Molecular cloning, nucleotide sequence, and occurrence of a 16.5-kilodalton outer membrane protein of Brucella abortus with similarity to pal lipoproteins.
ABSTRACT: Recombinant lambda gt11 phages were selected by screening a genomic library of Brucella abortus DNA with monoclonal antibodies specific for a 16.5-kDa Brucella outer membrane protein (Omp16). The corresponding gene, named pal, was subcloned on a 0.7-kb AluI fragment. Immunoblotting confirmed the expression of a recombinant Omp16 in the transformants. DNA sequence analysis revealed an open reading frame of 168 codons. The deduced amino acid sequence agrees with an internal peptide sequence of native Omp16 and contains a potential lipoprotein signal peptide cleavage site, giving rise to a predicted mature protein of 144 amino acids. The predicted sequence of Omp16 also shows a remarkable degree of similarity to the sequences of three peptidoglycan-associated bacterial lipoproteins. In immunoblotting with a monoclonal antibody specific for Omp16, we demonstrated that Omp16 was expressed in the 34 Brucella strains tested, representing all six species and known biovars.
Project description:The deduced sequences of the Omp10, Omp16, and Omp19 outer membrane proteins of Brucella spp. contain a potential bacterial lipoprotein processing sequence. After extraction with Triton X-114, these three proteins partitioned into the detergent phase. Processing of the three proteins is inhibited by globomycin, a specific inhibitor of lipoprotein signal peptidase. The three proteins were radioimmunoprecipitated from [(3)H]palmitic acid-labeled Brucella abortus lysates with monoclonal antibodies. These results demonstrate that Omp10, Omp16, and Omp19 are lipoproteins.
Project description:Screening of a Brucella abortus genomic library with two sets of monoclonal antibodies allowed the isolation of the genes corresponding to two minor outer membrane proteins (OMP10 and OMP19) found in this bacterial species. Sequence analysis of the omp10 gene revealed an open reading frame capable of encoding a protein of 126 amino acids. The nucleotide sequence of the insert producing the OMP19 protein contains two overlapping open reading frames, the largest of which (177 codons) was shown to encode the protein of interest. Analysis of the N-terminal sequences of both putative proteins revealed features of a bacterial signal peptide, and homology to the bacterial lipoprotein processing sequence was also observed. Immunoblotting with monoclonal antibodies specific for OMP10 or OMP19 showed that both proteins are present in the 34 Brucella strains tested, representing all six Brucella species and all their biovars. The OMP19 detected in the five Brucella ovis strains examined migrated at an apparent molecular weight that is slightly higher than those of the other Brucella species, confirming the divergence of B. ovis from these species. OMP10 and OMP19 were produced in recombinant Escherichia coli and purified to homogeneity for serological analysis. A large fraction of sera from sheep naturally infected with Brucella melitensis were reactive with these proteins in an enzyme-linked immunosorbent assay, whereas sera from B. abortus-infected cattle were almost completely unreactive in this assay.
Project description:A thus far unknown gene encoding a Brucella abortus protein has been isolated from a lambda gt11 expression library probed with sera from Brucella-infected sheep. Sequence analysis of the cloned gene revealed the presence of an open reading frame of 158 amino acids encoding a protein of 17.3 kDa (calculated molecular mass). The recombinant B. abortus protein, expressed in Escherichia coli, and the corresponding Brucella melitensis protein migrated at the same apparent molecular masses as shown by Western blotting (immunoblotting). Among a series of serum samples from B. melitensis- or B. abortus-infected sheep and cows, 51 and 39%, respectively, showed a signal at 17 kDa on Western blot analysis of total protein extract from Brucella bacteria. These figures amount to 70 and 61% for sheep and cattle, respectively, in a competitive enzyme-linked immunosorbent assay with a specific monoclonal antibody. These data indicate that the 17-kDa antigen may be useful for serological diagnosis of Brucella infection.
Project description:Monoclonal antibodies and polyclonal antisera recognizing a 39-kDa protein (P39) of brucellin, a cytoplasmic extract from Brucella melitensis rough strain B115, were produced. The P39 was purified by anion-exchange chromatography. Eleven of fourteen Brucella-infected cows whose infections had been detected by the delayed-type hypersensitivity (DTH) test with brucellergen also developed a DTH reaction when purified P39 was used as the trigger. The T-cell proliferative responses to P39 of peripheral blood lymphocytes from Brucella-infected cows were also positive. None of the animals infected with other bacterial species that are presumed to induce immunological cross-reactions with Brucella spp. reacted to P39, either in DTH tests or in lymphocyte proliferation assays. A lambda gt11 genomic library of Brucella abortus was screened with a monoclonal antibody specific for P39, and the gene coding for this protein was subsequently isolated. The nucleotide sequence of the P39 gene was determined, and the deduced amino acid sequence is in accordance with the sequence of an internal peptide isolated from P39.
Project description:BACKGROUND:Human brucellosis incidence in China was divided into 3 stages, high incidence (1950-1960s), decline (1970-1980s) and re-emergence (1990-2000s). Human brucellosis has been reported in all the 32 provinces, of which Inner Mongolia has the highest prevalence, accounting for over 40% of the cases in China. To investigate the etiology alteration of human brucellosis in Inner Mongolia, the species, biovars and genotypes of 60 Brucella isolates from this province were analyzed. METHODS:Species and biovars of the Brucella strains isolated from outbreaks were determined based on classical identification procedures. Strains were genotyped by multi locus sequence typing (MLST). Sequences of 9 housekeeping genes were obtained and sequence types were defined. The distribution of species, biovars and sequence types (STs) among the three incidence stages were analyzed and compared. RESULTS:The three stages of high incidence, decline and re-emergence were predominated by B. melitensis biovar 2 and 3, B. abortus biovar 3, and B. melitensis biovar 1, respectively, implying changes in the predominant biovars. Genotyping by MLST revealed a total of 14 STs. Nine STs (from ST28 to ST36), accounting for 64.3% of all the STs, were newly defined and different from those observed in other countries. Different STs were distributed among the three stages. ST8 was the most common ST in 1950-1960s and 1990-2000s, while ST2 was the most common in 1970-1980s. CONCLUSIONS:The prevalence of biovars and sequence types of Brucella strains from Inner Mongolia has changed over time in the three stages. Compared with those from other countries, new sequence types of Brucella strains exist in China.
Project description:BACKGROUND: We generated novel, effective candidate vaccine against Brucella abortus based on recombinant influenza viruses expressing the Brucella ribosomal protein L7/L12 or outer membrane protein (Omp)-16 from the NS1 open reading frame. The main purpose of this work was to evaluate the safety, immunogenicity and protectiveness of vaccine candidate in laboratory animals. METHODS AND RESULTS: Four recombinant influenza A viral constructs of the subtypes ?5N1 or H1N1 expressing the Brucella proteins L7/L12 or Omp16 were obtained by a reverse genetics method: Flu-NS1-124-L7/L12-H5N1, Flu-NS1-124-Omp16-H5N1, Flu-NS1-124-L7/L12-H1N1 and Flu-NS1-124-Omp16-H1N1. Despite of substantial modification of NS1 gene, all constructs replicated well and were retain their Brucella inserts over five passages in embryonated chicken eggs (CE). Administration of the mono- or bivalent vaccine formulation via prime-boost intranasal (i.n.), conjunctival (c.) or subcutaneous (s.c.) immunization was safe in mice; no deaths, body weight loss or pathomorphological changes were observed over 56 days. Moreover, guinea pigs vaccinated i.n. with vaccine vectors did not shed the vaccine viruses through their upper respiratory tract after the prime and booster vaccination. These findings confirmed the replication-deficient phenotype of viral vectors. The highest antibody response to Brucella antigen was obtained with constructs expressing L7/L12 (ELISA, GMT 242.5-735.0); whereas the highest T-cell immune response- with construct expressing Omp16 (ELISPOT, 337?±?52-651?±?45 spots/4×105cells), which was comparable (P?>?0.05) to the response induced by the commercial vaccine B. abortus 19. Interestingly, c. immunization appeared to be optimal for eliciting T-cell immune response. In guinea pigs, the highest protective efficacy after challenge with B. abortus 544 was achieved with Omp16 expressing constructs in both monovalent or bivalent vaccine formulations; protective efficacy was comparable to those induced by a commercial live B. abortus 19 vaccine. CONCLUSION: Thus, influenza vectors expressing Brucella protective antigens can be developed as novel influenza vectored vaccine against B. abortus infection.
Project description:A whole-cell hybridization assay with fluorescent oligonucleotide probes derived from the 16S rRNA sequence of Brucella abortus in combination with flow cytometry has been developed. With the three fluorescent probes selected, a positive signal was observed with all the representative strains of the species and biovars of Brucella and with a total of nine different Brucella clinical isolates. Using the B9 probe in the hybridization assay, it was possible to discriminate between Brucella suis biovars 2, 3, 4, and 5 and almost all the other Brucella spp. On the basis of differences in fluorescence intensities, no discrimination was established between Brucella spp. and other phylogenetically related microorganisms. No positive fluorescence signals were detected with any of the bacteria showing serological cross-reactions with Brucella spp. and with a total of 17 clinical isolates not belonging to the genus Brucella. These results suggest that the 16S rRNA whole-cell hybridization technique could be a valuable diagnostic tool for the detection and identification of Brucella spp.
Project description:The discovery of novel mucosal adjuvants will help to develop new formulations to control infectious and allergic diseases. In this work we demonstrate that U-Omp16 from Brucella spp. delivered by the nasal route (i.n.) induced an inflammatory immune response in bronchoalveolar lavage (BAL) and lung tissues. Nasal co-administration of U-Omp16 with the model antigen (Ag) ovalbumin (OVA) increased the amount of Ag in lung tissues and induced OVA-specific systemic IgG and T helper (Th) 1 immune responses. The usefulness of U-Omp16 was also assessed in a mouse model of food allergy. U-Omp16 i.n. administration during sensitization ameliorated the hypersensitivity responses of sensitized mice upon oral exposure to Cow's Milk Protein (CMP), decreased clinical signs, reduced anti-CMP IgE serum antibodies and modulated the Th2 response in favor of Th1 immunity. Thus, U-Omp16 could be used as a broad Th1 mucosal adjuvant for different Ag formulations.
Project description:BACKGROUND: A commercial biotyping system (Taxa Profile™, Merlin Diagnostika) testing the metabolization of various substrates by bacteria was used to determine if a set of phenotypic features will allow the identification of members of the genus Brucella and their differentiation into species and biovars. RESULTS: A total of 191 different amines, amides, amino acids, other organic acids and heterocyclic and aromatic substrates (Taxa Profile™ A), 191 different mono-, di-, tri- and polysaccharides and sugar derivates (Taxa Profile™ C) and 95 amino peptidase- and protease-reactions, 76 glycosidase-, phosphatase- and other esterase-reactions, and 17 classic reactions (Taxa Profile™ E) were tested with the 23 reference strains representing the currently known species and biovars of Brucella and a collection of 60 field isolates. Based on specific and stable reactions a 96-well "Brucella identification and typing" plate (Micronaut™) was designed and re-tested in 113 Brucella isolates and a couple of closely related bacteria.Brucella species and biovars revealed characteristic metabolic profiles and each strain showed an individual pattern. Due to their typical metabolic profiles a differentiation of Brucella isolates to the species level could be achieved. The separation of B. canis from B. suis bv 3, however, failed. At the biovar level, B. abortus bv 4, 5, 7 and B. suis bv 1-5 could be discriminated with a specificity of 100%. B. melitensis isolates clustered in a very homogenous group and could not be resolved according to their assigned biovars. CONCLUSIONS: The comprehensive testing of metabolic activity allows cluster analysis within the genus Brucella. The biotyping system developed for the identification of Brucella and differentiation of its species and biovars may replace or at least complement time-consuming tube testing especially in case of atypical strains. An easy to handle identification software facilitates the applicability of the Micronaut™ system for microbiology laboratories.
Project description:BACKGROUND: Brucella is an intracellular pathogen capable of infecting animals and humans. There are six recognized species of Brucella that differ in their host preference. The genomes of the three Brucella species have been recently sequenced. Comparison of the three revealed over 98% sequence similarity at the protein level and enabled computational identification of common and differentiating genes. We validated these computational predictions and examined the expression patterns of the putative unique and differentiating genes, using genomic and reverse transcription PCR. We then screened a set of differentiating genes against classical Brucella biovars and showed the applicability of these regions in the design of diagnostic tests. RESULTS: We have identified and tested set of molecular targets that are associated in unique patterns with each of the sequenced Brucella spp. A comprehensive comparison was made among the published genome sequences of B. abortus, B. melitensis and B. suis. The comparison confirmed published differences between the three Brucella genomes, and identified subsets of features that were predicted to be of interest in a functional comparison of B. melitensis and B. suis to B. abortus. Differentiating sequence regions from B. abortus, B. melitensis and B. suis were used to develop PCR primers to test for the existence and in vitro transcription of these genes in these species. Only B. suis is found to have a significant number of unique genes, but combinations of genes and regions that exist in only two out of three genomes and are therefore useful for diagnostics were identified and confirmed. CONCLUSION: Although not all of the differentiating genes identified were transcribed under steady state conditions, a group of genes sufficient to discriminate unambiguously between B. suis, B. melitensis, and B. abortus was identified. We present an overview of these genomic differences and the use of these features to discriminate among a number of Brucella biovars.