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

Protectivity conferred by immunization with intranasal recombinant outer membrane protein H from Pasteurella multocida serovar A:1 in chickens

Recombinant outer membrane protein H (rOmpH) is a potential fowl cholera vaccine candidate. The present study was aimed at developing rOmpH formulations for intranasal administration. The rOmpH was purified and formulated with either Escherichia coli enterotoxin B (LTB) or CpG oligodeoxynucleotides (ODN) as an adjuvant. Antibody responses in chickens intranasally immunized with rOmpH in combination with 2 different adjuvants were significantly increased (P<0.05) post immunization. Chicken survival rates showed that rOmpH formulated with ODN and LTB elicited 90% and 70% protection, respectively. Our findings indicated that rOmpH formulated with ODN elicited protection better than that formulated with LTB. Therefore, the vaccines formulations in the present study can be considered new intranasal vaccine formulations for fowl cholera in chickens.

Protection of chickens from fowl cholera by vaccination with recombinant adhesive protein of Pasteurella multocida

The recombinant adhesive protein (rCp39) of Pasteurella multocida strain P-1059 (serovar A:3) was prepared and purified with a hybrid condition of affinity chromatography. The rCp39 was highly protective for chickens from fowl cholera by challenge-exposure with parental strain P-1059 or heterologous strain X-73 (serovar A:1) compared to various kind of vaccines. Sixteen groups of ten chickens each were subcutaneously inoculated twice with 100, 200 or 400 microg proteins of rCp39, native Cp39, native outer membrane protein H (OmpH) or recombinant OmpH, or 100 microg proteins of crude capsular extract (CCE) of strains P-1059 or X-73 at 2 weeks interval. Five chickens of each group were challenge-exposed with each strain 2 weeks after the second inoculation. As the results, 60-100% protections were demonstrated in the chickens against both strains. Fisher's exact test indicated no significant differences (P<0.05) in vaccine types and dosages. ELISA and Western blot analysis indicated that the chicken anti-rCp39 sera reacted to whole-cell lysate of parental or heterologous strains. In conclusion, rCp39 is a cross-protective recombinant adhesive antigen of P. multocida capsular serogroup A strains. Moreover, a hybrid condition of affinity chromatography was successfully demonstrated and protected the immunogenicity of recombinant protein.

Isolation and characterization of a cytotoxin produced byPlesiomonas shigelloidesP-1 strain

In order to clarify the enteropathogenicity of Plesiomonas shigelloides, we investigated a cytotoxin produced by the P-1 strain isolated from patients suffering from diarrhea. The cytotoxicity of the culture filtrate of the strain reached a maximum in culture at 37 degrees C after 12 h shaken in BHI medium. The cytotoxin in the cultures was purified by (NH4)2SO4 precipitation, and Sephacryl S-100, Mono Q HR, and Superdex 200 HR column chromatographies. An approximate 340-fold purification was achieved, with a recovery of about 1.4%, from the culture supernatant. The cytotoxin is heat-stable, and is a complex of three major proteins (LPS-binding proteins with molecular weights of 32, 40, and 48 kDa), with lipopolysaccharide (LPS) giving a total a molecular weight of more than 600 kDa. The ratio of protein to LPS in the cytotoxin was 6-5. The cytotoxic activity was reduced by about 80% by proteinase K treatment or when incubated with anti-cholera toxin antibody (Anti-CT). Western blotting of the cytotoxin with Anti-CT demonstrated the presence of two anti-cholera toxin-reactive protein (ACRP) bands with molecular weights of 40 kDa (a major single protein band) and 48 kDa. The N-terminal amino acid sequence (20 residues) of the 40 kDa protein was 75% identical to Pasteurella multocida cell membrane proteins. The cytotoxin gave a positive reaction in the suckling mouse assay whereas LPS alone hardly exhibited any cytotoxic or enterotoxigenic activity. In conclusion, P. shigelloides produces a cytotoxin that consists of a complex of protein and LPS with the former component exhibiting both cytotoxicity and enteropathogenicity. This cytotoxin has the potential to have an important role in the enteropathogenicity of P. shigelloides.

Characterisation of bovine strains of Pasteurella multocida and comparison with isolates of avian, ovine and porcine origin

One hundred and fifty-three bovine Pasteurella multocida strains recovered primarily from cases of pneumonia and mastitis in England and Wales over an 11-year period were characterised by capsular PCR typing, comparison of outer membrane protein (OMP) profiles, and multilocus sequence analysis. All of the strains were of capsular type A with the exception of a single capsular type F isolate. Thirteen distinct OMP profiles (OMP-types) were identified based mainly on molecular mass heterogeneity of the heat-modifiable (OmpA) and porin (OmpH) proteins. However, 85% of the isolates were represented by just five OMP-types and 39% of the strains were of a single OMP-type. Multilocus sequence analysis revealed a limited degree of genetic diversity among bovine P. multocida isolates; strains of the same OMP-type have identical genetic backgrounds and represent distinct clones. Analysis of OMP variation was more discriminating than multilocus sequence analysis because strains of different OMP-types had the same, or similar, genetic backgrounds. The association of a small number of clones with the majority of cases of bovine pneumonia suggests that these clones have an increased capacity to cause disease compared to less frequently recovered clones. Molecular mass heterogeneity of OmpA and OmpH, in strains of the same or similar genetic background, suggests that these proteins are subject to diversifying selection within the host and might play important roles in host-pathogen interactions. Comparison of the OMP profiles of bovine isolates with those of avian, ovine and porcine strains showed that a high proportion of the respiratory tract infections in each of these species are caused by different strains of P. multocida. However, the presence of small numbers of closely related strains in more than one host species suggests that transmission of bacteria between different host species is also a factor in the population biology of P. multocida.

Diversity of avian Pasteurella multocida strains based on capsular PCR typing and variation of the OmpA and OmpH outer membrane proteins

One hundred avian Pasteurella multocida isolates recovered from cases of fowl cholera and related infections in England and Wales over a 13-year period were characterised by capsular PCR typing and analysis of outer membrane protein (OMP) profiles. Sixty-eight percent of the strains were of capsular type A, 14% were type F, 5% were type D, 4% were type B and 9% were untypable. Nineteen distinct OMP profiles (OMP-types) were identified based mainly on molecular mass heterogeneity of the heat-modifiable (OmpA) and porin (OmpH) proteins. Fifty-six percent of the isolates were represented by 15 OMP-types, whereas 44% of the isolates were associated with four OMP-types. The extensive molecular mass heterogeneity of the OmpA and OmpH proteins supports previous findings that avian P. multocida strains are very diverse. Furthermore, the isolates studied were associated with different clinical symptoms and were recovered from a wide range of lesions and tissues. The high degree of strain diversity together with the wide variety of clinical symptoms suggest that certain avian strains of P. multocida are opportunistic pathogens of relatively low virulence. Strains of capsular types B, D and F, as well as the untypable isolates, were associated exclusively with specific OMP-types and represent distinct and widely disseminated clonal groups. These observations support the view that avian strains of P. multocida have a clonal population structure. Based on previous studies, the molecular mass heterogeneity of the OmpA and OmpH proteins might provide a selective advantage to P. multocida by generating antigenic variation.

Characterization and comparison of Pasteurella multocida strains associated with porcine pneumonia and atrophic rhinitis

One hundred and fifty-eight porcine strains of Pasteurella multocida, recovered primarily from cases of pneumonic pasteurellosis or progressive atrophic rhinitis (PAR) in England and Wales, were characterized by determination of their capsular types, presence or absence of the toxA gene and molecular mass heterogeneity of the heat-modifiable (OmpA) and porin (OmpH) proteins. Eighteen groups (clones) of strains were identified on the basis of specific combinations of capsular type, toxA status and outer-membrane protein (OMP)-type. The data provided evidence that different subpopulations of P. multocida are responsible for pneumonia and PAR in pigs. The majority (88 %) of cases of pneumonia were associated exclusively with non-toxigenic capsular type A strains of OMP-types 1.1, 2.1, 3.1 and 5.1 and capsular type D isolates of OMP-type 6.1. These strains were recovered from widespread geographical locations within England and Wales over a 12-year period and represented mostly single sporadic cases. The association of a small number of P. multocida variants with the majority of cases of porcine pneumonia suggests that these strains are not opportunistic pathogens of low virulence but represent primary pathogens with a relatively high degree of virulence. In contrast, the majority (76 %) of cases of PAR were associated with toxA-containing capsular type D strains of OMP-type 4.1 and capsular type A and D strains of OMP-type 6.1. Toxigenic capsular type A strains associated with PAR and non-toxigenic capsular type A strains associated with pneumonia represent distinct subpopulations of P. multocida that can be differentiated by their OMP-types. The association of capsular types A and D with strains of the same OMP-types, and the absence and presence of the toxA gene in strains of the same OMP-types, suggest that horizontal transfer of capsular biosynthesis and toxA genes has occurred between strains representing certain subpopulations of P. multocida.

Isolation of immunogenic outer membrane proteins from Mannheimia haemolytica serotype 1 by use of selective extraction and immunoaffinity chromatography

OBJECTIVE

To use antibodies produced by calves in response to infection with Mannheimia haemolytica in immunoaffinity chromatography for the identification and subsequent isolation of the dominant immunogenic antigens from bacteria grown in iron-deficient media.

SAMPLE POPULATION

Serum from 10 calves actively infected with M haemolytica.

PROCEDURE

An outer membrane protein fraction was obtained from sonicated salt-extracted M haemolytica cells by extraction with N-lauroyl sarcosinate. The immunoglobulin fraction of serum from calves actively infected with M haemolytica was used to prepare an immunoaffinity column. The immunoaffinity column was used to isolate the dominant immunogenic proteins from the outer membrane protein fraction. The resultant immunogenic protein fraction was subjected to ELISA and immunoblot methods as well as carbohydrate quantification. Sequencing of the N-terminal was performed on the most prominent protein.

RESULTS

5 immunogenic proteins with molecular weights of 42, 30, 24, 20, and 15 kd were isolated. The immunogenic protein fraction was found to contain 51% carbohydrate. The immunoaffinity column capacity was 1 microg of immunogenic protein/mL of gel. The N-terminal sequence of the 42-kd protein was Tyr-Gln-Thr-Tyr-Gln-Ser-X-Leu-Gln, where X could not be identified.

CONCLUSIONS AND CLINICAL RELEVANCE

lmmunogenic proteins were isolated by use of immunoaffinity chromatography. A substantial amount of carbohydrates was co-purified in the process. Additional experiments are needed to determine whether the carbohydrates would hinder or enhance development of vaccine preparations. This method could potentially allow a more rapid production of antigens for use in vaccines.

Cloning of 87 kDa outer membrane protein gene of Pasteurella multocida P52

Pasteurella multocida serotype B:2 is the causative agent of haemorrhagic septicaemia, a fatal disease of cattle and buffaloes. Formalin inactivated whole cell bacterin is used to prepare vaccines in India. However, outer membrane proteins (OMPS) of P. multocida were reported to be potential immunogens. The 87-kDa OMP of P. multocida P52, serotype B:2 has been identified as one of the major antigens because this protein reacted with serum of vaccinated animals. The gene omp87, encoding an 87-kDa OMP was amplified and cloned into pBluescript SK(-) vector. This gene was found to localise in a 9.0 kb Hind III fragment of P. multocida genome.

Influence of culture conditions on expression of the 40-kilodalton porin protein of Vibrio anguillarum serotype O2

Vibrio anguillarum serotype O2 strains express a 40-kDa outer membrane porin protein. Immunoblot analysis revealed that antigenic determinants of the V. anguillarum O2 40-kDa porin were conserved within bacterial species of the genus Vibrio. The relative amounts of the V. anguillarum O2 40-kDa porin were enhanced by growth of V. anguillarum O2 in CM9 medium containing 5 to 10% sucrose or 0.1 to 0.5 M NaCl. In contrast, the levels of the porin were significantly reduced when cells were grown at 37 degrees C, and a novel 60-kDa protein was also observed. However, the osmolarity or ionic concentration of the growth medium did not influence expression of the 60-kDa protein. Growth in medium containing greater than 0.6 mM EDTA reduced production of the V. anguillarum O2 40-kDa porin and enhanced levels of a novel 19-kDa protein. Thus, expression of the V. anguillarum O2 40-kDa porin was osmoregulated and possibly coregulated by temperature. The N-terminal amino acid sequence of the V. anguillarum O2 40-kDa protein and the effect of environmental factors on the cellular levels of the porin suggested that the V. anguillarum O2 40-kDa porin was functionally similar to the OmpC porin of Escherichia coli. However, pore conductance assays revealed that the V. anguillarum O2 40-kDa porin was a general diffusion porin with a pore size in the range of that of the OmpF porin of E. coli.

Cloning and characterization of the major outer membrane protein gene (ompH) of Pasteurella multocida X-73

The major outer membrane protein (OmpH) of Pasteurella multocida X-73 was purified by selective extraction with detergents, followed by size exclusion chromatography. The planar lipid bilayer assay showed that OmpH has pore-forming function. The average single channel conductance in 1.0 M KCl was 0.62 nS. The gene (ompH) encoding OmpH has been isolated and sequenced by construction of a genomic library and PCR techniques. The coding region of this gene is 1,059 bp long. The predicted primary protein is composed of 353 amino acids, with a 20-amino-acid signal peptide. The mature protein is composed of 333 amino acids with a molecular mass of 36.665 kDa. The ompH gene encoding mature protein has been expressed in Escherichia coli by using a regulatable expression system. The ompH gene was distributed among 15 P. multocida serotypes and strain CU. Protection studies showed that OmpH was able to induce homologous protection in chickens. These findings demonstrate that OmpH is a protective outer membrane porin of strain X-73 and is conserved among P. multocida somatic serotypes.

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.

Characterization of an outer membrane protein of Pasteurella multocida belonging to the OmpA family

The outer membrane vesicle and N-lauroylsarcosine-insoluble protein preparations of Pasteurella multocida 656 were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A major outer membrane protein (OMP) was found to be heat-modifiable, having a molecular mass of 28 kDa when the OMP preparation was solubilized at 60 degrees C and a molecular mass of 37 kDa when it was solubilized at 100 degrees C. A monoclonal antibody, designated mAb MT4.1, was generated against heat-modifiable OMP of P. multocida. This mAb reacted with the heat-modifiable OMP irrespective of the temperature at which it was solubilized, as demonstrated by immunoblot results. The heat-modifiable OMP of P. multocida showed a significant N-terminal amino acid sequence homology with OmpA family. Immunoelectron microscopic study revealed that the mAb Mt4.1 epitope was not surface exposed on the intact bacterium. The mAb MT4.1 reacted with all the reference strains of 5 capsular and 16 somatic serotypes, as well as with 75 field strains of P. multocida in immunoblot assay. This mAb MT4.1 also reacted with strains of various other Pasteurella species such as P. stomatis, P. aerogenes P. gallinarum, P. betti, P. sp, B, P. SP-g and P. canis, but not with strains of 12 other Gram-negative bacteria. These results indicated that this protein carried a genus-specific epitope and mAb MT4.1 may be useful for identification of Pasteurella species. This is the first report in which a major heat-modifiable OMP has been identified and characterized using a mAb, and has been shown belonging to the OmpA family.