Brucella melitensis 16MΔTcfSR as a potential live vaccine allows for the differentiation between natural and vaccinated infection

Evasion of host defense by Brucella

Brucella , an adept intracellular pathogen, causes brucellosis, a zoonotic disease leading to significant global impacts on animal welfare and the economy. Regrettably, there is currently no approved and effective vaccine for human use. The ability of Brucella to evade host defenses is essential for establishing chronic infection and ensuring stable intracellular growth. Brucella employs various mechanisms to evade and undermine the innate and adaptive immune responses of the host through modulating the activation of pattern recognition receptors (PRRs), inflammatory responses, or the activation of immune cells like dendritic cells (DCs) to inhibit antigen presentation. Moreover, it regulates multiple cellular processes such as apoptosis, pyroptosis, and autophagy to establish persistent infection within host cells. This review summarizes the recently discovered mechanisms employed by Brucella to subvert host immune responses and research progress on vaccines, with the aim of advancing our understanding of brucellosis and facilitating the development of more effective vaccines and therapeutic approaches against Brucella .

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.

Evaluation of Brucellosis Vaccines: A Comprehensive Review

Brucellosis is a bacterial zoonosis caused by Brucella spp. which can lead to heavy economic losses and severe human diseases. Thus, controlling brucellosis is very important. Due to humans easily gaining brucellosis from animals, animal brucellosis control programs can help the eradication of human brucellosis. There are two popular vaccines against animal brucellosis. Live attenuated Brucella abortus strain 19 (S19 vaccine) is the first effective and most extensively used vaccine for the prevention of brucellosis in cattle. Live attenuated Brucella melitensis strain Rev.1 (Rev.1 vaccine) is the most effective vaccine against caprine and ovine brucellosis. Although these two vaccines provide good immunity for animals against brucellosis, the expense of persistent serological responses is one of the main problems of both vaccines. The advantages and limitations of Brucella vaccines, especially new vaccine candidates, have been less studied. In addition, there is an urgent need for new strategies to control and eradicate this disease. Therefore, this narrative review aims to present an updated overview of the available different types of brucellosis vaccines.

Evaluation and Differential Diagnosis of a Genetic Marked Brucella Vaccine A19ΔvirB12 for Cattle

Brucella abortus is an important zoonotic pathogen that causes severe economic loss to husbandry and poses a threat to human health. The B. abortus A19 live vaccine has been extensively used to prevent bovine brucellosis in China. However, it is difficult to distinguish the serological response induced by A19 from that induced by natural infection. In this study, a novel genetically marked vaccine, A19ΔvirB12, was generated and evaluated. The results indicated that A19ΔvirB12 was able to provide effective protection against B. abortus 2308 (S2308) challenge in mice. Furthermore, the safety and protective efficacy of A19ΔvirB12 have been confirmed in natural host cattle. Additionally, the VirB12 protein allowed for serological differentiation between the S2308 challenge/natural infection and A19ΔvirB12 vaccination. However, previous studies have found that the accuracy of the serological detection based on VirB12 needs to be improved. Therefore, we attempted to identify potential supplementary antigens with differential diagnostic functions by combining label-free quantitative proteomics and protein chip technology. Twenty-six proteins identified only in S2308 were screened; among them, five proteins were considered as potential supplementary antigens. Thus, the accuracy of the differential diagnosis between A19ΔvirB12 immunization and field infection may be improved through multi-antigen detection. In addition, we explored the possible attenuation factors of Brucella vaccine strain. Nine virulence factors were downregulated in A19ΔvirB12. The downregulation pathways of A19ΔvirB12 were significantly enriched in quorum sensing, ATP-binding cassette transporter, and metabolism. Several proteins related to cell division were significantly downregulated, while some proteins involved in transcription were upregulated in S2308. In conclusion, our results contribute to the control and eradication of brucellosis and provide insights into the mechanisms underlying the attenuation of A19ΔvirB12.

Deletion of the transcriptional regulator GntR down regulated the expression of Genes Related to Virulence and Conferred Protection against Wild-Type Brucella Challenge in BALB/c Mice

Brucellosis, which is caused by Brucella spp., is a zoonotic infectious disease that can cause great hazard to public health and safety. The virulence of Brucella is essential for survive and multiply in host macrophages. GntR is a transcriptional regulator in Brucella that is required for virulence in macrophages and mice, and involved in resistance to stress responses. To determine the expression levels of target genes of GntR, we detected the expression levels of the GntR target genes in Brucella infected BALB/c mice. The results showed that several genes related to virulence, including omp25, virB1, vjbR, dnaK, htrA and hfq, were regulated by GntR during infection in BALB/c mice. Moreover, the 2308ΔgntR mutant induced high protective immunity in BALB/c mice challenge with B. abortus 2308 (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). All together, these results indicated that gntR promoted the virulence of Brucella. The 2308ΔgntR was significantly attenuated in macrophages and mice and induced protective immune response during infection, suggested that 2308ΔgntR mutant is an attractive candidate for the design of a live attenuated vaccine against Brucella.

Brucella melitensis M5-90Δbp26 as a potential live vaccine that allows for the distinction between natural infection and immunization

Brucella is Gram-negative intracellular bacterial pathogen that infects humans and animals and contributes to great economic losses in developing countries. Presently, live attenuated Brucella vaccines (Brucella melitensis M5-90) are the most effective means of brucellosis control and prevention in animals. However, these vaccines have several drawbacks, such as an inability to distinguish between a natural infection and immunization and an association with abortions in pregnant animals. Therefore, this study constructed a Brucella M5-90Δbp26 mutant and evaluated its virulence. The survival of the M5-90Δbp26 mutant was attenuated in human placenta trophoblastic 8 cells (HPT-8 cells) and in BALB/c mice, with a high immunoprotectivity noted in mice. Furthermore, safety tests showed that the M5-90Δbp26 mutant was less virulent than the M5-90 vaccine strain. Additionally, an indirect enzyme-linked immunosorbent assay (ELISA) screening was shown to detect the presence of Brucella protein 26 (BP26) with high sensitivity, with M5-90Δbp26 inoculation accompanied with a lack of BP26 expression, and was further confirmed by western blotting. Together, the M5-90Δbp26 mutant and the indirect ELISA can be employed to distinguish vaccinated livestock from infected animals.