Effector Proteins of Type IV Secretion System: Weapons of Brucella Used to Fight Against Host Immunity

Molecular epidemiology, immunobiology, genomics and proteomics insights into bovine brucellosis

Brucella species are intracellular Gram-negative bacteria that cause brucellosis, a global zoonosis that impacts cattle productivity and public health. Both cattle and buffaloes are susceptible to bovine brucellosis, which can lead to severe degenerative changes in uterine mucosa of non-pregnant animals, including ulcerative endometritis and fibrosis. Vasculitis, localized coagulative necrosis, and ulceration of the uterine mucosa have all been reported in pregnant animals. Male testicles get inflamed due to Brucella, which results in infertility. This review article covers the molecular epidemiology, pathophysiology, immunobiology, genomics, and proteomics of Brucella, with an emphasis on novel discoveries and more recent research, especially on bovine brucellosis. The integration of molecular pathology and sero-prevalence data provide the insights into epidemiology, transmission dynamics, and genetic diversity of bovine brucellosis. The immunobiological response studies of brucellosis have provided insights into the tactics employed by Brucella to infect host cells and elude immune responses. Proteomics was utilized to find biomarkers for both acute and chronic brucellosis, which resulted in the identification of proteins with differential expression linked to immune response, inflammation, and extracellular matrix modulation. The genetic diversity, virulence factors, and evolution of Brucella strains were mostly investigated using genomics. The genomic makeup and architecture of Brucella isolates were examined using whole-genome sequencing, which revealed genetic markers linked to pathogenicity and drug resistance. This review provides possible treatment targets, diagnostic biomarkers, and vaccine candidates, contributing to molecular understanding of bovine brucellosis.

Preparation and evaluation of Brucella T4SS recombinant proteins in serodiagnosis of human brucellosis based on TMT-based proteomics technology

Introduction

Brucellosis, a significant zoonotic infectious disease, poses a global health threat. Accurate and efficient diagnosis is crucial for prevention, control, and treatment of brucellosis. VirB proteins, components of the Type IV secretion system (T4SS) in Brucella, play a pivotal role in bacterial virulence and pathogenesis but have been understudied for their diagnostic potential.

Methods

Tandem Mass Tag (TMT) proteomics technology was utilized to identify highly expressed VirB proteins from wild-type Brucella strains. Recombinant T4SS proteins were prepared, and an indirect ELISA method was established for serological diagnosis of human brucellosis.

Results

Seven T4SS proteins (rVirB3, rVirB4, rVirB9, rBMEII0036, rVirB8, rVirB11, and rVirB10) were expressed used to construct the indirect ELISA method which showed high diagnostic accuracy. Sensitivity and specificity of the proteins exceeded 0.9100 and 0.9167, respectively, demonstrating good performance comparable to traditional LPS and Rose Bengal Ag antigens. Cross-reactivity was observed in a limited number of serum samples from febrile patients without brucellosis.

Conclusions

The study highlights the potential of VirB proteins as novel diagnostic antigens for human brucellosis. Future research can further optimize the use of VirB proteins in diagnostic assays and explore their applications in vaccine development.

Insights into the regulatory role of bacterial sncRNA and its extracellular delivery via OMVs

Small noncoding RNAs (sncRNAs) play important regulatory roles in bacterial physiological processes and host-pathogen interactions. Meanwhile, bacterial outer membrane vesicles (OMVs), as naturally secreted outer membrane structures, play a vital role in the interaction between bacteria and their living environment, including the host environment. However, most current studies focus on the biological functions of sncRNAs in bacteria or hosts, while neglecting the roles and regulatory mechanisms of the OMVs that encapsulate these sncRNAs. Therefore, this review aims to summarize the intracellular regulatory roles of bacterial sncRNAs in promoting pathogen survival by regulating virulence, modulating bacterial drug resistance, and regulating iron metabolism, and their extracellular regulatory function for influencing host immunity through host-pathogen interactions. Additionally, we introduce the key role played by OMVs, which serve as important cargoes in bacterial sncRNA-host interactions. We propose emerging pathways of sncRNA action to further discuss the mode of host-pathogen interactions, highlighting that the inhibition of sncRNA delivery by OMVs may prevent the occurrence of infection to some extent. Hence, this review lays the foundation for future prophylactic treatments against bacterial infections and strategies for addressing bacterial drug resistance. KEY POINTS: •sncRNAs have intracellular and extracellular regulatory functions in bacterial physiological processes and host-pathogen interactions. •OMVs are potential mediators between bacterial sncRNAs and host cells. •OMVs encapsulating sncRNAs have more potential biological functions.