A three-way comparative genomic analysis of Mannheimia haemolytica isolates

BACKGROUND

Mannhemia haemolytica is a Gram-negative bacterium and the principal etiological agent associated with bovine respiratory disease complex. They transform from a benign commensal to a deadly pathogen, during stress such as viral infection and transportation to feedlots and cause acute pleuropneumonia commonly known as shipping fever. The U.S beef industry alone loses more than one billion dollars annually due to shipping fever. Despite its enormous economic importance there are no specific and accurate genetic markers, which will aid in understanding the pathogenesis and epidemiology of M. haemolytica at molecular level and assist in devising an effective control strategy.

DESCRIPTION

During our comparative genomic sequence analysis of three Mannheimia haemolytica isolates, we identified a number of genes that are unique to each strain. These genes are "high value targets" for future studies that attempt to correlate the variable gene pool with phenotype. We also identified a number of high confidence single nucleotide polymorphisms (hcSNPs) spread throughout the genome and focused on non-synonymous SNPs in known virulence genes. These SNPs will be used to design new hcSNP arrays to study variation across strains, and will potentially aid in understanding gene regulation and the mode of action of various virulence factors.

CONCLUSIONS

During our analysis we identified previously unknown possible type III secretion effector proteins, clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated sequences (Cas). The presence of CRISPR regions is indicative of likely co-evolution with an associated phage. If proven functional, the presence of a type III secretion system in M. haemolytica will help us re-evaluate our approach to study host-pathogen interactions. We also identified various adhesins containing immuno-dominant domains, which may interfere with host-innate immunity and which could potentially serve as effective vaccine candidates.

Characterization of carbohydrate structures of bovine MUC15 and distribution of the mucin in bovine milk

The present work reports the characterization of carbohydrate structures and the distribution of the newly identified mucin MUC15, a highly glycosylated protein associated with the bovine milk fat globule membrane (MFGM). Distribution of MUC15 was investigated in various fractions of bovine milk by densitometric scanning of Western blots. In raw milk, MUC15 was shown to constitute 0.08% (wt) of the protein and approximately 1.5% (wt) of the MFGM-associated proteins. Surprisingly, this study showed that in addition to the fat-containing fractions, such as MFGM and buttermilk, MUC15 was present in nonfat-containing fractions as well, such as skim milk and whey. Compositional and structural studies of the carbohydrates of bovine milk MUC15 showed that the glycans are composed of fucose, galactose, mannose, N-acetylgalactosamine, N-acetylglycosamine, and sialic acid. The carbohydrate was shown to constitute 65% of the total molecular weight, and the molar ratios of the individual sugars to protein of the O-linked glycans were determined. The glycan structures of MUC15 were further studied by enzymatic deglycosylation experiments using different endo- and exoglycosidases as well as a panel of lectins. The N-linked glycans were shown to contain mainly hybrid-type N-glycans. In addition, the N-glycans were shown to be sialylated and contain terminal poly-lactosamine structures. The O-linked glycans were found to constitute some unsubstituted Core-1 structures and a substantial number of sialylated Core-1 O-linked glycans. By comparing the results of peanut agglutinin lectin binding, enzymatic deglycosylation, and monosaccharide composition analysis, we concluded that bovine MUC15 also contains more complex O-glycans containing high amounts N-acetylglucosamine residues. Furthermore, a small subset of the O-linked glycans is decorated with lactosamine on their terminal ends.

Identification and characterization of transcriptional regulation of the Mannheimia haemolytica ferric uptake regulator

The ferric uptake regulator (Fur) is an iron-dependent transcriptional regulator that regulates genes related to iron acquisition, oxidative stress response, and various other functions. Transcription of fur is typically self-regulating and sensitive to iron and oxidative stress. Following the identification of a fur gene in the genome of the bovine pathogen Mannheimia haemolytica, an attempt was made to characterize the transcriptional control of M. haemolytica fur. Northern blotting, RT-PCR, and primer extension were done to determine that M. haemolytica fur is transcribed using three distinct promoters, two of which are located within the upstream fldA gene. The third promoter is located upstream of a conserved hypothetical protein and drives transcription of a tricistronic message. Quantitative real time PCR experiments indicated that unlike current models of Fur regulation, M. haemolytica fur transcription is unchanged by iron depletion at logarithmic phase and repressed by iron depletion at stationary phase.

Production of a d-glycero-d-manno-heptosyltransferase mutant of Mannheimia haemolytica displaying a veterinary pathogen specific conserved LPS structure; development and functionality of antibodies to this LPS structure

Previous structural studies of the lipopolysaccharides from the veterinary pathogens Mannheimia haemolytica (Mh), Actinobacillus pleuropneumoniae (Ap) and Pasteurella multocida (Pm) had identified a conserved inner core oligosaccharide structure that was present in all strains investigated. In order to examine the potential of this inner core structure as a vaccine, a mutagenesis strategy was adopted to interrupt a D-glycero-D-manno-heptosyltransferase gene (losB) of Mh. This gene encodes the enzyme responsible for the addition of a D-glycero-D-manno-heptose residue, the first residue beyond the conserved inner core, and its inactivation exposed the conserved inner core structure as a terminal unit on the mutant LPS molecule. Subsequent analyses confirmed the targeted structure of the mutant LPS had been obtained, and complementation with losB in trans confirmed that the losB gene encodes an alpha-1,6-D-glycero-D-manno-heptosyltransferase. Monoclonal antibodies raised in mice to this LPS structure were found to recognise LPS and whole-cells of the truncated mutant and wild-type Mh. The antibodies were bactericidal against a wild-type Mh strain and were able to passively protect mice in a model of Mh disease. This illustrates that it is possible to raise functional antibodies against the conserved inner core LPS structure.

Novel protease produced by a Pasteurella trehalosi serotype 10 isolate from a pneumonic bighorn sheep: characteristics and potential relevance to protection

A strain of Pasteurella trehalosi serotype 10, E(CO)-100, isolated from a bighorn sheep that had succumbed to pneumonic pasteurellosis during an epizootic, was compared to well-characterized strains of P. trehalosi serotype 10 and Mannheimia haemolytica serotype 1. The gene for leukotoxin A (lktA) from E(CO)-100 was sequenced and found to be identical on an amino acid basis to a published sequence for lktA from P. trehalosi serotype 10. However, the toxic activity in culture supernatant measured over time for E(CO)-100 was quite different from reference strains. Typically, the ability of the supernatant to lyse target cells increases over time corresponding to the logarithmic growth of the organism, peaks at mid to late phase, then declines gradually. Supernatant from E(CO)-100 exhibited a sharp decline in toxicity after mid-logarithmic growth to undetectable levels. Investigation of this anomaly using a commercial kit with a porcine gelatin/bovine albumin substrate matrix revealed high protease activity in the supernatant of this strain compared to another P. trehalosi serotype 10 and to a M. haemolytica serotype 1. Protease activity was also visualized using gelatin based zymogram gels. This protease was not substrate specific as it was shown to degrade leukotoxin. Activity was neutralized by bighorn sera in a titratable manner. There was an association between the ability to neutralize protease and low pneumonic lung scores in bighorn sheep experimentally challenged with E(CO)-100 (r=0.5, P=0.1). This previously unidentified protease may be an important protective antigen in vaccines designed to prevent pneumonic pasteurellosis resulting from P. trehalosi in bighorn sheep.

Efficacy of recombinant sialoglycoprotease in protection of cattle against pneumonic challenge with Mannheimia (Pasteurella) haemolytica A1

Secreted recombinant sialoglycoprotease fusion protein (Gcp-F) of Mannheimia (Pasteurella) haemolytica A1 was examined for its ability to protect cattle from experimental challenge with M. haemolytica A1. Five M. haemolytica vaccines were compared including Gcp-F, logarithmic phase culture supernate (Presponse) and Presponse enriched with Gcp-F, recombinant leukotoxin (rLkt) or both. All calves receiving Gcp-F had significant serum antibody responses to this antigen, measured by ELISA, prior to challenge. Those vaccinated with Gcp-F alone had significantly lower percent pneumonic tissue than unvaccinated controls and a trend (P=0.085, one-tailed test) to lower clinical scores. Calves receiving Presponse with Gcp-F and rLkt had lower percent pneumonic tissue than those receiving Presponse alone, and calves receiving Presponse enriched with Gcp-F and/or rLkt had lower mean clinical scores, but the differences were not significant. This trial demonstrates the protective capacity of sialoglycoprotease. While, remarkably, recombinant Gcp-F provided some protection alone the results support its practical potential as a component of a multiple antigen vaccine.

Kinetic properties of the acylneuraminate cytidylyltransferase from Pasteurella haemolytica A2

Neuroinvasive and septicaemia-causing pathogens often display a polysialic acid capsule that is involved in invasive behaviour. N-Acetylneuraminic acid (NeuAc) is the basic monomer of polysialic acid. The activated form, CMP-Neu5Ac, is synthesized by the acylneuraminate cytidylyltransferase (ACT; EC 2.7.7.43). We have purified this enzyme from Pasteurella haemolytica A2 to apparent homogeneity (522-fold). The protein behaved homogeneously on SDS/PAGE as a 43 kDa band, a size similar to that of Escherichia coli, calf, mouse and rat. Specific activity in crude lysate displayed one of the highest values cited in the literature (153 m-units/mg). We have studied the steady-state kinetic mechanism of the enzyme by using normalized plot premises. The catalysis proceeds through a Ping Pong Bi Bi mechanism, with CTP as the first substrate and CMP-NeuAc as the last product. The true Km values were 1.77 mM for CTP and 1.82 mM for NeuAc. The nucleotides CDP, UTP, UDP and TTP, and the modified sialic acid N-glycolylneuraminic acid were also substrates of the ACT activity. The enzyme is inhibited by cytidine nucleotides through binding to a second cytidyl-binding site. This inhibition is greater with nucleotides that display a long phosphate tail, and the genuine inhibitor is the substrate CTP. At physiological concentrations, ATP is an activator, and AMP an inhibitor, of the ACT activity. The activated sugar UDP-N-acetylglucosamine acts as an inhibitor, thus suggesting cross-regulation of the peptidoglycan and polysialic acid pathways. Our findings provide new mechanistic insights into the nature of sialic acid activation and suggest new targets for the approach to the pathogenesis of encapsulated bacteria.

Responses to aggregating agents after cleavage of GPIb of human platelets by the O-sialoglycoprotein endoprotease from Pasteurella haemolytica- potential surrogates for Bernard-Soulier platelets?

Most proteolytic enzymes that cleave glycoprotein lb (GPlb) also cleave other glycoproteins or receptors on the surface of platelets. We have used an O-sialoglycoprotein endoprotease from Pasteurella haemolytica that selectively cleaves the heavily O-glycosylated GPlb, but does not cleave N-linked glycoproteins or unglycosylated proteins. Isolated, [14C]serotonin-labeled platelets in Tyrode-albumin solution were incubated with 10 microg/mL endoprotease for 60 minutes at 37 degrees C. These platelets did not release [14C]serotonin, had no detectable GPIb, and were unresponsive to ristocetin/von Willebrand factor. Compared with control platelets, aggregation and release of [14C]serotonin by the endoprotease-pretreated platelets were inhibited in response to low concentrations of thrombin, SFLLRN (the PAR-1-activating peptide), collagen, and U46619 (a thromboxane A(2) mimetic); aggregates were smaller in size. The presence of fibrinogen overcame the inhibition of responses induced by SFLLRN, collagen, and U46619. With fibrinogen, primary ADP-induced aggregation was scarcely affected by pretreatment with the endoprotease. Thus, the PAR-1 receptor for thrombin, and receptors for collagen, thromboxane A(2), fibrinogen (GPIIb/IIIa), and ADP appear to function normally on the endoprotease-pretreated platelets. Since only GPIb is cleaved by the endoprotease, these platelets seem to provide potential surrogates for Bernard-Soulier syndrome platelets for further studies of platelet functions in this condition.

In vivo production of neuraminidase by Pasteurella haemolytica in market stressed cattle after natural infection

Pasteurella haemolytica (Ph) is the most important cause of the bovine acute fibrinohemorrhagic pneumonia that occurs in market stressed calves after shipment to feedyards. Recent characterization of neuraminidase production by these organisms has shown that all 16 serotypes produce an immunologically similar form of the enzyme. Anti-neuraminidase antibody against PhA1 and PhA6 was determined in 101 2- to 5-month-old calves, on their farms of origin, at the order buyer barn (OBB), and through 28 days in the feedyard. Half of the calves were vaccinated with a killed Ph serotype-A1 (PhA1) product. Nasal secretion and tonsil wash specimens were cultured for Ph and Pasteurella multocida (Pm). Serum antibody against PhA1 and PhA6 was measured by indirect hemagglutination (IHA), and anti-neuraminidase antibody was determined by the neutralization assay. At the feedyard, 73 calves had respiratory tract disease. IHA values ranged between 1:2 and 1:1024 for PhA1 and between 1:2 and 1:512 for Ph serotype A6 (PhA6). Forty-two, 24, and 28% of the calves were infected with PhA1, PhA6, and Pm, respectively. Ninety-six percent of the calves experienced an increase in anti-PhA1 neuraminidase antibody when sera drawn on feedyard day 28 were compared with sera drawn on the farm. These data demonstrate that the enzyme neuraminidase is produced in vivo in market stressed cattle after a natural Ph infection.

Biochemical conditions for the production of polysialic acid by Pasteurella haemolytica A2

The capsular polysaccharide of Pasteurella haemolytica A2 consists of a linear polymer of N-acetylneuraminic acid (Neu5Ac) with alpha(2-8) linkages. When the bacterium was grown at 37 degrees C for 90 h in 250 ml shake flasks at 200 rpm in Brain heart infusion broth (BHIB), it accumulated, attaining a level of 60 microg/ml. Release of this polymer was strictly regulated by the growth temperature, and above 40 degrees no production was detected. The pathway for the biosynthesis of this sialic acid capsular polymer was also examined in P. haemolytica A2 and was seen to involve the sequential presence of three enzymatic activities: Neu5Ac lyase activity, which synthesizes Neu5Ac by condensation of Nacetyl-D-mannosamine and pyruvate with apparent Km values of 91 mM and 73 mM, respectively; a CMP-Neu5Ac synthetase, which catalyzes the production of CMP-Neu5Ac from Neu5Ac and CTP with apparent Km values of 2 mM and 0.5 mM, respectively, and finally a membrane-associated polysialyltransferase, which catalyzes the incorporation of sialic acid from CMP-Neu5Ac into polymeric products with an apparent CMP-Neu5Ac Km of 250 microM.

Membrane protein proteolysis assayed by fluorescence quenching: assay of O-sialoglycoprotein endopeptidase

The assay of the O-sialoglycoprotein endopeptidase of Pasteurella haemolytica has previously used the cleavage of 125I-labeled glycophorin A, measured by SDS-PAGE, autoradiography, gel-slicing, and scintillation counting. A new assay is based on the increased fluorescence which results from proteolytic cleavage of a fluorescence-quenched micellar substrate, 4,4-difluor-5,7-dimethyl-4-bora-3 alpha, 4 alpha-diaza-s-indacene-3-propionic acid conjugated to glycophorin A (BODIPY-FL-glycophorin A). Micellar association of glycophorin A molecules results in 97% fluorescence quenching despite a low molar ratio of BODIPY-FL-glycophorin A. Proteolysis of the membrane protein causes greatly enhanced fluorescence which is used for a rapid one-step proteolysis assay. Direct monitoring of proteolysis in microcuvettes, or routine assay in microtiter plates can be used. Reproducibility is higher than with the radiolabeled substrate and the K(m) values for the two substrates are similar. The assay is suitable for the O-sialoglycoprotein endopeptidase activity of chromatographically purified enzyme or unpurified bacterial culture supernatants and can be used to monitor inhibition of the O-sialoglycoprotein endopeptidase by neutralizing antibodies. The O-sialoglycoprotein endopeptidase assay employing BODIPY-FL-glycophorin A provides a rapid and nonradioactive method for the assay of this highly specific enzyme.

Bovine platelet adhesion is enhanced by leukotoxin and sialoglycoprotease isolated from Pasteurella haemolytica A1 cultures

Platelet and fibrin deposits are among characteristic changes observed in lung alveoli of cattle with pasteurellosis induced by Pasteurella haemolytica (biotype A, serotype 1). To determine whether the platelet function could be directly affected by protein products produced by the bacterium, the effects of leukotoxin and O-sialoglycoprotease, culture supernatant antigen secreted by Pasteurella haemolytica A1, on bovine platelet activation were examined by evaluating the enhancement of platelet adhesion to a negatively charged surface relative to untreated control samples. The glycoprotease, or the leukotoxin, was added to plasma free suspensions of bovine platelets and platelet adhesion assessed by two parameters: (i) the number of 3H-adenine-labeled adherent platelets and (ii) the morphology of unlabeled platelets adhering to the charged surface under scanning electron microscopy (SEM). In the presence of calcium, the glycoprotease produced a dose-dependent increase in adhesion. At a concentration of 4.0 micrograms glycoprotease extract protein per 10(7) platelets, a 2-fold increase in adhesion was observed which was similar to the increase in adhesion induced by 0.10 units of thrombin, a known platelet agonist. Both increased platelet adhesion and platelet aggregation were observed with 0.8 microgram glycoprotease extract protein in the presence of calcium. The response of the bovine platelet suspensions to leukotoxin extract protein was dependent on the dosage of the leukotoxin. Adhesion was enhanced at dosages of 25 micrograms leukotoxin protein per 10(7) platelets and below, while at dosages of 50 micrograms and above adhesion was suppressed. Thus, the two proteins secreted by P. haemolytica may interact directly with bovine platelets to initiate platelet aggregation and fibrin formation in alveolar tissue in pneumonic pasteurellosis.

Genotypic relationships among strains classified under the (Pasteurella) haemolytica-complex as indicated by ribotyping and multilocus enzyme electrophoresis

Two-hundred and one strains classified under the (Pasteurella) haemolytica-complex isolated from cattle, sheep, deer, pigs, hares and rabbits were investigated by ribotyping. Fifty-nine of these strains were selected for further studies using multilocus enzyme electrophoresis (MEE). A correlation between the clusters identified by ribotyping and MEE was demonstrated and the results furthermore indicated that a genetic basis exists for most clusters previously outlined by the use of quantitative evaluation of phenotypic data. The taxonomic relevance of ornithine decarboxylase and fermentation of L-arabinose, D-sorbitol and glucosides for taxonomic delineation within the (P.) haemolytica-complex was supported. A taxonomic importance was further indicated for ONPG, ONPX, ONPF, meso-inositol, D-xylose, maltose, dextrine and NPG in relation to some of the taxa. Within the porcine taxon 15, however, differences in ornithine decarboxylase did not correspond to genetic clusters. Six lineages were revealed by MEE. Lineage A contained electrophoretic types (ETs) representing biogroups 1, 3A-3H, 8A and 9, indicating a genetic relationship between these groups--an observation which was supported by ribotyping. Lineage B included biogroup 8D, 3 strains from biogroup 10 and a single strain from biogroup 1 and taxon 18/biovar 1. Lineage C contained strains allocated to biogroup 6 from ruminants and the porcine taxon 15. The similarity between these two groups was accentuated by ribotyping. Lineage D and the single isolate in lineage E contained strains allocated to biogroups 7, 10, 8B and 8C, in addition to single strains from biogroups 6 and 9. The same strains were found in the heterogenous ribotype cluster 17. Lineage F contained strains representing the leprine taxon 20 and the ruminant (P.) granulomatis. Ribotyping indicated that the ruminant biogroup 3J was affiliated with both taxon 20 and (P.) granulomatis.

Refolding of recombinant Pasteurella haemolytica A1 glycoprotease expressed in an Escherichia coli thioredoxin gene fusion system

Pasteurella haemolytica A1 secretes an O-sialoglycoprotein endopeptidase (EC. 3.4.24.57) (glycoprotease: Gcp) which is specific for O-linked sialoglycoproteins. When the cloned gene is expressed in Escherichia coli, the recombinant glycoprotease (rGcp) is secreted to the periplasm where it is present as a disulfide-linked aggregate which lacks enzymatic activity. In vitro refolding and activation of rGcp by mammalian protein disulfide isomerase (PDI) or by the E. coli chaperones (DnaK, DnaJ and GrpE) indicate that the redox environment of rGcp is critical in restoring biological activity. A fusion protein, rTrx-Gcp, was constructed to investigate the role of thioredoxin (E. coli TrxA) in the production of enzymatically active rGcp. This 47 kDa protein was expressed at a high level, in a soluble, monomeric form, in the cytoplasm of E. coli. Cleavage of the fusion protein by enterokinase released the rGcp fragment (35 kDa) with glycoprotease activity. A higher recombinant glycoprotease activity was recovered after anion exchange chromatography of lysates of E. coli expressing rTrx-Gcp. Thus when E. coli TrxA is combined in a recombinant fusion protein with P. haemolytica A1 Gcp, productive folding of the glycoprotease can occur as a result of the chaperone action of the protein disulfide reductase coupled with its ability to retain the fusion gene product in the E. coli cytoplasm.

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.

Comparison of the recombinant and authentic forms of the Pasteurella haemolytica A1 glycoprotease

The O-sialoglycoprotein endopeptidase (glycoprotease, Gcp) is secreted by Pasteurella haemolytica A1, a Gram-negative pathogen associated with bovine pneumonic pasteurellosis. When the cloned gcp gene is expressed in Escherichia coli, the recombinant glycoprotease (rGcp) is exported to the periplasm but does not exhibit enzymatic activity. Polyclonal calf sera and murine monoclonal antibodies to rGcp were used for the further immunological and biochemical characterization of the authentic and recombinant Gcp. The results showed that the gcp gene product is the sole component of Gcp activity. Homologues to the P. haemolytica A1 Gcp were detected by Western immunoblot analysis in a number of Gram-negative bacteria, including E. coli. However, the secretion of Gcp with O-sialoglycoprotein endopeptidase activity appears to be restricted to P. haemolytica A serotypes.

The restriction-modification system of Pasteurella haemolytica is a member of a new family of type I enzymes

Genes encoding the type I restriction-modification (R-M) system of the bovine pathogen, Pasteurella haemolytica, have been identified immediately downstream of a locus that encodes a transcriptional activator of P. haemolytica leukotoxin expression. Type I enzymes are encoded by three genes called hsdM, hsdS and hsdR, and have fallen into three groups, called Ia, Ib and Ic. HsdS provides a sequence recognition function which in concert with HsdM forms an active methyltransferase (MTase). Inclusion of the HsdR subunit in the complex creates an active restriction endonuclease (ENase) capable of cleaving unmethylated target DNA. The P. haemolytica hsdMSR genes were mapped using transposon Tn10d-Cam insertions, and bacteriophage restriction and modification assays in Escherichia coli. We determined the nucleotide sequences of hsdM, hsdS and hsdR, and observed that the deduced amino acid (aa) sequences were very similar to predicted R-M subunits in the respiratory pathogen, Haemophilus influenzae. Phylogenetic comparisons of all known Hsd aa sequences placed the P. haemolytica and H. influenzae proteins into a new group which we labeled the Type Id R-M family. Expression of the P. haemolytica R-M genes in E. coli was inefficient and is likely to be a consequence of the unusual codon usage in P. haemolytica genes.

The sequence of a 20.3 kb DNA fragment from the left arm of Saccharomyces cerevisiae chromosome IV contains the KIN28, MSS2, PHO2, POL3 and DUN1 genes, and six new open reading frames

We report the sequence of a 20 300 bp DNA fragment from the left arm of Saccharomyces cerevisiae chromosome IV. This segment contains 13 complete open reading frames (ORFs) and part of another ORF, altogether covering 84.2% of the entire sequence, five of which correspond to the previously characterized KIN28, MSS2, PHO2, POL3/CDC2 and DUN1 genes. One putative protein, D2358p, shares considerable homology with an O-sialoglycoprotein endopeptidase from Pasteurella haemolytica serotype A1. The putative product of D2325 contains the characteristic consensus motif of triacylglycerol lipases. D2320p and D2352p have a putative 'leucine-zipper' structure and a RNA-binding region Rnp-1 signature, respectively.

Occurrence of [copper, zinc]-cofactored superoxide dismutase in Pasteurella haemolytica and its serotype distribution

Fifty-two ovine strains of Pasteurella haemolytica and P. trehalosi representing serotypes 1-16 were examined for the presence of [copper, zinc]superoxide dismutase DNA sequences. This was done using a combination of polymerase chain reaction with degenerate primers based on the sequence of the [Cu,Zn]superoxide dismutase gene (sodC) in related species and Southern hybridization using a fragment of sodC from P. haemolytica A2 serotype as a probe. Both detection methods identified a fragment of the sodC gene in 9/9 strains of P. haemolytica serotype 2 examined and in 5/8 strains of serotype 7. No evidence of this gene was found in any other serotype of P. haemolytica or in any P. trehalosi serotype. Comparison of DNA sequence showed near identity between sodC from the A2 and A7 serotypes of P. haemolytica and substantial similarity (70%) to sodC previously sequenced in P. multocida, Haemophilus parainfluenzae and H. influenzae. Analysis by gel electrophoresis of the superoxide dismutase activity present in cell lysates showed that one or more superoxide dismutase is present in all serotypes. However, cyanide-inhibitable activity, corresponding to [Cu,Zn]superoxide dismutase, was detected only in those strains of serotypes A2 and A7 which showed evidence of the sodC gene fragment.

Identification of CD34+ subsets after glycoprotease selection: engraftment of CD34+Thy-1+Lin- stem cells in fetal sheep

Epitopes on the CD34 molecule detected by some CD34 antibodies can be cleaved by a unique glycoprotease from Pasteurella haemolytica, which cleaves only glycoproteins rich in O-linked glycans. A method to isolate CD34+ cells from adult bone marrow was developed subsequently, in which CD34+ cells were isolated in high purity and yield following immunomagnetic bead selection and detachment with the glycoprotease. Using a variety of other cell-surface markers shown here to be insensitive to glycoprotease, committed progenitors of T lymphoid, B lymphoid, monomyeloid, megakaryoblastic, or erythroid lineages could be identified. Significantly, candidate hematopoietic stem cells (HSC) that are contained within a CD34+Lin- (CD2-, CD14-, CD15-, CD16-, CD19-) (or CD34+CD38-) subset expressing the Thy-1 antigen (CDw90), c-kit receptor (CD117), and CDw109 but lacking expression of CD71 and HLA-DR antigens also were detected. Functionally distinct subsets of glycoprotease-selected CD34+ cells were identified and subfractionated using flow cytometry and fluorescence-activated cell sorting (FACS). These subsets included candidate HSCs expressing the CD34+Thy-1+Lin- phenotype, which were sorted from a CD34+ fraction of a mobilized peripheral blood (MPB) sample. In a fetal sheep model, when CD34+Thy-1+Lin- cells were injected intraperitoneally, they were capable of homing to the marrow, where they generated long-term multilineage hematopoiesis and maintained human CD34+ cells, indicating that candidate HSC subsets of CD34+ cells selected with this highly specific enzyme were capable of engraftment in vivo. The ability to identify and purify virtually any phenotypically defined subset of glycoprotease-selected CD34+ stem/progenitor cells should facilitate the study of hematopoiesis in vitro and in animal models in vivo as well as the development of novel genetic techniques for the correction of specific blood cell disorders in humans.

Evidence of bovine immunoglobulin G1 (IgG1) protease activity in partially purified culture supernate of Pasteurella haemolytica A1

In the bovine respiratory tract, IgG1 is a major secretory immunoglobulin (Ig), and both IgG1 and IgG2 are believed to be important in defense against pneumonic pasteurellosis (shipping fever) in calves. Here we provide evidence for hydrolysis of IgG1 in the presence of partially purified culture supernate (ppCS) from the respiratory pathogen Pasteurella haemolytica A1. Bovine IgG1 was hydrolysed sequentially into three distinct bands (approximately 39, 12, and 7 kDa respectively). Furthermore, partial hydrolysis of bovine IgG2 was observed, but neither bovine IgA nor IgM were affected by incubation with ppCS. These findings suggest that the production of an IgG1-specific protease by P. haemolytica A1 may be a virulence mechanism contributing to the pathogenesis of bovine pneumonic pasteurellosis.

The Pasteurella haemolytica O-sialoglycoprotein endopeptidase is inhibited by zinc ions and does not cleave fetuin

Culture supernatants of Pasteurella haemolytica A1 contain an O-sialoglycoprotein endopeptidase that cleaves human glycophorin A. This enzyme is inhibited by micromolar concentrations of Zn2+. It can be separated from a neuraminidase activity in culture supernatants by ion-exchange chromatography. The neuraminidase activity can cause the de-sialation of the bovine soluble sialoglycoprotein, fetuin. However fetuin is not cleaved proteolytically either by culture supernatants from P. haemolytica A1 or by chromatographically purified O- sialoglycoprotein endopeptidase or neuraminidase.

Cloning and characterization of the galE locus of Pasteurella haemolytica A1

The enzyme UDP-galactose 4-epimerase (GalE) is involved in one of the major steps of galactose metabolism in bacteria. In many cases, GalE is required for the biosynthesis of extracellular polysaccharide materials such as lipopolysaccharide (LPS) and capsule. Mutants defective in galE have been shown to exhibit reduced virulence. Here we describe the cloning and characterization of the galE gene from the bovine pathogen Pasteurella haemolytica A1. This was achieved by the complementation of a Salmonella typhimurium galE mutant with a P. haemolytica A1 plasmid bank. Analysis of six clones recovered on minimal media with galactose as the carbon source showed that they all contained the same recombinant plasmid with a 5-kbp DNA insert. The galE-complementing activity was localized to a 2.2-kbp DNA region by subcloning. Biochemical, immunological, and phage sensitivity analyses of the recombinant LPS in S. typhimurium showed that it is essentially identical to that of the wild type. In vivo expression studies showed that a 37-kDa protein is expressed from the complementing plasmids, and the presence of GalE activity was confirmed by an assay for epimerase activity. Nucleotide sequence analysis of the cloned DNA identified the galE gene. Comparison of the deduced amino acid sequence analysis of P. haemolytica A1 GalE with published data showed high-level homology, 81.6%, with the GalE of Haemophilus influenzae type b. However, the sequences flanking galE do not show similarity with any other gal gene, suggesting that P. haemolytica A1 galE is not linked to the other genes of the gal operon, as is the case for Neisseria meningitidis, Neisseria gonorrhoeae, and H. influenzae. The separation of galE from the classical gal operon genes was confirmed by Southern blot hybridization studies, and a physical map showing the relative positions of galE, galT, and galK was constructed.

Extracellular neuraminidase production by Pasteurella species isolated from infected animals

A total of 721 field isolates of various Pasteurella species (haemolytica, multocida, and testudinis) from various regions of the United States were examined for extracellular neuraminidase production. All strains were grown and tested in the same way. Included were 372 P. haemolytica serotype 1 isolates, 181 P. haemolytica serotype 2 isolates, 63 P. haemolytica serotype 6 isolates, 101 Pasteurella multocida isolates, and 4 Pasteurella testudinis isolates. All Pasteurella species examined produced the enzyme. The data revealed the following: (1) Several transfers of P. haemolytica strains on blood agar medium did not cause a decrease in enzyme activity. (2) P. haemolytica serotypes 2 and 6 produce more neuraminidase than P. haemolytica serotype 1, P. multocida, and P. testudinis isolates. (3) There was no apparent change in neuraminidase production by P. haemolytica serotypes 1 and 2 obtained from the same animal taken on different days in the feedyard. (4) There was no significant change in neuraminidase production by P. haemolytica serotype 2 isolates taken from the same animal at the auction market and later at the feedyard.

Fetuin is a substrate for Pasteurella haemolytica O-sialoglycoprotease

A soluble bovine glycoprotein, fetuin, was used as an alternative substrate to identify O-sialoglycoprotease activity in culture supernatant protein fractions of Pasteurella haemolytica. An aliquot of a 24-hour incubation mixture containing fetuin and O-sialoglycoprotease was denatured and examined after gradient sodium dodecyl polyacrylamide gel electrophoresis. The Coomassie-Brilliant-Blue-stained gel was examined for the disappearance of the fetuin band at an apparent molecular mass of 64 KDa. Four major hydrolysis products were identified: an N-terminal fragment of 45 kDa, a 20 kDa fragment at Val50, and two C-terminal fragments at Val273 and His287.

Extracellular neuraminidase production by a Pasteurella multocida A:3 strain associated with bovine pneumonia

The properties of an extracellular neuraminidase produced by a Pasteurella multocida A:3 strain that was isolated in a case of bovine pneumonia were examined during growth in a defined medium. This enzyme (isolated from concentrated culture supernatants of P. multocida A:3) was active against N-acetylneuramin lactose, human alpha-1-acid glycoprotein, fetuin, colominic acid, and bovine submaxillary mucin. Enzyme elaboration was correlated with the growth of the organism in a defined medium, with maximum quantities produced in the stationary phase. The enzyme was purified by a combination of ammonium sulfate fractionation, ion exchange on DEAE-Sephacel, and gel filtration on Sephadex G-200. The purified neuraminidase possessed a specific activity of 9.36 mumol of sialic acid released per min per mg of protein against fetuin. The enzyme possessed a pH optimum of 6.0 and a Km of 0.03 mg/ml. The P. multocida A:3 neuraminidase had a molecular weight of approximately 500,000 as estimated by gel filtration. The enzyme was stable at 4 and 37 degrees C for 3 h. Approximately 75% of the neuraminidase activity was lost within 30 min at 50 degrees C. Greater than 90% of the enzyme activity was destroyed within 10 min at temperatures of > or = 65 degrees C. The P. multocida neuraminidase does not appear to be serologically related to the Pasteurella haemolytica A1 neuraminidase since antiserum prepared against the purified P. haemolytica enzyme did not neutralize the P. multocida enzyme.

Antigenic and virulence properties of Pasteurella haemolytica leukotoxin mutants

Antigenic properties of two mutants of Pasteurella haemolytica, strains 59B0071 and 59B0072, that do not produce detectable leukotoxin were investigated. Western blot (immunoblot) analysis with a number of polyclonal sera from animals recovering from pasteurellosis revealed that both mutants secreted a variety of antigens that were also present in cultures of several wild-type strains. These antigens ranged from about 100 to 15 kDa. Mutant strain 59B0071 was found to be totally deficient in leukotoxin, as judged not only by Western blotting but also by cytotoxicity assays with bovine lymphoma (BL-3) cells or bovine polymorphonuclear cells as targets. The mutant strain 59B0071 had normal levels of a secreted sialylglycoprotease, however. When strains were tested for virulence in goat and cattle challenge experiments, a reduction in mortality and lung lesions was observed with the mutant 59B0071 in comparison with results obtained with wild-type strains. These results are consistent with an important role for leukotoxin in P. haemolytica virulence and suggest that leukotoxin-negative mutants may be useful tools in the investigation of other virulence properties involved in P. haemolytica infections.

In vivo production of neuraminidase by Pasteurella haemolytica A1 in goats after transthoracic challenge

Nine goats were injected transthoracically with Pasteurella haemolytica A1 to determine if an extracellular bacterial enzyme, neuraminidase, was produced in vivo during infection with this organism. The principal group of goats (n = 9) each received 1 ml of 7.25 x 10(5) live P. haemolytica A1 cells in polyacrylate beads transthoracically in the left lung on days 0 and 21. Six goats were used as negative controls and received 0.3 g of polyacrylate beads subcutaneously in the right flank on days 0 and 21. Serum was obtained from all animals on days -4, 3, 7, 14, 21, 24, and 32. Preimmune serum from all animals showed no detectable antibody to P. haemolytica A1 neuraminidase in an enzyme neutralization assay. None of the sera from the negative control animals possessed a significant antibody concentration in response to the P. haemolytica A1 neuraminidase. On day 32, serum samples from the nine infected animals possessed enzyme neutralizing activity that ranged from 62% to 100%. Anti-neuraminidase antibody could be detected as early as day 14 by the enzyme neutralization assay. These data demonstrate that the enzyme neuraminidase is produced in vivo during an active P. haemolytica A1 lobar infection.

The detection of the sialoglycoprotease gene and assay for sialoglycoprotease activity among isolates of Pasteurella haemolytica A1 strains, serotypes A13, A14, T15 and A16

Polymerase chain reaction (PCR) using specific primers to the sialoglycoprotease gene (gcp) of Pasteurella haemolytica biotype A, serotype 1 amplified a 1-kb fragment from each of P. haemolytica serotypes A7, A13, A14 and A16, but not T15; which was confirmed by Southern blot hybridization analysis. Using a sialoglycoprotease (Gcp) activity assay, Gcp activity was found in serotypes A13, A14 and A16. Inclusion of these three serotypes confirms that all recognized A biotypes are positive for both gcp gene and activity, with the exception of serotype A11 (which has a different genetic organization and exhibits no Gcp activity). Furthermore, all recognized T biotypes are negative for both the gene and Gcp activity.

Characterization of a restriction endonuclease, PhaI, from Pasteurella haemolytica serotype A1 and protection of heterologous DNA by a cloned PhaI methyltransferase gene

Pasteurella haemolytica is the leading cause of economic loss to the beef cattle industry in the United States and an important etiologic agent worldwide. Study of P. haemolytica is hindered by researchers' inability to genetically manipulate the organism. A new restriction endonuclease, PhaI, an isoschizomer of SfaNI (R. J. Roberts, Methods Enzymol. 65:19-36, 1980), was isolated from P. haemolytica serotype 1, strain NADC-D60, obtained from pneumonic bovine lung. PhaI recognizes the 5-base nonpalindromic sequences 5'-GCATC-3' and 5'-GATGC-3'. Cleavage occurs 5 bases 3' from the former recognition site and 9 bases 5' from the latter recognition site. A gene encoding a methyltransferase which protects against PhaI cleavage was cloned from P. haemolytica NADC-D60 into Escherichia coli. Whereas unmethylated plasmid DNA containing a P. haemolytica origin of replication was unable to transform P. haemolytica when introduced by electroporation, the same plasmid DNA obtained from E. coli which contained a cloned PhaI methyltransferase gene could do so. The data indicate that PhaI is an effective barrier to the introduction and establishment of exogenous DNA in P. haemolytica.

Cleavage of epitectin, a mucin-type sialoglycoprotein, from the surface of human laryngeal carcinoma cells by a glycoprotease from Pasteurella haemolytica

In this study we have assessed the action of a novel glycoprotease, secreted by the bovine pneumonia pathogen Pasteurella haemolytica, on epitectin expressed on the surface of human laryngeal carcinoma (H.Ep.2) cells. Epitectin has been previously characterized as a high buoyant density glycoprotein of mass of over 350 kDa extensively glycosylated on serine and threonine by small oligosaccharides. Purified metabolically labeled epitectin was very effectively hydrolyzed by the glycoprotease. However, short- and long-term treatments yielded a complex mixture of products which could not be resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) or column chromatography, probably because of the heterogeneity of the structure and the distribution of the saccharides. Treatment of H.Ep.2 cells with glycoprotease followed by flow cytometric analysis revealed a significant loss in the cell surface epitopes detected by the anti-epitectin Ca2 monoclonal antibody. The action of the glycoprotease on cell surface epitectin was blocked by anti-glycoprotease antisera and was absent in an extract of a glycoprotease-negative strain of P. haemolytica. When extracts of cells treated with glycoprotease for 4 h were subjected to SDS-PAGE followed by 125I-wheat germ agglutinin overlay and autoradiography, the intensity of the characteristic epitectin bands was found to be drastically reduced compared to controls. H.Ep.2 cells metabolically labeled with [3H]glucosamine were also incubated with or without the glycoprotease and the released products were fractionated and analyzed. The enzyme-released products were found to be enriched in mucin-type glycopeptides. Thus the P. haemolytica glycoprotease could be used to selectively degrade mucin glycoproteins on cancer cell surface.

Sialoglycoprotease of Pasteurella haemolytica A1: detection of antisialoglycoprotease antibodies in sera of calves

Log phase culture supernate from Pasteurella haemolytica biotype A, serotype 1 contains a proteolytic enzyme specific for O-sialoglycoproteins. Using two methods, Western immunoblotting and enzyme neutralization assay, it was demonstrated that certain bovine sera from two previous P. haemolytica A1 vaccination and challenge trials contained antibodies (Ab) (isotypes IgG1 and IgG2 on Western immunoblot) to the sialoglycoprotease (Gcp). In these trials, selected calves were vaccinated twice with either the commercial culture supernate vaccine Presponse or given phosphate-buffered saline (PBS). One trial was conducted during spring, P. haem XIX, and the other during the winter, P. haem XXI. Although there was no clear evidence for induction of anti-Gcp in response to vaccination, several calves seroconverted following intrapulmonary challenge with live P. haemolytica A1. This is the first report of anti-Gcp Ab in bovine sera. The results indicated that the Gcp is immunogenic and that the bacterium produces the enzyme in vivo. Further, animals with an anti-Gcp response had less pneumonia at necropsy, suggesting the Gcp may induce protective immunity.

Preparation of recombinant glycoprotease of Pasteurella haemolytica A1 utilizing the Escherichia coli alpha-hemolysin secretion system

Three murine monoclonal antibodies were prepared against the recombinant glycoprotease of Pasteurella haemolytica A1 expressed in Escherichia coli. These monoclonal antibodies were able to recognize the authentic glycoprotease from P. haemolytica A1 culture supernatant. A recombinant plasmid which contained most of the glycoprotease gene of P. haemolytica A1 fused with the secretion signal sequence from hlyA of the E. coli alpha-hemolysin determinant was constructed. This recombinant plasmid expressed a fusion protein (Gcp-F) which was secreted into the culture supernatant by E. coli cells when the alpha-hemolysin secretion functions HlyB and HlyD are supplied in trans. Gcp-F could be readily recovered from the supernatant free from other cellular materials and is suitable for use in vaccine trials and challenge experiments in animals.

Characterization of neuraminidases produced by various serotypes of Pasteurella haemolytica

Neuraminidases produced by 16 strains of Pasteurella haemolytica (serotypes 1 to 16) were characterized by molecular weight, antigenic identity, and substrate specificity. After growth in a chemically defined medium, stage I (lyophilized) culture supernatants were assayed for activity with N-acetylneuramin lactose, human alpha-1-acid glycoprotein, fetuin, colominic acid, and bovine submaxillary mucin. Neuraminidase produced by P. haemolytica serotype A1 (Ph A1) was purified by a combination of salt fractionation, ion-exchange chromatography on DEAE-Sephacel, and gel filtration on Sephadex G-200. Purified Ph A1 neuraminidase was used to immunize rabbits, and the resultant antiserum reduced the activity of Ph A1 neuraminidase by 46%. This antiserum also reduced the activity of neuraminidase produced by the other serotypes by between 15 and 66%. Molecular weight estimates of the neuraminidases produced by the various serotypes were obtained by gel filtration chromatography on Sephadex G-200. Fifteen of the 16 serotypes examined produced a neuraminidase with a molecular weight of approximately 150,000 to 200,000. One serotype (serotype 11) produced no material with neuraminidase activity. In addition, all 15 high-molecular-weight neuraminidases showed similar substrate specificities. That is, they were all most active against N-acetylneuramin lactose and least active against bovine submaxillary mucin. On the basis of these results, it appears that the high-molecular-weight neuraminidases produced by the different P. haemolytica serotypes are quite similar.

Combined enzyme and antimicrobial susceptibility profiles of caprine Pasteurella haemolytica serovar 2 respiratory tract isolates

The present investigation describes a novel method of demonstrating strain diversity among Pasteurella haemolytica biovar A, serovar 2 (PhA2) nasal turbinate isolates from a flock of 32 experimental goats during a naturally occurring outbreak of pasteurellosis. After a 21 day conditioning period in a feedyard, 51 PhA2 isolates from 27 culture-positive goats were identified including 1 on day 22, 14 on day 25, 21 on day 39, and 15 on day 66. Each PhA2 isolate was evaluated for its enzyme activity against 19 substrates with a commercial semiquantitative enzyme system and for its antimicrobial susceptibility with 12 drugs, resulting in 7 different enzyme profiles and 8 different antimicrobial susceptibility profiles. A total of 14 combined enzyme and antimicrobial susceptibility profiles were produced. The same PhA2 strain was isolated from only 4 of the 12 goats with 2 PhA2 isolations, while the same PhA2 strain was isolated from only 1 of the 6 goats with 3 PhA2 isolations. The data from this investigation demonstrated that the PhA2 upper respiratory tract flora from goats is highly heterologous.

Epitopic structure of Tn glycophorin A for an anti-Tn antibody (MLS 128)

Glycophorin A was digested with glycoprotease (Pasteurella haemolytica) and the digest was fractionated by a combination of high-pressure column chromatographies to produce the glycopeptides GPA-1 to GPA-6. Sequence analysis of the glycopeptides revealed that two serine residues (Ser-14 and Ser-15) are not glycosylated, Thr-17 and Ser-19 being glycosylated instead, in disagreement with the accepted structure. The glycopeptides thus obtained were treated with sialidase and beta-galactosidase. The Tn antigenicity, as assayed by the binding to a monoclonal anti-Tn antibody (MLS 128), was found exclusively in the glycopeptides including three (cluster I) or four (cluster II) consecutive residues of GalNAc-Ser/Thr, whereas the glycopeptide (GPA-2) containing two nonconsecutive GalNAc-Ser/Thr residues had practically no Tn antigenicity. The immunoreactivities of GPA-1 and GPA-3, containing both clusters I and II, and GPA-4, containing cluster II, were 63% (calcd. 67%), 81% (calcd. 86%), and 50% (calcd. 50%), respectively, of the immunoreactivity of GPA-5 or GPA-6, containing cluster I (the average being taken as the basis), based on the reactivity per GalNAc residue. These results indicate that clusters I and II react with the antibody to the same extent. The structure consisting of three consecutive glycosylated Ser/Thr residues may be essential for Tn antigenicity in the light of previous results for ovine submaxillary mucin.

Further characterization of Pasteurella haemolytica-like bacteria isolated from swine enteritis

DNA-DNA hybridization studies were conducted on six Pasteurella haemolytica-like (PHL) organisms recovered from cases of swine enteritis. Chromosomal-enriched fractions of PHL organisms served as the source of DNA for Southern blots or as whole-chromosomal DNA probes. Under stringent hybridization conditions, chromosomal DNA probes of a prototype PHL (strain 6213A) organism distinguished other PHL organisms from Pasteurella haemolytica types A1 and T3, Pasteurella multiocida types A:1 and A:3, Escherichia coli, Pseudomonas aeruginosa, Actinobacillus pleuropneumoniae type 1, and Salmonella cholerasuis. The guanine-cytosine content of the DNA of three PHL strains was 41.2 to 42.8 mol % as calculated from the thermal denaturation midpoint temperatures. The PHL strains are Gram-negative, nonmotile, beta-hemolytic, pleomorphic, oxidase-positive, urease- and indole-negative, fermentative rods with the key characteristics of the species Pasteurella haemolytica. None of the PHL strains reacted with the type-specific antisera of P. haemolytica types 1 through 12 as tested by an agglutination procedure. These swine strains differed in their biochemical differentiation from P. haemolytica types A1 and T3 in that all produced acid from M-inositol and failed to grow on MacConkey agar. Acid production from trehalose and L-arabinose was variable with PHL strains. Leukotoxicity of PHL strains was evaluated by a colorimetric micro-titration assay. Sterile culture supernatants of three of five PHL strains were toxic to bovine neutrophils. Results of these studies suggest that the PHL organisms may belong to a new group of organisms under the genus Pasteurella.

Neuraminidase production by a Pasteurella haemolytica A1 strain associated with bovine pneumonia

The properties of an extracellular neuroaminidase produced by a Pasteurella haemolytica A1 strain (isolated from a case of bovine pneumonia) during growth in a defined medium were examined in this investigation. This enzyme, isolated from concentrated culture supernatants of P. haemolytica A1, was active against N-acetylneuramin lactose, human alpha 1-acid glycoprotein, fetuin, and bovine submaxillary mucin. Neuraminidase production paralleled bacterial growth in a defined medium and was maximal in the stationary phase of growth. The enzyme was purified to homogeneity by a combination of salt fractionation, ion-exchange chromatography on DEAE-Sephacel, and gel filtration on Sephadex G-200. These procedures yielded an enzyme preparation that possessed a specific activity of 100.62 mumol of sialic acid released per min per mg of protein against human alpha 1-acid glycoprotein. The Km value for this enzyme with human alpha 1-acid glycoprotein as the substrate was 1.1 mg/ml, and the enzyme possessed a pH optimum of 6.5. The P. haemolytica A1 neuraminidase had a molecular weight of approximately 150,000 as estimated by gel filtration and approximately 170,000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was stable at 4 degrees C for 3 h. At 37 degrees C for 3 h, 25% of enzymatic activity was lost. Approximately 55% of the enzyme activity was lost within 30 min at 50 degrees C, with greater than 70% of the enzyme activity being destroyed within 10 min at temperatures of > or = 65 degrees C.

Identification of Pasteurella haemolytica A1 isolates from market-stressed feeder calves by use of enzyme and antimicrobial susceptibility profiles

An epidemiologic study of Pasteurella haemolytica serovar 1 (Ph1) in market-stressed feeder calves from 7 farms in eastern Tennessee was conducted. The nasal mucus of each calf was cultured sequentially at the farm of origin (day 0), at an auction market (day 133), and at a feedyard in Texas (days 141, 148, 155, and 169). Of the 103 calves tested, 77 were culture-positive, including 1 on day 0, 1 on day 133, 20 on day 141, 57 on day 148, 50 on day 155, and 14 on day 169. From the 143 Ph1 isolates, 20 enzyme profiles were determined by use of a commercial enzyme system that detects 19 enzymatic reactions; 4 antimicrobial susceptibility profiles were obtained, using the disk-diffusion method, which evaluated susceptibility to 11 antibacterial drugs. All isolates were positive for acid phosphatase and alkaline phosphatase, but were negative for alpha-galactosidase, alpha-mannosidase, beta-glucosidase, beta-glucuronidase, cystine aminopeptidase, N-acetyl-beta-glucosaminidase, and trypsin. Other positive enzyme reactions included: leucine aminopeptidase, 140 Ph1 isolates; phosphohydrolase, 90 isolates; alpha-fucosidase, 63 isolates; esterase (C4), 59 isolates; valine aminopeptidase, 30 isolates; esterase lipase (C8), 24 isolates; beta-galactosidase, 2 isolates; and alpha-glucosidase, chymotrypsin and lipase (C14), 1 isolate each. Thirty-four Ph1 profiles were identified, using combined enzyme and antimicrobial susceptibility profiles. The data indicate that the strains isolated during the feedyard period may have been determined more by farm of origin (P < or = 0.001) than by habitation with calves from other farms while in the feedyard.(ABSTRACT TRUNCATED AT 250 WORDS)

The glycoprotease of Pasteurella haemolytica A1 eliminates binding of myeloid cells to P-selectin but not to E-selectin

HL-60 cells and neutrophils treated with the glycoprotease from Pasteurella haemolytica A1, an enzyme which is specific for O-sialoglycoproteins, were found to be incapable of binding P-selectin but still bound E-selectin. Comparative analysis of [35-S] cysteine labeled proteins from HL-60 cells by 2-dimensional electrophoresis indicated that two major proteins with M(r) 100 and 115 kd were significantly removed from cells which had been treated.

Distinct plasmid profiles of Pasteurella haemolytica serotypes and the characterization and amplification in Escherichia coli of ampicillin-resistance plasmids encoding ROB-1 beta-lactamase

Thirty-five isolates of Pasteurella haemolytica from cattle or sheep were screened for the presence of plasmids and for resistance to a range of antibiotics. Eight strains (four of serotype A1, three of serotype A2 and one untypable) contained plasmid DNA and isolates of the same serotype had similar plasmid profiles, which were different from those of the other serotypes. All but one of the plasmid-bearing strains were isolated from pneumonic animals or from animals in contact with pneumonic cattle or sheep. In A2 and untypable strains, there was no obvious correlation between antibiotic resistance and the presence of a specific plasmid. In contrast, all plasmid-bearing A1 strains exhibited ampicillin resistance (ApR), which was shown by transfer studies to be plasmid-mediated. Plasmid DNA prepared from E. coli transformants was not routinely detected on ethidium-bromide-stained agarose gels, but could be amplified to detectable levels by treatment of cultures with chloramphenicol (Cm) or by modifying the growth conditions. The ApR plasmids from P. haemolytica were identical by restriction enzyme analysis. Restriction analysis and hybridization data indicated that these plasmids were closely related to the prototype ROB-1 beta-lactamase-encoding plasmid, originally isolated from Haemophilus influenzae. From substrate profiles and isoelectric focusing data, the beta-lactamases encoded by the P. haemolytica plasmids were indistinguishable from the ROB-1 beta-lactamase.

Cleavage of the cell-surface O-sialoglycoproteins CD34, CD43, CD44, and CD45 by a novel glycoprotease from Pasteurella haemolytica

The study of structural/functional characteristics of the cell-surface glycoproteins of leukocytes has led to a better understanding of the differentiation and maturation of hematopoietic cells. We have assessed the ability of a unique metalloprotease that is secreted by the bovine fibrinous pneumonia pathogen Pasteurella haemolytica, to cleave cell-surface glycoproteins expressed on human leukocytes. Biochemical analysis shows that the O-glycosylated cell surface Ag CD34, CD43 (leukosialin), CD44 (hyaluronic acid receptor), and CD45 (leukocyte common Ag), are all cleaved by this protease. Although these enzyme-sensitive structures contain N-linked glycans, they are all extensively glycosylated with O-linked carbohydrates, which are especially abundant on CD34 and CD43. In contrast, the glycoproteins CD18/11a,b,c (leukocyte integrins), CD71 (transferrin receptor), HLA class I, and 8A3 Ag, which contain N-linked glycans but no O-sialo-glycans, were resistant to the action of the enzyme. Inasmuch as previous studies using glycophorin A had indicated that the substrate specificity of this enzyme may be uniquely restricted to the cleavage of O-sialoglycoproteins, we have designated this activity, P. haemolytica glycoprotease. Immunofluorescence analysis with a variety of antibodies to different epitopes of the P. haemolytica glycoprotease-sensitive structures indicate that this enzyme may have widespread applications in epitope-mapping studies, and represents a novel tool with which to study structure/function relationships for O-sialoglycosylated cell-surface proteins. However, most significantly these results suggest that the P. haemolytica glycoprotease may be of use in the affinity purification and recovery of clinically important leukocyte subsets, such as primitive hematopoietic progenitors that express CD34.

A neutral glycoprotease of Pasteurella haemolytica A1 specifically cleaves O-sialoglycoproteins

A neutral metalloprotease with marked specificity for an O-sialoglycoprotein has been isolated from culture supernatants of Pasteurella haemolytica A1. The 35-kDa enzyme cleaves human erythrocyte glycophorin A, which is O glycosylated, but does not cleave N-glycosylated proteins or nonglycosylated proteins. Glycophorin A was cleaved when it was present in situ in erythrocyte ghost plasma membranes or when it was free in solution. The glycoprotease did not hydrolyze glycophorin A from which sialate residues had been removed by neuraminidase treatment. An immobilized preparation of the enzyme cleaved glycophorin A at several positions, with a major site of cleavage at Arg-31-Asp-32. The glycoprotease is inhibited by EDTA, citrate, and ascorbate, but inhibition appears to be due to the masking of metal ion activators rather than to their removal. The enzyme is not inhibited by phosphoramidon, an inhibitor of other bacterial neutral metalloproteases.