Interactions of the human pathogenic Brucella species with their hosts

Anti-Brucella abortus antibodies in equids in the state of Goiás, Brazil

Brucellosis is a zoonosis caused by bacteria of Brucella genus, which affects domestic and wild animals and humans. In horses, the infection can be caused by Brucella canis, Brucella suis or Brucella abortus, through the ingestion of contaminated food, contact of bacteria with skin wounds or through the respiratory tract, manifesting with signs such as fistulous withers and reduced performance. The present study aimed to evaluate the seroprevalence of Brucella abortus infection in equids in the state of Goiás. Sampling was carried out on 299 farms across 132 municipalities, with a total of 897 equids, including horses, donkeys and mules. Among the animals tested, 111 reacted to the rose bengal plate agglutination test (RBPAT), with 40 confirmed as reactive by the 2-Mercaptoethanol (2-ME) test, resulting in a seroprevalence of 4.46 %. Among the reactive animals, 87.5 % were horses, 12.5 % were mules and no donkeys were reactive in this study. The distribution of seropositive animals was dispersed throughout the state of Goiás, suggesting that brucellosis is not restricted to a specific region. Furthermore, statistical analysis revealed no significant association between the variables age, species, sex, purpose, and stratum and positivity in the 2-ME test. Of the 34 herds with reactive animals, 82.35 % had only one reactive animal, which suggests that equines are becoming infected through contact with infected cattle. Thus, the results reinforce the need for integrated disease management for both bovine and equine brucellosis, due to its zoonotic potential and the possibility of cross-infection with other species.

A CRISPR-SpCas9M-reporting system for efficient and rapid genome editing in Caulobacter crescentus

As members of the α-proteobacteria group, Caulobacter crescentus and its relatives are wildly studied for their unique asymmetric life cycle and versatile applications in industry, agriculture, and biomedicine. However, genetic manipulation in these bacteria remains challenging, typically requiring time-consuming and labor-intensive procedures. Here, we report a practical CRISPR-SpCas9M-reporting system that overcomes the limitations of SpCas9 expression and CRISPR escape, enabling efficient, markerless, and rapid genome editing in C. crescentus. Two genes encoding for a pair of scaffold proteins were knocked out individually or iteratively, demonstrating their direct involvements in cellular signaling asymmetry. Key components, including the Cas protein, Cas inducer, sgRNA, homologous arms, and reporter, were systematically analyzed and optimized in the system, finally achieving the apparent editing efficiency up to 80% in C. crescentus. Furthermore, we applied the CRISPR-SpCas9M-reporting system to two C. crescentus relatives, Agrobacterium fabrum and Sinorhizobium meliloti, establishing it as an efficient and general editing strategy. We anticipate that this system could be applied to other CRISPR-Cas-recalcitrant organisms, accelerating both basic and applied research in α-proteobacteria.

In Silico Design and Characterization of a Multiepitope Vaccine Candidate Against Brucella canis Using a Reverse Vaccinology Approach

Brucella canis is a Gram-negative bacterium that causes canine brucellosis, a zoonotic disease with serious implications for public health and the global economy. Currently, there is no effective preventive vaccine for B. canis. Control measures include diagnostic testing, isolation, and euthanasia of infected animals. However, these measures face significant limitations, such as diagnostic challenges, ethical concerns, and limited success in preventing transmission. Epidemiologically, canine brucellosis exhibits seroprevalence rates ranging from less than 1% to over 15%, with higher rates reported in stray dogs and regions of low socioeconomic development. This study employed a reverse vaccinology approach to design and characterize a multiepitope vaccine candidate against B. canis, aiming to prevent infection caused by this pathogen. A comprehensive in silico analysis of the complete B. canis proteome was conducted to identify proteins with potential as vaccine targets. Predicted epitopes for B and T cells were analyzed, and those with the highest capacity to elicit a robust immune response were selected. These proteins were classified as plasma membrane proteins, outer membrane proteins (OMPs), or proteins with similarity to virulence factors. Selection criteria emphasized their essential roles in bacterial function, lack of homology with proteins from dogs or mice, and presence of fewer than two transmembrane domains. From this process, four candidate proteins were identified. Epitopes for B and T cells within these proteins were predicted and analyzed, selecting the most immunogenic sequences. The overlap between B- and T-cell epitopes narrowed the selection to six final epitopes. These selected epitopes were then assembled into a multiepitope vaccine construct using flexible linkers to ensure structural integrity and molecular adjuvants to enhance immunogenicity. The physicochemical properties, antigenicity, and toxicity of the designed vaccine were evaluated. Additionally, the secondary and tertiary structure of the vaccine was predicted and refined, followed by a molecular interaction analysis with the Toll-like receptor 4 (TLR4) receptor. The designed vaccine proved to be highly antigenic, nonallergenic, and nontoxic. Validation of its secondary and tertiary structures, along with molecular docking analysis, revealed a high binding affinity to the TLR4 receptor. Molecular dynamics simulations and normal mode analysis further confirmed the vaccine's structural stability and binding capacity. A multiepitope vaccine candidate against B. canis was successfully designed and characterized using a reverse vaccinology approach. This vaccine construct is expected to induce robust humoral and cellular immune responses, potentially conferring protective immunity against B. canis. The results of this study are promising; however, in vitro and in vivo tests are necessary to validate the vaccine's protective efficacy. Furthermore, the described method could serve as a framework for developing vaccines against other pathogens.

Systematic review, Meta-analysis, and Pan-genome analytics predict the surging of Brucella melitensis by China and India-specific strains, elucidating the demand for enhanced preparedness

BACKGROUND

Brucellosis is an infectious disease in lower to moderate-income countries. It primarily affects small ruminant (sheep and goat) populations and can also be transmitted to mammals (humans). Brucella melitensis (B. melitensis) is the primary cause, posing a zoonotic threat. Controlling the spread of B. melitensis, especially in regions with high risk to humans and small ruminants, remains challenging. Current research explores the prevalence, genetic diversity, and prediction of brucellosis transmission in ruminants and humans.

METHODS

In this study, we developed an integrated database providing information on B. melitensis incidence in livestock from 2003 to 2024 and a systematic review and meta-analysis to assess the prevalence by following the Cochran collaborators' Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. A comprehensive literature search was conducted using reputable sources. These included reputable sources of electronic databases such as PubMed, ScienceDirect, Scopus, Biomed Central, CeRA, Krishikosh, ProQuest Dissertations & Theses Global, and Web of Science, complemented by the Google Scholar search engine. We also utilized Zotero 5.0 and Rayyan QCR, two web-based tools. Time series model to predict incidence trends and pan-genomic analysis to determine genetic diversity across Asia and Africa.

RESULTS

Meta-analysis revealed an overall prevalence of 12 % of which the African continent rose at 7 % (95 % CI: 5-8 %, I2 = 99 %, τ2 = 0.03, P = 0), while the corresponding prevalence in the Asian continent constituted 12 % (95 % CI: 11-14 %, I2 = 99 %, τ2 = 0.02, P = 0). The Time series model predicts a rising trend in brucellosis incidence from 2023 to 2030. The pan-genome analysis identified Rev 1 (0.000712) strain from China and the CIIMS-PH-3 (0.000209) strains from India showed the highest branch length, considered to have more genetic diversity.

CONCLUSION

These findings underscore the critical need for ongoing surveillance models and research to monitor the evolving B. melitensis landscape. High-prevalence regions exhibit significant genetic diversity. Effective prevention & control and response & preparedness strategies, including precise detection through advanced diagnostics, robust surveillance models to track trends, and targeted vaccination of susceptible animals, are vital. Stringent quarantine protocols, biosecurity measures, and exploring herbal remedies as a complementary approach to conventional treatment are crucial to mitigate the brucellosis burden as a public health concern and its socioeconomic impact on livelihood.

Hidden threats: Brucellosis diagnosis and co-infection patterns in Crimean-Congo Hemorrhagic Fever suspects

PURPOSE

This study aims to investigate the frequency of brucellosis in patients with Crimean-Congo Hemorrhagic Fever (CCHF).

METHOD

In this study, 1231 patients were evaluated retrospectively, including 14 patients with CCHF and brucellosis coinfection and 25 patients with brucellosis alone. Statistical methods such as the Mann-Whitney U test and Fisher's exact test were used.

RESULT

Of the patients with a preliminary diagnosis of Crimean-Congo Hemorrhagic Fever (CCHF), 3.2% were found to have brucellosis. In the group co-infected with brucellosis and CCHF, the time to hospital admission was shorter. Additionally, tick exposure and headache were observed more frequently in this group. Creatine kinase levels were found to be higher in the co-infected group, while lymphocyte counts and fibrinogen levels were lower compared to the group with brucellosis alone.

CONCLUSION

Our study revealed a 3.2% rate of brucellosis in patients with a preliminary diagnosis of CCHF. Due to the similarity of symptoms and common risk factors, the differential diagnosis of brucellosis should be considered in patients diagnosed with CCHF. Additionally, the possibility of brucellosis coexisting with CCHF should always be considered. Even in patients diagnosed with CCHF, an evaluation for brucellosis must be conducted.

Brucella abortus transcriptional regulator ArsR6 inhibits host pyroptosis via BAB_RS28760 by triggering the endoplasmic reticulum stress pathway

Pyroptosis, which is accompanied by inflammatory responses, is critical for pathogen clearance. However, the mechanism through which Brucella evades host pyroptosis remains unclear. The transcriptional regulator ArsR6 maintains bacterial intracellular homeostasis and possibly influences host cell death. However, whether ArsR6 acts on cellular pyroptosis is unknown. Therefore, we investigated pathogen-host interactions within macrophages infected with Brucella abortus (B. abortus), and found that ArsR6 is crucial for inhibiting host cell pyroptosis after B. abortus infection. The downstream target gene, BAB_RS28760 of ArsR6 was screened using chromatin immunoprecipitation sequencing. BAB_RS28760 belongs to the BA14K protein family and is strongly immunoreactive and induces humoral and cellular immune responses in the host during infection. Deleting ArsR6 in B. abortuspromotes pyroptosis and enhancs the intracellular survival of B. abortus. In addition, ArsR6 negatively regulated its target gene BAB_RS28760, whereas BAB_RS28760 deletion downregulated cellular pyroptosis by inhibiting endoplasmic reticulum stress and decreasing the intracellular survival of B. abortus. Our results reveal for the first time that Brucella ArsR6 reduces endoplasmic reticulum stress activation by negatively regulating its downstream target genes, thus inhibiting host cell pyroptosis. Our study provides new insights into the pathogenic mechanisms of Brucella, which can provide potential selectivity for the development of anti-Brucella therapies.

Identification of Brucella RS15060 as a novel type IV secretion system effector associated with bacterial virulence

Brucella is an intracellular parasitic pathogen that causes the worldwide zoonotic disease brucellosis. The type IV secretion system (T4SS) is utilized to secrete various effectors to help Brucella form Brucella-containing vacuoles within the cell and accomplish intracellular trafficking and replication. Brucella has fewer recognized effector proteins than other intracellular parasites in the Proteobacteria, indicating that Brucella may contain a large number of unidentified effector proteins. In this study, the optimal conditions for inducing protein secretion from Brucella were screened, and the secreted proteins of 2308 and the T4SS-deficient mutant SV123 under optimal conditions were collected for comparative proteomics analysis. By label-free quantitative proteomics, we identified 15 differential proteins. Through the β-lactamase TEM1 assay and indirect immunofluorescence assay, we identified RS15060 and RS10635 as novel T4SS effectors. Furthermore, by constructing mutation strains and performing cell/mouse infection experiments, we found that deletion of the rs15060 gene reduced the capacity of Brucella to replicate in cells and cause chronic infection in mice. In conclusion, a novel Brucella T4SS effector protein, RS15060, was identified to be associated with virulence in this study, and the discovery of effector proteins is conducive to a more comprehensive elucidation of T4SS function as well as to uncovering the cryptic strategies of Brucella survival in cells.

Chronic brucellosis with sacroiliitis: A case report

Key Clinical Message

Brucellosis, especially with osteoarticular involvement, is uncommon and difficult to diagnose, but it should be considered in a case presenting with prolonged fever, joint pain, and back pain. The diagnosis requires a combination of history, serological examinations, and radiographic studies. When the condition is detected and treated early, the prognosis is good.

Abstract

Brucella exploits host immune defenses to establish the chronic infection brucellosis, an endemic zoonotic disease. While human brucellosis affects multiple organs, osteo articular involvement is rare. We report the case of a 41-year-old woman with a history of goat farming who presented with fewer associated with low back pain and multiple joint pain for 4 months. Brucellosis was documented by positive serological tests (ELISA). Radiological findings suggested of right sacroiliitis and fracture line on the right sacral ala though had no history of trauma. Treatment consisted of NSAIDs and multiple antibiotic therapy. At follow-up, her low back pain, joint pain, and fever had subsided. After 4 weeks of follow-up, her symptoms were completely relieved with no recurrence. Brucellosis with atypical localization should be considered with a high index of suspicion based on detailed history and physical examination to ensure timely diagnosis and treatment.

Transcriptome analysis of macrophages during Brucella abortus infection clarifies the survival mechanisms of the bacteria

Brucellosis is a critical zoonotic disease impacting humans and animals globally, causing symptoms like fever and arthritis in humans and reproductive issues in animals. The disease stems from the Brucella genus, adept at evading the immune system and proliferating within host cells. This study explores how Brucella abortus manipulates host cellular mechanisms to sustain infection, focusing on the interaction with murine macrophages over 24 h. Initial host defenses involve innate immune responses, while Brucella's survival strategies include evading lysosomal degradation and modulating host cell functions through various pathways. The research identified significant transcriptional changes in macrophages post-infection, highlighting pathways such as cytokine storm, pyroptosis signaling, Toll-like receptor pathways, and LXRs/RXRs signaling. The findings shed light on Brucella's complex mechanisms to undermine host defenses and underscore the need for further investigation into therapeutic targets to combat brucellosis.

A recombinase polymerase amplification-SYBR Green I assay for the rapid and visual detection of Brucella

Brucellosis is a zoonosis caused by Brucella, which poses a great threat to human health and animal husbandry. Pathogen surveillance is an important measure to prevent brucellosis, but the traditional method is time-consuming and not suitable for field applications. In this study, a recombinase polymerase amplification-SYBR Green I (RPAS) assay was developed for the rapid and visualized detection of Brucella in the field by targeting BCSP31 gene, a conserved marker. The method was highly specific without any cross-reactivity with other common bacteria and its detection limit was 2.14 × 104 CFU/mL or g of Brucella at 40 °C for 20 min. It obviates the need for costly instrumentation and exhibits robustness towards background interference in serum, meat, and milk samples. In summary, the RPAS assay is a rapid, visually intuitive, and user-friendly detection that is highly suitable for use in resource-limited settings. Its simplicity and ease of use enable swift on-site detection of Brucella, thereby facilitating timely implementation of preventive measures.

Genome-wide analysis of Brucella melitensis growth in spleen of infected mice allows rational selection of new vaccine candidates

Live attenuated vaccines (LAVs) whose virulence would be controlled at the tissue level could be a crucial tool to effectively fight intracellular bacterial pathogens, because they would optimize the induction of protective immune memory while avoiding the long-term persistence of vaccine strains in the host. Rational development of these new LAVs implies developing an exhaustive map of the bacterial virulence genes according to the host organs implicated. We report here the use of transposon sequencing to compare the bacterial genes involved in the multiplication of Brucella melitensis, a major causative agent of brucellosis, in the lungs and spleens of C57BL/6 infected mice. We found 257 and 135 genes predicted to be essential for B. melitensis multiplication in the spleen and lung, respectively, with 87 genes common to both organs. We selected genes whose deletion is predicted to produce moderate or severe attenuation in the spleen, the main known reservoir of Brucella, and compared deletion mutants for these genes for their ability to protect mice against challenge with a virulent strain of B. melitensis. The protective efficacy of a deletion mutant for the plsC gene, implicated in phospholipid biosynthesis, is similar to that of the reference Rev.1 vaccine but with a shorter persistence in the spleen. Our results demonstrate that B. melitensis faces different selective pressures depending on the organ and underscore the effectiveness of functional genome mapping for the design of new safer LAV candidates.

A subunit vaccine based on Brucella rBP26 induces Th1 immune responses and M1 macrophage activation

Brucellosis is a global zoonotic infection caused by Brucella bacteria, which poses a significant burden on society. While transmission prevention is currently the most effective method, the absence of a licenced vaccine for humans necessitates the urgent development of a safe and effective vaccine. Recombinant protein-based subunit vaccines are considered promising options, and in this study, the Brucella BP26 protein is expressed using prokaryotic expression systems. The immune responses are evaluated using the well-established adjuvant CpG-ODN. The results demonstrate that rBP26 supplemented with a CpG adjuvant induces M1 macrophage polarization and stimulates cellular immune responses mediated by Th1 cells and CD8 + T cells. Additionally, it generates high levels of rBP26-specific antibodies in immunized mice. Furthermore, rBP26 immunization activates, proliferates, and produces cytokines in T lymphocytes while also maintaining immune memory for an extended period of time. These findings shed light on the potential biological function of rBP26, which is crucial for understanding brucellosis pathogenesis. Moreover, rBP26 holds promise as an effective subunit vaccine candidate for use in endemic areas.

A Multidisciplinary "One Health" Tool for Tackling Brucellosis

Introduction: The Epizootiological Investigation Form (EIF) is a document issued for every notified human brucellosis case, with the aim to convey information from public health to veterinary authorities for farm animals epidemiologically linked with the patient. We assessed the integration of EIF to the routine collaboration among stakeholders and the efficiency in directing the veterinary efforts to identify Brucella-infected animals. Methods: EIFs were evaluated for the implementation, timeliness, and completeness of the shared information provided by the public health and the veterinary authorities. The efficiency of EIFs in identifying infected farms was compared with the Brucella infection rate of routinely screened farms in the frame of the national brucellosis program. Results: During 2017-2022, 344 EIFs were issued for equal number of human brucellosis cases and 118 (34.3%) were circulated successfully among all stakeholders, whereas 226 (65.7%) went missing. The highest rate of intersectoral circulation occurred in May (47.8%, p = 0.007). Veterinary investigation was performed, and result was provided in 62 (57.4%) of the 108 circulated EIFs that disclosed the contact details of the epidemiologically linked animal farms. Brucella was detected at a significantly higher rate (51.7%) in the investigated sheep and goats' farms than the infection rate (2.7%) of the national brucellosis program (p < 0.00001). Among the screened bovine herds, two were found infected of the eight tested (25%). The circulation among all competent authorities of EIFs with a farm screening outcome required a median (interquartile range) of 50 days (22, 88). The likelihood of a "complete" EIF per human case differed among geographic Regions (p = 0.010), and was higher for patients diagnosed in April (p = 0.001) and occupied as stockbreeders (p = 0.025). Conclusions: EIF is a useful tool for pinpointing suspected animals for brucellosis screening. Training of the collaborating personnel is essential for improving the implementation of EIF in the everyday practice.

A study of rural populations' knowledge, attitude, and practice about brucellosis: a descriptive, cross-sectional, multicenter study

OBJECTIVE

Brucellosis is a highly contagious disease which is transmitted from animals to humans. One of the populations at high risk of infection is those living in rural areas. The present study was conducted to investigate rural populations' knowledge, attitude, and practice about brucellosis in Iran. The study used a descriptive, cross-sectional design to assess 300 individuals who were living in rural areas. The subjects were selected using convenience sampling from six villages located in the south of Iran. The data gathered were analyzed using Analysis of variance (ANOVA), and Pearson correlation coefficient in SPSS version 23.

RESULTS

From the 300 individuals who were enrolled in this study, 189 were male and 111 were female. The mean age of the participants was 48.27 ± 4.28 years. The mean scores of the study population's knowledge, attitude, and practice about brucellosis were found to be low. A significant direct correlation was found between the subjects' knowledge, attitude, and practice regarding brucellosis.

Parenteral Vaccination with a Live Brucella melitensis Mutant Protects against Wild-Type B. melitensis 16M Challenge

Susceptibility to brucellosis remains prevalent, even in herds vaccinated with conventional vaccines. Efforts are underway to develop an improved brucellosis vaccine, and possibly a universal vaccine, given that Brucella species are highly homologous. To this end, two B. melitensis mutants were developed, znBM-lacZ (znBMZ) and znBM-mCherry (znBM-mC), and were tested for their ability to confer systemic immunity against virulent B. melitensis challenge. To assess the extent of their attenuation, bone-marrow-derived macrophages and human TF-1 myeloid cells were infected with both mutants, and the inability to replicate within these cells was noted. Mice infected with varying doses of znBM-mC cleared the brucellae within 6-10 weeks. To test for efficacy against systemic disease, groups of mice were vaccinated once by the intraperitoneal route with either znBMZ or B. abortus S19 vaccine. Relative to the PBS-dosed mice, znBMZ vaccination greatly reduced splenic brucellae colonization by ~25,000-fold compared to 700-fold for S19-vaccinated mice. Not surprisingly, both znBMZ and S19 strains induced IFN-γ+ CD4+ T cells, yet only znBMZ induced IFN-γ+ CD8+ T cells. While both strains induced CD4+ effector memory T cells (Tems), only znBMZ induced CD8+ Tems. Thus, these results show that the described znBM mutants are safe, able to elicit CD4+ and CD8+ T cell immunity without a boost, and highly effective, rendering them promising vaccine candidates for livestock.

Brucellosis: epidemiology, pathogenesis, diagnosis and treatment-a comprehensive review

Background: Brucellosis is a pervasive zoonotic disease caused by various Brucella species. It mainly affects livestock and wildlife and poses significant public health threats, especially in regions with suboptimal hygiene, food safety, and veterinary care standards. Human contractions occur by consuming contaminated animal products or interacting with infected animals. Objective: This study aims to provide an updated understanding of brucellosis, from its epidemiology and pathogenesis to diagnosis and treatment strategies. It emphasizes the importance of ongoing research, knowledge exchange, and interdisciplinary collaboration for effective disease control and prevention, highlighting its global health implications. Methods: Pathogenesis involves intricate interactions between bacteria and the host immune system, resulting in chronic infections characterized by diverse clinical manifestations. The diagnostic process is arduous owing to non-specific symptomatology and sampling challenges, necessitating a fusion of clinical and laboratory evaluations, including blood cultures, serological assays, and molecular methods. Management typically entails multiple antibiotics, although the rise in antibiotic-resistant Brucella strains poses a problem. Animal vaccination is a potential strategy to curb the spread of infection, particularly within livestock populations. Results: The study provides insights into the complex pathogenesis of brucellosis, the challenges in its diagnosis, and the management strategies involving antibiotic therapy and animal vaccination. It also highlights the emerging issue of antibiotic-resistant Brucella strains. Conclusions: In conclusion, brucellosis is a significant zoonotic disease with implications for public health. Efforts should be directed towards improved diagnostic methods, antibiotic stewardship to combat antibiotic resistance, and developing and implementing effective animal vaccination programs. Interdisciplinary collaboration and ongoing research are crucial for addressing the global health implications of brucellosis.

Outer membrane protein 25 of Brucella suppresses TLR-mediated expression of proinflammatory cytokines through degradation of TLRs and adaptor proteins

Toll-like receptors (TLRs) are essential components of innate immunity that serves as the first line of defense against the invaded microorganisms. However, successful infectious pathogens subvert TLR signaling to suppress the activation of innate and adaptive responses. Brucella species are infectious intracellular bacterial pathogens causing the worldwide zoonotic disease, brucellosis, that impacts economic growth of many countries. Brucella species are considered as stealthy bacterial pathogens as they efficiently evade or suppress host innate and adaptive immune responses for their chronic persistence. However, the bacterial effectors and their host targets for modulating the immune responses remain obscure. Brucella encodes various outer membrane proteins (Omps) that facilitate their invasion, intracellular replication, and immunomodulation. Outer membrane protein 25 (Omp25) of Brucella plays an important role in the immune modulation through suppression of proinflammatory cytokines. However, the mechanism and the signaling pathways that are targeted by Omp25 to attenuate the production of proinflammatory cytokines remain obscure. Here, we report that Omp25 and its variants, viz. Omp25b, Omp25c, and Omp25d, suppress production of proinflammatory cytokines that are mediated by various TLRs. Furthermore, we demonstrate that Omp25 and its variants promote enhanced ubiquitination and degradation of TLRs and their adaptor proteins to attenuate the expression of proinflammatory cytokines. Targeting multiple TLRs and adaptor proteins enables Omp25 to effectively suppress the expression of proinflammatory cytokines that are induced by diverse pathogen-associated molecular patterns. This can contribute to the defective adaptive immune response and the chronic persistence of Brucella in the host.

The Brucella Effector Protein BspF Regulates Apoptosis through the Crotonylation of p53

The Brucella type IV secretion system (T4SS) can promote the intracellular survival and reproduction of Brucella. T4SS secretes effector proteins to act on cellular signaling pathways to inhibit the host's innate immune response and cause a chronic, persistent Brucella infection. Brucella can survive in host cells for a long time by inhibiting macrophage apoptosis and avoiding immune recognition. The effector protein, BspF, secreted by T4SS, can regulate host secretory transport and accelerate the intracellular replication of Brucella. BspF has an acetyltransferase domain of the GNAT (GCN5-related N-acetyltransferases) family, and in our previous crotonylation proteomics data, we have found that BspF has crotonyl transferase activity and crotonylation regulation of host cell protein in the proteomics data. Here, we found that BspF attenuates the crotonylation modification of the interacting protein p53, which reduces the p53 expression through the GNAT domain. BspF can inhibit the transcription and protein expression of downstream apoptotic genes, thereby inhibiting host cell apoptosis. Additionally, the Brucella ΔbspF mutant stain promotes apoptosis and reduces the survival rate of Brucella in the cells. In conclusion, we identified that the T4SS effector protein BspF can regulate host cell apoptosis to assist Brucella in its long-term survival by attenuating crotonylation modification of p53 and decreasing p53 expression. Our findings reveal a unique mechanism of elucidating how Brucella regulates host cell apoptosis and promotes its proliferation through the secretion of effector proteins.

Ophthalmological findings in brucellosis

PURPOSE

To evaluate the ophthalmological findings in patients diagnosed with acute, subacute or chronic brucellosis and to determine the effects of this disease on ocular structures.

METHODS

Eighty-seven patients diagnosed with brucellosis and 71 healthy cases (as a control group) were enrolled in this prospective study. All participants underwent a complete ophthalmic evaluation, including slit lamp biomicroscopic examination, Goldman applanation tonometry, specular microscopy, optical coherence tomography and fundoscopy with pupil dilation.

RESULTS

Overall, ocular involvement was present in 47 eyes of 27 (31.03%) patients diagnosed with brucellosis and was most common in the chronic brucellosis group. In the acute brucellosis group, papillary conjunctivitis in 8 eyes of 4 patients and anterior uveitis in 10 eyes of 6 patients were noted. In the subacute brucellosis group, papillary conjunctivitis in 4 eyes of 2 patients and sequelae of anterior uveitis in 6 eyes of 3 patients were observed. In the chronic brucellosis group, panuveitis in 4 eyes of 2 patients, choroiditis in 4 eyes of 2 patients, and signs of previous anterior uveitis in 11 eyes of 6 patients were noted. Visual acuity was significantly worse in patients with acute anterior uveitis (AAU) or previous anterior uveitis (PAU) compared with the control cases.

CONCLUSION

Ocular involvement should be kept in mind in patients with brucellosis, especially acute, and brucellosis should be included in the differential diagnosis of patients with anterior uveitis living in endemic areas, since the clinical presentation of the disease may not be overt.

Bacillus Calmette-Guérin-Trained Macrophages Elicit a Protective Inflammatory Response against the Pathogenic Bacteria Brucella abortus

The bacillus Calmette-Guérin (BCG) can elicit enhanced innate immune responses against a wide range of infections, known as trained immunity. Brucella abortus is the causative agent of brucellosis, a debilitating disease that affects humans and animals. In this study, we demonstrate that C57BL/6 mouse bone marrow-derived macrophages under BCG training enhance inflammatory responses against B. abortus. BCG-trained macrophages showed increased MHC class II and CD40 expression on the cell surface and higher IL-6, IL-12, and IL-1β production. The increase in IL-1β secretion was accompanied by enhanced activation of canonical and noncanonical inflammasome platforms. We observed elevated caspase-11 expression and caspase-1 processing in BCG-trained macrophages in response to B. abortus compared with untrained cells. In addition, these BCG-trained cells showed higher NLRP3 expression after B. abortus infection. From a metabolic point of view, signaling through the Akt/mammalian target of rapamycin/S6 kinase pathway was also enhanced. In addition, BCG training resulted in higher inducible NO synthase expression and nitrite production, culminating in an improved macrophage-killing capacity against intracellular B. abortus. In vivo, we monitored a significant reduction in the bacterial burden in organs from BCG-trained C57BL/6 mice when compared with the untrained group. In addition, previous BCG immunization of RAG-1-deficient mice partially protects against Brucella infection, suggesting the important role of the innate immune compartment in this scenario. Furthermore, naive recipient mice that received BM transfer from BCG-trained donors showed greater resistance to B. abortus when compared with their untrained counterparts. These results demonstrate that BCG-induced trained immunity in mice results in better control of intracellular B. abortus in vivo and in vitro.

Host cell egress of Brucella abortus requires BNIP3L-mediated mitophagy

The facultative intracellular pathogen Brucella abortus interacts with several organelles of the host cell to reach its replicative niche inside the endoplasmic reticulum. However, little is known about the interplay between the intracellular bacteria and the host cell mitochondria. Here, we showed that B. abortus triggers substantive mitochondrial network fragmentation, accompanied by mitophagy and the formation of mitochondrial Brucella-containing vacuoles during the late steps of cellular infection. Brucella-induced expression of the mitophagy receptor BNIP3L is essential for these events and relies on the iron-dependent stabilisation of the hypoxia-inducible factor 1α. Functionally, BNIP3L-mediated mitophagy appears to be advantageous for bacterial exit from the host cell as BNIP3L depletion drastically reduces the number of reinfection events. Altogether, these findings highlight the intricate link between Brucella trafficking and the mitochondria during host cell infection.

To eat or not to eat mitochondria? How do host cells cope with mitophagy upon bacterial infection?

Mitochondria fulfil a plethora of cellular functions ranging from energy production to regulation of inflammation and cell death control. The fundamental role of mitochondria makes them a target of choice for invading pathogens, with either an intracellular or extracellular lifestyle. Indeed, the modulation of mitochondrial functions by several bacterial pathogens has been shown to be beneficial for bacterial survival inside their host. However, so far, relatively little is known about the importance of mitochondrial recycling and degradation pathways through mitophagy in the outcome (success or failure) of bacterial infection. On the one hand, mitophagy could be considered as a defensive response triggered by the host upon infection to maintain mitochondrial homeostasis. However, on the other hand, the pathogen itself may initiate the host mitophagy to escape from mitochondrial-mediated inflammation or antibacterial oxidative stress. In this review, we will discuss the diversity of various mechanisms of mitophagy in a general context, as well as what is currently known about the different bacterial pathogens that have developed strategies to manipulate the host mitophagy.

Lactiplantibacillus plantarum Lac16 Attenuates Enterohemorrhagic Escherichia coli O157:H7 Infection by Inhibiting Virulence Traits and Improving Intestinal Epithelial Barrier Function

Large-scale use of antimicrobials in agriculture and medicine contributes to antibiotic residues in raw foods, the spread of antimicrobial resistance (AMR) and drug pollution, which seriously threatens human health and imposes significant economic burdens on society, suggesting the need for novel therapeutic options that prevent or control zoonoses. In this study, four probiotics were selected to assess their capability to alleviate pathogen-induced damage. Results showed that a simulated gastrointestinal juice and bile tolerated L. plantarum Lac16 with high lactic acid secretion can significantly inhibit the growth of multiple zoonotic pathogens. Lac16 also significantly inhibited the biofilm formation and mRNA expression of virulence traits (genes related to virulence, toxins, flagella biogenesis and motility, antibiotic resistance, biofilm formation and AI-2 quorum sensing) of enterohemorrhagic E. coli O157:H7 (EHEC). Furthermore, Lac16 and Lac26 significantly protected C. elegans against zoonotic pathogen-induced (EHEC, S. typhimurium, C. perfringens) deaths. Moreover, Lac16 significantly promoted epithelial repair and ameliorated lipopolysaccharide (LPS)-induced intestinal epithelial apoptosis and barrier dysfunction by activating the Wnt/β-catenin signaling pathway, and markedly reduced LPS-induced inflammatory responses by inhibiting the TLR4/MyD88 signaling pathway. The present results indicate that Lac16 attenuates enterohemorrhagic E. coli infection-induced damage by inhibiting key virulence traits of E. coli, promoting epithelial repair and improving intestinal epithelial barrier function, which may be mediated by the activated Wnt/β-catenin signaling pathway and the inhibited TLR4/MyD88 signaling pathway of the intestinal epithelium.

Gene expression of Toll-like receptors, cytokines and a nuclear factor and cytokine secretion in DH82 canine macrophage cells infected with Brucella canis

Canine brucellosis caused by Brucella canis infection occurs mainly in dogs, and is a zoonotic disease that also has the possibility of infection in humans. Many studies have been conducted to understand the immunopathological mechanism of B. canis infection. However, the precise immune mechanism remains to be elucidated because compared to other Brucella spp., B. canis has different immune evasion mechanisms. In this study, gene expression levels of Toll-like receptors (TLRs) and TLR-associated molecules and cytokine production were analyzed to figure out the roles of immune-related host factors in B. canis infection. Time-dependent gene expression of TLRs (1-10) and TLR-related molecules (TNF-α, IL-5, IL-23, CCL4, CD40 and NFκ-B) and release of Th1, Th2 and Th17-related cytokines (IFN-γ, IL-1β, IL-4, IL-6, IL-10 and IL-17A) were investigated in DH82 canine macrophages infected with B. canis. Time-dependent induction of TLRs 3, 7 and 8 was observed, and TLR 7 had the highest expression level (p <0.05). The expression levels of all TLR-related genes were significantly increased after infection. In particular, the expression of the CCL4 and IL-23 genes was highly induced. The amounts of IL-1β, IL-6 and IL-10 were significantly increased by B. canis infection, but the amounts of IL-4 and IL-17A were not. The production of IL-1β and IL-6 was the highest at 24 hr after B. canis infection (p <0.05). This study demonstrates that TLRs 3, 7 and 8 are prominent sites of to immune response induction with the production of related cytokines and a nuclear factor in DH82 cells infected with B. canis. These results suggest a sequential immune mechanism of B. canis infection, involving TLRs, cytokines and their associated factors.

Activation of mucosal immunity as a novel therapeutic strategy for combating brucellosis

Brucellosis is a disease of livestock that is commonly asymptomatic until an abortion occurs. Disease in humans results from contact of infected livestock or consumption of contaminated milk or meat. Brucella zoonosis is primarily caused by one of three species that infect livestock, Bacillus abortus in cattle, B. melitensis in goats and sheep, and B. suis in pigs. To aid in disease prophylaxis, livestock vaccines are available, but are only 70% effective; hence, improved vaccines are needed to mitigate disease, particularly in countries where disease remains pervasive. The absence of knowing which proteins confer complete protection limits development of subunit vaccines. Instead, efforts are focused on developing new and improved live, attenuated Brucella vaccines, since these mimic attributes of wild-type Brucella, and stimulate host immune, particularly T helper 1-type responses, required for protection. In considering their development, the new mutants must address Brucella's defense mechanisms normally active to circumvent host immune detection. Vaccination approaches should also consider mode and route of delivery since disease transmission among livestock and humans is believed to occur via the naso-oropharyngeal tissues. By arming the host's mucosal immune defenses with resident memory T cells (TRMs) and by expanding the sources of IFN-γ, brucellae dissemination from the site of infection to systemic tissues can be prevented. In this review, points of discussion focus on understanding the various immune mechanisms involved in disease progression and which immune players are important in fighting disease.

Ocular Lesions in Brucella Infection: A Review of the Literature

Ocular lesions due to Brucella infection are uncommon and easily overlooked in clinical management, but must be differentiated from non-infectious eye diseases and treated promptly to protect the patient's vision. We reviewed the relevant literature and identified 47 patients with ocular complications of Brucella infection. Among them, 28 showed ocular neuropathy, 15 presented with uveitis, and four patients displayed other ocular symptoms. Ocular symptoms accompanying Brucella infection require prompt diagnosis and treatment. The main methods of diagnosis are intraocular fluid tests and blood tests. Early diagnosis and treatment with suitable antibiotics are central to protecting the patient's vision. Notably, in terms of mechanism of injury, Brucella infection is chronic and cannot be eliminated by phagocytes, and can cause damage to the eye by inducing autoimmune reactions, antigen-antibody complex production, release of endogenous and exogenous toxins, and bacterial production of septic thrombi in the tissues. In this review, we summarize the ocular symptoms, diagnosis, treatment and prognosis of Brucella infection, and discuss the mechanisms of Brucella in ocular lesions, providing a reference for the diagnosis and treatment of Brucella ocular lesions.

Brucella BtpB Manipulates Apoptosis and Autophagic Flux in RAW264.7 Cells

Brucella transfers effectors into host cells, manipulating cellular processes to its advantage; however, the mechanism by which effectors regulate cellular processes during infection is poorly understood. A growing number of studies have shown that apoptosis and autophagy are critical mechanisms for target cells to cope with pathogens and maintain cellular homeostasis. BtpB is a Brucella type IV secretion system effector with a complex mechanism for manipulating host infection. Here, we show that the ectopic expression of BtpB promoted DNA fragmentation. In contrast, an isogenic mutant strain, ΔbtpB, inhibited apoptosis compared to the wild-type strain B. suis S2 in RAW264.7 cells. In addition, BtpB inhibited autophagy, as determined by LC3-II protein levels, the number of LC3 puncta, and p62 degradation. We also found that BtpB reduced autophagolysosome formation and blocked the complete autophagic flux. Moreover, our results revealed that the autophagy inhibitor, chloroquine, reduces Brucella's intracellular survival. Overall, our data unveil new mechanisms of virulence implicating the effector BtpB in regulating host intracellular infection.

On the offense and defense: mitochondrial recovery programs amidst targeted pathogenic assault

Bacterial pathogens employ a variety of tactics to persist in their host and promote infection. Pathogens often target host organelles in order to benefit their survival, either through manipulation or subversion of their function. Mitochondria are regularly targeted by bacterial pathogens owing to their diverse cellular roles, including energy production and regulation of programmed cell death. However, disruption of normal mitochondrial function during infection can be detrimental to cell viability because of their essential nature. In response, cells use multiple quality control programs to mitigate mitochondrial dysfunction and promote recovery. In this review, we will provide an overview of mitochondrial recovery programs including mitochondrial dynamics, the mitochondrial unfolded protein response (UPR^mt ), and mitophagy. We will then discuss the various approaches used by bacterial pathogens to target mitochondria, which result in mitochondrial dysfunction. Lastly, we will discuss how cells leverage mitochondrial recovery programs beyond their role in organelle repair, to promote host defense against pathogen infection.

Live mucosal vaccination stimulates potent protection via varied CD4+ and CD8+ T cell subsets against wild-type Brucella melitensis 16M challenge

Re-emerging zoonotic pathogen Brucella spp. continues to impact developing countries and persists in expanding populations of wildlife species in the US, constantly threatening infection of our domestic herds. The development of improved animal and human vaccines remains a priority. In this study, immunity to a novel live attenuated B. melitensis strain, termed znBM-mC, was characterized. An oral prime, intranasal (IN) boost strategy conferred exquisite protection against pulmonary challenge, with wild-type (wt) B. melitensis providing nearly complete protection in the lungs and spleens from brucellae colonization. Vaccination with znBM-mC showed an IFN-γ⁺ CD8⁺ T-cell bias in the lungs as opposed to Rev 1-vaccinated mice showing IFN-γ⁺ CD4⁺ T-cell inclination. Lung CD4⁺ and CD8⁺ effector memory T cells (TEMs) increased over 200-fold; and lung CD4⁺ and CD8⁺ resident memory T cells (TRMs) increased more than 250- and 150-fold, respectively. These T cells served as the primary producers of IFN-γ in the lungs, which was essential for vaccine clearance and the predominant cytokine generated pre-and post-challenge with wt B. melitensis 16M; znBM-mC growth could not be arrested in IFN-γ^−/− mice. Increases in lung TNF-α and IL-17 were also induced, with IL-17 being mostly derived from CD4⁺ T cells. Vaccination of CD4^−/−, CD8^−/−, and B6 mice with znBM-mC conferred full protection in the lungs and spleens post-pulmonary challenge with virulent B. melitensis; vaccination of IL-17^−/− mice resulted in the protection of the lungs, but not the spleen. These data demonstrate the efficacy of mucosal vaccine administration for the generation of protective memory T cells against wt B. melitensis.

Brucella ceti and Brucella pinnipedialis genome characterization unveils genetic features that highlight their zoonotic potential

The Gram-negative bacteria Brucella ceti and Brucella pinnipedialis circulate in marine environments primarily infecting marine mammals, where they cause an often-fatal disease named brucellosis. The increase of brucellosis among several species of cetaceans and pinnipeds, together with the report of sporadic human infections, raises concerns about the zoonotic potential of these pathogens on a large scale and may pose a threat to coastal communities worldwide. Therefore, the characterization of the B. ceti and B. pinnipedialis genetic features is a priority to better understand the pathological factors that may impact global health. Moreover, an in-depth functional analysis of the B. ceti and B. pinnipedialis genome in the context of virulence and pathogenesis was not undertaken so far. Within this picture, here we present the comparative whole-genome characterization of all B. ceti and B. pinnipedialis genomes available in public resources, uncovering a collection of genetic tools possessed by these aquatic bacterial species compared to their zoonotic terrestrial relatives. We show that B. ceti and B. pinnipedialis genomes display a wide host-range infection capability and a polyphyletic phylogeny within the genus, showing a genomic structure that fits the canonical definition of closeness. Functional genome annotation led to identifying genes related to several pathways involved in mechanisms of infection, others conferring pan-susceptibility to antimicrobials and a set of virulence genes that highlight the similarity of B. ceti and B. pinnipedialis genotypes to those of Brucella spp. displaying human-infecting phenotypes.

Increased serum piwi-interacting RNAs as a novel potential diagnostic tool for brucellosis

Background

Piwi-interacting RNAs (piRNAs) have emerged as potential novel indicators for various diseases; however, their diagnostic value for brucellosis remains unclear. This study aimed to evaluate the diagnostic potential of altered serum piRNAs in patients with brucellosis.

Methods

Illumina sequencing via synthesis (SBS) technology was used to screen the serum piRNA profile in brucellosis patients, and markedly dysregulated piRNAs were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) assay in two sets from a cohort of 73 brucellosis patients and 65 controls.

Results

Illumina SBS technology results showed that seven piRNAs were markedly elevated in brucellosis patients compared to normal controls. The seven upregulated piRNAs were further validated individually by qRT-PCR, of which three piRNAs (piR-000753, piR-001312, and piR-016742) were confirmed to be significantly and steadily increased in the patients (> 2-fold, P < 0.01). The area under the receiver operating characteristic (ROC) curve (AUCs) for the three piRNAs ranged from 0.698 to 0.783. The AUC for the three piRNAs combination was 0.772, with a specificity of 86% and a positive predictive value of 90%, respectively.

Conclusions

The three-piRNA panel identified in this study has potential as a novel blood-based auxiliary tool for brucellosis detection.

Expression of NLRP3 and AIM2 inflammasome in Peripheral blood in Chinese patients with acute and chronic brucellosis

Brucellosis is a zoonotic disease caused by Brucella abortus. An efficient immune response is crucial for curing brucellosis. The inflammasome plays a significant role in the immune response. It is unclear which inflammasome is active in acute and chronic brucellosis and how its levels relate to inflammatory cytokines. A total of 40 patients with acute or chronic brucellosis and 20 healthy volunteers had peripheral blood samples collected. The expression levels of AIM2, NLRP3, ASC, and Caspase-1 were determined by a real-time polymerase chain reaction from RNA and serum samples, and IL-1β, IL-18, and IFN-γ were measured by enzyme-linked immunosorbent assay. In the acute brucellosis group, AIM2 expression was significantly higher, while ACS expression was significantly lower than that of healthy volunteers. In patients with chronic brucellosis, AIM2 expression was significantly lower, while Caspase-1 expression was significantly higher than that of healthy volunteers. Serum IL-18 and IFN-γ levels were significantly higher in patients with acute brucellosis than in healthy controls. The IFN-γ level was also significantly higher in patients with chronic brucellosis than in healthy controls. The inflammasome responds differently in different stages of brucellosis. The inflammasome may be the site of action of immune escape in brucellosis.

Brucella induces heme oxygenase-1 expression to promote its infection

Brucellosis is a zoonotic and contagious infectious disease caused by Brucella spp, which causes substantial economic losses to animal husbandry and leads to severe public health problems. Brucella have evolved multiple strategies to escape host immunity and survive within host cells. Elucidating the immune evasion strategies during Brucella infection will facilitate the control of brucellosis. The host enzyme, heme oxygenase-1 (HO-1), is a multifunctional protein that functions during inflammatory diseases and microbial infections. However, how HO-1 functions during Brucella infection is rarely studied. In this study, we evaluated the role of HO-1 during Brucella infection. We found that Brucella infection induced HO-1 expression in macrophages. We further showed that HO-1 was regulated by PI3K, AMPK kinase, and nuclear erythroid-related factor 2 (Nrf2) in macrophages. Interestingly, knocking out HO-1 or inhibiting the activity of HO-1 significantly decreased Brucella intracellular growth. Inducing the expression of HO-1 by treatment with CoPP promoted Brucella intracellular growth. Mechanistic analyses indicated that the effect of HO-1 was not meditated by HO-1 metabolites, but by decreasing the production of reactive oxygen species (ROS), TNF-α, and IL-1β. Moreover, Brucella induced HO-1 expression in bone marrow-derived macrophages (BMDMs) and mice. When the expression of HO-1 was knocked down in BMDMs, the intracellular survival of Brucella was reduced. Furthermore, the induction of HO-1 by CoPP significantly increased bacterial loads in vivo. Thus, we demonstrated that Brucella induced HO-1 expression to promote its survival and growth in vitro and in vivo. This study also identified HO-1 as a novel innate immune evasion factor during Brucella infection.

Genome-wide transcription start site mapping in the facultative intracellular pathogen Brucella melitensis by Capping-seq

Brucella melitensis (B. melitensis) is an important facultative intracellular bacterium that causes global zoonotic diseases. Continuous intracellular survival and replication are the main obstruction responsible for the accessibility of prevention and treatment of brucellosis. Bacteria respond to complex environment by regulating gene expression. Many regulatory factors function at loci where RNA polymerase initiates messenger RNA synthesis. However, limited gene annotation is a current obstacle for the research on expression regulation in bacteria. To improve annotation and explore potential functional sites, we proposed a novel genome-wide method called Capping-seq for transcription start site (TSS) mapping in B. melitensis. This technique combines capture of capped primary transcripts with Single Molecule Real-Time (SMRT) sequencing technology. We identified 2,369 TSSs at single nucleotide resolution by Capping-seq. TSSs analysis of Brucella transcripts showed a preference of purine on the TSS positions. Our results revealed that -35 and -10 elements of promoter contained consensus sequences of TTGNNN and TATNNN, respectively. The 5' ends analysis showed that 57% genes are associated with more than one TSS and 47% genes contain long leader regions, suggested potential complex regulation at the 5' ends of genes in B. melitensis. Moreover, we identified 52 leaderless genes that are mainly involved in the metabolic processes. Overall, Capping-seq technology provides a unique solution for TSS determination in prokaryotes. Our findings develop a systematic insight into the primary transcriptome characterization of B. melitensis. This study represents a critical basis for investigating gene regulation and pathogenesis of Brucella.

Assays for Identification and Differentiation of Brucella Species: A Review

Brucellosis is one of the most important and widespread bacterial zoonoses worldwide. Cases are reported annually across the range of known infectious species of the genus Brucella. Globally, Brucella melitensis, primarily hosted by domestic sheep and goats, affects large proportions of livestock herds, and frequently spills over into humans. While some species, such as Brucella abortus, are well controlled in livestock in areas of North America, the Greater Yellowstone Ecosystem supports the species in native wild ungulates with occasional spillover to livestock. Elsewhere in North America, other Brucella species still infect domestic dogs and feral swine, with some associated human cases. Brucella spp. patterns vary across space globally with B. abortus and B. melitensis the most important for livestock control. A myriad of other species within the genus infect a wide range of marine mammals, wildlife, rodents, and even frogs. Infection in humans from these others varies with geography and bacterial species. Control in humans is primarily achieved through livestock vaccination and culling and requires accurate and rapid species confirmation; vaccination is Brucella spp.-specific and typically targets single livestock species for distribution. Traditional bacteriology methods are slow (some media can take up to 21 days for bacterial growth) and often lack the specificity of molecular techniques. Here, we summarize the molecular techniques for confirming and identifying specific Brucella species and provide recommendations for selecting the appropriate methods based on need, sensitivity, and laboratory capabilities/technology. As vaccination/culling approaches are costly and logistically challenging, proper diagnostics and species identification are critical tools for targeting surveillance and control.

Molecular Detection of Zoonotic and Veterinary Pathogenic Bacteria in Pet Dogs and Their Parasitizing Ticks in Junggar Basin, North-Western China

Despite the recognized epidemiological importance of ticks as vectors for pathogens that cause numerous zoonotic and veterinary diseases, data regarding the pathogens of pet dogs and their parasitic ticks in the Junggar Basin are scarce. In this study, a total of 178 blood samples and 436 parasitic ticks were collected from pet dogs in Junggar Basin, Xinjiang Uygur Autonomous Region (XUAR), north-western China. All ticks were identified as Rhipicephalus turanicus sensu stricto (s.s.) according to morphological and molecular characteristics. Rh. turanicus s.s. ticks were collected from pet dogs in China for the first time. Seven tick-borne pathogens, such as Ehrlichia chaffeensis, Anaplasma phagocytophilum, Rickettsia massiliae, Candidatus R. barbariae, Brucella spp., Rickettsia sibirica, and Anaplasma ovis, were detected from ticks, whereas the first five bacteria were detected from blood samples of dogs. Brucella spp. was the most predominant pathogen in both blood samples and ticks of pet dogs, with the detection rates of 16.29 and 16.74%, respectively. Moreover, 17 ticks and 1 blood sample were co-infected with two pathogens, and 1 tick was co-infected with three pathogens. This study provided molecular evidence for the occurrence of Anaplasma spp., Ehrlichia spp., Rickettsia spp., and Brucella spp. circulating in pet dogs and their parasitic ticks in Junggar Basin, north-western China. These findings extend our knowledge of the tick-borne pathogens in pet dogs and their parasitic ticks in Central Asia; therefore, further research on these pathogens and their role in human and animal diseases is required.

Brucella spp. distribution, hosting ruminants from Greece, applying various molecular identification techniques

Background

Brucellosis still remains an endemic disease for both livestock and human in Greece, influencing the primary sector and national economy in general. Although farm animals and particularly ruminants constitute the natural hosts of the disease, transmission to humans is not uncommon, thus representing a serious occupational disease as well. Under this prism, knowledge concerning Brucella species distribution in ruminants is considered a high priority. There are various molecular methodologies for Brucella detection with however differential discriminant capacity. Hence, the aim of this survey was to achieve nationally Brucella epidemiology baseline genotyping data at species and subtype level, as well as to evaluate the pros and cons of different molecular techniques utilized for detection of Brucella species. Thirty-nine tissue samples from 30 domestic ruminants, which were found positive applying a screening PCR, were tested by four different molecular techniques i.e. sequencing of the 16S rRNA, the BP26 and the OMP31 regions, and the MLVA typing panel 1 assay of minisatellite markers.

Results

Only one haplotype was revealed from the 16S rRNA sequencing analysis, indicating that molecular identification of Brucella bacteria based on this marker might be feasible solely up to genus level. BP26 sequencing analysis and MLVA were in complete agreement detecting both B. melitensis and B. abortus. An interesting exception was observed in 11 samples, of lower quality extracted DNA, in which not all expected MLVA amplicons were produced and identification was based on the remaining ones as well as on BP26. On the contrary OMP31 failed to provide a clear band in any of the examined samples.

Conclusions

The present study reveals the constant circulation of Brucella bacteria in ruminants throughout Greece. Further, according to our results, BP26 gene represents a very good alternative to MLVA minisatellite assay, particularly in lower quality DNA samples.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03295-4.

Functional insights into Brucella transcriptional regulator ArsR

ArsR-family transcriptional factors regulates diverse physiological functions necessary for Brucella adaptation to environmental changes. However, whether the ArsR-family transcriptional regulator are related to virulence, and the precise determination of ArsR direct targets in Brucella are still unknown. Therefore, we created a 2308ΔArsR6 mutant of B. abortus 2308 (S2308). Virulence assay was performed using a murine macrophage cell line (RAW 264.7). We performed chromatin immunoprecipitation of ArsR6 followed by next-generation sequencing (ChIP-seq). We also selected the target gene pobA (BAB2_0600), and created the mutant (2308ΔpobA). The survival capability of 2308ΔpobA strain in RAW 264.7 was detected and the levels of tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ), interleukin-12 (IL-12) and interleukin-18 (IL-18) were also measured. The results showed that 2308ΔArsR6 reduced survival capability in RAW 264.7. We detected 40 intergenic ChIP-seq peaks of ArsR6 binding distributed across the Brucella genome. 2308ΔpobA was significantly reduced survival capability in RAW 264.7. After the macrophages were infected with 2308ΔpobA, the levels of TNF-α, IFN-γ, IL-12 and IL-18 were decreased and were significantly lower than that for the S2308-infected group, indicating that the 2308ΔpobA could reduce the secretion of inflammatory cytokines. Taken together, the research provided new insights into the functionality of ArsR6 and great significance to clarify the function of ArsR6.

A LysR Transcriptional Regulator Manipulates Macrophage Autophagy Flux During Brucella Infection

Brucella, the intracellular bacteria, have evolved subtle strategies to efficiently survive and replicate in macrophages. However, the virulence effector proteins involved are still unclear. LysR-type transcriptional regulators (lttrs) are the largest regulator family with diverse function in prokaryotes. However, very little is known about the role of LysR regulators in the Brucella spp. Here, a BSS2_II0858 gene, encoded as one of the LysR-type regulators, was studied. We successfully constructed a BSS2_II0858 deletion mutant, Δ0858, and complementation strain CΔ0858 in Brucella suis S2. The cell apoptosis induced by B. suis S2 and its derivatives were detected by flow cytometry. The autophagy was then assessed by immunoblot analysis using the IL3I/II and p62 makers. In addition, the autophagy flux was evaluated by double fluorescent labeling method for autophagy marker protein LC3. Our studies demonstrated that B. suis S2 and its derivatives inhibited the programmed cell death in early stage and promoted apoptosis in the later stage during infection in RAW264.7 cells. The BSS2_II0858 gene was found to play no role during apoptosis according to these results. Compared with the wild-type strain, Δ0858 mutant can stimulate the conversion of LC3-I to LC3-II and markedly inhibited the autophagy flux at early stage leading to obvious autophagosome accumulation. This study explored the function of BSS2_II0858 gene and may provide new insights for understanding the mechanisms involved in the survival of Brucella in macrophages.

Tumor Necrosis Factor Alpha Contributes to Inflammatory Pathology in the Placenta during Brucella abortus Infection

Research on Brucella pathogenesis has focused primarily on its ability to cause persistent intracellular infection of the mononuclear phagocyte system. At these sites, Brucella abortus evades innate immunity, which results in low-level inflammation and chronic infection of phagocytes. In contrast, the host response in the placenta during infection is characterized by severe inflammation and extensive extracellular replication of B. abortus. Despite the importance of reproductive disease caused by Brucella infection, our knowledge of the mechanisms involved in placental inflammation and abortion is limited. To understand the immune responses specifically driving placental pathology, we modeled placental B. abortus infection in pregnant mice. B. abortus infection caused an increase in the production of tumor necrosis factor alpha (TNF-α), specifically in the placenta. We found that placental expression levels of Tnfa and circulating TNF-α were dependent on the induction of endoplasmic reticulum stress and the B. abortus type IV secretion system (T4SS) effector protein VceC. Blockade of TNF-α reduced placental inflammation and improved fetal viability in mice. This work sheds light on a tissue-specific response of the placenta to B. abortus infection that may be important for bacterial transmission via abortion in the natural host species.

Immunization with a combination of recombinant Brucella abortus proteins induces T helper immune response and confers protection against wild-type challenge in BALB/c mice

Protective efficiency of a combination of four recombinant Brucella abortus (B. abortus) proteins, namely, ribosomal protein L7/L12, outer membrane protein (OMP) 22, OMP25 and OMP31, was evaluated as a combined subunit vaccine (CSV) against B. abortus infection in RAW 264.7 cell line and murine model. Four proteins were cloned, expressed and purified, and their immunocompetence was analysed. BALB/c mice were immunized subcutaneously with single subunit vaccines (SSVs) or CSV. Cellular and humoral immune responses were determined by ELISA. Results of immunoreactivity showed that these four recombinant proteins reacted with Brucella‐positive serum individually but not with Brucella‐negative serum. A massive production of IFN‐γ and IL‐2 but low degree of IL‐10 was observed in mice immunized with SSVs or CSV. In addition, the titres of IgG2a were heightened compared with IgG1 in SSV‐ or CSV‐immunized mice, which indicated that SSVs and CSV induced a typical T‐helper‐1‐dominated immune response in vivo. Further investigation of the CSV showed a superior protective effect in mice against brucellosis. The protection level induced by CSV was significantly higher than that induced by SSVs, which was not significantly different compared with a group immunized with RB51. Collectively, these antigens of Brucella could be potential candidates to develop subunit vaccines, and the CSV used in this study could be a potential candidate therapy for the prevention of brucellosis.

Acute brucellosis associated with isolated splenic and left gastric artery vasculitis and acute ischemic bowel infarction. A systematic review of the most recent cases

Brucellosis is a multisystem bacterial zoonosis caused by Gram-negative bacteria Brucella spp. Ingestion of infected food products, direct contact with an infected animal, or inhalation of aerosols are all ways for germs to spread from animals to humans. Intestinal vasculitis with gangrene due to brucellosis has rarely been reported. We report a 62-year-old male patient presenting with acute onset of recurrent attacks of abdominal pain, remittent fever, malaise, and weight loss, which were followed by severe left hypochondrium abdominal pain with rigidity and signs of acute abdomen. Brucellosis was clinically suspected and confirmed by an enzyme-linked immunosorbent assay against the Brucella melitensis species. An abdominal CT scan revealed isolated splenic and left gastric artery vasculitis, leading to acute bowel ischemia, bowel infarction and gangrenous jejunal bowel segment. Histopathological examination of the resected gangrenous bowel segment revealed leucocytoclastic vasculitis. The patient was successfully treated with a standardized antimicrobial therapy for brucellosis and a short course of steroids with a complete resolution of the symptoms and signs. The case is discussed and the literature is reviewed.

Virulence factors perforate the pathogen-containing vacuole to signal efferocytosis

Intracellular pathogens commonly reside within macrophages to find shelter from humoral defenses, but host cell death can expose them to the extracellular milieu. We find intracellular pathogens solve this dilemma by using virulence factors to generate a complement-dependent find-me signal that initiates uptake by a new phagocyte through efferocytosis. During macrophage death, Salmonella uses a type III secretion system to perforate the membrane of the pathogen-containing vacuole (PCV), thereby triggering complement deposition on bacteria entrapped in pore-induced intracellular traps (PITs). In turn, complement activation signals neutrophil efferocytosis, a process that shelters intracellular bacteria from the respiratory burst. Similarly, Brucella employs its type IV secretion system to perforate the PCV membrane, which induces complement deposition on bacteria entrapped in PITs. Collectively, this work identifies virulence factor-induced perforation of the PCV as a strategy of intracellular pathogens to generate a find-me signal for efferocytosis.

Modelling Human Brucellosis Based on Infection Rate and Vaccination Coverage of Sheep and Goats

In this study, the vaccination coverage, serological sampling and infection rate of sheep and goats were evaluated as predictors for the modeling of human brucellosis in Greece. The human brucellosis disease frequency per local regional unit (RU) varied significantly (RR90) among consecutive years. The notification rate was higher (p < 0.001) in the RUs with implementation of vaccination in sheep and goats (vaccination zone—VZ) with a median of 1.4 (IQR 0.0–3.1) compared with the RUs of the eradication zone (EZ) with a median of 0.0 (IQR 0.0–0.0). In VZ, the increased frequency of human cases was associated with delayed vaccine administration (estimate: 0.14 (0.04; 0.29), p = 0.03) and higher vaccination coverage of the animals (estimate: −0.349 (−0.72; −0.07), p < 0.01). However, the flock sampling rate was highly heterogenous among RUs (IQR 10.56–52.93), and inconsistent within RUs throughout the period of the study 2013–2017 (p = 0.001), limiting the reliable estimation of the infection rate in livestock and the design of an integrated One Health model for human disease.

Brucella abortus Encodes an Active Rhomboid Protease: Proteome Response after Rhomboid Gene Deletion

Rhomboids are intramembrane serine proteases highly conserved in the three domains of life. Their key roles in eukaryotes are well understood but their contribution to bacterial physiology is still poorly characterized. Here we demonstrate that Brucella abortus, the etiological agent of the zoonosis called brucellosis, encodes an active rhomboid protease capable of cleaving model heterologous substrates like Drosophila melanogaster Gurken and Providencia stuartii TatA. To address the impact of rhomboid deletion on B. abortus physiology, the proteomes of mutant and parental strains were compared by shotgun proteomics. About 50% of the B. abortus predicted proteome was identified by quantitative proteomics under two experimental conditions and 108 differentially represented proteins were detected. Membrane associated proteins that showed variations in concentration in the mutant were considered as potential rhomboid targets. This class included nitric oxide reductase subunit C NorC (Q2YJT6) and periplasmic protein LptC involved in LPS transport to the outer membrane (Q2YP16). Differences in secretory proteins were also addressed. Differentially represented proteins included a putative lytic murein transglycosylase (Q2YIT4), nitrous-oxide reductase NosZ (Q2YJW2) and high oxygen affinity Cbb3-type cytochrome c oxidase subunit (Q2YM85). Deletion of rhomboid had no obvious effect in B. abortus virulence. However, rhomboid overexpression had a negative impact on growth under static conditions, suggesting an effect on denitrification enzymes and/or high oxygen affinity cytochrome c oxidase required for growth in low oxygen tension conditions.

Spinal pain revealing brucellar spondylodiscitis: a case report

Background

Brucellosis is an anthropozoonosis. It is an endemic disease in the Mediterranean basin. The clinical presentation is polymorphic. The osteoarticular form is the most frequent of the focal forms affecting mainly the spine. In our endemic context, the diagnosis can lead to confusion with tuberculosis.

Case presentation

We report a case of brucellar spondylodiscitis treated initially as tubercular spondylodiscitis with a good initial evolution. Then, the diagnosis was rectified towards a Brucella origin, after a clinical and biological relapse. Diagnostic confirmation was based on the isolation of Brucella spp in the disco-vertebral CT-guided biopsy and the positive Brucella serology. Then, the patient was put on three antibacterial treatments with doxycycline, rifampicin, plus streptomycin over a period of 6 months with a good evolution.

Conclusion

Brucellar spondylodiscitis is still common in the Maghreb. It is generally insidious and leads to a delay in diagnosis. The clinician must always mention it when faced with spondylodiscitis in an endemic country and ask for brucella serology.

Vaccination with a Brucella ghost developed through a double inactivation strategy provides protection in Guinea pigs and cattle

Vaccination can prevent and control animal brucellosis. Currently, live attenuated vaccines are extensively used to prevent Brucella infection. However, traditional vaccines such as live attenuated vaccines are associated with biological safety risks for both humans and animals. The bacterial ghost (BG) is a new form of vaccine with great prospects. However, bacterial cells cannot be completely inactivated by biological lysis, conferring a safety risk associated with the vaccine. In this study, we developed a Brucella abortus A19 bacterial ghost (A19BG) through a double inactivation strategy with sequential biological lysis and hydrogen peroxide treatment. This strategy resulted in 100% inactivation of Brucella, such that viable bacterial cells were not detected even at an ultrahigh concentration of 10¹⁰ colony-forming units/mL. Furthermore, A19BG had a typical BG morphology and good genetic stability. Moreover, it did not induce adverse reactions in guinea pigs. The levels of antibodies, interferon-γ, interleukin-4, and CD4⁺ T cells in guinea pigs inoculated with the A19BG vaccine were similar to those inoculated with the existing A19 vaccine. Immunization with A19BG conferred a similar level of protection with that of A19 against Brucella melitensis M28 in both guinea pigs and cattle. In conclusion, the combination of biological lysis and H₂O₂-mediated inactivation is a safe and effective strategy that can serve as a reference for the preparation of BG vaccines.

microRNAs in human brucellosis: A promising therapeutic approach and biomarker for diagnosis and treatment

INTRODUCTION

Human brucellosis is a zoonotic bacterial disease with up to 500,000 new cases each year. The major evasion mechanisms from the host immune system by Brucella are restraint of complement pathway and Toll-like receptors signaling pathways, interference with efficient antigen presentation to CD4-positive T lymphocytes, selective subversion of autophagy pathways, inhibition of dendritic cell stimulation, inhibition of autophagolysosomal fusion, and macrophage apoptosis. Many molecular and cellular pathways contribute to brucellosis that microRNAs have a vital function in the immunopathogenesis of this disease. In this regard, these molecules apply for their roles by modulating various events like inflammatory reactions and immune defense. Recently, in the case of immunity to human brucellosis, it has been shown that microRNAs play an important role in immunity against these bacteria.

METHODS AND RESULTS

In this study, we tried to review the immune defense and immunopathogenesis of Brucella infection and highlight the current knowledge of the microRNAs in infected cells by Brucella pathogens. The recent findings suggest that the regulation of microRNAs expression is impaired during brucellosis infection, which may contribute to disease progression or inhibition by modulating immune responses against this pathogen.

CONCLUSIONS

The interplay between miRNAs and Brucella pathogens and the underlying process required comprehensive examination to unravel the novel therapeutic or diagnostic approaches.