopolysaccharide (R-LPS), the main surface antigens of Brucella ovis, display surface-exposed epitopes. Mixtures of monoclonal antibodies (mAbs) to both antigens were previously shown to protect mice against a B. ovis challenge. To further identify the antigens involved, seven mAbs against Brucella OMPs (Omp10, Omp16, Omp19, Omp25, Omp31, Omp2b and Omp1) and three to R-LPS were tested for protection either individually or in combinations. Significant reduction in spleen infection in challenged mice, relative to controls, was used as the protection criteri. Controls included nonimmunized mice and mice given an irrelevant, anti-O-polysaccharide (OPS), mAb. For comparison, a group received a mouse serum containing antibodies to both OMPs and R-LPS; this serum was prepared by immunization with a B. ovis hot-saline extract which, as described previously, induces protective immunity in mice and rams. Significant protection was observed with both mAbs to OMPs and R-LPS. mAbs to Omp16, Omp19 and Omp31 afforded the highest protection and prevented the development of splenomegaly. The protective effect of mAb to Omp31 was not interfered with by nonprotective mAbs in different mixtures. The data presented confirm the protective role of antibodies to OMPs and R-LPS against B. ovis, and identify several OMPs, especially Omp31, which are promising candidates for a subunit vaccine against ram epididymitis.

Role of Pasteurella multocida porin on cytokine expression and release by murine splenocytes

The aim of this study was to verify whether Pasteurella multocida porin can affect the expression and release of IL-1alpha, IL-6, TNF-alpha, IL-4, IFN-gamma, IL-10 and IL-12 by murine splenocytes in vitro. P. multocida porin and lipopolysaccharide (LPS) were able to induce the release of IL-1alpha, IL-6, TNF-alpha, IFN-gamma and IL-12 in a dose-dependent fashion. The greatest release of these cytokines was obtained using P. multocida porin at a concentration of 5 microg ml(-1) and LPS at a concentration of 1 microg ml(-1). The time-courses of release showed that P. multocida LPS was able to stimulate the production of IL-1alpha, IL-6, TNF-alpha, IFN-gamma and IL-12 earlier than porin and at a greater rate. No effect was observed on IL-4 and IL-10 release under the same experimental conditions. P. multocida porin and LPS were also able to up-regulate the mRNA expression of IL-1alpha, IL-6, TNF-alpha, IFN-gamma and IL-12 p40. Our findings suggest that P. multocida porin is able to modulate inflammatory and immunological responses by affecting the release of several cytokines and the expression of their genes.

Role of outer membrane protein H (OmpH)- and OmpA-specific monoclonal antibodies from hybridoma tumors in protection of mice against Pasteurella multocida

Two major outer membrane proteins of Pasteurella multocida, designated OmpH and OmpA, were characterized and shown to be related to the families of porin and heat-modifiable proteins, respectively. The backpack hybridoma tumor system in BALB/c mice was used to continuously deliver immunoglobulin G2b (IgG2b) monoclonal antibodies (MAbs) specific for OmpH (MAb MT1) and OmpA (MAb MT4.1). MAbs were detected in serum and peritoneal lavage samples of mice bearing hybridoma tumors by an enzyme-linked immunosorbent assay and an immunoblot assay. Highly significant protection was observed in mice bearing MT1 hybridoma tumors against both intraperitoneal and intranasal challenge infections with homologous nontoxigenic P. multocida strains possessing MAb MT1-reacting epitopes, whereas the mice bearing MT4.1 hybridoma tumors were not protected. The numbers of P. multocida organisms in the lungs of mice bearing MT1 hybridoma tumors were significantly less than those in lungs of mice bearing MT4.1 hybridoma tumors at 48 h postchallenge. These results indicate that the OmpH-specific MAb inhibited proliferation of P. multocida in the lungs. MAb MT1 was unable to kill P. multocida in vitro in the presence of complement. However, an enhanced phagocytosis by polymorphonuclear cells (PMNs) was observed in mice bearing MT1 hybridoma tumors. P. multocida induced a more extensive and rapid influx of PMNs into the peritoneal cavity of mice bearing MT1 hybridoma tumors than of mice bearing MT4.1 hybridoma tumors. The results of this study demonstrate for the first time that IgG MAbs against OmpH of P. multocida are involved in the protection of mice against lethal challenge infection by means of opsonization and inhibition of proliferation of P. multocida as a result of increased influx of PMNs into the infection site.

Outer membrane proteins of bovine Pasteurella multocida serogroup A isolates

The outer membrane proteins (OMPs) of P. multocida serotypes A3 (7 isolates), A4 (2 isolates), A3,4 and A2 (one isolate each) obtained from pneumonic cattle (10 isolates) and from one pig isolate were investigated to identify potential immunogens. SDS-PAGE of P. multocida OM isolated by SDG centrifugation of spheroplasts revealed eight major OMPs. Outer membranes isolated by sarcosyl extraction or SDG had similar protein composition on Coomassie blue-stained SDS-PA gel and on immunoblots. Two major OMPs (M(r)s of 35 and 46 kDa at 100 degrees C) demonstrated heat modifiability with apparent M(r)s of 30 and 34 kDa at 37 degrees C, respectively. The N-terminal aa sequences of these heat modifiable proteins revealed homology with E. coli OmpA and Hib P1 proteins, respectively. Protease treatment of whole cells followed by western immunoblots using bovine convalescent sera identified several immunogenic, surface-exposed and conserved OMPs among the eleven P. multocida isolates examined. The whole organism SDS-PAGE profiles of the eleven P. multocida isolates differed such that six patterns were seen. These patterns could potentially be used as a typing system for P. multocida bovine isolates based on the molecular weights of whole cell proteins. The above observations have potentially important implications relative to the immunity to infection.

Detection of Antibodies to Pasteurella multocida by capture enzyme immunoassay using a monoclonal antibody against P37 antigen

As infection with Pasteurella multocida is common in rabbits, an enzyme immunoassay (EIA) was developed for its detection. A murine immunoglobulin G monoclonal antibody was used to capture a 37-kDa polypeptide of P. multocida serotype A:12 in an EIA to detect antibodies to P. multocida. The 37-kDa antigen was selected since it was previously shown to be a major immunogen during P. multocida infection in rabbits. The sensitivity of the P37 EIA, determined with sera from 56 rabbits infected with P. multocida, was 98%. Specificity, evaluated with sera from 62 rabbits from colonies free of P. multocida, was 92%. Titration curves of sera from rabbits immunized with P. multocida serotype A:3 or A:12 coincided, indicating that the P37 EIA was equally efficient in detecting antibodies to the two major serotypes of the organism. Comparison of the P37 EIA with the current serodiagnostic test, a bacterial lysate EIA, revealed relatively good correlation (r = 0.68). However, specificity was greatly improved, as 34% of uninfected rabbits were falsely positive by the lysate EIA whereas only 3% of uninfected rabbits were falsely positive by the P37 EIA. The coefficient of variation for same-day tests was 10%, and that for interday tests was 15%, indicating good reproducibility. The greater sensitivity and specificity of the P37 EIA should significantly enhance diagnostic capability to identify rabbits infected with P. multocida.

A comparative study of the major outer membrane proteins of the avian haemophili and Pasteurella gallinarum

A polyclonal antibody prepared against the 35 kDa outer membrane protein (a putative porin) of Pasteurella (P.) multocida revealed binding to the 36 kDa major outer membrane protein (major Omp) of Haemophilus (H.) paragallinarum, to the 38 kDa major Omp of P.gallinarum, to the 39 kDa major Omp of P.volantium and to the 38.5 kDa major Omp of P. avium in immunoblotting studies. Comparison of N-terminal amino acid sequences also confirmed the relationship between the major Omps of most of the members of the family Pasteurellaceae.

The 32 kDa major outer-membrane protein of Pasteurella multocida capsular serotype D

The major outer-membrane protein (MOMP) of Pasteurella multocida serotype D strain P210, with an apparent molecular mass of 32 kDa, was purified and characterized. The purification method involved selective extraction of MOMP with N-lauroylsarcosine and SDS, followed by immunoaffinity chromatography using a murine monoclonal antibody (mAb). The N-terminal sequence and amino acid composition of the MOMP showed considerable similarity to other Gram-negative bacterial porins, notably to the 37 kDa MOMP (porin H) of P. multocida. Immunoelectron microscopy and colony blotting assays were used to demonstrate the surface localization of the 32 kDa MOMP on bacterial cells. The colony blotting assay provided a simple, sensitive and rapid screening method for visualizing accessibility of the antibody on the cells. In a Western blot assay, murine polyclonal hyperimmune serum against the purified 32 kDa MOMP recognized both serotype B and D strains bearing either a 32 kDa or a 37 kDa MOMP, whereas the mAb recognized only serotype D strains bearing a 32 kDa but not a 37 kDa MOMP. The present data indicate that the 32 kDa MOMPs of P. multocida are antigenically heterogeneous and possess both specific and cross-reacting epitopes. Detection of type-specific epitopes on the 32 kDa MOMP using an mAb may have potential implications regarding the feasibility of developing a serotyping system for P. multocida.

Identification of Pasteurella multocida tryptophan synthase beta-subunit by antisera against strain P1059

Pasteurella multocida strain P1059 is a highly virulent bacterium which causes fowl cholera in turkeys and chickens. A genomic library of P. multocida P1059 DNA was constructed using pUC19, expressed in Escherichia coli DH5 alpha, and screened with chicken antisera generated against P. multocida P1059. Twelve out of the 4100 clones screened were immunoreactive. Plasmids isolated from these twelve clones were transformed into E. coli CSR603 for maxicell analysis. Five proteins, with molecular masses of 34, 37, 43, 46 and 55 kDa, were expressed. Further work focused on the 43 kDa protein because it was expressed at levels detectable by SDS-PAGE and immunoblot analysis. The nucleotide sequence of the 1.8 kbp insert containing the gene encoding this protein was determined. The sequence contained three open reading frames (ORFs). The first ORF (ORF1) did not appear to code for any known protein. The second ORF (ORF2) encoded a protein of 403 amino acids (43,662 Da). The deduced amino acid sequence showed 77% identity (84% similarity) with the tryptophan synthase beta subunit (TrpB) of Salmonella typhimurium and Vibrio parahaemolyticus. The eight conserved regions of TrpB are observed in the P. multocida enzyme, including the conserved lysine (Lys-88) and consensus sequence (GGGSNA) implicated in pyridoxal phosphate binding. The expression and identity of the P. multocida TrpB were confirmed by complementation studies using E. coli W3110 tnaA2 trpB9578. The third ORF (ORF3) consisted of the first 77 nucleotides of the gene encoding the alpha-subunit of tryptophan synthase (trpA), and overlapped the 3'-end of trpB by 14 nucleotides. The deduced amino acid sequence of the 77 nucleotides of the P. multocida TrpA had 68% identity (92% similarity) with the analogous region of TrpA from Klebsiella aerogenes (K. pneumoniae).

Identification and characterization of outer membrane proteins of Pasteurella multocida serotype D by using monoclonal antibodies

Monoclonal antibodies (MAbs) against Pasteurella multocida serotype D were obtained by fusion of spleen cells from BALB/c mice immunized with outer membrane proteins (OMPs) with SP2/0-Ag 14 murine myeloma cells. Desirable MAbs were selected by enzyme-linked immunosorbent assay (ELISA) with OMP as the antigen. MAbs MT1 and MT2 identified two different proteins (H [heavy] and W [weak]), each with a molecular mass of 32 kDa, in Western blots (immunoblots). Treatment of the OMPs with proteolytic enzymes and sodium periodate indicated that the binding sites of MAbs MT1 and MT2 are of protein and glycoprotein natures, respectively. The epitopes reactive with MAbs were surface exposed, as visualized by immunoelectron microscopy. Among field isolates of P. multocida serotype D, two distinct OMP patterns were recognized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and these patterns were designated types I and II. In both the ELISA and the Western blot, MAb MT1 recognized only type I isolates, whereas MAb MT2 recognized both type I and II isolates. Neither MAb MT1 nor MAb MT2 reacted with either reference strains of capsular serotypes A, B, E, and F or field isolates of capsular serotype A of P. multocida. This is the first report of MAbs identifying the serotype D-specific OMP of P. multocida.

Isolation of the major outer-membrane protein of Actinobacillus pleuropneumoniae and Haemophilus parasuis

A polyclonal antibody against the 35 kDa major outer-membrane protein of Pasteurella multocida cross-reacted with the 40 kDa major outer-membrane protein of Actinobacillus pleuropneumoniae and the 42 kDa major outer-membrane protein of Haemophilus parasuis. The N-terminal amino-acid sequences of these proteins revealed a strong homology with the putative 35 kDa porin protein of Pasteurella multocida (66.7 and 76.2%, respectively). Significant homologies were also evident between the 40 kDa and the 42 kDa protein (76.2%), and with non-specific porins of gram-negative bacteria.

Isolation and partial characterization of the major protein of the outer membrane of Pasteurella haemolytica and Pasteurella multocida

The N-terminal amino acid sequence of the 35 kDa (p35) major outer membrane protein (MOMP) of P. multocida shared a strong homology with those of homotrimeric nonspecific porins of gram-negative bacteria. The capacity of outer membrane protein (OMP) preparations of P. multocida to bind to respiratory mucosal surface preparations was inhibited significantly by using a polyclonal anti-p35 antiserum in an adhesion ELISA. Anti-p35 antiserum cross-reacted with a 44 kDa (p44) MOMP of P. haemolytica. N-terminal sequencing of MOMP p44 revealed a homology of 81% with the putative porin MOMP p35 of P. multocida.

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)

The outer membrane of Pasteurella multocida 3:A protects rabbits against homologous challenge

The protective efficacy of a vaccine purified from the Pasteurella multocida 3:A outer membrane (OM) was evaluated in rabbits by homologous challenge. Twenty-seven rabbits were divided into four groups: 1, vaccinated with OM and challenged; 2, nonvaccinated and challenged; 3, vaccinated with OM only; and 4, nonvaccinated and not challenged. Rabbits were immunized intranasally with 1 mg of OM protein on days 0, 7, 14, and 35, challenged intranasally on day 49, and killed on day 63. Mortality rates were 0, 67, 0, and 0% for groups 1 through 4, respectively. The prevalence of pneumonia was reduced from 73 (group 2) to 20% (group 1). The severity of pneumonia was reduced from 0.62 (group 2) to 0.07 (group 1), as measured by the group lesion index. The number of P. multocida in nasal cavities was reduced from 3.89 x 10(5) (group 2) to 6.19 x 10(2) (group 1). The geometric mean number of P. multocida in lungs was 8,360,000-fold less in group 1 than in group 2. Similarly, the prevalence of P. multocida colonization in nonrespiratory organs was reduced from 47 (group 2) to 4% (group 1). Furthermore, group 1 and 3 rabbits developed significantly elevated immunoglobulin A antibodies in nasal secretions and lung lavages and significantly elevated immunoglobulin G antibodies in lung lavages and sera. In addition, rabbit immune sera contained antibodies against P. multocida OM proteins and lipopolysaccharides and inhibited P. multocida proliferation in mouse lungs. These results indicate that a vaccine prepared from the OM of P. multocida provides a significant protection in rabbits against homologous challenge.

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.