Brucellosis: a worldwide zoonosis

Brucellosis in Colombia: Current Status and Challenges in the Control of an Endemic Disease

Brucellosis is a zoonosis of nearly worldwide distribution. The disease is considered to be endemic in most of the developing countries with a substantial impact on both human and animal health as well as on the economy. The aim of this scoping review is to provide an overview of the brucellosis status in Colombia and the factors associated with its persistence, to highlight the strengths and gaps of the adopted countermeasures and to supply evidence to policy-makers on the best approaches to mitigate the disease burden. Due to the presence of brucellosis in several susceptible production livestock systems scattered throughout the country, a plan for its control, prevention and eradication was established almost 20 years ago. However, despite extensive efforts, brucellosis prevalence has fluctuated over the years without any trend of decreasing. The restricted budget allocated for brucellosis control is a limiting factor for the success of the program. For instance, the absence of indemnities for farmers results in infected animals remaining on farms which potentially increases the risk of disease spread. Likewise, disease surveillance is restricted to Brucella abortus and excludes other Brucella species of importance, such as B. melitensis and B. suis. The countermeasures are mostly focused on cattle and only a few actions are in place for the management of brucellosis in other livestock species. In humans, cases of brucellosis are annually diagnosed, although the disease remains highly underreported. High impact educational and training programs are required to address the disease in a comprehensive manner, including vulnerable groups, such as traditional smallholders and low-productivity regions, as well as other stakeholders, such as healthcare and veterinary authorities. Important financial investments based on sustained cooperation between governmental institutions, industry, and farmers are important for developing affordable and effective strategies to control the disease.

Recombinant Omp2b antigen-based ELISA is an efficient tool for specific serodiagnosis of animal brucellosis

Control of brucellosis as a worldwide zoonotic disease is based on vaccination of animals and diagnosis of infected cases to be eradicated. Accurate and rapid detection of infected animals is of critical importance for preventing the spread of disease. Current detection of brucellosis is based on whole-cell antigens and investigating serum antibodies against Brucella lipopolysaccharide (LPS). The critical disadvantage is misdiagnosis of vaccinated animals as infected ones and also cross-reactions with other Gram-negative bacteria. Recombinant outer membrane protein 2b (Omp2b) of Brucella abortus was evaluated as a novel serodiagnostic target in comparison to conventional tests which are based on LPS. Recombinant Omp2b (rOmp2b) was expressed in Escherichia coli BL21 and purified by Ni²⁺-based chromatography. rOmp2b was evaluated in an indirect enzyme-linked immunosorbent assay (ELISA) system for diagnosis of brucellosis, with sera from Brucella-infected mice along with negative sera and sera from mice which were inoculated with other Gram-negative species for assurance of specificity. Thereafter, cattle sera collected from different regions were assessed along with known negative and known positive serum samples. We found that Omp2b can discriminate between Brucella-infected animals and non-infected ones. Results for assessment of two hundred and fifty cattle sera by Omp2b-based indirect ELISA which were compared to Rose Bengal plate agglutination test (RBPT) and serum tube agglutination test (SAT) showed that our proposed procedure has the sensitivity of 88.5%, specificity of 100%, and accuracy of 90.8%. We suggest that recombinant Omp2b could be used as a protein antigen for diagnosis of brucellosis in domestic animals and can be evaluated for detection of human brucellosis.

Brucella - Virulence Factors, Pathogenesis and Treatment

Brucellae are Gram-negative, small rods infecting mammals and capable of causing disease called brucellosis. The infection results in abortion and sterility in domestic animals (sheeps, pigs, rams etc). Especially dangerous for humans are: Brucella melitensis, Brucella suis, Brucella abortus, and Brucella canis that trigger unspecific symptoms (flu-like manifestation). Brucella rods are introduced via host cells, by inhalation, skin abrasions, ingestion or mucosal membranes. The most important feature of Brucella is the ability to survive and multiply within both phagocytic and non-phagocytic cells. Brucella does not produce classical virulence factors: exotoxin, cytolisins, exoenzymes, plasmids, fimbria, and drug resistant forms. Major virulence factors are: lipopolysaccharide (LPS), T4SS secretion system and BvrR/BvrS system, which allow interaction with host cell surface, formation of an early, late BCV (Brucella Containing Vacuole) and interaction with endoplasmic reticulum (ER) when the bacteria multiply. The treatment of brucellosis is based on two-drug therapy, the most common combinations of antibiotics are: doxycycline with rifampicin or fluoroquinolones with rifampicin. Currently, also other methods are used to disrupt Brucella intracellular replication (tauroursodeoxycholic acid or ginseng saponin fraction A).

Prediction of the Omp16 Epitopes for the Development of an Epitope-based Vaccine Against Brucellosis

BACKGROUND

Brucellosis is an infectious disease caused by Brucella bacteria that cause disease in animals and humans. Brucellosis is one of the most common zoonotic diseases transmitted from animals-to-human through direct contact with infected animals and also consumption of unpasteurized dairy products. Due to the wide incidence of brucellosis in Iran and economical costs in industrial animal husbandry, Vaccination is the best way to prevent this disease. All of the available commercial vaccines against brucellosis are derived from live attenuated strains of Brucella but because of the disadvantage of live attenuated vaccines, protective subunit vaccine against Brucella may be a good candidate for the production of new recombinant vaccines based on Brucella Outer Membrane Protein (OMP) antigens. In the present study, comprehensive bioinformatics analysis has been conducted on prediction software to predict T and B cell epitopes, the secondary and tertiary structures and antigenicity of Omp16 antigen and the validation of used software confirmed by experimental results.

CONCLUSION

The final epitope prediction results have proposed that the three epitopes were predicted for the Omp16 protein with antigenicity ability. We hypothesized that these epitopes likely have the protective capacity to stimulate both the B-cell and T-cell mediated immune responses and so may be effective as an immunogenic candidate for the development of an epitope-based vaccine against brucellosis.

Design and development of novel therapeutics for brucellosis treatment based on carbonic anhydrase inhibition

Carbonic anhydrase is a metalloprotein, an enzyme with strong inhibition in antibacterial treatment. This study presents QSAR modeling for a series of 41 chemical compounds, 40 sulfonamides and one sulfamate, including 13 clinically tested drugs as carbonic anhydrase inhibitors based on the Monte Carlo optimization with molecular descriptors based on the SMILES notation and local invariants of the molecular graph, and field 3D based methods. Conformation independent QSAR models were developed for three random splits and a 3D QSAR model for one random split into the training and test sets. The statistical quality of the developed models, including robustness and predictability, was tested using various statistical approaches and the results that were obtained were very good. An excellent correlation between the results from the conformation independent and the 3D QSAR model was obtained. A novel statistical metric known as the index of ideality of correlation was used for the final assessment of the model, and the obtained results were good. Molecular fragments responsible for the increases and decreases of a studied activity were defined and further used for the computer-aided design of new compounds as potential carbonic anhydrase inhibitors. Molecular docking was applied for the final assessment of the developed QSAR model and designed inhibitors, and an excellent correlation between the results from QSAR modeling and molecular docking studies was obtained.Communicated by Ramaswamy H. Sarma.

A review of the immunopathogenesis of Brucellosis

Brucellosis, caused by the intracellular pathogens Brucella, is one of the major zoonotic infections. Considering the economic burden, its prevalence has been a health concern especially in endemic regions. Brucella is able to survive and replicate within host cells by expressing different virulence factors and using various strategies to avoid the host's immune response. This leads to progression of the disease from an acute phase to chronic brucellosis. Exploration of genetic variations has confirmed the expected influence of gene polymorphisms on susceptibility and resistance to brucellosis of humans. Since there is no approved human vaccine and treatment is uncertain with risk of relapse, it is important to increase knowledge about pathogenesis, diagnosis and treatment of brucellosis in order to manage and control this infection, especially in endemic regions.

Identification of novel genes essential for Brucella abortus to establish infection by signature-tagged mutagenesis

Brucella is a facultative intracellular bacterium, causing brucellosis, an important zoonosis worldwide. Brucella has no classic virulence factors, thus virulence is dependent on invasion of host cells and subsequent intracellular replication. Identification of key genes involved in Brucella virulence is important to further elucidate its pathogenesis. In this study, signature-tagged mutagenesis was used to identify novel genes involved in B. abortus infection in a mouse model. In total 3600 mutants were obtained, of which 56 were identified as attenuated mutants. Furthermore, 53 genes were identified to be inactivated by transposon insertion, including 19 genes previously reported to be essential for Brucella virulence and 34 others that were newly identified in this study. These genes were catalogued into 16 functional classifications, except for three that were not cited in the Clusters of Orthologous Groups database. Bioinformatics analysis revealed that energy production and conversion, amino acid transport and metabolism, as well as inorganic ion transport and metabolism were predominant functional classifications, suggesting that genes involved in these functions were crucial for Brucella virulence. In addition, the function of the identified pyruvate carboxylase (pyc) gene in bacterial virulence was confirmed using an allelic replacement pyc mutant and a mouse model. These findings provide novel genetic information associated with Brucella infection.

Lable-free based comparative proteomic analysis of secretory proteins of rough Brucella mutants

Brucella rough mutants are reported to induce infected macrophage death, which is type IV secretion system (T4SS) dependent. T4SS and its secretory proteins play a major role in host-bacteria interactions, but the crucial secretory proteins to promote macrophage death during Brucella rough mutant infection have not been characterized. In this study, we found that T4SS components played no role for macrophage death induced by Brucella rough mutant infection, but some T4SS effectors did. Proteomics of secretory proteins from Brucella rough mutants ΔrfbE and ΔrfbEΔvirB123 was analyzed by liquid chromatography/tandem mass spectrometry and 861 unique proteins were identified, among which 37 were differential secretory proteins. Gene ontology and pathway analysis showed that differential secretory proteins involved in cellular process and metabolic process, distributed in the cell and membrane, possessed molecular function of catalytic activity and binding, and were associated with ribosome, NOD-like receptor signaling pathway, two-component system and bacterial secretion system. Cell death analysis showed that T4SS effector VceC, and two differential secretory proteins OmpW family protein (BAB1_1579) and protein BAB1_1185 were associated with Brucella cytotoxicity. This study provides new insights into the molecular mechanisms associated with Brucella cytotoxicity and valuable information for screening vaccine candidates for Brucella. SIGNIFICANCE: Brucella rough mutants induce infected macrophage death, which is T4SS dependent. In the present report, a comparative proteomics analysis revealed 37 differential secretory proteins between Brucella rough mutants ΔrfbE and ΔrfbEΔvirB123. Further study demonstrated OmpW family protein (BAB1_1579) and uncharacterized protein BAB1_1185, two differential secretory proteins, were associated with Brucella cytotoxicity. This study provides novel information of the secretory proteins from the Brucella rough mutants and their effects on the Brucella cytotoxicity.

Comparative Ecology of Bartonella and Brucella Infections in Wild Carnivores

Phylogenetic sister clades Bartonella and Brucella within the order Rhizobiales present some common biological characteristics as well as evident differences in adaptations to their mammalian reservoirs. We reviewed published data on Bartonella and Brucella infections in wild carnivores to compare the ecology of these bacteria in relatively similar host environments. Arthropod vectors are the main mechanism for Bartonella species transmission between mammalian hosts. The role of arthropods in transmission of Brucella remains disputed, however experimental studies and reported detection of Brucella in arthropods indicate potential vector transmission. More commonly, transmission of Brucella occurs via contact exposure to infected animals or the environment contaminated with their discharges. Of 26 species of carnivores tested for both Bartonella and Brucella, 58% harbored either. Among them were bobcats, African lions, golden jackals, coyotes, wolves, foxes, striped skunks, sea otters, raccoons, and harbor seals. The most common species of Bartonella in wild carnivores was B. henselae, found in 23 species, followed by B. rochalimae in 12, B. clarridgeiae in ten, and B. vinsonii subsp. berkhoffii in seven. Among Brucella species, Br. abortus was reported in over 30 terrestrial carnivore species, followed by Br. canis in seven. Marine carnivores, such as seals and sea lions, can host Br. pinnipedialis. In contrast, there is no evidence of a Bartonella strain specific for marine mammals. Bartonella species are present practically in every sampled species of wild felids, but of 14 Brucella studies of felids, only five reported Brucella and those were limited to detection of antibodies. We found no reports of Bartonella in bears while Brucella was detected in these animals. There is evident host-specificity of Bartonella species in wild carnivores (e.g., B. henselae in felids and B. vinsonii subsp. berkhoffii in canids). A co-adaptation of Brucella with terrestrial wild carnivore hosts is not as straightforward as in domestic animals. Wild carnivores often carry the same pathogens as their domesticated relatives (cats and dogs), but the risk of exposure varies widely because of differences in biology, distribution, and historical interactions.

Clinical features of 2041 human brucellosis cases in China

BACKGROUND

Human brucellosis has become a major public health problem in China. However, the available clinical data on brucellosis cases are limited.

METHODS

We retrospectively reviewed medical charts of 2041 patients with confirmed human brucellosis and prospectively recorded their outcomes by telephone interview. These patients were admitted to the Sixth People's Hospital of the Xinjiang Uygur Autonomous region between 1st January and 31st December 2014. Data on these patients were collected from hospital medical records.

RESULTS

Many patients presented with fatigue (67%), fever (64%), arthralgia (63%) and sweating (54%). High erythrocyte sedimentation rate (ESR) (69%), high C-reactive protein (CRP) (39%), high alanine aminotransferase (ALT) (33%) and high aspartate aminotransferase (AST) (20%) were the most common laboratory findings, especially in acute patients. There was evidence of focal involvement in 90% of patients. A total of 61.5% of brucellosis patients recovered. Multivariate logistic regression analyses suggested that the risk factors key to unfavorable prognosis were: age≥45 years (OR = 1.75, 95% CI 1.36-2.24), back pain (OR = 1.50, 95% CI 1.16-1.94) and joint tenderness (OR = 1.73, 95% CI 1.13-2.65). The increasing duration of the illness increased the risk of poor prognosis.

CONCLUSION

Patients with brucellosis showed different characteristics in different clinical stages. In China, the chronicity rate of human brucellosis is high. The risk of poor prognosis is increased in patients aged 45 years or older, patients who have had brucellosis for a substantial period of time, and patients with back pain or joint tenderness. The clinical management of brucellosis should be improved to include sensitive diagnostic methods for subacute and chronic brucellosis.

Predominance of Brucella abortus antibodies among women with spontaneous abortion in the city of Mwanza: unrecognized link or coincidence?

OBJECTIVE

This study investigated the association of Brucella seropositivity and spontaneous abortions in human population in the city of Mwanza, Tanzania.

RESULTS

A comparative cross sectional study which used 148 sera from women with spontaneous abortion and 250 sera from full-term delivered women was conducted in July 2017. Detection of Brucella abortus and Brucella melitensis antibodies was done using slide agglutination test. Data were analyzed using STATA version 13 software. The median age of the study participants was 25 (interquartile range 21-30) years. The overall seropositivity of Brucella antibodies was significantly higher among sera from women with spontaneous abortion than full term delivered women; (86/148, 58.1%: 95% CI 50-66 vs. 65/250, 26%: 95% CI 18-33, P < 0.001). Seropositivity of B. abortus was significantly higher among sera from women with spontaneous abortion than full-term delivered women (31.8% vs. 10.8%, P < 0.001). Women with abortion had 3.59 odds of being brucella seropositive compared to full term women (OR: 3.59, 95% CI; 2.25-5.74, P < 0.001). Seropositivity of Brucella antibodies is significantly higher among women with spontaneous abortion than full-term delivered women necessitating a need to investigate the relationship between Brucellosis and adverse pregnancy outcomes.

AIM2 senses Brucella abortus DNA in dendritic cells to induce IL-1β secretion, pyroptosis and resistance to bacterial infection in mice

Absent in melanoma 2 (AIM2) is a sensor of cytosolic dsDNA and is responsible for the activation of inflammatory and host immune responses to DNA viruses and intracellular bacteria. AIM2 is a member of the hematopoietic interferon-inducible nuclear proteins with a 200 amino-acid repeat (HIN200) family, containing a pyrin domain (PYD) at the N-terminus. Several studies have demonstrated that AIM2 is responsible for host defense against intracellular bacteria such as Francisella tularensis, Listeria monocytogenes and Mycobacerium tuberculosis. However, the role of AIM2 in host defenses against Brucella is poorly understood. In this study, we have shown that AIM2 senses Brucella DNA in dendritic cells to induce pyroptosis and regulates type I IFN. Confocal microscopy of infected cells revealed co-localization between Brucella DNA and endogenous AIM2. Dendritic cells from AIM2 KO mice infected with B. abortus showed impaired secretion of IL-1β as well as compromised caspase-1 cleavage. AIM2 KO mice displayed increased susceptibility to B. abortus infection in comparison to wild-type mice, and this susceptibility was associated with defective IL-1β production together with reduced IFN-γ responses. In summary, the increased bacterial burden observed in vivo in AIM2 KO animals confirmed that AIM2 is essential for an effective innate immune response against Brucella infection.

Analysis of protein expression in Brucella abortus mutants with different growth rates by two-dimensional gel electrophoresis and LC-MS/MS peptide analysis

Brucella abortus is a bacterium that causes brucellosis and is the causative agent of worldwide zoonoses. Pathogenesis of the B. abortus infection is complicated, and several researchers have attempted to elucidate the infection mechanism of B. abortus. While several proteins have been revealed as pathogenic factors by previous researchers, the underlying mechanism of B. abortus infection is unresolved. In this study, we identified proteins showing different expression levels in B. abortus mutants with different biological characteristics that were generated by random insertion of a transposon. Five mutants were selected based on biological characteristics, in particular, their growth features. Total proteins of mutant and wild-type B. abortus were purified and subjected to two-dimensional gel electrophoresis. Thirty protein spots of each mutant with expression increases or decreases were selected; those with a change of more than 2-fold were compared with the wild-type. Selected spots underwent liquid chromatography tandem mass spectrometry for peptide analysis. DnaK and ClpB, involved in protein aggregation, increased. SecA and GAPDH, associated with energy metabolism, decreased in some mutants with a growth rate slower than that of the wild-type. Mutants with slower growth showed a decrease in energy metabolism-related proteins, while mutants with faster growth showed an increase in pathogenicity-related proteins.

Recent Advances in the Synthesis of Glycoconjugates for Vaccine Development

During the last decade there has been a growing interest in glycoimmunology, a relatively new research field dealing with the specific interactions of carbohydrates with the immune system. Pathogens’ cell surfaces are covered by a thick layer of oligo- and polysaccharides that are crucial virulence factors, as they mediate receptors binding on host cells for initial adhesion and organism invasion. Since in most cases these saccharide structures are uniquely exposed on the pathogen surface, they represent attractive targets for vaccine design. Polysaccharides isolated from cell walls of microorganisms and chemically conjugated to immunogenic proteins have been used as antigens for vaccine development for a range of infectious diseases. However, several challenges are associated with carbohydrate antigens purified from natural sources, such as their difficult characterization and heterogeneous composition. Consequently, glycoconjugates with chemically well-defined structures, that are able to confer highly reproducible biological properties and a better safety profile, are at the forefront of vaccine development. Following on from our previous review on the subject, in the present account we specifically focus on the most recent advances in the synthesis and preliminary immunological evaluation of next generation glycoconjugate vaccines designed to target bacterial and fungal infections that have been reported in the literature since 2011.

An Overview of Brucellosis in Cattle and Humans, and its Serological and Molecular Diagnosis in Control Strategies

Brucellosis is one of the most common contagious and communicable zoonotic diseases with high rates of morbidity and lifetime sterility. There has been a momentous increase over the recent years in intra/interspecific infection rates, due to poor management and limited resources, especially in developing countries. Abortion in the last trimester is a predominant sign, followed by reduced milk yield and high temperature in cattle, while in humans it is characterized by undulant fever, general malaise, and arthritis. While the clinical picture of brucellosis in humans and cattle is not clear and often misleading with the classical serological diagnosis, efforts have been made to overcome the limitations of current serological assays through the development of PCR-based diagnosis. Due to its complex nature, brucellosis remains a serious threat to public health and livestock in developing countries. In this review, we summarized the recent literature, significant advancements, and challenges in the treatment and vaccination against brucellosis, with a special focus on developing countries.

Childhood Brucellosis in Eastern India

OBJECTIVE

To investigate the presence of childhood brucellosis presenting as PUO (pyrexia of unknown origin) cases in Eastern zone of India.

METHODS

Blood samples were collected from PUO patients aged ≤18 y. The main diagnostic tools were STAT, RBPT, ELISA- IgM, IgG and PCR. Although mainly PUO cases were selected for the study, other associated clinical manifestations were also noted.

RESULTS

The findings revealed significantly higher percentage of infection in female children (14.3%) than in male children (10.9%). The positive results by different diagnostic tools, STAT, RBPT, ELISA- IgM, ELISA-IgG and brucella genus specific PCR were 10.6%, 7.2%, 7.2%, 0.85% and 1.3% respectively. Main associated clinical symptoms were joint pain, low backache, fatigue and night sweat.

CONCLUSIONS

This hospital based study reflects a significant number of childhood brucellosis cases in Eastern zone of India, and thus emphasizes the need for further monitoring of such subjects.

The putative amino acid ABC transporter substrate-binding protein AapJ2 is necessary for Brucella virulence at the early stage of infection in a mouse model

Brucellosis is a zoonotic bacterial disease caused by Brucella spp. The virulence of these bacteria is dependent on their ability to invade and replicate within host cells. In a previous study, a putative gene bab_RS27735 encoding an amino acid ABC transporter substrate-binding protein homologous to AapJ protein was found to be involved in Brucella abortus virulence. In this study, we successfully constructed a bab_RS27735 deletion mutant, Δ27735. Compared with the wild-type strain, the lipopolysaccharide pattern of the mutant was not changed, but the growth ability was slightly defected in the exponential phase. In tolerance tests, sensitivity of the Δ27735 mutant to oxidative stress, bactericidal peptides or low pH was not different from that of the wild-type strain. Cell infection assay showed that the mutant was reduced survival within macrophages but could efficiently escape lysosome degradation. The results of a virulence test showed that the Δ27735 mutant was attenuated in a mouse model at the early stage of infection but recovered its virulence at the late stage of infection. Meanwhile, the development of splenomegaly and histopathological lesions was observed in mice infected with either the wild-type strain or the mutant. These results are in line with the release of IL-12p40 and TNF-α into the peripheral blood of infected mice. Besides, expression of diverse genes was up-regulated in the Δ27735 mutant, which may contribute to the reduced virulence of the mutant. These data elucidated that the bab_RS27735 gene is necessary for B. abortus virulence at the early stage of infection in a mouse model.

A single-tube approach for in vitro diagnostics using diatomaceous earth and optical sensor

Versatile, simple and efficient sample preparation is desirable for point-of-care testing of emerging diseases such as zoonoses, but current sample preparation assays are insensitive, labour-intensive and time-consuming and require multiple instruments. We developed a single-tube sample preparation approach involving direct pathogen enrichment and extraction from human specimens using diatomaceous earth (DE). Amine-modified DE was used to directly enrich a zoonotic pathogen, Brucella, in a large sample volume. Next, a complex of amine-modified DE and dimethyl suberimidate was used for nucleic acid extraction from the enriched pathogen. Using our single-tube approach, the pathogen can be enriched and extracted within 60min at a level of 1 colony formation unit (CFU) from a 1ml sample volume in the same tube. The performance of this approach is 10-100 times better than that of a commercial kit (102 to 103CFU/ml) but does not require a large centrifuge. Finally, we combined the single-tube approach with a bio-optical sensor for rapid and accurate zoonotic pathogen detection in human urine samples. Using the combination system, Brucella in human urine can be efficiently enriched (~ 8-fold) and the detection limit is enhanced by up to 100 times (1CFU/ml bacteria in urine) compared with the commercial kit. This combined system is fast and highly sensitive and thus represents a promising approach for disease diagnosis in the clinical setting.

An account of evolutionary specialization: the AbcR small RNAs in the Rhizobiales

The AbcR small RNAs (sRNAs) are a fascinating example of two highly conserved sRNAs that differ tremendously at the functional level among organisms. From their transcriptional activation to their regulatory capabilities, the AbcR sRNAs exhibit varying characteristics in three well-studied bacteria belonging to the Rhizobiales order: the plant symbiont Sinorhizobium meliloti, the plant pathogen Agrobacterium tumefaciens, and the animal pathogen Brucella abortus. This review outlines the similarities and differences of the AbcR sRNAs between each of these organisms, and discusses reasons as to why this group of sRNAs has diverged in their genetic organization and regulatory functions across species. In the end, this review will shed light on how regulatory systems, although seemingly conserved among bacteria, can vary based on the environmental niche and lifestyle of an organism.

Modulation of Microtubule Dynamics Affects Brucella abortus Intracellular Survival, Pathogen-Containing Vacuole Maturation, and Pro-inflammatory Cytokine Production in Infected Macrophages

The microtubule (MT) cytoskeleton regulates several cellular processes related to the immune system. For instance, an intricate intracellular transport mediated by MTs is responsible for the proper localization of vesicular receptors of innate immunity and its adaptor proteins. In the present study, we used nocodazole to induce MTs depolymerization and paclitaxel or recombinant (r) TIR (Toll/interleukin-1 receptor) domain containing protein (TcpB) to induce MT stabilization in bone marrow-derived macrophages infected with Brucella abortus. Following treatment of the cells, we evaluated their effects on pathogen intracellular replication and survival, and in pro-inflammatory cytokine production. First, we observed that intracellular trafficking and maturation of Brucella-containing vesicles (BCVs) is affected by partial destabilization or stabilization of the MTs network. A typical marker of early BCVs, LAMP-1, is retained in late BCVs even 24 h after infection in the presence of low doses of nocodazole or paclitaxel and in the presence of different amounts of rTcpB. Second, microscopy and colony forming unit analysis revealed that bacterial load was increased in infected macrophages treated with lower doses of nocodazole or paclitaxel and with rTcpB compared to untreated cells. Third, innate immune responses were also affected by disturbing MT dynamics. MT depolymerization by nocodazole reduced IL-12 production in infected macrophages. Conversely, rTcpB-treated cells augmented IL-12 and IL-1β secretion in infected cells. In summary, these findings demonstrate that modulation of MTs affects several crucial steps of B. abortus pathogenesis, including BCV maturation, intracellular survival and IL-12 secretion in infected macrophages.

Informal value chain actors' knowledge and perceptions about zoonotic diseases and biosecurity in Kenya and the importance for food safety and public health

Zoonotic diseases, transmitted from animals to humans, are a public health challenge in developing countries. Livestock value chain actors have an important role to play as the first line of defence in safeguarding public health. However, although the livelihood and economic impacts of zoonoses are widely known, adoption of biosecurity measures aimed at preventing zoonoses is low, particularly among actors in informal livestock value chains in low and middle-income countries. The main objective of this study was to investigate knowledge of zoonoses and adoption of biosecurity measures by livestock and milk value chain actors in Bura, Tana River County, in Kenya, where cattle, camels, sheep and goats are the main livestock kept. The study utilised a mixed methods approach, with a questionnaire survey administered to 154 value chain actors. Additional information was elicited through key informant interviews and participatory methods with relevant stakeholders outside the value chain. Our results found low levels of knowledge of zoonoses and low levels of adherence to food safety standards, with only 37% of milk traders knowing about brucellosis, in spite of a sero-prevalence of 9% in the small ruminants tested in this study, and no slaughterhouse worker knew about Q fever. Actors had little formal education (between 0 and 10%) and lacked training in food safety and biosecurity measures. Adoption of biosecurity measures by value chain actors was very low or non-existent, with only 11% of butchers wearing gloves. There was a gendered dimension, evidenced by markedly different participation in value chains and lower adoption rates and knowledge levels among female actors. Finally, cultural and religious practices were shown to play an important role in exposure and transmission of diseases, influencing perceptions and attitudes to risks and adoption of biosecurity measures.

Brucella Rough Mutant Induce Macrophage Death via Activating IRE1α Pathway of Endoplasmic Reticulum Stress by Enhanced T4SS Secretion

Brucella is a Gram-negative facultative intracellular pathogen that causes the worldwide zoonosis, known as brucellosis. Brucella virulence relies mostly on its ability to invade and replicate within phagocytic cells. The type IV secretion system (T4SS) and lipopolysaccharide are two major Brucella virulence factors. Brucella rough mutants reportedly induce the death of infected macrophages, which is T4SS dependent. However, the underlying molecular mechanism remains unclear. In this study, the T4SS secretion capacities of Brucella rough mutant and its smooth wild-type strain were comparatively investigated, by constructing the firefly luciferase fused T4SS effector, BPE123 and VceC. In addition, quantitative real-time PCR and western blotting were used to analyze the T4SS expression. The results showed that T4SS expression and secretion were enhanced significantly in the Brucella rough mutant. We also found that the activity of the T4SS virB operon promoter was notably increased in the Brucella rough mutant, which depends on quorum sensing-related regulators of VjbR upregulation. Cell infection and cell death assays revealed that deletion of vjbR in the Brucella rough mutant absolutely abolished cytotoxicity within macrophages by downregulating T4SS expression. This suggests that up-regulation of T4SS promoted by VjbR in rough mutant ΔrfbE contribute to macrophage death. In addition, we found that the Brucella rough mutant induce macrophage death via activating IRE1α pathway of endoplasmic reticulum stress. Taken together, our study provide evidence that in comparison to the Brucella smooth wild-type strain, VjbR upregulation in the Brucella rough mutant increases transcription of the virB operon, resulting in overexpression of the T4SS gene, accompanied by the over-secretion of effecter proteins, thereby causing the death of infected macrophages via activating IRE1α pathway of endoplasmic reticulum stress, suggesting novel insights into the molecular mechanisms associated with Brucella rough mutant-induced macrophage cytotoxicity.

Immunization with recombinant GntR plasmid confers protection against Brucella challenge in BALB/c mice

It is essential to improve animal vaccine for brucellosis since conventional vaccines are residual virulent and poor protective effect, limit their applications. To solve these problems, the recombinant DNA vaccines were appeared, which could improve protective immunity and were attenuated to animals. In current research, the recombinant DNA vaccine (pVGntR) based on transcriptional regulator GntR of Brucella abortus (B. abortus) was constructed. The results show that pVGntR is significantly more protective than the conventional RB51 vaccine. Immunization with pVGntR increases the production of immunoglobulin G (IgG) and elicits elevated numbers of gamma interferon (IFN-γ) and interleukin-4 (IL-4). These results suggest that pVGntR is a highly efficacious vaccine candidate that confers protection against wild-type B. abortus challenge.

Prevalence and risk factors of brucellosis among veterinary health care professionals

The study describes prevalence, clinical symptoms and risk factors for brucellosis in personnel engaged in veterinary health care in Karnataka, India. A total of 1050 sera samples were collected from animal handlers, veterinarians, veterinary students, para-veterinarians and persons engaged in artificial insemination of animals. The sera samples were tested for brucellosis by Rose Bengal plate test (RBPT), serum agglutination test (SAT), IgG and IgM indirect ELISA and PCR. Age, sex, clinical symptoms and risk factors were recorded in structured questionnaire. Of the 1050 samples tested, 6.76, 6.38, 3.90, 2.67 and 2.0% were positive by IgG ELISA, RBPT, SAT, IgM ELISA and PCR, respectively and overall prevalence recorded was 7.04%. The prominent clinical symptoms observed were intermittent fever (71.62%) followed by joint pain and body aches. A high degree of suspicion, awareness and multimodal diagnostic approach is suggested for early diagnosis, treatment and disease follow up.

Molecular investigation of virulence factors of Brucella melitensis and Brucella abortus strains isolated from clinical and non-clinical samples

Brucella is zoonotic pathogen that induces abortion and sterility in domestic mammals and chronic infections in humans called Malta fever. It is a facultative intracellular potential pathogen with high infectivity. The virulence of Brucella is dependent upon its potential virulence factors such as enzymes and cell envelope associated virulence genes. The aim of this study was to investigate the Brucella virulence factors among strains isolated from humans and animals in different parts of Iran. Seventy eight strains of Brucella species isolated from suspected human and animal cases from several provinces of Iran during 2015-2016 and identified by phenotypic and molecular methods. The multiplex-PCR (M-PCR) assay was performed in order to detect the ure, wbkA, omp19, mviN, manA and perA genes by using gene specific primers. Out of 78 isolates of Brucella spp., 57 (73%) and 21 (27%) isolates were detected as B. melitensis and B. abortus, respectively, by molecular method. The relative frequency of virulence genes ure, wbkA, omp19, mviN, manA and perA were 74.4%, 89.7%, 93.6%, 94.9%, 100% and 92.3%, respectively. Our results indicate that the most of Brucella strains isolated from this region possess high percent of virulence factor genes (ure, wbkA, omp19, mviN, manA and perA) in their genome. So, each step of infection can be mediated by a number of virulence factors and each strain may have a unique combination of these factors that affected the rate of bacterial pathogenesis.

Knowledge, attitudes and practices (KAP) relating to brucellosis in smallholder dairy farmers in two provinces in Pakistan

The present study aimed to assess the extent of knowledge and understanding of brucellosis in smallholder dairy farmers and identify practices at the farm and household level that might pose a risk for humans contracting brucellosis. Between February and June 2015 a cross-sectional study was conducted among smallholder farms (n = 420) in five districts of Punjab and two districts of Sindh province. Farmers were interviewed using a questionnaire to obtain information on farmers' knowledge about brucellosis and the potential risks for contracting the disease that are present for dairy farmers and their families. Logistic regression and ordinal logistic models were used to investigate potential predictors for risky behaviours. The results show almost all farmers (97%) were not aware of the modes of transmission of brucellosis. Relating to risk, the majority (66%) of the farmers' families were reported to consume raw milk and its products, live in shared housing with animals (49%) and not cover hand cuts during contact with animals (74%). All farmers performed at least one risky practice on a regular basis for brucellosis transmission from animal to human. A multivariable analysis highlighted that the respondents with no formal education and those who had not heard of the disease displayed greater risky behaviour. Poor understanding of the disease, presence of multiple risky practices on farm and at the household, and incorrect perception supports the need for an educational awareness program in order to ensure uptake of improved practices.

Trend of human brucellosis over a decade at tertiary care centre in North Karnataka

BACKGROUND

Brucellosis is an important zoonotic disease. India having a major agrarian population is expected to have a higher prevalence. However, due to lack of laboratory facility or awareness among clinicians, the disease is largely underreported. The aim of this study was to know the prevalence and trend of human brucellosis over a decade, in patients attending a teaching hospital in North Karnataka, and to understand their geographical distribution.

MATERIALS AND METHODS

The study was conducted from January 2006 to December 2015 at a tertiary care teaching hospital in North Karnataka. A total of 3610 serum samples were evaluated from suspected cases of brucellosis. All serum samples were initially screened by Rose Bengal plate test, and positive samples were further analysed by Serum agglutination test (SAT) using standard Brucella abortus antigen from Indian Veterinary Research Institute, Izatnagar, Uttar Pradesh, India. A titre above or equal to 1:80 IU/ml was considered as positive. Demographic data such as age, sex and native place of these patients were also analysed.

RESULTS

We observed that human brucellosis is present in North Karnataka. The overall seropositivity of brucellosis in suspected cases was 5.1%. The positive titres ranged from 1:80 to 163,840 IU/ml. The majority of the patients were from Gadag, Koppal and Haveri districts of North Karnataka.

CONCLUSION

Our study confirms the presence of human brucellosis in the northern part of Karnataka. Further studies to understand the prevalence of animal brucellosis in these areas will help in implementing prevention measures.

Pathogens of Food Animals: Sources, Characteristics, Human Risk, and Methods of Detection

Pathogens associated with food production (livestock) animals come in many forms causing a multitude of disease for humans. For the purpose of this review, these infectious agents can be divided into three broad categories: those that are associated with bacterial disease, those that are associated with viruses, and those that are parasitic in nature. The goal of this chapter is to provide the reader with an overview of the most common pathogens that cause disease in humans through exposure via the food chain and the consequence of this exposure as well as risk and detection methods. We have also included a collection of unusual pathogens that although rare have still caused disease, and their recognition is warranted in light of emerging and reemerging diseases. These provide the reader an understanding of where the next big outbreak could occur. The influence of the global economy, the movement of people, and food makes understanding production animal-associated disease paramount to being able to address new diseases as they arise.

A Novel PCR Assay for Detecting Brucella abortus and Brucella melitensis

OBJECTIVES

Brucellosis is a major zoonotic disease that poses a significant public health threat worldwide. The classical bacteriological detection process used to identify Brucella spp. is difficult and time-consuming. This study aimed to develop a novel molecular assay for detecting brucellosis.

METHODS

All complete sequences of chromosome 1 with 2.1-Mbp lengths were compared among all available Brucella sequences. A unique repeat sequence (URS) locus on chromosome 1 could differentiate Brucella abortus from Brucella melitensis. A primer set was designed to flank the unique locus. A total of 136 lymph nodes and blood samples were evaluated and classified by the URS-polymerase chain reaction (PCR) method in 2013-2014.

RESULTS

Biochemical tests and bacteriophage typing as the golden standard indicated that all Brucella spp. isolates were B. melitensis biovar 1 and B. abortus biovar 3. The PCR results were the same as the bacteriological method for detecting Brucella spp. The sensitivity and specificity of the URS-PCR method make it suitable for detecting B. abortus and B. melitensis.

CONCLUSION

Quick detection of B. abortus and B. melitensis can provide the most effective strategies for control of these bacteria. The advantage of this method over other presented methods is that both B. abortus and B. melitensis are detectable in a single test tube. Furthermore, this method covered 100% of all B. melitensis and B. abortus biotypes. The development of this URS-PCR method is the first step toward the development of a novel kit for the molecular identification of B. abortus and B. melitensis.

Brucella abortus 2308ΔNodVΔNodW double-mutant is highly attenuated and confers protection against wild-type challenge in BALB/c mice

Brucellosis is an important zoonotic disease of worldwide distribution, which causes animal and human disease. However, the current Brucella abortus (B. abortus) vaccines (S19 and RB51) have several drawbacks, including residual virulence for animals and humans. Moreover, S19 cannot allow serological differentiation between infected and vaccinated animals. We constructed double deletion (ΔNodVΔNodW) mutant from virulent B. abortus 2308 (S2308) by deleting the genes encoding two-component regulatory system (TCS) in chromosome II in S2308.2308ΔNodVΔNodW was significantly reduced survival in murine macrophages (RAW 264.7) and BALB/c mice. Moreover, the inoculated mice showed no splenomegaly. The mutant induced high protective immunity in BALB/c mice against challenge with S2308, and elicited an anti-Brucella-specific immunoglobulin G (IgG) response and induced the secretion of gamma interferon (IFN-γ) and interleukin-4 (IL-4). Moreover, NODV and NODW antigens would allow the serological differentiation between infected and vaccinated animals. These results suggest that 2308ΔNodVΔNodW mutant is a potential live attenuated vaccine candidate and can be used effectively against bovine brucellosis.

Meta-Analysis and Advancement of Brucellosis Vaccinology

Background/Objectives

In spite of all the research effort for developing new vaccines against brucellosis, it remains unclear whether these new vaccine technologies will in fact become widely used. The goal of this study was to perform a meta-analysis to identify parameters that influence vaccine efficacy as well as a descriptive analysis on how the field of Brucella vaccinology is advancing concerning type of vaccine, improvement of protection on animal models over time, and factors that may affect protection in the mouse model.

Methods

A total of 117 publications that met the criteria were selected for inclusion in this study, with a total of 782 individual experiments analyzed.

Results

Attenuated (n = 221), inactivated (n = 66) and mutant (n = 102) vaccines provided median protection index above 2, whereas subunit (n = 287), DNA (n = 68), and vectored (n = 38) vaccines provided protection indexes lower than 2. When all categories of experimental vaccines are analyzed together, the trend line clearly demonstrates that there was no improvement of the protection indexes over the past 30 years, with a low negative and non significant linear coefficient. A meta-regression model was developed including all vaccine categories (attenuated, DNA, inactivated, mutant, subunit, and vectored) considering the protection index as a dependent variable and the other parameters (mouse strain, route of vaccination, number of vaccinations, use of adjuvant, challenge Brucella species) as independent variables. Some of these variables influenced the expected protection index of experimental vaccines against Brucella spp. in the mouse model.

Conclusion

In spite of the large number of publication over the past 30 years, our results indicate that there is not clear trend to improve the protective potential of these experimental vaccines.

Confinement of a β-barrel protein in nanoperforated free-standing nanomembranes for ion transport

Bioinspired free-standing nanomembranes (FSNMs) for selective ion transport have been tailored by immobilizing the Omp2a β-barrel membrane protein inside nanoperforations created in flexible poly(lactic acid) (PLA) nanomembranes. Perforated PLA FSNMs have been prepared by spin-coating a 99 : 1 PLA : poly(vinyl alcohol) mixture, and through a phase segregation process nanofeatures with dimensions similar to the entire nanomembrane thickness (∼110 nm) were induced. These nanofeatures have subsequently been transformed into nanoperforations (diameter: ∼51 nm) by selective solvent etching. The protein confined inside the nanopores of PLA FSNMs preserves the β-barrel structure and organizes in ovoid aggregates. The transport properties of Na⁺, K⁺, and Ca²⁺ across non-perforated PLA, nanoperforated PLA, and Omp2a-filled nanoperforated PLA have been monitored by measuring the nanomembrane resistance with electrochemical impedance spectroscopy (EIS). The incorporation of nanoperforations enhances the transport of ions across PLA nanomembranes, whereas the functionality of immobilized Omp2a is essential to exhibit effects similar to those observed in biological nanomembranes. Indeed, Omp2a-filled nanoperforated PLA nanomembranes exhibit stronger affinity towards Na⁺ and Ca²⁺ ions than towards K⁺. In summary, this work provides a novel bioinspired strategy to develop mechanically stable and flexible FSNMs with channels for ion transport, which are precisely located inside artificial nanoperforations, thus holding great potential for applications in biofiltration and biosensing.

Expression and regulation of the ery operon of Brucella melitensis in human trophoblast cells

Brucellosis is primarily a disease of domestic animals in which the bacteria localizes to fetal tissues such as embryonic trophoblast cells and fluids containing erythritol, which stimulates Brucella spp. growth. The utilization of erythritol is a characteristic of the genus Brucella. The ery operon contains four genes (eryA, eryB, eryC and eryD) for the utilization of erythritol, and plays a major role in the survival and multiplication of Brucella spp. The objective of the present study was to conduct a preliminary characterization of differential genes expression of the ery operon at several time points after Brucella infected embryonic trophoblast cells (HPT-8 cells). The result showed that the ery operon expression was higher in HPT-8 cells compared with the medium. The relative expression of eryA, eryB and eryC peaked at 2 h post-infection in HPT-8 cells, and eryD expression peaked at 3 h post-infection. The expression of eryA, eryB and eryC may be inhibited by increased eryD expression. However, the expression of the ery operon was stable in the presence of erythritol in cells. 2308Δery and 027Δery mutants of the ery operon were successfully constructed by homologous recombination, which were attenuated in RAW 264.7 murine macrophages. The characterization of the ery operon genes and their expression profiles in response to Brucella infection further contributes to our understanding of the molecular mechanisms of infection and the pathogenesis of brucellosis.

OMP31 of Brucella melitensis 16M impairs the apoptosis of macrophages triggered by TNF-α

Outer membrane proteins (OMPs) of microorganisms play important roles in directly interacting with host cells. Brucella species inhibit the apoptosis of host cells to benefit their own intracellular survival and replication. However, the association between OMP31 of Brucella and host cell apoptosis, and the underlying mechanism are unclear. In this study, an OMP31 gene deletion mutant based on B. melitensis 16M was constructed. Following the infection of RAW264.7 cells with B. melitensis 16M or the mutant strain, colony formation, apoptosis, tumor necrosis factor (TNF)-α levels and the levels of key downstream factors of the apoptosis pathways triggered by TNF-α, namely caspase-3, -8 and -9, cytochrome c, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were detected. The mutant strain was shown to have the same phenotype as the parent strain using traditional microbiological tests. However, the mutant strain had impaired intracellular survival, with higher levels of apoptosis and TNF-α expression in infected RAW164.7 macrophages than the parent strain. The downstream factors of apoptosis triggered by TNF-α, including increased caspase-8, -3 and -9, cytochrome c and Bax, and decreased Bcl-2, indicated that the classical and mitochondrial cell death pathways were involved. It may be concluded that OMP31 from Brucella inhibited apoptosis and benefitted the intracellular survival of this microorganism. Furthermore, TNF-α may have served as a switch triggering classical death and mitochondrial cell death pathways.

Full-Length cDNA Cloning, Molecular Characterization and Differential Expression Analysis of Lysophospholipase I from Ovis aries

Lysophospholipase I (LYPLA1) is an important protein with multiple functions. In this study, the full-length cDNA of the LYPLA1 gene from Ovis aries (OaLypla1) was cloned using primers and rapid amplification of cDNA ends (RACE) technology. The full-length OaLypla1 was 2457 bp with a 5′-untranslated region (UTR) of 24 bp, a 3′-UTR of 1740 bp with a poly (A) tail, and an open reading frame (ORF) of 693 bp encoding a protein of 230 amino acid residues with a predicted molecular weight of 24,625.78 Da. Phylogenetic analysis showed that the OaLypla1 protein shared a high amino acid identity with LYPLA1 of Bos taurus. The recombinant OaLypla1 protein was expressed and purified, and its phospholipase activity was identified. Monoclonal antibodies (mAb) against OaLypla1 that bound native OaLypla1 were generated. Real-time PCR analysis revealed that OaLypla1 was constitutively expressed in the liver, spleen, lung, kidney, and white blood cells of sheep, with the highest level in the kidney. Additionally, the mRNA levels of OaLypla1 in the buffy coats of sheep challenged with virulent or avirulent Brucella strains were down-regulated compared to untreated sheep. The results suggest that OaLypla1 may have an important physiological role in the host response to bacteria. The function of OaLypla1 in the host response to bacterial infection requires further study in the future.

The role of NLRP3 and AIM2 in inflammasome activation during Brucella abortus infection

The innate immune system is essential for the detection and elimination of bacterial pathogens. Upon inflammasome activation, caspase-1 cleaves pro-IL-1β and pro-IL-18 to their mature forms IL-1β and IL-18, respectively, and the cell undergoes inflammatory death termed pyroptosis. Here, we reviewed recent findings demonstrating that Brucella abortus ligands activate NLRP3 and AIM2 inflammasomes which lead to control of infection. This protective effect is due to the inflammatory response caused by IL-1β and IL-18 rather than cell death. Brucella DNA is sensed by AIM2 and bacteria-induced mitochondrial reactive oxygen species is detected by NLRP3. However, deregulation of pro-inflammatory cytokine production can lead to immunopathology. Nervous system invasion by bacteria of the genus Brucella results in an inflammatory disorder termed neurobrucellosis. Herein, we discuss the mechanism of caspase-1 activation and IL-1β secretion in glial cells infected with B. abortus. Our results demonstrate that the ASC inflammasome is indispensable for inducing the activation of caspase-1 and secretion of IL-1β upon infection of astrocytes and microglia with Brucella. Moreover, our results demonstrate that secretion of IL-1β by Brucella-infected glial cells depends on NLRP3 and AIM2 and leads to neurobrucellosis. Further, the inhibition of the host cell inflammasome as an immune evasion strategy has been described for bacterial pathogens. We discuss here that the bacterial type IV secretion system VirB is required for inflammasome activation in host cells during infection. Taken together, our results indicate that Brucella is sensed by ASC inflammasomes mainly NLRP3 and AIM2 that collectively orchestrate a robust caspase-1 activation and pro-inflammatory response.

Proteomic Profile of Brucella abortus-Infected Bovine Chorioallantoic Membrane Explants

Brucella abortus is the etiological agent of bovine brucellosis, a zoonotic disease that causes significant economic losses worldwide. The differential proteomic profile of bovine chorioallantoic membrane (CAM) explants at early stages of infection with B. abortus (0.5, 2, 4, and 8 h) was determined. Analysis of CAM explants at 0.5 and 4 h showed the highest differences between uninfected and infected CAM explants, and therefore were used for the Differential Gel Electrophoresis (DIGE). A total of 103 spots were present in only one experimental group and were selected for identification by mass spectrometry (MALDI/ToF-ToF). Proteins only identified in extracts of CAM explants infected with B. abortus were related to recognition of PAMPs by TLR, production of reactive oxygen species, intracellular trafficking, and inflammation.

Serological diagnostic potential of recombinant outer membrane proteins (rOMPs) from Brucella melitensis in mouse model using indirect enzyme-linked immunosorbent assay

BACKGROUND

Brucella melitensis is the most important pathogenic species of Brucella spp. which affects goats and sheep and causes caprine and ovine brucellosis, respectively. Serological tests for diagnosis of brucellosis such as Rose Bengal plate test (RBPT) and enzyme-linked immunosorbent assay (ELISA) usually utilize smooth lipopolysaccharides (S-LPS) as a diagnostic antigen which could give false positive serological reactions. Outer membrane proteins (OMP) of B. melitensis have been used as alternative diagnostic antigens rather than S-LPS for differential serological diagnosis of brucellosis, mainly in ELISA with single recombinant OMP (rOMP) as a diagnostic antigen. Nevertheless, the use of single format mainly showed lack of sensitivity against the desired rOMP. Therefore, this study aimed to determine whether a newly developed rOMPs indirect ELISA (rOMPs I-ELISA), based on combination of rOMP25, rOMP28 and rOMP31of B. melitensis, has a potential benefit for use in the serodiagnosis of brucellosis.

METHODS

In this study, omp25, omp28 and omp31 of B. melitensis were cloned and expressed using prokaryotic pET-32 Ek/LIC system and their respective rOMPs were combined as one coating antigen to develop rOMPs I-ELISA. Three groups of BALB/c mice were used to elicit antibody response. Group 1, infected with B. melitensis strain 0331 field strain; group 2, injected with B. melitensis Rev.1 vaccine strain and group 3, infected with Yersinia enterocolitica O:9. Antibody responses in three groups of mice were investigated using Rose Bengal plate test (RBPT) and rOMPs I-ELISA.

RESULTS

The production of rOMP25, rOMP28 and rOMP31 of B. melitensis were achieved and Western immunoblotting analysis demonstrated their reactivity. The RBPT was unable to differentiate the vaccinated mice (group 2) and mice infected with Y. enterocolitica O:9 (group 3) and categorized them wrongly as positive for brucellosis. In contrast, the rOMPs I-ELISA was able to differentiate the mice infected with B. melitensis strain 0331 (group 1) from both of group 2 and group 3, and recorded 100% sensitivity and 100% specificity.

CONCLUSIONS

The results of this study suggested that rOMPs of B. melitensis has potential diagnostic ability to differentiate the FPSR in serological diagnosis of brucellosis.

The abcEDCBA-Encoded ABC Transporter and the virB Operon-Encoded Type IV Secretion System of Brucella ovis Are Critical for Intracellular Trafficking and Survival in Ovine Monocyte-Derived Macrophages

Brucella ovis infection is associated with epididymitis, orchitis and infertility in rams. Most of the information available on B. ovis and host cell interaction has been generated using murine macrophages or epithelial cell lines, but the interaction between B. ovis and primary ovine macrophages has not been studied. The aim of this study was to evaluate the role of the B. ovis abcEDCBA-encoded ABC transporter and the virB operon-encoded Type IV Secretion System (T4SS) during intracellular survival of B. ovis in ovine peripheral blood monocyte-derived macrophages. ΔabcBA and ΔvirB2 mutant strains were unable to survive in the intracellular environment when compared to the WT B. ovis at 48 hours post infection (hpi). In addition, these mutant strains cannot exclude the lysosomal marker LAMP1 from its vacuolar membrane, and their vacuoles do not acquire the endoplasmic reticulum marker calreticulin, which takes place in the WT B. ovis containing vacuole. Higher levels of nitric oxide production were observed in macrophages infected with WT B. ovis at 48 hpi when compared to macrophages infected with the ΔabcBA or ΔvirB2 mutant strains. Conversely, higher levels of reactive oxygen species were detected in macrophages infected with the ΔabcBA or ΔvirB2 mutant strains at 48 hpi when compared to macrophages infected with the WT strain. Our results demonstrate that B. ovis is able to persist and multiply in ovine macrophages, while ΔabcBA and ΔvirB2 mutations prevent intracellular multiplication, favor phagolysosome fusion, and impair maturation of the B. ovis vacuole towards an endoplasmic reticulum-derived compartment.

RNA-seq reveals the critical role of OtpR in regulating Brucella melitensis metabolism and virulence under acidic stress

The response regulator OtpR is critical for the growth, morphology and virulence of Brucella melitensis. Compared to its wild type strain 16 M, B. melitensis 16 MΔotpR mutant has decreased tolerance to acid stress. To analyze the genes regulated by OtpR under acid stress, we performed RNA-seq whole transcriptome analysis of 16 MΔotpR and 16 M. In total, 501 differentially expressed genes were identified, including 390 down-regulated and 111 up-regulated genes. Among these genes, 209 were associated with bacterial metabolism, including 54 genes involving carbohydrate metabolism, 13 genes associated with nitrogen metabolism, and seven genes associated with iron metabolism. The 16 MΔotpR also decreased capacity to utilize different carbon sources and to tolerate iron limitation in culture experiments. Notably, OtpR regulated many Brucella virulence factors essential for B. melitensis intracellular survival. For instance, the virB operon encoding type IV secretion system was significantly down-regulated, and 36 known transcriptional regulators (e.g., vjbR and blxR) were differentially expressed in 16 MΔotpR. Selected RNA-seq results were experimentally confirmed by RT-PCR and RT-qPCR. Overall, these results deciphered differential phenomena associated with virulence, environmental stresses and cell morphology in 16 MΔotpR and 16 M, which provided important information for understanding the detailed OtpR-regulated interaction networks and Brucella pathogenesis.

MLVA as an Epidemiological Tool To Trace Back Brucella melitensis Biovar 1 Re-Emergence in Italy

Brucellosis is an important zoonosis caused by Brucella spp., still prevalent in most areas of the world. Brucellosis control in animals is the key to protect humans. The knowledge of Brucella spp. prevailing genotypes in a territory represents an important epidemiological tool to formulate policies and strategies for disease control and to trace back the introduction of new strains previously considered as exotic. In the last years, multiple-locus variable number tandem repeat analysis (MLVA) has been proposed as complementary to classical biotyping methods. MLVA may add important information to the classical epidemiological investigation techniques, to help in tracing back sources of infection in brucellosis outbreaks. Sardinia is an Italian region officially free from sheep and goats brucellosis since 1998. In 2011, Brucella melitensis biovar 1, a biotype not reported in Italy since 1995, was isolated in one flock in the region. The genotyping MLVA-16 showed that isolates belonged to a rare American lineage, confirming it was introduced from other countries. The strain was considered as probably originating from Spain, where this lineage is endemic. BrucellaMLVA-16 has been proved to be useful to analyse the epidemiological correlation of strains enabling to trace its geographic origin by comparing their previously reported genetic patterns.