Development of an auxotrophic, live-attenuated Brucella suis vaccine strain capable of expressing multimeric GnRH

Feral swine cost around $1.5 billion each year in agricultural, environmental, and personal property damages. They are also the most widespread carriers of the zoonotic disease brucellosis, which threatens both livestock bio-security and public health. Currently, there is no approved vaccine against brucellosis in pigs. This is a preliminary report on the development of a live-attenuated B. suis vaccine that could be employed to deliver heterologous antigens to control swine populations. An attenuated vaccine strain provided significant protection against B. suis challenge in mice. Leucine auxotrophy in the vaccine strain allowed the over-expression of heterologous antigens without the use of antibiotic resistant markers. Vaccinated mice showed the development of antibodies against expressed antigen. Further evaluation is required to assess its ability to cause infertility using the mouse model prior to further testing for use as a tool for feral swine population and disease control.

Donor-Derived Metastatic Melanoma and Checkpoint Inhibition

Donor-derived malignancy, particularly melanoma, is a rare but known complication of organ transplantation. Here we describe a case of metastatic melanoma in a deceased-donor kidney transplant recipient. After diagnosis, the patient was successfully treated with cessation of immunosuppression, explantation of the renal allograft, and novel melanoma therapies, including the mutation-targeted agents dabrafenib and trametinib and the immune checkpoint inhibitor nivolumab. These 2 new classes of melanoma therapy have revolutionized the course of metastatic melanoma, altering it from one of nearly certain mortality to one of potential cure. This case reviews the mechanisms of action of these therapies and reports our experience with them in the rare setting of donor-derived melanoma in a dialysis-dependent patient.

Low rates of vaccination in listed kidney transplant candidates

Despite clear consensus and strong recommendations, vaccination rates of kidney transplant (KT) recipients have remained below targets. As vaccination is most effective if it is given prior to transplantation and the initiation of immunosuppression, patients should ideally have their vaccination status assessed and optimized in the pre-transplant period. We performed a retrospective chart review to characterize vaccination rates and factors associated with gaps in vaccination in a single-center population of waitlisted patients being evaluated for kidney transplantation. We evaluated 362 KT patients. Three-quarters were receiving dialysis at the time of evaluation. Immunization rates were low with 35.9% of patients having completed vaccination for Pneumococcus, 55% for influenza, 6.9% for zoster, and 2.5% for tetanus. On multivariable analysis, patients who received other vaccines, including influenza, tetanus, or zoster vaccine (odds ratio [OR] 10.55, 95% confidence interval [CI] 5.65-19.71) were more likely to receive pneumococcal vaccine. Blacks (OR 0.24, 95% CI 0.12-0.47) were less likely to receive pneumococcal vaccine compared to whites. Patients on dialysis, and those active on the waiting list were more likely to receive pneumococcal vaccine than other groups (OR 2.81, 95% CI 1.44-5.51, and OR 1.84, 95% CI 1.08-3.14, respectively). We found that the overall immunization rate against common vaccine-preventable infections was low among patients evaluated for kidney transplantation. A significant gap remains between recommendations and vaccine uptake in clinical practice among this high-risk population.

The first detection of Brucella canis in cattle in the Republic of Korea

Twenty mammary lymph node samples were collected from cattle on a farm in the Republic of Korea. These cattle were serologically negative for Brucella by tube agglutination test (≤ 1:50) and serum agglutination test (≤ 1:50). Out of 20 lymph node samples, two samples were positive for Brucella growth on Brucella agar as well as blood agar. Tests for urease, hydrogen sulphide and reactions against monospecific sera A and M indicated that these two isolates (No. 15 and 16) belong to the genus Brucella. Genus specific, AMOS (abortus, melitensis, ovis, suis) and Bruce-ladder multiplex polymerase chain reaction (PCR) assays confirmed the Brucella isolates as either a B. abortus or a B. canis strain. This is the first report of the occurrence of a B. canis infection in cattle in Korea. More survey data are needed to determine whether B. canis is a significant aetiology in the cases of cattle brucellosis in Korea.

PATRIC: the VBI PathoSystems Resource Integration Center

The PathoSystems Resource Integration Center (PATRIC) is one of eight Bioinformatics Resource Centers (BRCs) funded by the National Institute of Allergy and Infection Diseases (NIAID) to create a data and analysis resource for selected NIAID priority pathogens, specifically proteobacteria of the genera Brucella, Rickettsia and Coxiella, and corona-, calici- and lyssaviruses and viruses associated with hepatitis A and E. The goal of the project is to provide a comprehensive bioinformatics resource for these pathogens, including consistently annotated genome, proteome and metabolic pathway data to facilitate research into counter-measures, including drugs, vaccines and diagnostics. The project's curation strategy has three prongs: ‘breadth first’ beginning with whole-genome and proteome curation using standardized protocols, a ‘targeted’ approach addressing the specific needs of researchers and an integrative strategy to leverage high-throughput experimental data (e.g. microarrays, proteomics) and literature. The PATRIC infrastructure consists of a relational database, analytical pipelines and a website which supports browsing, querying, data visualization and the ability to download raw and curated data in standard formats. At present, the site warehouses complete sequences for 17 bacterial and 332 viral genomes. The PATRIC website () will continually grow with the addition of data, analysis and functionality over the course of the project.

Vaccination with gamma-irradiated Neospora caninum tachyzoites protects mice against acute challenge with N. caninum

Neospora caninum, an apicomplexan parasite, is a leading cause of bovine abortions worldwide. The efficacy of gamma-irradiated N. caninum strain NC-1 tachyzoites as a vaccine for neosporosis was assessed in C57BL6 mice. A dose of 528 Gy of gamma irradiation was sufficient to arrest replication but not host cell penetration by tachyzoites. Female C57BL6 mice were vaccinated with two intraperitoneal inoculations of 1 x 10(6) irradiated tachyzoites at 4-wk intervals. When stimulated with N. caninum tachyzoite lysates, splenocytes of vaccinated mice, cultured 5 and 10 wk after vaccination, secreted significant (P<0.05) levels of interferon gamma, interleukin (IL)-10, and small amounts of IL-4. Antibody isotype-specific ELISA of sera from vaccinated mice exhibited both IgG1 and IgG2a isotypes of antibodies. Vaccinated mice were challenged intraperitoneally with 2 x 10(7)N. caninum tachyzoites. All vaccinated mice remained healthy and showed no obvious signs of neosporosis up to the 25th day post-challenge when the study was terminated. All unvaccinated control mice died within 1 wk of infection. Gamma-irradiated N. caninum tachyzoites can serve as an effective, attenuated vaccine for N. caninum.

Deletion of wboA enhances activation of the lectin pathway of complement in Brucella abortus and Brucella melitensis

Brucella spp. are gram-negative intracellular pathogens that survive and multiply within phagocytic cells of their hosts. Smooth organisms present O polysaccharides (OPS) on their surface. These OPS help the bacteria avoid the bactericidal action of serum. The wboA gene, coding for the enzyme glycosyltransferase, is essential for the synthesis of O chain in Brucella. In this study, the sensitivity to serum of smooth, virulent Brucella melitensis 16M and B. abortus 2308, rough wboA mutants VTRM1, RA1, and WRR51 derived from these two Brucella species, and the B. abortus vaccine strain RB51 was assayed using normal nonimmune human serum (NHS). The deposition of complement components and mannose-binding lectin (MBL) on the bacterial surface was detected by flow cytometry. Rough B. abortus mutants were more sensitive to the bactericidal action of NHS than were rough B. melitensis mutants. Complement components were deposited on smooth strains at a slower rate compared to rough strains. Deposition of iC3b and C5b-9 and bacterial killing occurred when bacteria were treated with C1q-depleted, but not with C2-depleted serum or NHS in the presence of Mg-EGTA. These results indicate that (i) OPS-deficient strains derived from B. melitensis 16M are more resistant to the bactericidal action of NHS than OPS-deficient strains derived from B. abortus 2308, (ii) both the classical and the MBL-mediated pathways are involved in complement deposition and complement-mediated killing of Brucella, and (iii) the alternative pathway is not activated by smooth or rough brucellae.

PI3K inhibitors reverse the suppressive actions of insulin on CYP2E1 expression by activating stress-response pathways in primary rat hepatocytes

Insulin-associated signaling pathways are critical in the regulation of hepatic physiology. Recent inhibitor-based studies have implicated a mechanistic role for phosphatidylinositol 3' kinase (PI3K) in the insulin-mediated suppression of CYP2E1 mRNA levels in hepatocytes. We investigated the dose dependence for this response and for the effects of insulin and extracellular matrix on PI3K signaling and CYP2E1 mRNA expression levels using a highly defined rat primary hepatocyte culture system. The PI3K inhibitors wortmannin and LY294002 stimulated stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation in a rapid and concentration-dependent manner that paralleled the inhibition of protein kinase B (PKB) phosphorylation. Although PI3K inhibitors reversed the suppressive effects of insulin on CYP2E1 expression, these effects only occurred at concentrations well in excess of those required to achieve complete inhibition of PKB phosphorylation. These same concentrations produced cytotoxic responses as evidenced by perturbed cellular morphology and elevated release of lactate dehydrogenase. Wortmannin-mediated activation of the SAPK/JNK and p38 MAPK pathways also resulted in the mobilization of activator protein-1 complex to the nuclear compartment. We conclude that the suppression of CYP2E1 mRNA expression by insulin is not directly associated with PI3K-dependent pathway activation, but rather is linked to a cytotoxic response stemming from acute challenge with PI3K inhibitors.

Humoral immune response of BALB/c mice to a vaccinia virus recombinant expressing Brucella abortus GroEL does not correlate with protection against a B. abortus challenge

This work is a part of an ongoing effort to develop vaccinia virus recombinants expressing various Brucella abortus proteins. The B. abortus groEL gene encoding the antigenic heat shock protein GroEL was subcloned into vaccinia virus via homologous recombination and expression confirmed by Western blotting. Female BALB/c mice inoculated with recombinant vaccinia virus/GroEL produced GroEL and vaccinia virus specific antibodies. Mice were challenged 8 weeks post-inoculation with virulent B. abortus strain 2308 and protection measured by the rate of clearance of live Brucella from spleens. Although induction of specific immune response to GroEL and vaccinia virus was demonstrated by the appearance of antibodies in mice, no significant level of protection was demonstrable.

Complementation of Brucella abortus RB51 with a functional wboA gene results in O-antigen synthesis and enhanced vaccine efficacy but no change in rough phenotype and attenuation

Brucella abortus RB51 is a stable rough, attenuated mutant vaccine strain derived from the virulent strain 2308. Recently, we demonstrated that the wboA gene in RB51 is disrupted by an IS711 element (R. Vemulapalli, J. R. McQuiston, G. G. Schurig, N. Srirauganathan, S. M. Halling, and S. M. Boyle, Clin. Diagn. Lab. Immunol. 6:760-764, 1999). Disruption of the wboA gene in smooth, virulent B. abortus, Brucella melitensis, and Brucella suis results in rough, attenuated mutants which fail to produce the O polysaccharide (O antigen). In this study, we explored whether the wboA gene disruption is responsible for the rough phenotype of RB51. We complemented RB51 with a functional wboA gene, and the resulting strain was designated RB51WboA. Colony and Western blot analyses indicated that RB51WboA expressed the O antigen; immunoelectron microscopy revealed that the O antigen was present in the cytoplasm. Crystal violet staining, acryflavin agglutination, and polymyxin B sensitivity studies indicated that RB51WboA had rough phenotypic characteristics similar to those of RB51. Bacterial clearance studies of BALB/c mice indicated no increase in the survival ability of RB51WboA in vivo compared to that of RB51. Vaccination of mice with live RB51WboA induced antibodies to the O antigen which were predominantly of the immunoglobulin G2a (IgG2a) and IgG3 isotypes. After in vitro stimulation of splenocytes with killed bacterial cells, quantitation of gamma interferon in the culture supernatants indicated that RB51WboA immunization induced higher levels of gamma interferon than immunization with RB51. Mice vaccinated with RB51WboA were better protected against a challenge infection with the virulent strain 2308 than those vaccinated with RB51. These studies indicate that in addition to the disruption of the wboA gene there is at least one other mutation in RB51 responsible for its rough phenotype. These studies also suggest that the expressed O antigen in RB51WboA is responsible either directly or indirectly for the observed enhancement in the T-cell response.

Brucella abortus strain RB51 as a vector for heterologous protein expression and induction of specific Th1 type immune responses

Brucella abortus strain RB51 is a stable, rough, attenuated mutant widely used as a live vaccine for bovine brucellosis. Our ultimate goal is to develop strain RB51 as a preferential vector for the delivery of protective antigens of other intracellular pathogens to which the induction of a strong Th1 type of immune response is needed for effective protection. As a first step in that direction, we studied the expression of a foreign reporter protein, beta-galactosidase of Escherichia coli, and the 65-kDa heat shock protein (HSP65) of Mycobacterium bovis in strain RB51. We cloned the promoter sequences of Brucella sodC and groE genes in pBBR1MCS to generate plasmids pBBSODpro and pBBgroE, respectively. The genes for beta-galactosidase (lacZ) and HSP65 were cloned in these plasmids and used to transform strain RB51. An enzyme assay in the recombinant RB51 strains indicated that the level of beta-galactosidase expression is higher under the groE promoter than under the sodC promoter. In strain RB51 containing pBBgroE/lacZ, but not pBBSODpro/lacZ, increased levels of beta-galactosidase expression were observed after subjecting the bacteria to heat shock or following internalization into macrophage-like J774A.1 cells. Mice vaccinated with either of the beta-galactosidase-expressing recombinant RB51 strains developed specific antibodies of predominantly the immunoglobulin G2a (IgG2a) isotype, and in vitro stimulation of their splenocytes with beta-galactosidase induced the secretion of gamma interferon (IFN-gamma), but not interleukin-4 (IL-4). A Th1 type of immune response to HSP65, as indicated by the presence of specific serum IgG2a, but not IgG1, antibodies, and IFN-gamma, but not IL-4, secretion by the specific-antigen-stimulated splenocytes, was also detected in mice vaccinated with strain RB51 containing pBBgroE/hsp65. Studies with mice indicated that expression of beta-galactosidase or HSP65 did not alter either the attenuation characteristics of strain RB51 or its vaccine efficacy against B. abortus 2308 challenge.

Overexpression of protective antigen as a novel approach to enhance vaccine efficacy of Brucella abortus strain RB51

Brucella abortus strain RB51 is an attenuated rough strain that is currently being used as the official live vaccine for bovine brucellosis in the United States and several other countries. We reasoned that overexpression of a protective antigen(s) of B. abortus in strain RB51 should enhance its vaccine efficacy. To test this hypothesis, we overexpressed Cu/Zn superoxide dismutase (SOD) protein of B. abortus in strain RB51. This was accomplished by transforming strain RB51 with a broad-host-range plasmid, pBBR1MCS, containing the sodC gene along with its promoter. Strain RB51 overexpressing SOD (RB51SOD) was tested in BALB/c mice for its ability to protect against challenge infection with virulent strain 2308. Mice vaccinated with RB51SOD, but not RB51, developed antibodies and cell-mediated immune responses to Cu/Zn SOD. Strain RB51SOD vaccinated mice developed significantly (P < 0.05) more resistance to challenge than those vaccinated with strain RB51 alone. The presence of the plasmid alone in strain RB51 did not alter its vaccine efficacy. Also, overexpression of SOD did not alter the attenuation characteristic of strain RB51.

Characterization of a DNA region containing 5'-(CAAT)(n)-3' DNA sequences involved in lipooligosaccharide biosynthesis in Haemophilus somnus

Repetitive tetranucleotide sequences of 5'-(CAAT)(n)-3' have been identified at the 5' end of an open reading frame (ORF) named lob1 from Haemophilus somnus strain 738. Based on sequence analysis, lob1 has 59% DNA homology to lex2B, which is involved in lipooligosaccharide (LOS) biosynthesis in H. influenzae. We now report that the number of 5'-CAAT-3' repeats in lob1 varied from 31-35, but that 94% of colonies contained 33 repeats of 5'-CAAT-3' downstream of two potential start codons, as determined by DNA sequence analysis of the 5'-CAAT-3' region from individual colonies. If transcription began with the start codon closest to the 5'-CAAT-3' repeats, a protein of 34.5 kDa would be encoded when 33 repeats were present. However, we could not establish a correlation between the number of 5'-CAAT-3' repeats in lob1 with a specific LOS electrophoretic profile or reactivity with two LOS monoclonal antibodies, indicating multiple genes control LOS phase variation in H. somnus. Complementation of strain 129Pt with lob1 containing 33 5 '-CAAT-3' repeats in shuttle vector pLS88 resulted in transformants 129Pt(pLSlob1-33A) and 129Pt(pLSlob1-33B), both of which demonstrated the same altered LOS electrophoretic profile. Unlike strain 129Pt, both transformants underwent limited LOS phase variation, which correlated with variation in the number of 5'-CAAT-3' repeats in pLSlob1-33. Nanoelectrospray-mass spectrometry of O-deacylated LOS indicated that transformant 129Pt(pLSlob1-33A) LOS was composed of a different distribution of glycoforms than LOS of the parent strain. The ratio of glucose to galactose changed from 1:2 in strain 129Pt LOS to 2:1 in transformant 129Pt(pLSlob1-33A) LOS, as determined by gas chromatography-mass spectrometry. Nuclear magnetic resonance spectroscopy confirmed and extended these observations. Transformant 129Pt(pLSlob1-33A) was constitutively more reactive in colony immunoblotting to polyclonal antiserum made to purified strain 738 LOS, and was more susceptible to complement-mediated killing in the presence of anti-738 LOS serum than parent strain 129Pt. Based on these results, Lob1 appears to be a phase variable galactosyl transferase involved in LOS biosynthesis in H. somnus.

Characterization of specific immune responses of mice inoculated with recombinant vaccinia virus expressing an 18-kilodalton outer membrane protein of Brucella abortus

Using the shuttle vector pMCO2 and the vaccinia virus wild-type WR strain, we constructed a recombinant virus expressing an 18-kDa outer membrane protein of Brucella abortus. BALB/c mice inoculated with this virus produced 18-kDa protein-specific antibodies, mostly of immunoglobulin G2a isotype, and in vitro stimulation of splenocytes from these mice with purified maltose binding protein-18-kDa protein fusion resulted in lymphocyte proliferation and gamma interferon production. However, these mice were not protected against a challenge with the virulent strain B. abortus 2308. Disruption of the 18-kDa protein's gene in vaccine strain B. abortus RB51 did not affect either the strain's protective capabilities or its in vivo attenuation characteristics. These observations suggest that the 18-kDa protein plays no role in protective immunity.

Identification of an IS711 element interrupting the wboA gene of Brucella abortus vaccine strain RB51 and a PCR assay to distinguish strain RB51 from other Brucella species and strains

Brucella abortus vaccine strain RB51 is a natural stable attenuated rough mutant derived from the virulent strain 2308. The genetic mutations that are responsible for the roughness and the attenuation of strain RB51 have not been identified until now. Also, except for an assay based on pulsed-field gel electrophoresis, no other simple method to differentiate strain RB51 from its parent strain 2308 is available. In the present study, we demonstrate that the wboA gene encoding a glycosyltransferase, an enzyme essential for the synthesis of O antigen, is disrupted by an IS711 element in B. abortus vaccine strain RB51. Exploiting this feature, we developed a PCR assay that distinguishes strain RB51 from all other Brucella species and strains tested.

Genetic characterization of a Tn5-disrupted glycosyltransferase gene homolog in Brucella abortus and its effect on lipopolysaccharide composition and virulence

We constructed a rough mutant of Brucella abortus 2308 by transposon (Tn5) mutagenesis. Neither whole cells nor extracted lipopolysaccharide (LPS) from this mutant, designated RA1, reacted with a Brucella O-side-chain-specific monoclonal antibody (MAb), Bru-38, indicating the absence of O-side-chain synthesis. Compositional analyses of LPS from strain RA1 showed reduced levels of quinovosamine and mannose relative to the levels in the parental, wild-type strain, 2308. We isolated DNA flanking the Tn5 insertion in strain RA1 by cloning a 25-kb XbaI genomic fragment into pGEM-3Z to create plasmid pJM6. Allelic exchange of genomic DNA in B. abortus 2308 mediated by electroporation of pJM6 produced kanamycin-resistant clones that were not reactive with MAb Bru-38. Southern blot analysis of genomic DNA from these rough clones revealed Tn5 in a 25-kb XbaI genomic fragment. A homology search with the deduced amino acid sequence of the open reading frame disrupted by Tn5 revealed limited homology with various glycosyltransferases. This B. abortus gene has been named wboA. Transformation of strain RA1 with a broad-host-range plasmid bearing the wild-type B. abortus wboA gene resulted in the restoration of O-side-chain synthesis and the smooth phenotype. B. abortus RA1 was attenuated for survival in mice. However, strain RA1 persisted in mice spleens for a longer time than the B. abortus vaccine strain RB51, but as expected, neither strain induced antibodies specific for the O side chain.

Association with the cellular export receptor CRM 1 mediates function and intracellular localization of Epstein-Barr virus SM protein, a regulator of gene expression

Splicing and posttranscriptional processing of eukaryotic gene transcripts are linked to their nuclear export and cytoplasmic expression. Unspliced pre-mRNAs and intronless transcripts are thus inherently poorly expressed. Nevertheless, human and animal viruses encode essential genes as single open reading frames or in the intervening sequences of other genes. Many retroviruses have evolved mechanisms to facilitate nuclear export of their unspliced mRNAs. For example, the human immunodeficiency virus RNA-binding protein Rev associates with the soluble cellular export receptor CRM 1 (exportin 1), which mediates nucleocytoplasmic translocation of Rev-HIV RNA complexes through the nuclear pore. The transforming human herpesvirus Epstein-Barr virus (EBV) expresses a nuclear protein, SM, early in its lytic cycle; SM binds RNA and posttranscriptionally activates expression of certain intronless lytic EBV genes. Here we show that both the trans-activation function and cytoplasmic translocation of SM are dependent on association with CRM 1 in vivo. SM is also shown to be associated in vivo with other components of the CRM 1 export pathway, including the small GTPase Ran and the nucleoporin CAN/Nup214. SM is shown to be present in the cytoplasm, nucleoplasm, and nuclear envelope of transfected cells. Mutation of a leucine-rich region (LRR) of SM inhibited CRM 1-mediated cytoplasmic translocation and SM activity, as did leptomycin B, an inhibitor of CRM 1 complex formation. Surprisingly, however, leptomycin B treatment and mutation of the LRR both led to SM becoming more tightly attached to intranuclear structures. These findings suggest a model in which SM is not merely a soluble carrier protein for RNA but rather is bound directly to intranuclear proteins, possibly including the nuclear pore complex.

Cloning and sequencing of yajC and secD homologs of Brucella abortus and demonstration of immune responses to YajC in mice vaccinated with B. abortus RB51

To identify Brucella antigens that are potentially involved in stimulating a protective cell-mediated immune response, a gene library of Brucella abortus 2308 was screened for the expression of antigens reacting with immunoglobulin G2a antibodies from BALB/c mice vaccinated with B. abortus RB51. One selected positive clone (clone MCB68) contained an insert of 2.6 kb; nucleotide sequence analysis of this insert revealed two open reading frames (ORFs). The deduced amino acid sequences of the first and second ORFs had significant similarities with the YajC and SecD proteins, respectively, of several bacterial species. Both the YajC and SecD proteins were expressed in Escherichia coli as fusion proteins with maltose binding protein (MBP). In Western blots, sera from mice vaccinated with B. abortus RB51 recognized YajC but not SecD. Further Western blot analysis with purified recombinant YajC protein indicated that mice inoculated with B. abortus 19 or 2308 or B. melitensis RM1 also produced antibodies to YajC. In response to in vitro stimulation with recombinant MBP-YajC fusion protein, splenocytes from mice vaccinated with B. abortus RB51 were able to proliferate and produce gamma interferon but not interleukin-4. This study demonstrates, for the first time, the involvement of YajC protein in an immune response to an infectious agent.

Cytochromes P450 in crustacea

Since the last review of this topic, further insight has been gained into the presence and functions of cytochrome P450 proteins in the hepatopancreas and other organs of aquatic crustacean species, although progress has been slow relative to the advances in other species. Recent studies with several lobster, shrimp, crab and crayfish species suggest that cytochromes P450 in the 2 and 3 families are the most abundant forms in hepatopancreas microsomes. Substrates normally metabolized by CYP2 and CYP3 family members are monooxygenated more rapidly by crustacea than substrates normally metabolized by CYP1 family enzymes, e.g. erythromycin, testosterone and aminopyrine are much more rapidly monooxygenated than ethoxyresorufin. Some progress has been made in cloning and sequencing crustacean P450 forms. CYP2L1 and CYP2L2 cDNA sequences have been cloned from spiny lobster hepatopancreas libraries, and there was evidence for at least two more cytochromes P450 in spiny lobster hepatopancreas. An area of continued interest, but of no consensus or general findings, relates to the presence and inducibility of CYP1 family members in crustacea. Some studies indicate weak induction of total cytochrome P450 and increased turnover of substrates normally associated with CYP1, while others show no effect of the classic inducers that act at the Ah receptor in vertebrates. A few studies of the roles of cytochromes P450 in the biosynthesis and degradation of steroids, including ecdysteroids, have been published. Further studies are needed to understand the regulation and normal function of the crustacean cytochromes P450.

Evaluation of a rough mutant of Brucella melitensis in pregnant goats

Brucella melitensis strain VTRM1, a rough derivative of B melitensis strain 16M, is able to colonise the lymph nodes of goats, does not induce abortion in pregnant goats when used at doses leading to abortions with virulent strain 16M, and does not induce anti-O chain antibodies. However, strain VTRM1 as a single dose vaccine induces only partial protection against both infection and abortion following challenge.

Phase variation and conservation of lipooligosaccharide epitopes in Haemophilus somnus

The bovine-specific pathogen Haemophilus somnus is capable of undergoing structural and antigenic phase variation in its lipooligosaccharide (LOS) components after in vivo and in vitro passage. However, commensal isolates from the reproductive tract have not been observed to vary in phase (T. J. Inzana, R. P. Gogolewski, and L. B. Corbeil, Infect. Immun. 60:2943-2951, 1992). We now report that specific monoclonal antibodies (MAbs) to the LOSs of Haemophilus aegyptius, Neisseria gonorrhoeae, and Haemophilus influenzae, as well as H. somnus, reacted with some phase-variable epitopes in H. somnus LOS. All reactive MAbs bound to LOS components of about 4.3 kDa in the same H. somnus isolates, including a non-phase-varying strain. Following in vitro passage of a clonal variant of strain 738 that was nonreactive with the MAbs, 11.8% of young colonies shifted to a reactive phenotype. A digoxigenin-labelled 5'-CAATCAATCAATCAATCAATCAATCAAT-3' oligonucleotide probe hybridized to genomic DNA from strain 738 but did not react with DNA from a non-phase-varying strain. Sequence analysis of the gene containing 5'-CAAT-3' tandem sequences revealed 48% amino acid homology with the lex-2B gene-encoded protein of H. influenzae type b. Our results indicate that some LOS epitopes are conserved between H. somnus and other Haemophilus and Neisseria species, that LOS phase variation may occur at a high rate in some strains of H. somnus, and that phase variation may, in part, be due to 5'-CAAT-3' tandem sequences present in H. somnus genes.

cDNA and protein sequence of a major form of P450, CYP2L, in the hepatopancreas of the spiny lobster, Panulirus argus

A P450 fraction was previously isolated from spiny lobster hepatopancreas microsomes and shown in reconstitution experiments to be efficient in catalyzing the monooxygenation of benzphetamine, aminopyrine, benzo(a)pyrene, progesterone, and testosterone. In this study, N-terminal sequence information up to residue 39 was obtained from this P450 and used to design degenerate primers for screening a cDNA library constructed from hepatopancreas mRNA. Clones were obtained that contained part of the coding region of a P450 protein. Further exact primers were designed that permitted the isolation of clones containing coding information for other parts of the P450 sequence, as well as a clone that coded for the complete P450 protein sequence. The open reading frame of the complete coding region corresponded to a protein of 492 amino acids. The deduced amino acid sequence of this P450 was about 36% similar to individual mammalian P450s in the 2 family and did not show strong matches with other proteins in the data base. Based on sequence and the previously determined function, this spiny lobster P450 was assigned by the P450 nomenclature committee to a new P450 subfamily, CYP2L. This is the first description of a P450 primary sequence from a marine crustacean species and the first assignment of an invertebrate P450 into the 2 family.

Protection of BALB/c mice against homologous and heterologous species of Brucella by rough strain vaccines derived from Brucella melitensis and Brucella suis biovar 4

OBJECTIVE

To evaluate stable rough mutants derived from Brucella melitensis 16M and B suis 2579 (biovar 4) as vaccines against homologous and heterologous Brucella spp in the BALB/c mouse model. DESIGN, ANIMALS, AND PROCEDURE: Rough mutants VTRM1 and VTRS1 were obtained from B melitensis 16M and B suis 2579, respectively, by allelic exchange of rfbU gene encoding mannosyltransferase with a Tn5-disrupted rfbU gene. Mice were vaccinated with VTRM1 or VTRS1 and challenge exposed 8 weeks later.

RESULTS

VTRM1 and VTRS1 replicated extensively in the spleen during the first 3 weeks of infection, then decreased rapidly. Antibodies specific for the O polysaccharide were not detected in sera of mice inoculated with either rough strain. Vaccination with VTRM1 or VTRS1 induced protection against virulent strains of B abortus (2308), B melitensis (16M), B suis biovar 1 (750), and B suis biovar 4 (2579). VTRM1 also protected against B ovis (PA) and against 4 field isolates of B abortus from bison or elk. VTRS1 conferred protection against 4 field isolates of B suis biovar 4 from reindeer. Vaccines prepared from live VTRM1 or VTRS1 provided significantly greater protection than that afforded by vaccines of killed cells in QS-21 adjuvant. Vaccination with VTRM1 containing VTRS1 gave minimal protection against the antigenically unrelated Listeria monocytogenes, thus demonstrating the immunologic specificity of protection against Brucella spp.

CONCLUSIONS AND CLINICAL RELEVANCE

Results encourage evaluation, in primary host species, of VTRM1 and VTRS1, along with RB51, as alternative vaccines to strain 19, Rev 1, or other smooth phase vaccines.

Detailed physical and deletion mapping of 8p with isolation of YAC clones from tumour suppressor loci involved in colorectal cancer

Loss of heterozygosity (LOH) of markers at chromosome 8p is frequently noted in many different tumour types, including colorectal cancer. Numerous investigations indicate the presence of more than tumour suppressor gene (TSG) located on 8p. In this study, we describe a detailed LOH map in colorectal cancer and relate this to physical mapping data from reduced radiation 8p hybrids, yeast artificial chromosome (YAC) co-localisation of markers and fluorescence in situ hybridisation data. These data indicate the presence of two regions harbouring putative TSG's between the polymorphic markers for the LPL gene-D8S298 (approximately 4 Mb) and the markers D8S136-D8S137 (approximately 8 Mb). Yeast Artificial Chromosomes (YAC) have been isolated from these regions of interest to aid the localisation of the putative TSG's.

Characterization of the haemorrhagic enteritis virus genome and the sequence of the putative penton base and core protein genes

Haemorrhagic enteritis virus (HEV) is a member of a genetically ill-defined group within the genus Aviadenovirus which causes significant clinical disease in gallinaceous fowl. Using DNA obtained from a low virulence isolate of HEV passed in turkeys, we developed a genomic restriction map and estimated an apparent genomic length of 25.5 kb. No evidence for extensive DNA hybridization was found between the HEV genome and either the hexon or penton base genes of human adenovirus 2 (HAdV-2) and fowl adenovirus 10 (FAdV-10). The HEV penton base gene was identified by PCR using primers based on conserved adenoviral DNA sequences. The penton base gene was expressed in Escherichia coli as a fusion protein and detected by anti-HEV serum in both colony and denaturing gel immunoblots. DNA sequencing revealed a putative penton base ORF with a predicted amino acid sequence showing approximately 39.0%, 53.0% and 44.2% similarity with the penton base of HAdV-2, human adenovirus 40 (HAdV-40) and FAdV-10, respectively. The penton base gene was located at 43.3-48.6 m.u. on the HEV genome and had a remarkably low G+C content (33.8%). DNA sequencing also revealed ORFs for putative core proteins resembling pVII, p-mu and a partial ORF similar to pVI (hexon-associated protein) of HAdV-2 and HAdV-40. The results support the claim that HEV represents a distinct group of viruses within the genus Aviadenovirus.

Selective humoral immune response of Balb/C mice to Brucella abortus proteins expressed by vaccinia virus recombinants

Genes encoding Brucella abortus Cu/Zn superoxide dismutase (SOD) and a 54 kDa Escherichia coli HtrA homologue were cloned into shuttle plasmids pUV-1 and pSC11, and transfected into vaccinia virus to develop recombinants vUBSOD and vSB54. Control vaccinia virus recombinants vUV-1 and vSC11, carrying only the beta-gal reporter gene but no B. abortus DNA were also developed. Recombinants were analyzed in Western blotting using a polyclonal B. abortus immune serum. vUBSOD expressed a protein of apparent molecular weight of 28 kDa, composed of the 20 kDa B. abortus Cu/Zn-SOD and a protein approximately 8 kDa encoded by a portion of the vaccinia virus TK gene. vSB54 expressed a 54 kDa protein corresponding to the 54 kDa HtrA homologue. Recombinants vUSV-1 and vSC11 did not express B. abortus proteins. Groups of mice were inoculated intraperitoneally with 10(7) TCID50 of 1 of the 4 different recombinant vaccinia viruses and 5 weeks later their sera were analyzed for antibodies against vaccinia virus and B. abortus proteins. Each group of mice responded with antibodies to vaccinia virus. Sera of vSB54-inoculated mice recognized the 54 kDa HtrA homologue. vUBSOD did not induce a humoral immune response. These results represent the first report on the expression of B. abortus proteins by vaccinia virus recombinants and the first demonstrated immune response against a B. abortus protein expressed by such a recombinant.

Primary structure of the speC gene encoding biosynthetic ornithine decarboxylase in Escherichia coli

A 2.91-kb fragment of the Escherichia coli chromosome containing the speC gene, encoding biosynthetic ornithine decarboxylase (ODC) was sequenced. The speC gene is encoded by a 2133-bp ORF; the deduced amino-acid sequence contains 711 residues whose predicted molecular mass is 79,505 Da.

Identification of an immunoreactive Brucella abortus HtrA stress response protein homolog

An 11-kb fragment of Brucella abortus genomic DNA cloned into the BamHI site of pUC9 expressed a 60-kDa protein in Escherichia coli DH5-alpha. Antibodies reactive with this 60-kDa protein were detected by Western blot (immunoblot) analysis in sera from mice, cattle, and goats experimentally infected with B. abortus, in sera from mice experimentally infected with Brucella melitensis, and in serum from a dog experimentally infected with Brucella canis. Similar results were seen with sera obtained from cattle and dogs with naturally acquired brucellosis. The gene encoding the 60-kDa Brucella protein was localized to a 2-kb EcoRI fragment which was also reactive in Southern blots with genomic DNA from other strains of B. abortus as well as with genomic DNA from B. melitensis and B. canis. Nucleotide sequence analysis of the cloned EcoRI fragment revealed an open reading frame encoding a protein with a predicted molecular mass of 51,847 Da and an isoelectric point of 5.15. Comparison of the deduced amino acid sequence of the immunoreactive Brucella protein with the SWISS-PROT protein sequence data base revealed that it shares > 40% amino acid sequence identity with the E. coli and Salmonella typhimurium HtrA stress response proteins. Computer-assisted analysis of this amino acid sequence also predicted that the putative Brucella HtrA homolog contains an export signal sequence and a serine protease active site, two structural features characteristic of previously described HtrA proteins. A potential sigma E type heat shock promoter sequence was detected upstream of the cloned Brucella htrA gene, and Northern (RNA) blot analysis demonstrated that exposure of B. abortus 2308 to heat shock conditions resulted in a transient elevation of htrA transcription. These results strongly suggest that the immunoreactive 60-kDa Brucella protein is a member of the HtrA class of stress response proteins.

Malabsorption of vitamin A in preruminating calves infected with Cryptosporidium parvum

Serum retinol, retinyl palmitate, and total vitamin A concentrations, and jejunoileal morphology were examined in neonatal calves infected with Cryptosporidium parvum. Group-1 calves served as noninfected controls and, after an adjustment period, were given 50 ml of saline solution i.v. every 12 hours for 6 days. Group-2 calves were inoculated with 10(7) C parvum oocysts and, after the onset of diarrhea, were given 50 ml of saline solution i.v. every 12 hours for 6 days. Group-3 calves were inoculated with 10(7) C parvum oocysts and, after the onset of diarrhea, were treated with difluoromethylornithine (DFMO, 200 mg/kg of body weight i.v., q 12 h) for 6 days. Group-4 calves were naturally infected with C parvum. Jejunoileal biopsy specimens were excised from calves of groups 1-3 at 3 and again at 15 to 16 days of age. During the course of diarrhea and 3 days after saline or DFMO administration, water-miscible retinyl palmitate was administered orally (2,750 micrograms/kg) to each calf in each group. Cryptosporidium parvum infection was associated with significant (P < or = 0.05) reduction in postadministration serum retinol, retinyl palmitate, and total vitamin A concentrations in calves of groups 2, 3, and 4. Cryptosporidium parvum infection caused significant (P < or = 0.05) reduction in villus height. Decreased villus height, villus blunting and fusion, and attenuation of the intestinal mucosa were associated with reduced absorption of vitamin A, as indicated by lower peak postadministration retinyl palmitate concentration in C parvum-infected calves. Intravenous administration of DFMO to group-3 calves did not improve retinol absorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Brucella abortus deficient in copper/zinc superoxide dismutase is virulent in BALB/c mice

The gene encoding the Cu/Zn superoxide dismutase (SOD) of Brucella abortus strain 2308 was identified in a Brucella genomic library utilizing a combination of Western blotting and native gel electrophoresis. The Cu/Zn SOD gene was inactivated in vitro by ligation of a kanamycin resistance gene into the open reading frame encoding SOD. The plasmid born construct was introduced back into B. abortus by electroporation. Replacement of the wild-type Cu/Zn SOD by recombination was demonstrated by showing that both the KnR gene and the Cu/Zn SOD gene hybridized to the same band in a Southern analysis of genomic DNA. In addition, KnR strains were deficient in Cu/Zn SOD activity as assessed by lack of Cu/Zn SOD activity on a native gel and by lack of reactivity with specific serum in a Western analysis. Either strain 2308 or the Cu/Zn SOD deficient mutant injected intraperitoneally into BALB/c mice, exhibited no differences in their ability to colonize the spleen at 7 and 28 days post-inoculation. Thus, the inability to produce Cu/Zn SOD by B. abortus does not significantly impair its virulence in mice.

Influence of cyclic AMP, agmatine, and a novel protein encoded by a flanking gene on speB (agmatine ureohydrolase) in Escherichia coli

The speB gene of Escherichia coli encodes agmatine ureohydrolase (AUH), a putrescine biosynthetic enzyme. The speB gene is transcribed either from its own promoter or as a polycistronic message from the promoter of the speA gene encoding arginine decarboxylase. Two open reading frames (ORF1 and ORF2) are present on the strand complementary to speB; approximately 90% of ORF2 overlaps the speB coding region. Analysis of transcriptional and translational fusions of ORF1 or ORF2 to lacZ revealed that ORF1 encoded a novel protein while ORF2 was not transcribed. Deletion of ORF1 from a plasmid containing ORF1, ORF2, and speB reduced the activity of AUH by 83%. In contrast, the presence of plasmid-encoded ORF1 caused an 86% increase in chromosomally encoded AUH activity. ORF1 did not stimulate alkaline phosphatase expressed from a phi(speB-phoA) transcriptional fusion encoded on the same plasmid. Western analysis (immunoblot) of a phi(ORF1-lacZ) translational fusion revealed that ORF1 encodes a 25.3-kDa protein. Agmatine induced transcription of phi(speB-phoA) but not phi(speA-phoA) fusions. Consequently, agmatine affects selection between the monocistronic and the polycistronic modes of speB transcription. In contrast, cyclic AMP (cAMP) repressed AUH activity of chromosomally encoded AUH but had no effect on plasmid-borne speB nor phi(speB-phoA). It is concluded that ORF1 encodes a protein which is a posttranscriptional regulator of speB, agmatine induces speB independent of speA, and cAMP regulates speB indirectly.

Molecular cloning and nucleotide sequence analysis of the gene encoding the immunoreactive Brucella abortus Hsp60 protein, BA60K

A recombinant 60 kDa Brucella abortus protein expressed in Escherichia coli was recognized in immunoblots by sera from mice experimentally infected with B. abortus and a dog experimentally infected with B. canis. Sera from humans and dogs with naturally acquired brucellosis also recognized this protein, which was designated BA60K. The gene encoding BA60K was localized within an 18 kb B. abortus genomic fragment and its direction of transcription determined by subcloning and maxicell analysis of selected restriction fragments. The nucleotide sequence of 1800 bases encompassing the predicted gene location was determined, revealing an open reading frame encoding a protein of 546 amino acids (predicted relative molecular mass of 57515). Solid phase micro-sequencing of BA60K eluted from two-dimensional polyacrylamide gels confirmed the predicted amino acid sequence. Comparison of the predicted amino acid sequence of BA60K with a protein sequence database revealed that BA60K shares 67.9% identity with the GroEL protein of E. coli, a member of the Hsp60 family of chaperonins. The immunodominant Hsp60 homologs from Legionella pneumophila, Chlamydia trachomatis and Mycobacterium tuberculosis were also found to share greater than 59% amino acid sequence identity with the BA60K protein. The identification of BA60K as a member of the Hsp60 family of chaperonins supports its role in stimulating a prominent host immune response during the course of Brucella infections. It also indicates that BA60K is an important candidate for studies aimed at identifying the antigens responsible for eliciting the protective immune response to brucellosis.

Conditions for transformation of Pasteurella multocida by electroporation

Conditions for electroporation of plasmid DNA into Pasteurella multocida were determined for use in developing a cloning system to study virulence factors of P. multocida. The highest efficiency of transformation (1.25 x 10(7) cfu/micrograms DNA) was obtained when 7.6 x 10(10) cells of P. multocida strain R473 were electroporated at 12.5 kV/cm (10 ms, 5 ng of pVM109). Transformation efficiencies of cells prepared at mid-log-phase were approximately 0.5 log10 lower than early, late, or stationary phases. Neither pBR322 nor pUC-19 were able to transform strain R473 under these conditions, even when DNA concentrations were increased to 1 microgram. When pBR322 was ligated with a Pasteurella plasmid, pLAR-1, the hybrid was able to transform strain R473 at an efficiency between 4.5 x 10(2) and 8 x 10(4) cfu/micrograms DNA. Six strains of P. multocida including serotypes A, B, D, and E were transformed successfully.

Cyclic AMP inhibits and putrescine represses expression of the speA gene encoding biosynthetic arginine decarboxylase in Escherichia coli

The speA gene of Escherichia coli encodes biosynthetic arginine decarboxylase (ADC), the first of two enzymes in a putrescine biosynthetic pathway. The activity of ADC is negatively regulated by mechanisms requiring cyclic AMP (cAMP) and cAMP receptor protein (CRP) or putrescine. A 2.1-kb BamHI fragment containing the speA-metK intergenic region, speA promoter, and 1,389 bp of the 5' end of the speA coding sequence was used to construct transcriptional and translational speA-lacZ fusion plasmids. A single copy of either type of speA-lacZ fusion was transferred into the chromosomes of Escherichia coli KC14-1, CB806, and MC4100, using bacteriophage lambda. The speA gene in lysogenized strains remained intact and served as a control. Addition of 5 mM cAMP to lysogenic strains resulted in 10 to 37% inhibition of ADC activity, depending on the strain used. In contrast, the addition of 5 or 10 mM cAMP to these strains did not inhibit the activity of beta-galactosidase (i.e., ADC::beta-galactosidase). Addition of 10 mM putrescine to lysogenized strains resulted in 24 to 31% repression of ADC activity and 41 to 47% repression of beta-galactosidase activity. E. coli strains grown in 5 mM cAMP and 10 mM putrescine produced 46 to 61% less ADC activity and 41 to 52% less beta-galactosidase activity. cAMP (0.1 to 10 mM) did not inhibit ADC activity assayed in vitro. The effects of cAMP and putrescine on ADC activity were additive, indicating the use of independent regulatory mechanisms. These results show that cAMP acts indirectly to inhibit ADC activity and that putrescine causes repression of speA transcription.

Superoxide dismutases of virulent and avirulent strains of Brucella abortus

Extracts of Brucella abortus strains 2308,RB51,45/20 and ST 19 had no significant differences in superoxide dismutase (SOD) activity as measured by the epinephrine assay. These B. abortus strains represent smooth, intermediate and rough colony forms. SOD activity was inhibited 60 to 75% by 2 mM KCN and suggests the presence of Cu/Zn SOD. The SOD activities were similar when the strains were grown in trypticase soy broth containing either 0.5% glucose or erythritol. There were two distinct SOD activity bands in native polyacrylamide gel electrophoresis with identical mobilities for each of the strains. When the native gel was stained for SOD activities in the presence of 2 mM KCN, the SOD band that co-migrated with the bovine erythrocyte Cu/Zn SOD activity disappeared. The band of SOD activity that migrated similar to E. coli iron SOD activity was unaffected by KCN. There were no significant differences in either the total SOD or Cu/Zn SOD activities among the strains. As the Brucella strains represent ranges of virulence, it is difficult to associate any primary role for SOD as a virulence factor.

Southern flounder hepatic and intestinal metabolism and DNA binding of benzo[a]pyrene (BaP) metabolites following dietary administration of low doses of BaP, BaP-7,8-dihydrodiol or a BaP metabolite mixture

Certain finfish species living in chemically polluted environments exhibit a high incidence of gastrointestinal tract tumors. Carnivorous fish in such environments are likely to consume invertebrates which contain chemical procarcinogens and the invertebrate biotransformation products of these compounds. The retention in tissues, extent of DNA adduct formation in liver and intestine, and metabolite composition of bile was investigated in southern flounder following gavage with pure [3H]- or [14C]benzo[a]pyrene (BaP), pure [14C]benzo[a]pyrene-7,8-dihydrodiol (BaP-7,8D), or hepatopancreas from spiny lobsters previously dosed with [3H]- or [14C]BaP (Metab.HP). Metab.HP contained mainly polar conjugates of BaP diols, triols and tetraols. BaP-7,8D was retained in fish tissues and bile at 24 h to a greater extent (33.6% of the dose), than either BaP (19.00%) or Metab.HP (6.6%). Hepatic and intestinal DNA isolated from all dosed fish contained covalently bound radioactivity, but exposure to BaP-7,8D or BaP resulted in significantly higher binding in both tissues than exposure to Metab.HP. Hepatic DNA from BaP and BaP-7,8D-dosed flounder contained 0.24 +/- 0.07 and 0.33 +/- 0.06 pmol BaP equivalents/mg DNA respectively (mean +/- S.E.), while hepatic DNA isolated from Metab.HP-dosed flounder contained 0.006 +/- 0.002 pmol BaP equivalents/mg DNA. Binding of radioactivity to intestinal DNA was significantly higher than to hepatic DNA for flounder dosed with Metab.HP (0.026 +/- 0.003) or with BaP (0.76 +/- 0.27) but not for flounder dosed with BaP-7,8D (0.44 +/- 0.09). These studies show that dietary BaP, and metabolites likely to be present in invertebrates, can be absorbed by the southern flounder and form DNA adducts in target organs.

Electroporation of a suicide plasmid bearing a transposon into Brucella abortus

The creation of bacterial mutants by transposon mutagenesis has facilitated the identification of regulatory and structural genes. In the case of B. abortus the number of reported transposon mutants created by mating or P1 infection has been relatively small. We studied the conditions necessary to introduce Tn5 bearing a kanamycin resistance gene (KnR) into B. abortus by electroporation. The highest frequency of Tn5 transposition was obtained using B. abortus 2308 harvested at a density of 5.2 x 10(8) cells/ml; 0.5 microgram of plasmid was electroporated for 10 ms at 625 V (equivalent to 12.5 kV/cm). The frequency of Tn5 transposition obtained under optimum conditions was estimated to be around 18-20 insertions per 10(10) Brucella. The phase of growth (or the number of generations) had a strong influence on the frequency of transposition. Dot blot analysis confirmed that all KnR clones appearing after 4 days of incubation at 37 degrees C carried Tn5 in their genomes. Furthermore, the randomnes of Tn5 insertion was verified by Southern analysis of chromosomal DNA extracted from knR clones and hybridized with labeled Tn5.

Nucleotide sequence and analysis of the speA gene encoding biosynthetic arginine decarboxylase in Escherichia coli

The DNA sequence of a 3.23-kilobase fragment of the Escherichia coli chromosome encoding biosynthetic arginine decarboxylase (ADC) was determined. This sequence contained the speA open reading frame (ORF) as well as partial speB and metK ORFs. The ADC ORF is 1,974 nucleotides long; the deduced polypeptide contains 658 amino acids with a molecular size of 73,980 daltons. The molecular weight and predicted ADC amino acid composition are nearly identical to the amino acid analysis of purified ADC performed by Wu and Morris (J. Biol. Chem. 248:1687-1695, 1973). A translational speA-lacZ fusion, pRM65, including 1,389 base pairs (463 amino acids) of the 5' end of speA was constructed. Western blots (immunoblots) with beta-galactosidase antisera revealed two ADC::beta-galactosidase fusion proteins in E. coli bearing pRM65: 160,000 and 156,000 daltons representing precursor and mature hybrid proteins, respectively. The predicted amino acid sequence of ADC contains a region of six amino acid residues found in two bacterial diaminopimelic acid decarboxylases and three eucaryotic ornithine decarboxylases. This conserved sequence is located approximately eight amino acids from the putative pyridoxal phosphate-binding site of ADC and is predicted to be involved in substrate binding.

Analysis and sequence of the speB gene encoding agmatine ureohydrolase, a putrescine biosynthetic enzyme in Escherichia coli

The speB gene of Escherichia coli encodes the enzyme agmatine ureohydrolase (AUH). AUH catalyzes the hydrolysis of agmatine to urea and putrescine in one of the two polyamine biosynthetic pathways in E. coli. Sequencing of a 2.97-kilobase-pair fragment of the E. coli chromosome containing speB revealed the presence of three intact open reading frames (ORFs), ORF1 and ORF2 on one strand and ORF3 on the opposite strand, as well as a truncated ORF, ORF4, which terminated 92 kilobase pairs upstream from ORF3. ORF3 contained the coding sequence of the speB gene, as confirmed by complementation analysis. Two ORF3 transcripts were detected: a shorter transcript that included only ORF3 and a longer transcript that included both ORF3 and ORF4. The short transcript was abundantly expressed when the ORF4 sequences were deleted, but when ORF4 and its upstream sequences were present, the polycistronic message predominated and the amount of the monocistronic message was drastically reduced. The promoter from which the shorter transcript was produced contained a TATACT sequence at position -12, but sequences upstream from the -12 position seemed to be irrelevant for promoter activity. The predicted amino acid sequence of AUH contained three regions of high homology to the arginases of yeasts, rats, and humans.

Molecular mechanisms of the synergistic induction of ornithine decarboxylase by asparagine and glucagon in primary cultured hepatocytes

In primary cultures of adult rat hepatocytes maintained in a salts/glucose medium, a more than 100-fold increase in ornithine decarboxylase (EC 4.1.1.17) activity was caused by asparagine and glucagon in a synergistic manner. The synthesis rate of ornithine decarboxylase was determined by [35S]methionine incorporation into the enzyme protein, and the amount of ornithine decarboxylase-mRNA was measured by hybridization with a cloned rat liver ornithine decarboxylase-cDNA. The synthesis rate of ornithine decarboxylase was stimulated more than 20-fold by asparagine and glucagon together, but the amount of ornithine decarboxylase-mRNA was increased only 3-4-fold, indicating that translational stimulation was involved in the induction process. Asparagine alone stimulated the synthesis of ornithine decarboxylase without substantial effect on the amount of ornithine decarboxylase-mRNA, whereas glucagon alone increased the amount of ornithine decarboxylase-mRNA about 3-fold without a detectable change in either enzyme activity or enzyme synthesis. Asparagine, at least in part, also suppressed degradation of ornithine decarboxylase.

Purification and properties of agmatine ureohydrolyase, a putrescine biosynthetic enzyme in Escherichia coli

The putrescine biosynthetic enzyme agmatine ureohydrolase (AUH) (EC 3.5.3.11) catalyzes the conversion of agmatine to putrescine in Escherichia coli. AUH was purified approximately 1,600-fold from an E. coli strain transformed with the plasmid pKA5 bearing the speB gene encoding the enzyme. The purification procedure included ammonium sulfate precipitation, heat treatment, and DEAE-sephacel column chromatography. The molecular mass of nondenatured AUH is approximately 80,000 daltons as determined by gel-sieving column chromatography, while on denaturing polyacrylamide gels, the molecular mass is approximately 38,000 daltons; thus, native AUH is most likely a dimer. A radiolabeled protein extracted from minicells carrying the pKA5 plasmid comigrated with the purified AUH in both sodium dodecyl sulfate-polyacrylamide and native polyacrylamide gels. The pI of purified AUH is between 8.2 and 8.4, as determined by either chromatofocusing or isoelectric focusing. The Km of purified AUH for agmatine is 1.2 mM; the pH optimum is 7.3. Neither the numerous ions and nucleotides tested nor polyamines affected AUH activity in vitro. EDTA and EGTA [ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] at 1 mM inactivated AUH activity by 53 and 74%, respectively; none of numerous divalent cations tested restored AUH activity. Ornithine inhibited AUH activity noncompetitively (Ki = 6 X 10(-3) M), while arginine inhibited AUH activity competitively (Ki = 9 X 10(-3) M).

Transcription of the speC (ornithine decarboxylase) gene of Escherichia coli is repressed by cyclic AMP and its receptor protein

The speC gene encoding ornithine decarboxylase (ODC) in Escherichia coli is negatively regulated by cAMP and the cAMP receptor protein (CRP). In minicells transformed with the plasmid pODC bearing speC, cAMP supplementation repressed ODC synthesis. In a cell-free protein synthesizing system directed by pODC, cAMP at 10(-5) M repressed ODC synthesis by 90%. This repression required a functional CRP as cAMP failed to repress ODC synthesis in vitro in an extract prepared from a crp- strain; the addition of purified CRP to the crp- extract restored the ability of cAMP to repress ODC synthesis. In a prototroph transformed with the plasmid pCOD bearing a speC::tet chimeric gene, cAMP supplementation decreased tetracycline (Tc) resistance. In contrast, in crp- strains transformed with pCOD or pTET (TcR), cAMP supplementation did not change their Tc resistance. When a cya- strain was supplemented with 2 mM cAMP, steady state levels of ODC mRNA were repressed by 80%. However, when a isogenic crp- strain was supplemented with 2 mM cAMP, no repression of ODC mRNA was observed. These results indicate that the cAMP-CRP complex exerts negative transcriptional control of ODC synthesis as a function of the speC promoter.

Biosynthetic arginine decarboxylase in Escherichia coli is synthesized as a precursor and located in the cell envelope

The biosynthetic form of arginine decarboxylase (ADC) catalyzes the synthesis of agmatine, a precursor of putrescine, in Escherichia coli. Selective disruption of the cell envelope and an assessment of ADC activity or immunoprecipitable ADC in various fractions demonstrated its location between the cytoplasmic membrane and peptidoglycan layer. Expression in minicells of the speA gene encoding ADC resulted in the production of two immunoprecipitable species (74 and 70 kilodaltons). Studies in vivo with a pulse and chase of radiolabeled amino acid into the two species suggest a precursor-product relationship. This relationship was corroborated by demonstrating the accumulation of the 74-kilodalton species in a strain of E. coli unable to process signal sequences. Peptide mapping experiments with V8 protease, trypsin, and alpha-chymotrypsin demonstrated that the two species of ADC were very similar except for a minor difference. These data were used to substantiate the compartmentalization hypothesis as to how exogenous arginine can be channeled preferentially into putrescine.

Expression of the cloned genes encoding the putrescine biosynthetic enzymes and methionine adenosyltransferase of Escherichia coli (speA, speB, speC and metK)

The speA, speB and speC genes, which code for arginine decarboxylase (ADCase), agmatine ureohydrolase (AUHase) and ornithine decarboxylase (ODCase), respectively, and the metK gene, which encodes methionine adenosyltransferase (MATase), have been cloned. The genes were isolated from hybrid ColE1 plasmids of the Clarke-Carbon collection and were ligated into plasmid pBR322. Escherichia coli strains transformed with the recombinant plasmids exhibit a 7- to 17-fold overproduction of the various enzymes, as estimated from increases in the specific activities of the enzymes assayed in crude extracts. Minicells bearing the pBR322 hybrid plasmids and labeled with radioactive lysine synthesize radiolabeled proteins with Mrs corresponding to those reported for purified ODCase, ADCase and MATase. Restriction enzyme analysis of the plasmids, combined with measurements of specific activities of the enzymes in crude extracts of cells bearing recombinant plasmids, clarified the relative position of speA and speB. The gene order in the 62- to 64-min region is serA speB speA metK speC glc.

Intergeneric homology of the speC gene encoding biosynthetic ornithine decarboxylase in Escherichia coli

A 32P-labeled fragment of DNA containing the speC gene, which encodes the biosynthetic enzyme ornithine decarboxylase of Escherichia coli, was used as a hybridization probe for homologous sequences in the genomes of gram-negative and gram-positive bacteria. The speC probe detected homologous sequences in the DNA of only four members of the Enterobacteriaceae (Citrobacter freundii, Salmonella typhimurium, Klebsiella pneumoniae, and Enterobacter aerogenes); no homology was detected with the DNA of other representative members of the Enterobacteriaceae and gram-negative and gram-positive bacteria.

Antagonistic transcriptional regulation of the putrescine biosynthetic enzyme agmatine ureohydrolase by cyclic AMP and agmatine in Escherichia coli

The putrescine biosynthetic enzyme agmatine ureohydrolase (AUH) (agmatinase; EC 3.5.3.11) catalyzes the conversion of agmatine to putrescine in Escherichia coli. The specific activity of AUH was determined in crude extracts prepared from wild-type strains and from strains with mutations in the adenylate cyclase gene (cya) or the cAMP receptor protein gene (crp) or both. In glucose minimal medium, a delta cya strain exhibited 70 to 90% higher AUH activity than a cya+ strain. Addition of 1 to 10 mM cAMP to cya+ and delta cya strains cultured in glucose repressed AUH activity in a dose-dependent manner. Addition of 1 to 10 mM cAMP to a delta crp strain failed to repress AUH activity. Addition of agmatine resulted in a three- to fourfold induction of AUH in delta cya and delta crp strains. This induction could be blocked by the addition of chloramphenicol. Simultaneous additions of various proportions of cAMP and agmatine resulted in reduced levels of induction and repression of AUH activity. This antagonistic regulation was shown to be exerted by independent mechanisms since AUH activity could be induced by agmatine in a delta crp strain supplemented with cAMP. These results suggest that both agmatine and cAMP antagonistically regulate AUH activity at the level of transcription. In minimal medium supplemented with 1 mM putrescine, the strains did not exhibit repression of AUH activity. In contrast, in minimal medium supplemented with 1 mM ornithine or arginine, cya+ or delta cya strains exhibited induced AUH activity as a result of conversion of these substrates to agmatine. Further experiments in vitro demonstrated that the effects observed with cAMP, agmatine, and arginine were not post-translationally mediated.