Cell-mediated immunity in human brucellosis

New biological markers in diagnosis and follow-up of brucellosis cases

Brucellosis remains a significant public health issue in some parts of the world. It is clear that new laboratory methods are needed to diagnose brucellosis. Currently, no test method meets the criteria of high specificity, sensitivity, reliability, and low cost for the diagnosis of brucellosis, which could also predict chronicity. This study was conducted based on the data from a study conducted in 2015, which aimed to reveal genes with different transcript levels in chronic and acute patients and to evaluate their effects on the progression to chronicity by studying mRNA microarray and miRNA array in peripheral blood mononuclear cells in acute, chronic brucellosis and healthy control groups. According to the data obtained in this study, a second study was conducted to determine new markers that could aid in diagnosis and/or predict chronicity, with the most prominent gene products being [ABI3 (ABL interactor), PIAS4 (Protein Inhibitor of Activated STAT 4), PPP2R4 (Protein Phosphatase 2 Phosphatase Activator), DDIT4L (DNA Damage Inducible Transcript 4 Like), WDR33 (WD Repeat-Containing Protein 33), and IDO (Indoleamine 2,3-Dioxygenase)]. The study speculates that increased levels of ABI3, CLEC12B, PPP2R4 and decreased levels of DDIT4L, PIAS4, and IDO may be used as markers for the diagnosis of acute brucellosis, decreased levels of ABI3, CLEC12B, PPP2R4 and increased levels of DDIT4L, PIAS4, IDO may be assessed for treatment response. The study also suggested that maintaining consistent levels of ABI3, CLEC12B, PIAS4, PPP2R4, and IDO in subsequent titers may serve as a potential marker to predict chronic progression.

The Goat Cytotoxic T Lymphocyte-Associated Antigen-4 Gene: mRNA Expression and Association Analysis of Insertion/Deletion Variants with the Risk of Brucellosis

The cytotoxic T lymphocyte-associated antigen-4 (CTLA4) gene, a member of the immunoglobulin superfamily, is crucial for maintaining immune homeostasis and preventing autoimmune diseases. Studies have shown that polymorphisms in the CTLA4 gene are linked to an increased risk of brucellosis in humans, but its association with brucellosis in goats remains unexplored. In this study, the tissue expression profile of CTLA4 in goats was investigated, and the correlation between InDel polymorphisms in the CTLA4 gene and susceptibility to brucellosis in goats was examined. The findings reveal the widespread expression of CTLA4 in goat tissues, particularly in the spleen and testes. The tested goat populations presented genotypes insertion/insertion (II), insertion/deletion (ID), and deletion/deletion (DD) at both the P1 and P2 loci, and an association analysis revealed significant differences in the distribution of genotypes and allele frequencies at the P1 and P2 loci of the CTLA4 gene between the Brucella goat case and the control groups (p < 0.05). Specifically, compared with the II genotype, the P1 and P2 loci were significantly associated with an elevated risk of brucellosis development in goats under both the codominant (ID/II) and dominant (ID + DD/II) models (P1, p = 0.042, p = 0.016; P2, p = 0.011, p = 0.014). Additionally, haplotype analysis indicated that haplotypes IP1DP2, DP1IP2, and DP1DP2 were significantly associated with an increased risk of brucellosis in goats compared to the reference haplotype IP1IP2 (p = 0.029, p = 0.012, p = 0.034). Importantly, the Lipopolysaccharide (LPS) stimulation of peripheral blood monocytes and/or macrophages from goats with the II, ID, and DD genotypes resulted in increased CTLA4 expression levels in the II genotype, leading to a robust LPS-induced inflammatory response. Through bioinformatic analysis, the observed effect of the InDel locus on Brucella pathogenesis risk in goats could be attributed to the differential binding of the transcription factors nuclear factor kappaB (NF-κB) and CCAAT/enhancer-binding protein α (C/EBPα). These findings offer potential insights for breeding strategies against brucellosis.

Single-cell landscape revealed immune characteristics associated with disease phases in brucellosis patients

A comprehensive immune landscape for Brucella infection is crucial for developing new treatments for brucellosis. Here, we utilized single-cell RNA sequencing (scRNA-seq) of 290,369 cells from 35 individuals, including 29 brucellosis patients from acute (n = 10), sub-acute (n = 9), and chronic (n = 10) phases as well as six healthy donors. Enzyme-linked immunosorbent assays were applied for validation within this cohort. Brucella infection caused a significant change in the composition of peripheral immune cells and inflammation was a key feature of brucellosis. Acute patients are characterized by potential cytokine storms resulting from systemic upregulation of S100A8/A9, primarily due to classical monocytes. Cytokine storm may be mediated by activating S100A8/A9-TLR4-MyD88 signaling pathway. Moreover, monocytic myeloid-derived suppressor cells were the probable contributors to immune paralysis in acute patients. Chronic patients are characterized by a dysregulated Th1 response, marked by reduced expression of IFN-γ and Th1 signatures as well as a high exhausted state. Additionally, Brucella infection can suppress apoptosis in myeloid cells (e.g., mDCs, classical monocytes), inhibit antigen presentation in professional antigen-presenting cells (APCs; e.g., mDC) and nonprofessional APCs (e.g., monocytes), and induce exhaustion in CD8+ T/NK cells, potentially resulting in the establishment of chronic infection. Overall, our study systemically deciphered the coordinated immune responses of Brucella at different phases of the infection, which facilitated a full understanding of the immunopathogenesis of brucellosis and may aid the development of new effective therapeutic strategies, especially for those with chronic infection.

Beyond its preferential niche: Brucella abortus RNA down-modulates the IFN-γ-induced MHC-I expression in epithelial and endothelial cells

Brucella abortus (Ba) is a pathogen that survives inside macrophages. Despite being its preferential niche, Ba infects other cells, as shown by the multiple signs and symptoms humans present. This pathogen can evade our immune system. Ba displays a mechanism of down-modulating MHC-I on monocytes/macrophages in the presence of IFN-γ (when Th1 response is triggered) without altering the total expression of MHC-I. The retained MHC-I proteins are located within the Golgi Apparatus (GA). The RNA of Ba is one of the PAMPs that trigger this phenomenon. However, we acknowledged whether this event could be triggered in other cells relevant during Ba infection. Here, we demonstrate that Ba RNA reduced the surface expression of MHC-I induced by IFN-γ in the human bronchial epithelium (Calu-6), the human alveolar epithelium (A-549) and the endothelial microvasculature (HMEC) cell lines. In Calu-6 and HMEC cells, Ba RNA induces the retention of MHC-I in the GA. This phenomenon was not observed in A-549 cells. We then evaluated the effect of Ba RNA on the secretion of IL-8, IL-6 and MCP-1, key cytokines in Ba infection. Contrary to our expectations, HMEC, Calu-6 and A-549 cells treated with Ba RNA had higher IL-8 and IL-6 levels compared to untreated cells. In addition, we showed that Ba RNA down-modulates the MHC-I surface expression induced by IFN-γ on human monocytes/macrophages via the pathway of the Epidermal Growth Factor Receptor (EGFR). So, cells were stimulated with an EGFR ligand-blocking antibody (Cetuximab) and Ba RNA. Neutralization of the EGFR to some extent reversed the down-modulation of MHC-I mediated by Ba RNA in HMEC and A-549 cells. In conclusion, this is the first study exploring a central immune evasion strategy, such as the downregulation of MHC-I surface expression, beyond monocytes and could shed light on how it persists effectively within the host, enduring unseen and escaping CD8+ T cell surveillance.

Brucella infection and Toll-like receptors

Brucella consists of gram-negative bacteria that have the ability to invade and replicate in professional and non-professional phagocytes, and its prolonged persistence in the host leads to brucellosis, a serious zoonosis. Toll-like receptors (TLRs) are the best-known sensors of microorganisms implicated in the regulation of innate and adaptive immunity. In particular, TLRs are transmembrane proteins with a typical structure of an extracellular leucine-rich repeat (LRR) region and an intracellular Toll/interleukin-1 receptor (TIR) domain. In this review, we discuss Brucella infection and the aspects of host immune responses induced by pathogens. Furthermore, we summarize the roles of TLRs in Brucella infection, with substantial emphasis on the molecular insights into its mechanisms of action.

Role of myeloid-derived suppressor cells in chronic brucellosis

Introduction

Human brucellosis, a Brucella infection caused most common zoonosis in the world, remains a serious public health burden in China. Brucella chronic infection always causes immunosuppressive status and results in severe organ or tissue damages. The aim of this work was to study the role of the myeloid-derived suppressor cells (MDSCs) in human chronic brucellosis.

Methods

Fifty cases of chronic brucellosis and 40 healthy individual controls were enrolled in this study. We analyzed the frequency and subsets of MDSCs in PBMC between the chronic brucellosis and healthy control groups by flow cytometry. Furthermore, we also measured the inflammatory-related cytokines in serum samples and the MDSCs inhibition ability to the proliferation of T cells in vitro.

Results

We found that the frequency of MDSCs in peripheral blood and the level of IL-6 and IL-10 Th2 cytokines and Arginase-1 were significantly increased in chronic brucellosis patients. In addition, we also found that the T cell function was suppressed in vitro by co-culturing with MDSCs from brucellosis patients.

Conclusion

Our study described an increase of immunosuppressive MDSCs in peripheral blood of chronic brucellosis patients. These results contribute to the understanding of Brucella persistent infection, which may provide an insight for effective treatment of chronic brucellosis patients in clinical practice.

Design of a multi-epitope vaccine against brucellosis fused to IgG-fc by an immunoinformatics approach

Introduction

Brucella, a type of intracellular Gram-negative bacterium, has unique features and acts as a zoonotic pathogen. It can lead to abortion and infertility in animals. Eliminating brucellosis becomes very challenging once it spreads among both humans and animals, putting a heavy burden on livestock and people worldwide. Given the increasing spread of brucellosis, it is crucial to develop improved vaccines for susceptible animals to reduce the disease's impact.

Methods

In this study, we effectively used an immunoinformatics approach with advanced computer software to carefully identify and analyze important antigenic parts of Brucella abortus. Subsequently, we skillfully designed chimeric peptides to enhance the vaccine's strength and effectiveness. We used computer programs to find four important parts of the Brucella bacteria that our immune system recognizes. Then, we carefully looked for eight parts that are recognized by a type of white blood cell called cytotoxic T cells, six parts recognized by T helper cells, and four parts recognized by B cells. We connected these parts together using a special link, creating a strong new vaccine. To make the vaccine even better, we added some extra parts called molecular adjuvants. These included something called human β-defensins 3 (hBD-3) that we found in a database, and another part that helps the immune system called PADRE. We attached these extra parts to the beginning of the vaccine. In a new and clever way, we made the vaccine even stronger by attaching a part from a mouse's immune system to the end of it. This created a new kind of vaccine called MEV-Fc. We used advanced computer methods to study how well the MEV-Fc vaccine interacts with certain receptors in the body (TLR-2 and TLR-4).

Results

In the end, Immunosimulation predictions showed that the MEV-Fc vaccine can make the immune system respond strongly, both in terms of cells and antibodies.

Discussion

In summary, our results provide novel insights for the development of Brucella vaccines. Although further laboratory experiments are required to assess its protective effect.

Immuno-profiling of Brucella proteins for developing improved vaccines and DIVA capable serodiagnostic assays for brucellosis

Brucellosis remains a worldwide zoonotic disease with a serious impact on public health and livestock productivity. Controlling brucellosis in livestock is crucial for limiting human infections in the absence of effective human vaccines. Brucellosis control measures are majorly dependent on rigorous monitoring of disease outbreaks and mass vaccination of livestock. Live attenuated vaccines are available for livestock vaccination that play a vital role in brucellosis control programs in many countries. Even though the existing animal vaccines confer protection against brucellosis, they carry some drawbacks, including their infectivity to humans and interference with sero-monitoring. The available serodiagnostic assays for brucellosis depend on detecting anti-LPS antibodies in the serum. Since diagnosis plays a vital role in controlling brucellosis, developing improved serodiagnostic assays with enhanced specificity, sensitivity and DIVA capability is required. Therefore, it is essential to identify novel antigens for developing improved vaccines and serodiagnostic assays for brucellosis. In the present study, we performed a high throughput immunoprofiling of B. melitensis protein microarray using brucellosis-positive human and animal serum samples. The screening identified several serodominant proteins of Brucella that exhibited common or differential reactivity with sera from animals and humans. Subsequently, we cloned, expressed, and purified ten serodominant proteins, followed by analyzing their potential to develop next-generation vaccines and improved serodiagnostic assays for brucellosis. Further, we demonstrated the protective efficacy of one of the serodominant proteins against the B. melitensis challenge in mice. We found that the seroreactive protein, Dps (BMEI1980), strongly reacted with brucellosis-positive serum samples, but it did not react with sera from B. abortus S19-vaccinated cattle, indicating DIVA capability. A prototype lateral flow assay and indirect ELISA based on Dps protein exhibited high sensitivity, specificity, and DIVA capability. Thus, the present study identified promising candidates for developing improved vaccines and affordable, DIVA-capable serodiagnostic assays for animal and human brucellosis.

Brucella abortus Rough-Type Mutant Induces Ferroptosis and More Oxidative Stress in Infected Macrophages

Brucella is an intracellular parasitic bacterium that uses multiple strategies to evade the host's defense mechanisms. However, how Brucella manipulates the host-induced oxidative stress and relevant biological processes are still poorly understood. In this study, a comparative transcriptome assay of macrophages infected with Brucella abortus S2308 and its rough mutant RB14 was performed to investigate the differentially expressed genes which might be associated with the pathogenic mechanism of Brucella. Our results showed that numerous host pro-oxidative and antioxidative stress genes were differentially expressed in macrophages infected with B. abortus S2308 and mutant RB14 at 4, 8, 24, and 48 h post-infection. Interestingly, we found that several ferroptosis-associated genes were differentially expressed during B. abortus RB14 infection. Moreover, we found that the rough mutant RB14-induced macrophage death was associated with reduced levels of host glutathione and glutathione peroxidase 4, together with increased free iron, lipid peroxidation, and ROS, all of which are important hallmarks of ferroptosis. The ferroptosis occurring during infection with RB14 was reduced by treatment with the inhibitor ferrostatin-1. However, B. abortus S2308 infection did not induce these hallmarks of ferroptosis. Taken together, our results demonstrate that ferroptosis is involved in rough B. abortus infection. Investigating how Brucella manipulates oxidative stress and ferroptosis in its host will be helpful to clarify the pathogenicity of B. abortus.

A Rare Case of Neuralgic Amyotrophy Associated with Brucella Infection

Multiple micro-organisms associated with Neuralgic Amyotrophy (NA) have been reported and Brucella species should be an important and overlooked infectious cause or trigger.We report a rare case of neuralgic amyotrophy associated with Brucella infection and is believed to be the first such case report in China. A 42-year-old male with brucellosis was confirmed serologically, who presented recurrent fever and fatigue and suddenly developed severe pain in the right shoulder within one week, followed by the inability to lift and abduct the proximal end of the right upper limb. Based on typical clinical manifestions, MRI neuroimaging of the brachial plexus and neuro-electrophysiological studies to confirm a diagnosis of NA and presented spontaneous recovery during this period, immunomodulatory treatment with corticosteroid or intravenous immunoglobulin had not been attempted, leaving a serious movement disorder in the right upper limb. Even rare, NA and other neurobrucellosis forms should be considered as complications of Brucella infection.

Recent advancement, immune responses, and mechanism of action of various vaccines against intracellular bacterial infections

Emerging and re-emerging bacterial infections are a serious threat to human and animal health. Extracellular bacteria are free-living, while facultative intracellular bacteria replicate inside eukaryotic host cells. Many serious human illnesses are now known to be caused by intracellular bacteria such as Salmonella enterica, Escherichia coli, Staphylococcus aureus, Rickettsia massiliae, Chlamydia species, Brucella abortus, Mycobacterium tuberculosis and Listeria monocytogenes, which result in substantial morbidity and mortality. Pathogens like Mycobacterium, Brucella, MRSA, Shigella, Listeria, and Salmonella can infiltrate and persist in mammalian host cells, particularly macrophages, where they proliferate and establish a repository, resulting in chronic and recurrent infections. The current treatment for these bacteria involves the application of narrow-spectrum antibiotics. FDA-approved vaccines against obligate intracellular bacterial infections are lacking. The development of vaccines against intracellular pathogenic bacteria are more difficult because host defense against these bacteria requires the activation of the cell-mediated pathway of the immune system, such as CD8+ T and CD4+ T. However, different types of vaccines, including live, attenuated, subunit, killed whole cell, nano-based and DNA vaccines are currently in clinical trials. Substantial development has been made in various vaccine strategies against intracellular pathogenic bacteria. This review focuses on the mechanism of intracellular bacterial infection, host immune response, and recent advancements in vaccine development strategies against various obligate intracellular bacterial infections.

Brucella abortus RNA does not polarize macrophages to a particular profile but interferes with M1 polarization

Monocytes and macrophages play a central role in chronic brucellosis. Brucella abortus (Ba) is an intracellular pathogen that survives inside these cells. On the other hand, macrophages could be differentiated into classical (M1), alternative (M2) or other less-identified profiles. We have previously shown that Ba RNA (a bacterial viability-associated PAMP or vita-PAMP) is a key molecule by which Ba can evade the host immune response. However, we did not know if macrophages could be polarized by this vita-PAMP. To assess this, we used two different approaches: we evaluated if Ba RNA per se was able to differentiate macrophages to M1 or M2 or, given that Ba survives inside macrophages once a Th1 response is established (i.e., in the presence of IFN-γ), we also analysed if Ba RNA could interfere with M1 polarization. We found that Ba RNA alone does not polarize to M1 or M2 but activates human macrophages instead. However, our results show that Ba RNA does interfere with M1 polarization while they are being differentiated. This vita-PAMP diminished the M1-induced CD64, and MHC-II surface expression on macrophages at 48 h. This phenomenon was not associated with an alternative activation of these cells (M2), as shown by unchanged CD206, DC-SIGN and CD163 surface expression. When evaluating glucose metabolism, we found that Ba RNA did not modify M1 glucose consumption or lactate production. However, production of Nitrogen Reactive Species (NRS) did diminish in Ba RNA-treated M1 macrophages. Overall, our results show that Ba RNA could alter the proper immune response set to counterattack the bacteria that could persist in the host establishing a chronic 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.

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.

Key immunity characteristics of diverse stages of brucellosis in rural population from Inner Mongolia, China

Background

Brucellosis poses a serious threat to human and animal health, particularly in developing countries such as China. The Inner Mongolia Autonomous Region is one of the most severely brucellosis-endemic provinces in China. Currently, the host immune responses functioning to control Brucella infection and development remain poorly understood. The aim of this study is to further clarify the key immunity characteristics of diverse stages of brucellosis in Inner Mongolia.

Methods

We collected a total of 733 blood samples from acute (n = 137), chronic (n = 316), inapparent (n = 35), recovery (n = 99), and healthy (n = 146) groups from the rural community of Inner Mongolia between 2014 and 2015. The proportions of CD4⁺, CD8⁺, Th1, Th2, and Th17 T cells in peripheral blood and the expression of TLR2 and TLR4 in lymphocytes, monocytes and granulocytes were examined using flow cytometry analysis. The differences among the five groups were compared using one-way ANOVA and the Kruskal–Wallis method, respectively.

Results

Our results revealed that the proportions of CD4⁺ and CD8⁺ T cells were significantly different among the acute, chronic, recovery, and healthy control groups (P < 0.05), with lower proportions of CD4⁺ T cells and a higher proportion of CD8⁺ T cells in the acute, chronic, and recovery groups. The proportion of Th1 cells in the acute, chronic, and inapparent groups was higher than that in the healthy and recovery groups; however, there was no significant difference between patients and healthy individuals (P > 0.05). The proportion of Th2 lymphocytes was significantly higher in the acute and healthy groups than in the inapparent group (P < 0.05). The proportion of Th17 cells in the acute group was significantly higher than that in the healthy control, chronic, and inapparent groups (P < 0.05). Finally, the highest expression of TLR4 in lymphocytes, monocytes and granulocytes was observed in the recovery group, and this was followed by the acute, chronic, healthy control, and inapparent groups. There was a significant difference between the recovery group and the other groups, except for the acute group (P < 0.05). Moreover, a correlation in TLR4 expression was observed in lymphocytes, monocytes and granulocytes among the five groups (r > 0.5), except for the inapparent group between lymphocytes and granulocytes (r = 0.34).

Conclusions

Two key factors (CD8⁺ T cells and TLR4) in human immune profiles may closely correlate with the progression of brucellosis. The detailed function of TLR4 in the context of a greater number of cell types or tissues in human or animal brucellosis and in larger samples should be further explored in the future.

Graphical Abstract

Serum Levels of Seven General Cytokines in Acute Brucellosis Before and After Treatment

Purpose

Human brucellosis is the most common bacterial zoonosis globally that poses a severe health threat. Despite the availability of antibiotic therapy for human brucellosis, its tendencies of chronicity and persistence may lead to severe debilitating and disabling conditions in patients. Comprehensive understanding of the immune response in brucellosis will be helpful in improving the treatment strategies. In this study, we measured serum levels of T helper cell type 1 (Th1), Th2, and Th17 cytokines in patients with acute brucellosis before and after treatment.

Patients and Methods

Overall, 30 patients with acute brucellosis from the Beijing Di Tan Hospital and 26 healthy controls were enrolled in this study. All the patients received a 6-week therapy regimen comprising ceftriaxone, doxycycline, and rifampicin. Serum samples were collected from patients with acute Brucella infection and healthy controls before and after treatment. Serum seven cytokine levels of Th1 (IL-2, IFN-γ, and TNF-α), Th2 (IL-4, IL-6, IL-10), and Th17 (IL-17A) were measured using cytometric bead array.

Results

In patients with acute infection, the IL-2, IFN-γ, and IL-10 levels were significantly increased compared with those in healthy controls (P < 0.001). After treatment, IL-2, IFN-γ, and IL-10 levels significantly decreased (P < 0.05) and the TNF-α level significantly increased compared with the corresponding baseline levels and those in healthy controls (P < 0.05). Furthermore, the IFN-γ, IL-4, and IL-10 levels were higher in patients after treatment than in healthy controls (P < 0.05). IL-2 and IL-6 levels exhibited a positive correlation with the C-reactive protein (CRP) level in acute brucellosis (P < 0.05).

Conclusion

Levels of most serum Th1 and Th2 cytokines were simultaneously increased in acute infection, followed by reduction in the corresponding cytokine levels and residual cytokine response during treatment. This residual immune response could represent a therapeutic opportunity that may improve the long-term clinical outcomes in patients with acute brucellosis after treatment.

Nucleomodulin BspJ as an effector promotes the colonization of Brucella abortus in the host

BACKGROUND

Brucella infection induces brucellosis, a zoonotic disease. The intracellular circulation process and virulence of Brucella mainly depend on its type IV secretion system (T4SS) expressing secretory effectors. Secreted protein BspJ is a nucleomodulin of Brucella that invades the host cell nucleus. BspJ mediates host energy synthesis and apoptosis through interaction with proteins. However, the mechanism of BspJ as it affects the intracellular survival of Brucella remains to be clarified.

OBJECTIVES

To verify the functions of nucleomodulin BspJ in Brucella's intracellular infection cycles.

METHODS

Constructed Brucella abortus BspJ gene deletion strain (B. abortus ΔBspJ) and complement strain (B. abortus pBspJ) and studied their roles in the proliferation of Brucella both in vivo and in vitro.

RESULTS

BspJ gene deletion reduced the survival and intracellular proliferation of Brucella at the replicating Brucella-containing vacuoles (rBCV) stage. Compared with the parent strain, the colonization ability of the bacteria in mice was significantly reduced, causing less inflammatory infiltration and pathological damage. We also found that the knockout of BspJ altered the secretion of cytokines (interleukin [IL]-6, IL-1β, IL-10, tumor necrosis factor-α, interferon-γ) in host cells and in mice to affect the intracellular survival of Brucella.

CONCLUSIONS

BspJ is extremely important for the circulatory proliferation of Brucella in the host, and it may be involved in a previously unknown mechanism of Brucella's intracellular survival.

Impact of immune checkpoint molecules on FoxP3+ Treg cells and related cytokines in patients with acute and chronic brucellosis

Background

The immunoregulatory functions of regulatory T cells (Tregs) in the development and progression of some chronic infectious diseases are mediated by immune checkpoint molecules and immunosuppressive cytokines. However, little is known about the immunosuppressive functions of Tregs in human brucellosis, which is a major burden in low-income countries. In this study, expressions of immune checkpoint molecules and Treg-related cytokines in patients with acute and chronic Brucella infection were evaluated to explore their impact at different stages of infection.

Methods

Forty patients with acute brucellosis and 19 patients with chronic brucellosis admitted to the Third People’s Hospital of Linfen in Shanxi Province between August 2016 and November 2017 were enrolled. Serum and peripheral blood mononuclear cells were isolated from patients before antibiotic treatment and from 30 healthy subjects. The frequency of Tregs (CD4⁺ CD25⁺ FoxP3⁺ T cells) and expression of CTLA-4, GITR, and PD-1 on Treg cells were detected by flow cytometry. Levels of Treg-related cytokines, including IL-35, TGF-β1, and IL-10, were measured by customised multiplex cytokine assays using the Luminex platform.

Results

The frequency of Tregs was higher in chronic patients than in healthy controls (P = 0.026) and acute patients (P = 0.042); The frequency of CTLA-4⁺ Tregs in chronic patients was significantly higher than that in healthy controls (P = 0.011). The frequencies of GITR⁺ and PD-1⁺ Tregs were significantly higher in acute and chronic patients than in healthy controls (P < 0.05), with no significant difference between the acute and chronic groups (all P > 0.05). Serum TGF-β1 levels were higher in chronic patients (P = 0.029) and serum IL-10 levels were higher in acute patients (P = 0.033) than in healthy controls. We detected weak correlations between serum TGF-β1 levels and the frequencies of Tregs (R = 0.309, P = 0.031) and CTLA-4⁺ Tregs (R = 0.302, P = 0.035).

Conclusions

Treg cell immunity is involved in the chronicity of Brucella infection and indicates the implication of Tregs in the prognosis of brucellosis. CTLA-4 and TGF-β1 may contribute to Tregs-mediated immunosuppression in the chronic infection stage of a Brucella infection.

Clinical and laboratory characteristics of childhood brucellosis in high-risk area of Western China

Childhood brucellosis present various non-specific clinical symptoms, and limited laboratory data exist for clinical diagnosis. A better understanding of these clinical and laboratory characteristics can avoid clinical misdiagnosis and mistreatment. In this case-series study, a total of 78 children with confirmed diagnosis of brucellosis were evaluated retrospectively. We observed that the incidence rate was higher in the first two quarters every year. The most common symptom was fever. Osteoarticular involvement was found in 44.87% of the patients. Laboratory tests showed that the values of erythrocyte sedimentation rate(ESR), C-reactive protein(CRP), Hemoglobin(Hb), Neutrophils(NEU), Alanine aminotransfease(ALT) and Ferritin in childhood brucellosis with osteoarticular involvement had significant differences than those without osteoarticular involvement or control group (P<0.05). Childhood brucellosis without osteoarticular involvement often accompanied by decrease of NEU , increase of CRP and ALT compared with that control group (P<0.05). The Receiver Operating Curves (ROC) analysis revealed that NEU, CRP and ALT can be used as adjunct parameters in the differential diagnosis of childhood brucellosis. These data suggest that clinical and laboratory characteristics are very important for every clinician, which may have a complementary role in diagnosis of childhood brucellosis.

Protective efficacy of attenuated Salmonella Typhimurium strain expressing BLS, Omp19, PrpA, or SOD of Brucella abortus in goats

Background

Attenuated Salmonella strain can be used as a vector to transport immunogens to the host antigen-binding sites.

Objectives

The study aimed to determine the protective efficacy of attenuated Salmonella strain expressing highly conserved Brucella immunogens in goats.

Methods

Goats were vaccinated with Salmonella vector expressing individually lipoprotein outer-membrane protein 19 (Omp19), Brucella lumazine synthase (BLS), proline racemase subunit A (PrpA), Cu/Zn superoxide dismutase (SOD) at 5 × 10⁹ CFU/mL and challenge of all groups was done at 6 weeks after vaccination.

Results

Among these vaccines inoculated at 5 × 10⁹ CFU/mL in 1 mL, Omp19 or SOD showed significantly higher serum immunoglobulin G titers at (2, 4, and 6) weeks post-vaccination, compared to the vector control. Interferon-γ production in response to individual antigens was significantly higher in SOD, Omp19, PrpA, and BLS individual groups, compared to that in the vector control (all p < 0.05). Brucella colonization rate at 8 weeks post-challenge showed that most vaccine-treated groups exhibited significantly increased protection by demonstrating reduced numbers of Brucella in tissues collected from vaccinated groups. Real-time polymerase chain reaction revealed that Brucella antigen expression levels were reduced in the spleen, kidney, and parotid lymph node of vaccinated goats, compared to the non-vaccinated goats. Besides, treatment with vaccine expressing individual antigens ameliorated brucellosis-related histopathological lesions.

Conclusions

These results delineated that BLS, Omp19, PrpA, and SOD proteins achieved a definite level of protection, indicating that Salmonella Typhimurium successfully delivered Brucella antigens, and that individual vaccines could differentially elicit an antigen-specific immune response.

Immunometabolism in human brucellosis: An emerging field of investigation

In recent years, extreme attention has been focused on the role of immunometabolism in the regulation of immune cell responses in healthy individuals during infection, autoimmunity, and cancer. In the infection biology area, it has been shown that there is a close relationship between the immune system and the host metabolic changes. Brucella species is an intracellular coccobacillus that infects humans and mammals, which led to brucellosis. Brucella species with host-specific evolutionary mechanisms allow it to hide from or manipulate cellular immunity and achieve intracellular persistence. Intracellular bacterial pathogens such as Brucella species also employ host cell resources to replicate and persist inside the host. Targeting these host systems is one promising strategy for developing novel antimicrobials to tackle intracellular infections. This study will summarize the role of metabolic reprogramming in immune cells and their relationship to brucellosis.

RNA-Seq Analysis Reveals the Role of Omp16 in Brucella-Infected RAW264.7 Cells

Brucellosis is an endemic zoonotic infectious disease in the majority of developing countries, which causes huge economic losses. As immunogenic and protective antigens at the surface of Brucella spp., outer membrane proteins (Omps) are particularly attractive for developing vaccine and could have more relevant role in host–pathogen interactions. Omp16, a homolog to peptidoglycan-associated lipoproteins (Pals), is essential for Brucella survival in vitro. At present, the functions of Omp16 have been poorly studied. Here, the gene expression profile of RAW264.7 cells infected with Brucella suis vaccine strain 2 (B. suis S2) and ΔOmp16 was analyzed by RNA-seq to investigate the cellular response immediately after Brucella entry. The RNA-sequence analysis revealed that a total of 303 genes were significantly regulated by B. suis S2 24 h post-infection. Of these, 273 differentially expressed genes (DEGs) were upregulated, and 30 DEGs were downregulated. These DEGs were mainly involved in innate immune signaling pathways, including pattern recognition receptors (PRRs), proinflammatory cytokines, and chemokines by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. In ΔOmp16-infected cells, the expression of 52 total cells genes was significantly upregulated and that of 9 total cells genes were downregulated compared to B. suis S2-infected RAW264.7 cells. The KEGG pathway analysis showed that several upregulated genes were proinflammatory cytokines and chemokines, such as interleukin (IL)-6, IL-11, IL-12β, C–C motif chemokine (CCL2), and CCL22. All together, we clearly demonstrate that ΔOmp16 can alter macrophage immune-related pathways to increase proinflammatory cytokines and chemokines, which provide insights into illuminating the Brucella pathogenic strategies.

Soluble IL-2Rα correlates with imbalances of Th1/Th2 and Tc1/Tc2 cells in patients with acute brucellosis

Background

Previous studies showed that soluble IL-2Rα is an important marker of cellular immune activation and might be a marker of treatment efficacy for children with brucellosis. However, data regarding adult patients with brucellosis were unknown. The aim of study was to explore the potential role of serum sIL-2Rα evaluating treatment responses in adult patients with brucellosis, and T cell immune status was also examined.

Methods

During January 2016–April 2017, 30 patients with acute brucellosis from the Third People’s Hospital of Linfen in Shanxi Province and Beijing Di Tan Hospital, and 28 healthy controls were included in this study. Peripheral blood samples were collected before and after six weeks of antibiotic treatment. Serum sIL-2Rα levels were measured by enzyme-linked immunosorbent assay, and the percentage of Th1, Th2, Tc1, Tc2, and Tregs was detected by flow cytometry after intracellular staining for cytokines (interferon-γ and interleukin-4) and Foxp3 in T lymphocytes from peripheral blood. The obtained data were analyzed with Wilcoxon ranked sum tests for paired values, Mann-Whitney U-tests for comparisons between patients and healthy controls, and Spearman rank tests for correlation analyses.

Results

Serum sIL-2Rα levels were significantly higher in patients than in controls (P = 0.001). A significant decline was observed in patients after the cessation of treatment (P < 0.001) and return to normal (P > 0.05). Th1, Tc1, Th2, and Tc2 cell frequencies were higher in patients than in healthy subjects (P < 0.05), while the Th1/Th2 and Tc1/Tc2 ratios were significantly lower (P = 0.0305 and 0.0005, respectively) and returned to normal levels after treatment. In patients with acute brucellosis, serum sIL-2Rα levels were negatively correlated with the Th1/Th2 ratio (r = − 0.478, P = 0.028), Tc1/Tc2 ratio (r = − 0.677, P = 0.001), and Tc1 percentage (r = − 0.516, P = 0.017). Serum sIL-2Rα and Tc2 percentages were positively correlated (r = 0.442, P = 0.045).

Conclusions

Based on the correlations with Th1/Th2 and Tc1/Tc2 ratios, serum sIL-2Rα levels may reflect the immune response status. sIL-2Rα may be a marker for therapeutic efficacy in acute brucellosis.

Investigation of Linc-MAF-4 expression as an effective marker in brucellosis

Brucellosis is a zoonotic disease that is one of the most common infectious diseases. Cellular immunity is the main immune response against brucella. Long non coding RNAs are a new subset of genes that could regulate cell function and may gene regulation. We aim to investigate whether the level of Linc-MAF-4 and cMAF have considerable differences in brucella infection. In this experiment 99 patients with brucellosis were divided into three groups of acute, undertreatment and relapse and 30 volunteers with negative serologic tests as control group. The expression levels were detected using quantitative polymerase chain reaction (qPCR). Statistical analysis was performed using SPSS software version 25.0. Results showed that the expression of Linc-MAF-4 was significantly increased in the acute group in comparison to control and relapse groups. Also, cMAF expression was significantly increased in the relapse group versus the control group. Our study showed these genes play important roles in the immune response include regulating naïve T cell differentiation to T helper cells in Brucella infection. We propose that Linc-MAF-4 could be a potential biomarker for the screening, diagnosis and treatment of brucellosis.

Brucella Infection Regulates Thioredoxin-Interacting Protein Expression to Facilitate Intracellular Survival by Reducing the Production of Nitric Oxide and Reactive Oxygen Species

Thioredoxin-interacting protein (TXNIP) is a multifunctional protein that functions in tumor suppression, oxidative stress, and inflammatory responses. However, how TXNIP functions during microbial infections is rarely reported. In this study, we demonstrate that Brucella infection decreased TXNIP expression to promote its intracellular growth in macrophages by decreasing the production of NO and reactive oxygen species (ROS). Following Brucella abortus infection, TXNIP knockout RAW264.7 cells produced significantly lower levels of NO and ROS, compared with wild-type RAW264.7 cells. Inducible NO synthase (iNOS) inhibitor treatment reduced NO levels, which resulted in a dose-dependent restoration of TXNIP expression, demonstrating that the expression of TXNIP is regulated by NO. In addition, the expression of iNOS and the production of NO were dependent on the type IV secretion system of Brucella Moreover, Brucella infection reduced TXNIP expression in bone marrow-derived macrophages and mouse lung and spleen. Knocked down of the TXNIP expression in bone marrow-derived macrophages increased intracellular survival of Brucella These findings revealed the following: 1) TXNIP is a novel molecule to promote Brucella intracellular survival by reducing the production of NO and ROS; 2) a negative feedback-regulation system of NO confers protection against iNOS-mediated antibacterial effects. The elucidation of this mechanism may reveal a novel host surveillance pathway for bacterial intracellular survival.

Myeloid differentiation factor 88 (Myd88) is involved in the innate immunity of black carp (Mylopharyngodon piceus) defense against pathogen infection

Myeloid differentiation factor 88 (MyD88) is an important transduction protein in the Toll-like receptor signaling pathway. In this study, we identified the cDNA of the MpMyD88 gene in black carp. We found that MpMyD88 was widely distributed in the tissues tested and showed significant immune responses both in vitro and in vivo after stimulation with bacterial and pathogen-associated molecular patterns. After MpMyD88 overexpression/silencing, proinflame-matory cytokines (TNF-α, IFN-α, IL-6, and IL-8) also showed significant up-regulation/down-regulation. Moreover, we found that the antibacterial ability of cells over-expressing MpMyD88 was significantly stronger than that of control cells, while that of silenced MpMyD88 was significantly lower than that in control cells. Besides, we found that the overexpression of MpMyD88 significantly increased the activity of NF-κB. These results indicate that MpMyD88 plays an important role in the innate immune response.

A potential marker in brucellosis, long non coding RNA IFNG-AS1

Brucellosis is the most common bacterial zoonotic infection. This pathogen may survive and sustain in host. The aim of this study is to define relationship between long noncoding (lnc) RNA-IFNG-AS1 and interferon gamma (IFN-γ) in different groups of patients with brucellosis compared to control group. In this study, associations of lncRNA IFNG-AS1 expression with secretion of IFN-γ level in Sixty patients with brucellosis, which were divided into 3 groups (acute, chronic and relapse groups), as a case group were compared with 20 subjects with negative serological tests and brucellosis clinical manifestation as a control group. In this regard, RNA were extracted from isolated peripheral blood mononuclear cells (PBMCs). LncRNA IFNG-AS1, T-box transcription factor (T-bet) and IFN-γ expressions were detected using quantitative polymerase chain reaction (qPCR). Serum level IFN-γ was assessed using enzyme linked immunosorbent assay (ELISA). The results showed that expression level of LncRNA IFNG-AS1, T-bet and IFN-γ increased significantly in all patient groups in compared to healthy subjects (P < 0.0001, P < 0.01, P < 0.001). However, there was no significant difference in T-bet expression between chronic and healthy groups (P = 0.98). Additionally, further analysis revealed that the serum level of IFN-γ in acute and relapsed groups were higher than control group (P < 0.0001, P < 0.001). The effective role of IFNG-AS1 in many protective actions, including enhancing the expression of INF-γ in the immune response of brucellosis patients, revealed new potential marker, LncRNA IFNG-AS1 in screening, diagnosis or treatment of brucellosis.

Dynamic Changes of Th1 Cytokines and the Clinical Significance of the IFN-γ/TNF-α Ratio in Acute Brucellosis

Background

T-helper type 1 (Th1) cells and Th1-produced cytokines play essential roles in the immune response to foreign pathogens, such as Brucella spp. The aim of this study was to evaluate the dynamic changes of Th1 cells and Th1-produced cytokines in patients with acute brucellosis and their impact on clinical decision-making.

Methods

Fifty-one individuals with acute brucellosis and 17 healthy subjects were enrolled in this study. The brucellosis patients were diagnosed based on clinical symptoms, laboratory tests, and clinical examination. The levels of serum gamma-interferon (IFN-γ) and tumor necrosis factor-alpha (TNF-α), along with the percentage of Th1 cells, were determined by flow cytometry bead arrays (CBA).

Results

The frequency of Th1 cells, along with the levels of IFN-γ and TNF-α, was negatively correlated with the clinical parameters. The mean serum levels of IFN-γ and TNF-α and the frequency of Th1 cells were significantly higher in the brucellosis patients in comparison with the healthy subjects (p < 0.05). Besides, the cytokine levels were not significantly different between the positive and negative blood culture groups. IFN-γ levels significantly decreased from 6 months to 12 months post treatment (p < 0.05). However, the IFN-γ levels remained higher than those of the healthy subjects by 12 months post treatment (p < 0.05). The IFN-γ/TNF-α ratio was significantly higher in severe cases than in nonsevere cases (p < 0.05).

Conclusions

The IFN-γ levels secreted by Th1 cells remain significantly higher than those of healthy subjects more than 12 months after treatment with antibiotics. This finding is different from similar studies. The IFN-γ/TNF-α ratio may be a feasible parameter for assessing clinical severity, yet further longitudinal studies of the immunization and inflammatory reaction of brucellosis are needed in larger patient populations.

Bacterial RNA Contributes to the Down-Modulation of MHC-II Expression on Monocytes/Macrophages Diminishing CD4+ T Cell Responses

Brucella abortus, the causative agent of brucellosis, displays many resources to evade T cell responses conducive to persist inside the host. Our laboratory has previously showed that infection of human monocytes with B. abortus down-modulates the IFN-γ-induced MHC-II expression. Brucella outer membrane lipoproteins are structural components involved in this phenomenon. Moreover, IL-6 is the soluble factor that mediated MHC-II down-regulation. Yet, the MHC-II down-regulation exerted by lipoproteins was less marked than the one observed as consequence of infection. This led us to postulate that there should be other components associated with viable bacteria that may act together with lipoproteins in order to diminish MHC-II. Our group has recently demonstrated that B. abortus RNA (PAMP related to pathogens' viability or vita-PAMP) is involved in MHC-I down-regulation. Therefore, in this study we investigated if B. abortus RNA could be contributing to the down-regulation of MHC-II. This PAMP significantly down-modulated the IFN-γ-induced MHC-II surface expression on THP-1 cells as well as in primary human monocytes and murine bone marrow macrophages. The expression of other molecules up-regulated by IFN-γ (such as co-stimulatory molecules) was stimulated on monocytes treated with B. abortus RNA. This result shows that this PAMP does not alter all IFN-γ-induced molecules globally. We also showed that other bacterial and parasitic RNAs caused MHC-II surface expression down-modulation indicating that this phenomenon is not restricted to B. abortus. Moreover, completely degraded RNA was also able to reproduce the phenomenon. MHC-II down-regulation on monocytes treated with RNA and L-Omp19 (a prototypical lipoprotein of B. abortus) was more pronounced than in monocytes stimulated with both components separately. We also demonstrated that B. abortus RNA along with its lipoproteins decrease MHC-II surface expression predominantly by a mechanism of inhibition of MHC-II expression. Regarding the signaling pathway, we demonstrated that IL-6 is a soluble factor implicated in B. abortus RNA and lipoproteins-triggered MHC-II surface down-regulation. Finally, CD4⁺ T cells functionality was affected as macrophages treated with these components showed lower antigen presentation capacity. Therefore, B. abortus RNA and lipoproteins are two PAMPs that contribute to MHC-II down-regulation on monocytes/macrophages diminishing CD4⁺ T cell responses.

Human NK cell receptor KIR2DS4 detects a conserved bacterial epitope presented by HLA-C

Natural killer (NK) cells have an important role in immune defense against viruses and cancer. Activation of human NK cell cytotoxicity toward infected or tumor cells is regulated by killer cell immunoglobulin-like receptors (KIRs) that bind to human leukocyte antigen class I (HLA-I). Combinations of KIR with HLA-I are genetically associated with susceptibility to disease. KIR2DS4, an activating member of the KIR family with poorly defined ligands, is a receptor of unknown function. Here, we show that KIR2DS4 has a strong preference for rare peptides carrying a Trp at position 8 (p8) of 9-mer peptides bound to HLA-C*05:01. The complex of a peptide bound to HLA-C*05:01 with a Trp at p8 was sufficient for activation of primary KIR2DS4+ NK cells, independent of activation by other receptors and of prior NK cell licensing. HLA-C*05:01+ cells that expressed the peptide epitope triggered KIR2DS4+ NK cell degranulation. We show an inverse correlation of the worldwide allele frequency of functional KIR2DS4 with that of HLA-C*05:01, indicative of functional interaction and balancing selection. We found a highly conserved peptide sequence motif for HLA-C*05:01-restricted activation of human KIR2DS4+ NK cells in bacterial recombinase A (RecA). KIR2DS4+ NK cells were stimulated by RecA epitopes from multiple human pathogens, including Helicobacter, Chlamydia, Brucella, and Campylobacter. We predict that over 1,000 bacterial species could activate NK cells through KIR2DS4, and propose that human NK cells also contribute to immune defense against bacteria through recognition of a conserved RecA epitope presented by HLA-C*05:01.

Brucella infection regulates peroxiredoxin-5 protein expression to facilitate intracellular survival by reducing the production of nitric oxide and reactive oxygen species

Peroxiredoxin-5 (Prdx5) is a multifunctional protein involved in oxidative stress, apoptosis and inflammatory responses. However, how Prdx5 functions during microbial infections is rarely reported. In this study, we demonstrate that Brucella infection increased Prdx5 expression to promote its intracellular growth in macrophages. Further study show that B. abortus infection promoted its intracellular growth by decreasing the production of nitric oxide and reactive oxygen species. In addition, the expression of Prdx5 was independent on live Brucella and the type IV secretion system of Brucella. Instead, its expression was regulated by the lipopolysaccharide of Brucella. Moreover, Brucella infection increased Prdx5 expression in primary macrophage and mice. Collectively, these findings demonstrate for the first time that Prdx5 promotes Brucella intracellular growth by decreasing the production of NO and ROS. This finding provides new insights into the evasive strategies of Brucella and will be useful for the development of novel effective therapeutic approaches to treat Brucella infections.

Direct correlation between Th1 and Th17 responses in immunity to Brucella infection

Th1 cells play a central role in immunity to brucellosis, while the exact role of Th17 cells has remained unknown. This study aimed to evaluate the peripheral distributions of Th1 and Th17 cells and serum levels of IFN-γ, IL-17A and IL-22 cytokines in brucellosis patients. One hundred patients (36 acute, 41 under-treatment and 23 relapsed) and 30 age- and sex-matched healthy controls were included. The frequencies of Th1 and Th17 cells were determined by flow cytometric analysis. Serum levels of IFN-γ, IL-17A and IL-22 were measured by multi-analyte flow assay. Increased frequencies of Th1 and Th17 cells were observed in acute and relapsed brucellosis versus under-treatment patients and healthy controls (P < 0.05). The mean serum levels of IFN-γ were significantly elevated in acute and relapsed groups compared to under-treatment patients (P = 0.002 and P = 0.01 respectively). Acute patients showed higher levels of IL-22 than under-treatment (P = 0.008). Direct correlations were found between increased frequencies of Th1 and Th17 cells in acute and relapsed patients (P = 0.007 and P = 0.001 respectively) and between IL-17A and IL-22 in both groups of patients. Our findings indicate a cooperative role for Th1 and Th17 cells in immunity to brucellosis which is more evident during acute and relapse phases of brucellosis.

A review of the immunopathogenesis of Brucellosis

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

Inhibition of antigen presentation by Brucella: many more than many ways

Brucella infection activates the immune system and favors the differentiation of CD4⁺ and CD8⁺ T cells. To persist during a long time inside macrophages evading immune surveillance of these T cells the pathogen must exploit different evasion strategies. We review the mechanisms whereby Brucella, through TLR signaling, inhibits MHC class I and II antigen presentation, allowing infected macrophages to become effective niches for Brucella survival.

Transcriptome analysis and histopathology of black carp (Mylopharyngodon piceus) spleen infected by Aeromonas hydrophila

Aeromonas hydrophila causes serious economic losses to the black carp (Mylopharyngodon piceus) industry. In this study, we analyzed the spleen of disease-resistant and susceptible black carp by RNA-seq. Overall, a total of 5243 terms were enriched in the gene ontology (GO) analysis, and 323 related pathways were found in the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. A total of 1935 differentially expressed genes were found and were primarily involved in cell adhesion, pathogen recognition, cellular immunity, cytokines, complement systems, and iron transport. Sixteen of the differently expressed genes involved in the immune response and the accuracy of the transcriptome data were further validated by quantitative real-time PCR (qRT-PCR). We observed Tissue sections of the spleen infected with A. hydrophila and the control group and found that the spleen of the infected group had necrosis.

A Neglected Animal Model for a Neglected Disease: Guinea Pigs and the Search for an Improved Animal Model for Human Brucellosis

Brucellosis is a bacterial disease caused by species of the Brucella genus and affects a wide variety of domestic and wildlife species and is also an important zoonosis. The global burden of disease is difficult to assess but Brucella spp. have a worldwide distribution and are endemic in the Middle East, Africa, South America, and Asia. The clinical signs of fever and malaise are non-specific, and the available serological diagnostic tests lack a high degree specificity in endemic regions compared to other important public health diseases such as malaria. A better understanding of the pathogenesis of brucellosis through discoveries in animal models could lead to improved diagnostics and potentially a vaccine for human use. Mouse models have played an important role in elucidating the pathogenesis but do not replicate key features of the disease such as fever. Guinea pigs were instrumental in exploring the pathogenesis of brucellosis in the early nineteenth century and could offer an improvement on the mouse model as a model for human brucellosis.

The immunomodulatory effect of antimicrobial peptide HPA3P restricts Brucella abortus 544 infection in BALB/c mice

The discovery of antimicrobial peptides (AMPs) in recent years has been promising for the treatment of multidrug resistant pathogenic microbes. Brucellosis is still considered one of the most common zoonoses in the world. In this study, we evaluated the effect HPA3P peptide in the bacterial uptake and intracellular growth of Brucella abortus (B. abortus) 544 in murine macrophages RAW 264.7. HPA3P was further utilized in a mouse model for infection and treatment. This peptide did not show cytotoxicity or bactericidal effect to B. abortus. However, it inhibited bacterial internalization at 0, 15 and 30 min incubation at two different doses at 12 and 24 μM as well as reduced intracellular growth after 2, 24 and 48 h incubation. Mice treated with HPA3P demonstrated a significant 1.01-log reduction (P < 0.0001) and spleen weight reduction compared to the nanocarrier control (P < 0.01). Significant increases in key cytokines Interferon-γ (IFN-γ) and Tumor necrosis factor (TNF) at 3, 7 and 14 days post-infection were observed in HPA3P treated mice similar to the antibiotic control group with both compared to the nanocarrier control. Monocyte chemoattractant protein-1 (MCP-1) was also heightened at 14 days post-infection. Histopathological analysis also suggests reduced bacterial granuloma in the liver and spleens of HPA3P treated group compared with the nanocarrier control group. In this study, the modulation of crucial cytokines IFN-γ and TNF might have led to a considerable reduction in the proliferation of B. abortus in a mouse model of brucellosis. Further investigation might be required to maximize the efficacy of HPA3P treatment in murine brucellosis.

The relationship between caspase-1 related inflammasome expression and serum inflammatory cytokine levels during acute brucellosis

OBJECTIVE

Brucellosis is a zoonotic disease caused by Brucella in domestic and wild animals. It also causes systemic diseases with the involvement of different parts of the human body. An efficient innate immune response is crucial to cure brucellosis with optimum antibiotic treatment. The inflammasomes are innate immune system receptors and sensors that regulate the activation of cysteine-dependent aspartate specific protease-1 (caspase-1) and caspase-1-induced cell death process known as pyroptosis. The aim of the present study was to investigate the expression levels of CASPASE-1 and associated inflammasomes AIM2, NLRP3, and NLRC4 to analyze their relationship with the inflammatory cytokine interleukin (IL)-1β, IL-18, and interferon-gamma (IFN-γ) in peripheral blood samples of patients with acute brucellosis with healthy controls.

METHODS

Peripheral blood samples were obtained from 20 healthy volunteers and 20 patients with acute brucellosis. RNA and serum samples were isolated to examine the expression levels of AIM2, NLRP3, NLRC4, and CASPASE-1 by real-time polymerase chain reaction, and IL-1β, IL-18, and IFN-γ were measured by enzyme-linked immunosorbent assay.

RESULTS

In the acute brucellosis group, AIM2 and NLRC4 expressions were significantly higher than in healthy volunteers. A significant increase on caspase-1 expression in patients with acute brucellosis was not observed. Serum IL-18 and IFN-γ levels were significantly higher in patients with acute brucellosis than in healthy controls.

CONCLUSION

Caspase-1-related inflammasomes are sufficiently activated to induce the secretion of cytokines, such as IFN-γ and IL-18, to induce cellular immune response. Caspase-1 activation level should be investigated at different periods of disease in a group with high number of patients to understand the role of pyroptosis and caspase-1 in brucellosis.

Global gene-expression profiles of intracellular survival of the BruAb2_1031 gene mutated Brucella abortus in professional phagocytes, RAW 264.7 cells

Background

Since recognizing the interaction between Brucella and host cells is crucial to the elucidation of the infectious process, Brucella researches have prioritized the investigation of genes related to pathogenicity. To demonstrate the roles of Brucella genes, RAW 264.7 cells were infected with the Brucella abortus wild-type and mutant strains (generated using transposon mutagenesis), after which the different transcriptional responses of the infected cells were determined using microarray.

Results

Following infection, enhanced strategies for intracellular survival, such as down-regulation of genes associated with cytokine responses and apoptosis, were observed in RAW 264.7 cells infected with C3 mutant strain when compared to the transcriptional responses of wild-type infected cells. Using sequence analysis, we determined the mutation site of a C3 mutant strain as the ATP-binding cassette transporter permease (BruAb2_1031). These results were evidenced by an increased level of intracellular survival of the C3 mutant strain.

Conclusions

Characteristics of each mutant strain including bacterial growth rate, abilities to induce cytokine production in macrophages after infection, internalization, and levels of intracellular survival and replication, were investigated by performing RAW 264.7 cell infection experiments. Our results indicate that the BruAb2_1031 gene might be closely related with intracellular survival of B. abortus in RAW 264.7 cells.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1223-7) contains supplementary material, which is available to authorized users.

Study of serum bactericidal and splenic activity of Total-OMP- CagA combination from Brucella abortus and Helicobacter pylori in BALB/c mouse model

BACKGROUND

Brucella is a Gram-negative and facultative intracellular organism that causes brucellosis, a common zoonotic disease. Over 500,000 people are annually affected by brucellosis. Brucella is highly infectious through inhalation route; for this reason it is used for biological warfare aims. This study aimed to study the serum bactericidal and splenic activity of Total-OMP-r CagA immunogens from Brucella abortus and Helicobacter pylori in a BALB/c mouse model.

METHODS

Immunization of BALB/c mice was performed with immunogenic proteins three times subcutaneously (S.C.) at 14-day intervals. The protective effects of two component vaccines with CpG adjuvant were evaluated after mice were challenged with H. pylori ss1 and Brucella abortus strain 544. The specific IgG1 and IgG2a antibodies in sera were assessed using ELISA test. For measuring the antigen-specific IL-4, IL-12 and IFN-γ responses in sera of immunized mice after challenge, RT-PCR technique was applied. Twenty days after the challenge, mice were killed then gastric, splenic and serum samples were assessed and bacterial colony count was measured based on the pour plate count agar.

RESULTS

The results indicated that rCagA + OMP decreased bacterial colonization in these tissues, and significant difference was observed between test and control groups (p value˂0.001).

CONCLUSION

Our results showed that the combination vaccine was effective against an oral exposure and the bacterial burden in the spleen, serum and gastric tissues were reduced in mice immunized with the Total- OMP-CagA.

Assessment of TGF-β and IL10 levels in human brucellosis

The recent study assessed TGF-β and IL-10 as immunosuppressive cytokines of the cell mediated immunity (CMI) against Brucella in the serum of some brucellosis patients. Serum from 15 patients and 15 healthy individuals were obtained, and then cytokine concentrations above were investigated. Concentrations of TGF-β induced in the serum of acute patients (89.73 ± 15.55 ng/ml) were higher than healthy group (58.86 ± 17.89 ng/ml, P < 0.0001). While, no significant differences were found in the concentration of IL-10 between two groups. Based upon the findings of our study, the contribution of these cytokines to the pathobiology of infection had been shown. Therefore, assessment of immunosuppressive cytokines as TGF-β and IL-10 levels may be a potential diagnostic strategy for patients with brucellosis.

An Autoimmune Disease-Associated Risk Variant in the TNFAIP3 Gene Plays a Protective Role in Brucellosis That Is Mediated by the NF-κB Signaling Pathway

Naturally occurring functional variants (rs148314165 and rs200820567, collectively referred to as TT>A) reduce the expression of the tumor necrosis factor alpha-induced protein 3 (TNFAIP3) gene, a negative regulator of NF-κB signaling, and predispose individuals to autoimmune disease. In this analysis, we conducted a genetic association study of the TT>A variants in 1,209 controls and 150 patients with brucellosis, an infectious disease, and further assessed the role of the variants in brucellosis. Our data demonstrated that the TT>A variants were correlated with cases of brucellosis (P = 0.002; odds ratio [OR] = 0.34) and with individuals who had a positive serum agglutination test (SAT) result (titer of >1/160) (P = 4.2 × 10-6; OR = 0.23). A functional study demonstrated that brucellosis patients carrying the protective allele (A) showed significantly lower expression levels of the TNFAIP3 gene in their peripheral blood mononuclear cells and showed increased NF-κB signaling. Monocytes from individuals carrying the A allele that were stimulated with Brucella abortus had lower mRNA levels of TNFAIP3 and produced more interleukin-10 (IL-10), IL-6, and IL-1β than those from TT allele carriers. These data showed that autoimmune disease-associated risk variants, TT>A, of the TNFAIP3 locus play a protective role in the pathogenesis of brucellosis. Our findings suggest that a disruption of the normal function of the TNFAIP3 gene might serve as a therapeutic target for the treatment of brucellosis.

B. abortus RNA is the component involved in the down-modulation of MHC-I expression on human monocytes via TLR8 and the EGFR pathway

Despite eliciting a potent CD8⁺ T cell response, Brucella abortus is able to persist and establish a chronic infection inside its host. We have previously reported that the infection of human monocytes/macrophages with B. abortus inhibits the IFN-γ-induced MHC-I cell surface expression down-modulating cytotoxic CD8⁺ T cell responses. MHC-I down-modulation depends on bacterial viability and results from the capacity of B. abortus to retain the MHC-I molecules within the Golgi apparatus. Furthermore, we recently demonstrated that epidermal growth factor receptor (EGFR) pathway is involved in this phenomenon and that this is an early event during infection. However, the components and mechanisms whereby B. abortus is able to down-modulate MHC-I remained to be elucidated. In this study we demonstrated that the down-modulation of MHC-I expression is not mediated by well-known Brucella virulence factors but instead by B. abortus RNA, a PAMP associated to viability (vita-PAMP). Surprisingly, completely degraded RNA was also able to inhibit MHC-I expression to the same extent as intact RNA. Accordingly, B. abortus RNA and its degradation products were able to mimic the MHC-I intracellular retention within the Golgi apparatus observed upon infection. We further demonstrated that TLR8, a single-stranded RNA and RNA degradation products sensor, was involved in MHC-I inhibition. On the other hand, neutralization of the EGFR reversed the MHC-I inhibition, suggesting a connection between the TLR8 and EGFR pathways. Finally, B. abortus RNA-treated macrophages display diminished capacity of antigen presentation to CD8⁺ T cells. Overall, our results indicate that the vita-PAMP RNA as well as its degradation products constitute novel virulence factors whereby B. abortus, by a TLR8-dependent mechanism and through the EGFR pathway, inhibits the IFN-γ-induced MHC-I surface expression on human monocytes/macrophages. Thus, bacteria can hide within infected cells and avoid the immunological surveillance of cytotoxic CD8⁺ T cells.

Brucella abortus is one of the intracellular bacterial species that cause brucellosis, a zoonotic worldwide disease. An intricate enigma of Brucella immunity is its long-term persistence inside host despite a vigorous and specific immune response. Our study describes a novel immune evasion strategy exploited by B. abortus: the down-modulation of the IFN-γ-induced expression of the molecules responsible for antigen presentation to CD8⁺ T cells on the surface of monocytes, Major Histocompatibility Complex Class I (MHC-I) molecules. We found that the bacterial component responsible for this phenomenon is its RNA, a component associated with bacterial viability itself. Specifically, we demonstrated that not only does intact RNA down-modulate MHC-I but also the RNA degradation products. Bacterial RNA is sensed by pattern recognition receptors (PRRs), among which TLRs family has gained more attention. In this study, we demonstrated that the receptor involved in this phenomenon is TLR8, a single-stranded RNA and RNA degradation products sensor. By means of this mechanism, Brucella impairs antigen presentation to CD8⁺ T cells, hiding within infected cells and avoiding the immunological surveillance of cytotoxic cells. On balance, these results provide new evidence to understand how B. abortus can survive inside the host and persist chronically.

Inhibition of MHC-I by Brucella abortus is an early event during infection and involves EGFR pathway

Brucella abortus is able to persist inside the host despite the development of potent CD8⁺ T-cell responses. We have recently reported the ability of B. abortus to inhibit the interferon-γ-induced major histocompatibility complex (MHC)-I cell surface expression on human monocytes. This phenomenon was due to the B. abortus-mediated retention of MHC-I molecules within the Golgi apparatus and was dependent on bacterial viability. However, the implications of bacterial virulence or replicative capacity and the signaling pathways remained unknown. Here we demonstrated that the B. abortus mutant strains RB51 and virB10^- are able to inhibit MHC-I expression in the same manner as wild-type B. abortus, even though they are unable to persist inside human monocytes for a long period of time. Consistent with this, the phenomenon was triggered early in time and could be observed at 8 h postinfection. At 24 and 48 h, it was even stronger. Regarding the signaling pathway, targeting epidermal growth factor (EGF) receptor (EGFR), ErbB2 (HER2) or inhibition of tumor necrosis factor-α-converting enzyme, one of the enzymes which generates soluble EGF-like ligands, resulted in partial recovery of MHC-I surface expression. Moreover, recombinant EGF and transforming growth factor-α as well as the combination of both were also able to reproduce the B. abortus-induced MHC-I downmodulation. Finally, when infection was performed in the presence of an extracellular signal-regulated kinase 1/2 (Erk1/2) inhibitor, MHC-I surface expression was significantly recovered. Overall, these results describe how B. abortus evades CD8⁺ T-cell responses early during infection and exploits the EGFR-ERK signaling pathway to escape from the immune system and favor chronicity.