Chronic exposure to staphylococcal superantigen elicits a systemic inflammatory disease mimicking lupus

Topical Mupirocin Treatment Reduces Interferon and Myeloid Signatures in Cutaneous Lupus Erythematous Lesions Through Targeting of Staphyloccal Species

OBJECTIVE

Cutaneous lupus erythematosus (CLE) is an inflammatory skin manifestation of systemic lupus erythematosus. Type I interferons (IFNs) promote inflammatory responses and are elevated in CLE lesions. We recently reported that CLE lesions are frequently colonized with Staphylococcus aureus. Here, we follow up via a proof-of-concept study to investigate whether type I IFN and inflammatory gene signatures in CLE lesions can be modulated with mupirocin, a topical antibiotic treatment against S aureus-mediated skin infections.

METHODS

Participants with active CLE lesions (n = 12) were recruited and randomized into a week of topical treatment with either 2% mupirocin or petroleum jelly vehicle. Paired samples were collected before and after seven days of treatment to assess microbial lesional skin responses. Microbial samples from nares and lesional skin were used to determine baseline and posttreatment Staphylococcus abundance and microbial community profiles by 16S ribosomal RNA gene sequencing. Inflammatory responses were evaluated by bulk RNA sequencing of lesional skin biopsies.

RESULTS

We identified 173 differentially expressed genes in CLE lesions after topical mupirocin treatment. Decreased lesional Staphylococcus burden correlated with decreased IFN pathway signaling and inflammatory gene expression and barrier dysfunction. Interestingly, mupirocin treatment lowered skin monocyte levels, and this mupirocin-associated depletion of monocytes correlated with decreased inflammatory gene expression.

CONCLUSION

Mupirocin treatment decreased lesional Staphylococcus, and this correlated with decreased IFN signaling and inflammatory gene expression. This study suggests a topical antibiotic could be employed to decrease lupus skin inflammation and type I IFN responses by reducing Staphylococcus colonization.

Novel insights into the immune response to bacterial T cell superantigens

Bacterial T cell superantigens (SAgs) are a family of microbial exotoxins that function to activate large numbers of T cells simultaneously. SAgs activate T cells by direct binding and crosslinking of the lateral regions of MHC class II molecules on antigen-presenting cells with T cell receptors (TCRs) on T cells; these interactions alter the normal TCR-peptide-MHC class II architecture to activate T cells in a manner that is independent of the antigen specificity of the TCR. SAgs have well-recognized, central roles in human diseases such as toxic shock syndrome and scarlet fever through their quantitative effects on the T cell response; in addition, numerous other consequences of SAg-driven T cell activation are now being recognized, including direct roles in the pathogenesis of endocarditis, bloodstream infections, skin disease and pharyngitis. In this Review, we summarize the expanding family of bacterial SAgs and how these toxins can engage highly diverse adaptive immune receptors. We highlight recent findings regarding how SAg-driven manipulation of the adaptive immune response may operate in multiple human diseases, as well as contributing to the biology and life cycle of SAg-producing bacterial pathogens.

Autoimmunity: A New Focus on Nasal Polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) has long been considered a benign, chronic inflammatory, and hyperplastic disease. Recent studies have shown that autoimmune-related mechanisms are involved in the pathology of nasal polyps. Activated plasma cells, eosinophils, basophils, innate type 2 lymphocytes, mast cells, and proinflammatory cytokine in polyp tissue indicate the mobilization of innate and adaptive immune pathways during polyp formation. The discovery of a series of autoantibodies further supports the autoimmune nature of nasal polyps. Local homeostasis dysregulation, infection, and chronic inflammation may trigger autoimmunity through several mechanisms, including autoantigens overproduction, microbial translocation, molecular mimicry, superantigens, activation or inhibition of receptors, bystander activation, dysregulation of Toll-Like Receptors (TLRs), epitope spreading, autoantigens complementarity. In this paper, we elaborated on the microbiome-mediated mechanism, abnormal host immunity, and genetic changes to update the role of autoimmunity in the pathogenesis of chronic rhinosinusitis with nasal polyps.

Infectious diseases, autoantibodies, and autoimmunity

Infections are known to trigger flares of autoimmune diseases in humans and serve as an inciting cause of autoimmunity in animals. Evidence suggests a causative role of infections in triggering antigen-specific autoimmunity, previous thought mainly through antigen mimicry. However, an infection can induce bystander autoreactive T and B cell polyclonal activation, believed to result in non-pathogenic and pathogenic autoimmune responses. Lastly, epitope spreading in autoimmunity is a mechanism of epitope changes of autoreactive cells induced by infection, promoting the targeting of additional self-epitopes. This review highlights recent research findings, emphasizes infection-mediated autoimmune responses, and discusses the possible mechanisms involved.

Staphylococcus aureus skin colonization promotes SLE-like autoimmune inflammation via neutrophil activation and the IL-23/IL-17 axis

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by inflammation of various organs such as skin, kidneys, bones, and brain and the presence of autoantibodies. Although the cause of SLE is not completely understood, environmental factors, genetic susceptibility, hormone factors, and environmental factors are thought to play essential roles in the pathogenesis of SLE. Among environmental factors, the microbiota are linked to the development of different autoimmune diseases. The microbiota in the nasal cavity and gut are involved in SLE development, but the influence of skin microbiota is still unclear. Here, we demonstrated that epithelial cell-specific IκBζ-deficient (Nfkbiz^ΔK5) mice showed spontaneous skin inflammation with increased abundance of Staphylococcus aureus on the skin. When S. aureus was epicutaneously applied on Nfkbiz^ΔK5 mice, Nfkbiz^ΔK5 mice developed SLE-associated autoantibodies, anti-dsDNA antibodies, anti-Sm antibodies, and glomerulonephritis with IgG deposition. Epicutaneous S. aureus application significantly increased staphylococcal colonization on the skin of Nfkbiz^ΔK5 mice with reduced expression of several antimicrobial peptides in the skin. This staphylococcal skin colonization promoted caspase-mediated keratinocyte apoptosis and neutrophil activation, inducing the interleukin-23 (IL-23)/IL-17 immune response by activating dendritic cells and T cells. Furthermore, the subcutaneous administration of anti-IL-23p19 and anti-IL-17A antibodies alleviated the systemic autoimmune response. Together, these findings underscore epithelial-immune cross-talk disturbances caused by skin dysbiosis as an essential mediator inducing autoimmune diseases.

Amyloid-containing biofilms and autoimmunity

Bacteria are microscopic, single-celled organisms known for their ability to adapt to their environment. In response to stressful environmental conditions or in the presence of a contact surface, they commonly form multicellular aggregates called biofilms. Biofilms form on various abiotic or biotic surfaces through a dynamic stepwise process involving adhesion, growth, and extracellular matrix production. Biofilms develop on tissues as well as on implanted devices during infections, providing the bacteria with a mechanism for survival under harsh conditions including targeting by the immune system and antimicrobial therapy. Like pathogenic bacteria, members of the human microbiota can form biofilms. Biofilms formed by enteric bacteria contribute to several human diseases including autoimmune diseases and cancer. However, until recently the interactions of immune cells with biofilms had been mostly uncharacterized. Here, we will discuss how components of the enteric biofilm produced in vivo, specifically amyloid curli and extracellular DNA, could be interacting with the host's immune system causing an unpredicted immune response.

Multisystem Inflammatory Syndrome in Children and Long COVID: The SARS-CoV-2 Viral Superantigen Hypothesis

Multisystem inflammatory syndrome in children (MIS-C) is a febrile pediatric inflammatory disease that may develop weeks after initial SARS-CoV-2 infection or exposure. MIS-C involves systemic hyperinflammation and multiorgan involvement, including severe cardiovascular, gastrointestinal (GI) and neurological symptoms. Some clinical attributes of MIS-C-such as persistent fever, rashes, conjunctivitis and oral mucosa changes (red fissured lips and strawberry tongue)-overlap with features of Kawasaki disease (KD). In addition, MIS-C shares striking clinical similarities with toxic shock syndrome (TSS), which is triggered by bacterial superantigens (SAgs). The remarkable similarities between MIS-C and TSS prompted a search for SAg-like structures in the SARS-CoV-2 virus and the discovery of a unique SAg-like motif highly similar to a Staphylococcal enterotoxin B (SEB) fragment in the SARS-CoV-2 spike 1 (S1) glycoprotein. Computational studies suggest that the SAg-like motif has a high affinity for binding T-cell receptors (TCRs) and MHC Class II proteins. Immunosequencing of peripheral blood samples from MIS-C patients revealed a profound expansion of TCR β variable gene 11-2 (TRBV11-2), which correlates with MIS-C severity and serum cytokine levels, consistent with a SAg-triggered immune response. Computational sequence analysis of SARS-CoV-2 spike further identified conserved neurotoxin-like motifs which may alter neuronal cell function and contribute to neurological symptoms in COVID-19 and MIS-C patients. Additionally, autoantibodies are detected during MIS-C, which may indicate development of post-SARS-CoV-2 autoreactive and autoimmune responses. Finally, prolonged persistence of SARS-CoV-2 RNA in the gut, increased gut permeability and elevated levels of circulating S1 have been observed in children with MIS-C. Accordingly, we hypothesize that continuous and prolonged exposure to the viral SAg-like and neurotoxin-like motifs in SARS-CoV-2 spike may promote autoimmunity leading to the development of post-acute COVID-19 syndromes, including MIS-C and long COVID, as well as the neurological complications resulting from SARS-CoV-2 infection.

Superantigens and SARS-CoV-2

It has been posited SARS-CoV-2 contains at least one unique superantigen-like motif not found in any other SARS or endemic coronaviruses. Superantigens are potent antigens that can send the immune system into overdrive. SARS-CoV-2 causes many of the biological and clinical consequences of a superantigen, and, in the context of reinfection and waning immunity, it is important to better understand the impact of a widely circulating, airborne pathogen that may be a superantigen, superantigen-like or trigger a superantigenic host response. Urgent research is needed to better understand the long-term risks being taken by governments whose policies enable widespread transmission of a potential superantigenic pathogen, and to more clearly define the vaccination and public health policies needed to protect against the consequences of repeat exposure to the pathogen.

Renal autoimmunity: The role of bacterial and viral infections, an extensive review

Autoimmunity is a process by which the loss of self-tolerance results in an immune attack against the body own tissues and organs. For autoimmunity to occur, various elements serving as triggers were described by which infections are considered one of the leading factors. In turn, renal involvement in autoimmune diseases, whether by an organ-specific attack, or as part of a systemic disease process, is well known. As bacterial and viral infections are considered to be common triggers for autoimmunity in general, we aimed to study their association with renal autoimmunity in particular. We performed an extensive search of the recent and relevant medical literature regarding renal autoimmunity syndromes such as infection-associated glomerulonephritis and vasculitis, associated with bacterial and viral infections. By utilizing PubMed and Google Scholar search engines, over 200 articles and case reports were reviewed. Among other mechanisms, direct infection of the renal parenchyma, molecular mimicry, induction of B-cells or secretion of superantigens, bacterial and viral pathogens were found to correlate with the development of renal autoimmunity. Nevertheless, this was not true for all pathogens, as some mimic autoimmune diseases and others show a surprisingly protective effect. The exact immunopathogenesis is yet to be determined, however. For conclusion, bacterial and viral infections are linked to renal autoimmunity by both direct damage and as mediators of systemic diseases. Further research particularly on the immunopathogenetic mechanisms of renal autoimmunity associated with infections is required.

Altered Mitochondrial Homeostasis during Systemic Lupus Erythematosus Impairs Neutrophil Extracellular Trap Formation Rendering Neutrophils Ineffective at Combating Staphylococcus aureus

Inflammation involves a delicate balance between pathogen clearance and limiting host tissue damage, and perturbations in this equilibrium promote disease. Patients suffering from autoimmune diseases, such as systemic lupus erythematosus (SLE), have higher levels of serum S100A9 protein and increased risk for infection. S100A9 is highly abundant within neutrophils and modulates antimicrobial activity in response to bacterial pathogens. We reasoned that increased serum S100A9 in SLE patients reflects accumulation of S100A9 protein in neutrophils and may indicate altered neutrophil function. In this study, we demonstrate elevated S100A9 protein within neutrophils from SLE patients, and MRL/lpr mice associates with lower mitochondrial superoxide, decreased suicidal neutrophil extracellular trap formation, and increased susceptibility to Staphylococcus aureus infection. Furthermore, increasing mitochondrial superoxide production restored the antibacterial activity of MRL/lpr neutrophils in response to S. aureus These results demonstrate that accumulation of intracellular S100A9 associates with impaired mitochondrial homeostasis, thereby rendering SLE neutrophils inherently less bactericidal.

Genome Sequencing of a Historic Staphylococcus aureus Collection Reveals New Enterotoxin Genes and Sheds Light on the Evolution and Genomic Organization of This Key Virulence Gene Family

We take advantage of a historic collection of 133 Staphylococcus aureus strains accessioned between 1924 and 2016, whose genomes have been long-read sequenced as part of a major National Collection of Type Cultures (NCTC) initiative, to conduct a gene family-wide computational analysis of enterotoxin genes. We identify two novel staphylococcal enterotoxin (pseudo)genes (sel29p and sel30), the former of which has not been observed in any contemporary strain to date. We provide further information on five additional enterotoxin genes or gene variants that either have recently entered the literature or for which the nomenclature or description is currently unclear (selz, sel26, sel27, sel28, and ses-2p). An examination of over 11,000 RefSeq genomes in search of wider support for these seven (pseudo)genes led to the identification of an additional three novel enterotoxin gene family members (sel31, sel32, and sel33) plus two new variants (seh-2p and ses-3p). We cast light on the genomic distribution of the enterotoxin genes, further defining their arrangement in gene clusters. Finally, we show that cooccurrence of enterotoxin genes is prevalent, with individual NCTC strains possessing as many as 18 enterotoxin genes and pseudogenes, and that clonal complex membership rather than time of isolation is the key factor in determining enterotoxin load.IMPORTANCE Staphylococcus aureus strains pose a significant health risk to both human and animal populations. Key among this species' virulence factors is the staphylococcal enterotoxin gene family. Certain enterotoxin forms can induce a potentially life-threatening immune response, while others are implicated in less fatal though often severe conditions such as food poisoning. Genetic characterization of staphylococcal enterotoxin gene family members has steadily accumulated over recent decades, with over 20 genes now established in the literature. Despite the current wealth of knowledge on this important gene family, questions remain about the presence of additional enterotoxin genes and the genomic composition of family members. This study further expands knowledge of the staphylococcal enterotoxins while shedding light on their evolution over the last century.

Bacterial infections in lupus: Roles in promoting immune activation and in pathogenesis of the disease

BACKGROUND

Bacterial infections of the lung, skin, bloodstream and other tissues are common in patients with systemic lupus erythematosus (lupus) and are often more severe and invasive than similar infections in control populations. A variety of studies have explored the changes in bacterial abundance in lupus patients, the rates of infection and the influence of particular bacterial species on disease progression, using both human patient samples and mouse models of lupus.

OBJECTIVE

The aim of this review is to summarize human and mouse studies that describe changes in the bacterial microbiome in lupus, the role of a leaky gut in stimulating inflammation, identification of specific bacterial species associated with lupus, and the potential roles of certain common bacterial infections in promoting lupus progression.

METHODS

Information was collected using searches of the Pubmed database for articles relevant to bacterial infections in lupus and to microbiome changes associated with lupus.

RESULTS

The reviewed studies demonstrate significant changes in the bacterial microbiome of lupus patients as compared to control subjects and in lupus-prone mice compared to control mice. Furthermore, there is evidence supporting the existence of a leaky gut in lupus patients and in lupus-prone mice. This leaky gut may allow live bacteria or bacterial components to enter the circulation and cause inflammation. Invasive bacterial infections are more common and often more severe in lupus patients. These include infections caused by Staphylococcus aureus, Salmonella enterica, Escherichia coli, Streptococcus pneumoniae and mycobacteria. These bacterial infections can trigger increased immune activation and inflammation, potentially stimulating activation of autoreactive lymphocytes and leading to worsening of lupus symptoms.

CONCLUSIONS

Together, the evidence suggests that lupus predisposes to infection, while infection may trigger worsening lupus, leading to a feedback loop that may reinforce autoimmune symptoms.

Population Analysis of Staphylococcus aureus Reveals a Cryptic, Highly Prevalent Superantigen SElW That Contributes to the Pathogenesis of Bacteremia

Staphylococcus aureus is an important human and animal pathogen associated with an array of diseases, including life-threatening necrotizing pneumonia and infective endocarditis. The success of S. aureus as a pathogen has been linked in part to its ability to manipulate the host immune response through the secretion of toxins and immune evasion molecules. The staphylococcal superantigens (SAgs) have been studied for decades, but their role in S. aureus pathogenesis is not well understood, and an appreciation for how SAgs manipulate the host immune response to promote infection may be crucial for the development of novel intervention strategies. Here, we characterized a widely prevalent, previously cryptic, staphylococcal SAg, SElW, that contributes to the severity of S. aureus infections caused by an important epidemic clone of S. aureus CC398. Our findings add to the understanding of staphylococcal SAg diversity and function and provide new insights into the capacity of S. aureus to cause disease.

Staphylococcal superantigens (SAgs) are a family of secreted toxins that stimulate T cell activation and are associated with an array of diseases in humans and livestock. Most SAgs produced by Staphylococcus aureus are encoded by mobile genetic elements, such as pathogenicity islands, bacteriophages, and plasmids, in a strain-dependent manner. Here, we carried out a population genomic analysis of >800 staphylococcal isolates representing the breadth of S. aureus diversity to investigate the distribution of all 26 identified SAg genes. Up to 14 SAg genes were identified per isolate with the most common gene selw (encoding a putative SAg, SElW) identified in 97% of isolates. Most isolates (62.5%) have a full-length open reading frame of selw with an alternative TTG start codon that may have precluded functional characterization of SElW to date. Here, we demonstrate that S. aureus uses the TTG start codon to translate a potent SAg SElW that induces Vβ-specific T cell proliferation, a defining feature of classical SAgs. SElW is the only SAg predicted to be expressed by isolates of the CC398 lineage, an important human and livestock epidemic clone. Deletion of selw in a representative CC398 clinical isolate, S. aureus NM001, resulted in complete loss of T cell mitogenicity in vitro, and in vivo expression of SElW by S. aureus increased the bacterial load in the liver during bloodstream infection of SAg-sensitive HLA-DR4 transgenic mice. Overall, we report the characterization of a novel, highly prevalent, and potent SAg that contributes to the pathogenesis of S. aureus infection.

Staphylococcal enterotoxin B increased severity of experimental model of multiple sclerosis

BACKGROUND

Superantigens can be absorbed trans-mucosal and trans-cutaneous in individuals colonized with superantigen producing Staphylococcus aureus. Ability of superantigens to activate a large numbers of T cells suggests that they may play a role in the course of autoimmune diseases including human multiple sclerosis and experimental autoimmune encephalomyelitis (EAE). In this study we investigated the role of staphylococcal enterotoxin B in immunologic and pathologic changes in experimental animal model of multiple sclerosis.

METHODS

C57BL/6 female mice were treatment with SEB protein prior or post immunization with MOG33-35 peptide. Mice were monitored daily and scored for clinical symptoms following EAE induction. Spleen and spinal cord of mice were removed and used for ELISA and histological studies, respectively.

RESULTS

Treatment with SEB prior induction of EAE, increased clinical score, the concentration of IL-17A, IFN-γ and histological changes compared to control group. Treatment with SEB after induction of EAE caused these changes, but less severe.

DISCUSSION

Since SEB causes demyelination of spinal cord and increases the level of pro-inflammatory cytokine response, infiltration of T-lymphocytes and macrophages to CNS, it may exacerbate the clinical signs of EAE in mice and multiple sclerosis in human.

Staphylococcus aureus Colonization Is Increased on Lupus Skin Lesions and Is Promoted by IFN-Mediated Barrier Disruption

Cutaneous inflammation is recurrent in systemic lupus erythematosus (SLE), yet mechanisms that drive cutaneous inflammation in SLE are not well defined. Type I IFNs are elevated in nonlesional SLE skin and promote inflammatory responses. Staphylococcus aureus, known to induce IFN production, could play a role in cutaneous inflammation in SLE. We show here that active cutaneous lupus erythematosus lesions are highly colonized (∼50%) by S. aureus. To define the impact of IFNs on S. aureus colonization, we examined the effects of type I and type II IFNs on S. aureus adherence and invasion. An increase in adherent S. aureus was observed after exposure to both IFN-α and -γ, whereas IFN-γ appeared to inhibit invasion of S. aureus. Cutaneous lupus erythematosus lesional skin microarray data and RNA sequencing data from SLE keratinocytes identified repression of barrier gene expression, such as filaggrin and loricrin, and SLE keratinocytes exhibited increased S. aureus-binding integrins. These SLE-associated changes could be replicated by IFN treatment of keratinocytes. Further, SLE keratinocytes exhibited increased binding to S. aureus. Together, these data suggest that chronic exposure to IFNs induces barrier disruption that allows for higher S. aureus colonization in SLE skin.

Staphylococcus aureus Nasal Carriage and Autoimmune Diseases: From Pathogenic Mechanisms to Disease Susceptibility and Phenotype

The role of infective agents in autoimmune diseases (ADs) development has been historically investigated, but in the last years has been strongly reconsidered due to the interest in the link between the microbiome and ADs. Together with the gut, the skin microbiome is characterized by the presence of several microorganisms, potentially influencing innate and adaptive immune response. S. aureus is one of the most important components of the skin microbiome that can colonize anterior nares without clinical manifestations. Data from the literature demonstrates a significantly higher prevalence of nasal colonization in ADs patients in comparison with healthy subjects, suggesting a possible role in terms of disease development and phenotypes. Thus, in the present narrative review we focused on the mechanisms by which S. aureus could influence the immune response and on its relationship with ADs, in particular granulomatosis with polyangiitis, rheumatoid arthritis, and systemic lupus erythematosus.

Staphylococcal Superantigens: Pyrogenic Toxins Induce Toxic Shock

Staphylococcal enterotoxin B (SEB) and related superantigenic toxins produced by Staphylococcus aureus are potent activators of the immune system. These protein toxins bind to major histocompatibility complex (MHC) class II molecules and specific Vβ regions of T-cell receptors (TCRs), resulting in the activation of both monocytes/macrophages and T lymphocytes. The bridging of TCRs with MHC class II molecules by superantigens triggers an early “cytokine storm” and massive polyclonal T-cell proliferation. Proinflammatory cytokines, tumor necrosis factor α, interleukin 1 (IL-1), IL-2, interferon γ (IFNγ), and macrophage chemoattractant protein 1 elicit fever, inflammation, multiple organ injury, hypotension, and lethal shock. Upon MHC/TCR ligation, superantigens induce signaling pathways, including mitogen-activated protein kinase cascades and cytokine receptor signaling, which results in NFκB activation and the phosphoinositide 3-kinase/mammalian target of rapamycin pathways. In addition, gene profiling studies have revealed the essential roles of innate antimicrobial defense genes in the pathogenesis of SEB. The genes expressed in a murine model of SEB-induced shock include intracellular DNA/RNA sensors, apoptosis/DNA damage-related molecules, endoplasmic reticulum/mitochondrial stress responses, immunoproteasome components, and IFN-stimulated genes. This review focuses on the signaling pathways induced by superantigens that lead to the activation of inflammation and damage response genes. The induction of these damage response genes provides evidence that SEB induces danger signals in host cells, resulting in multiorgan injury and toxic shock. Therapeutics targeting both host inflammatory and cell death pathways can potentially mitigate the toxic effects of staphylococcal superantigens.

Manipulation of Innate and Adaptive Immunity by Staphylococcal Superantigens

Staphylococcal superantigens (SAgs) constitute a family of potent exotoxins secreted by Staphylococcus aureus and other select staphylococcal species. SAgs function to cross-link major histocompatibility complex (MHC) class II molecules with T cell receptors (TCRs) to stimulate the uncontrolled activation of T lymphocytes, potentially leading to severe human illnesses such as toxic shock syndrome. The ubiquity of SAgs in clinical S. aureus isolates suggests that they likely make an important contribution to the evolutionary fitness of S. aureus. Although the apparent redundancy of SAgs in S. aureus has not been explained, the high level of sequence diversity within this toxin family may allow for SAgs to recognize an assorted range of TCR and MHC class II molecules, as well as aid in the avoidance of humoral immunity. Herein, we outline the major diseases associated with the staphylococcal SAgs and how a dysregulated immune system may contribute to pathology. We then highlight recent research that considers the importance of SAgs in the pathogenesis of S. aureus infections, demonstrating that SAgs are more than simply an immunological diversion. We suggest that SAgs can act as targeted modulators that drive the immune response away from an effective response, and thus aid in S. aureus persistence.

A new tactics for the detection of S. aureus via paper based geno-interface incorporated with graphene nano dots and zeolites

Staphylococcus aureus (S. aureus) is a pathogenic bacteria which causes infectious diseases and food poisoning. Current diagnostic methods for infectious disease require sophisticated instruments, long analysis time and expensive reagents which restrict their application in resource-limited settings. Electrochemical paper based analytical device (EPAD) was developed by integrating graphene nano dots (GNDs) and zeolite (Zeo) using specific DNA probe. The ssDNA/GNDs-Zeo modified paper based analytical device (PAD) was characterized using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The genosensor was optimized at pH7.4 and incubation temperature of 30°C. A linear current response with respect to target DNA concentrations was obtained. The limit of detection (LOD) of the proposed sensor was found out to be 0.1nM. The specificity was confirmed by introducing non-complimentary target DNA to ssDNA/GNDs-Zeo modified PAD. The suitability of the proposed EPAD genosensor was demonstrated with fruit juice samples mixed with S. aureus. The proposed EPAD genosensor is a low cost, highly specific, easy to fabricate diagnostic device for detection of S. aureus bacteria which requires very low sample volume and minimum analysis time of 10s.

Prevalence of sea, seb, sec, sed, and tsst-1 genes of Staphylococcus aureus in nasal carriage and their association with multiple sclerosis

Background

Microbial superantigens might initiate or exacerbate autoimmune responses against particular tissues, organs or systems. This study aimed to examine the prevalence of sea, seb, sec, sed, and tsst-1 genes of Staphylococcus aureus in nasal carriage and their association with multiple sclerosis (MS).

Methods

Nasal swabs were collected from 150 MS patients and 150 healthy individuals (control group) to isolate S. aureus and investigate their superantigen genes (sea, seb, sec, sed and tsst-1) using PCR.

Results

A total of 300 participants were enrolled in the study, matched for age and gender (150 patients in the MS group and 150 in the control group). The prevalence of S. aureus colonization in MS patients and control groups was 42% and 23.3%, respectively. There was a statistically significant association between S. aureus colonization and MS disease (p<0.001; odds ratio 2.4; 95% confidence interval 1.4-3.9). No significant association was observed between the presence of S. aureus harboring sea, seb, sec, sed and tsst-1 genes with MS disease.

Conclusion

The rate of S. aureus nasal carriage is higher in patients with MS. Our study's results suggest that further investigation into whether there is a connection between MS and nasal exposure to staphylococcal superantigens is warranted.

The pathogenesis of Staphylococcus aureus in autoimmune diseases

Autoimmune disease are defined as the attacks on host tissue by the immune system. Several factors, e.g. genetic and environmental triggers (in particular, viruses, bacteria, and other infectious pathogens) play a role in the development of autoimmune diseases. Bacterial infections are related to several autoimmune diseases, e.g. chronic inflammations and demyelination. Nowadays, an estimated 20-30% of the general human population carry Staphylococcus aureus (S. aureus). This organism can asymptomatically colonize healthy individuals. S. aureus carriers show no sign of infection and can thus spread this bacterium in the community. Several studies investigated the potential involvement of this bacterium as the etiological agents of autoimmune diseases. The present review focused on the role of S. aureus infections in the pathogenesis of autoimmune, inflammatory, and demyelinating diseases. Possible modes of the pathogenic action of bacteria are discussed in association with the ways in which S. aureus can initiate or exacerbate autoimmunity.

Role of Microbial Agents in Pulmonary Fibrosis

Pulmonary fibrosis is a form of lung disease that develops due to aberrant wound-healing following repeated alveoli injury in genetically susceptible individuals, resulting in chronic inflammation, excess deposition of the extracellular matrix components, mainly collagen, and scarring of lung tissue. In addition to irradiation, environmental agents such occupational inhalants, and chemotherapeutic agents, microbial agents also play a role in the etiology of the disease. While viruses have received the most attention, emerging evidence suggest that bacteria and fungi also play a part in the etiology of pulmonary fibrosis. Furthermore, successful use of antibiotics, antiviral and antifungal drugs in several studies to attenuate fibrosis progression is also an indication of microbial involvement in the pathogenesis of the disease and could be a promising therapeutic modality for treating pulmonary fibrosis initiated or exacerbated by infectious agents.

Concomitant Disruption of CD4 and CD8 Genes Facilitates the Development of Double Negative αβ TCR+ Peripheral T Cells That Respond Robustly to Staphylococcal Superantigen

Mature peripheral double negative T (DNT) cells expressing αβ TCR but lacking CD4/CD8 coreceptors play protective as well as pathogenic roles. To better understand their development and functioning in vivo, we concomitantly inactivated CD4 and CD8 genes in mice with intact MHC class I and class II molecules with the hypothesis that this would enable the development of DNT cells. We also envisaged that these DNT cells could be activated by bacterial superantigens in vivo as activation of T cells by superantigens does not require CD4 and CD8 coreceptors. Because HLA class II molecules present superantigens more efficiently than murine MHC class II molecules, CD4 CD8 double knockout (DKO) mice transgenically expressing HLA-DR3 or HLA-DQ8 molecules were generated. Although thymic cellularity was comparable between wild type (WT) and DKO mice, CD3⁺ αβ TCR⁺ thymocytes were significantly reduced in DKO mice, implying defects in thymic-positive selection. Splenic CD3⁺ αβ TCR⁺ cells and Foxp3⁺ T regulatory cells were present in DKO mice but significantly reduced. However, the in vivo inflammatory responses and immunopathology elicited by acute challenge with the staphylococcal superantigen enterotoxin B were comparable between WT and DKO mice. Choric exposure to staphylococcal enterotoxin B precipitated a lupus-like inflammatory disease with characteristic lympho-monocytic infiltration in lungs, livers, and kidneys, along with production of anti-nuclear Abs in DKO mice as in WT mice. Overall, our results suggest that DNT cells can develop efficiently in vivo and chronic exposure to bacterial superantigens may precipitate a lupus-like autoimmune disease through activation of DNT cells.

FDA-approved immunosuppressants targeting staphylococcal superantigens: mechanisms and insights

Immunostimulating staphylococcal enterotoxin B (SEB) and related superantigenic toxins cause diseases in human beings and laboratory animals by hyperactivating cells of the immune system. These protein toxins bind to the major histocompatibility complex class II (MHC II) molecules and specific Vβ regions of T-cell receptors (TCRs), resulting in the stimulation of both monocytes/macrophages and T lymphocytes. The bridging of TCR with MHC II molecules by superantigens triggers intracellular signaling cascades, resulting in excessive release of proinflammatory mediators and massive polyclonal T-cell proliferation. The early induction of tumor necrosis factor α, interleukin 1 (IL-1), interleukin 2 (IL-2), interferon gamma (IFNγ), and macrophage chemoattractant protein 1 promotes fever, inflammation, and multiple organ injury. The signal transduction pathways for staphylococcal superantigen-induced toxicity downstream from TCR/major histocompatibility complex (MHC) ligation and interaction of cell surface co-stimulatory molecules include the mitogen-activated protein kinase cascades and cytokine receptor signaling, activating nuclear factor κB (NFκB) and the phosphoinositide 3-kinase/mammalian target of rapamycin pathways. Knowledge of host regulation within these activated pathways and molecules initiated by SEB and other superantigens enables the selection of US Food and Drug Administration (FDA)-approved drugs to interrupt and prevent superantigen-induced shock in animal models. This review focuses on the use of FDA-approved immunosuppressants in targeting the signaling pathways induced by staphylococcal superantigens.

Mini-Osmotic Pump Infusion Model to Investigate the Systemic Effects of Chronic Continuous Exposure to Staphylococcal Superantigen in Mice

Staphylococcus aureus can exist as a colonizer or can cause a spectrum of diseases. S. aureus elaborates several exotoxins and the superantigens are one among them. Staphylococcal superantigens (SSAg) cause robust activation of the immune system and acute exposure to significant amounts of SSAg can be potentially lethal. However, chronic exposure to SSAg is also possible. Administering SSAg using mini-osmotic pumps may mimic chronic recurrent exposure to SSAg. This is a relatively simple and safe way to administer purified SSAg or any other toxin/agent. In this chapter, we describe the mini-osmotic pump-mediated delivery of SSAg.

Superantigen-Producing Staphylococcus aureus Elicits Systemic Immune Activation in a Murine Wound Colonization Model

Staphylococcus aureus, the most common cause of wound infection, produces several exotoxins, including superantigens (SAgs). SAgs are the potent activators of the immune system. Given this unique property, we hypothesized that SAgs produced by S. aureus in wounds would have local, as well as systemic immunologic effects. We tested our hypothesis using a novel staphylococcal skin wound infection model in transgenic mice expressing HLA-DR3. Skin wounds were left uninfected or colonized with S. aureus strains producing SAgs or an isogenic strain not producing any SAg. Animals with wounds challenged with SAg-producing S. aureus had increased morbidity and lower serum IL-17 levels compared to those challenged with the SAg non-producing S. aureus (p = 0.027 and p = 0.032, respectively). At Day 8 following microbial challenge, compared to mice with uninfected wounds, the proportion of Vβ8⁺CD4⁺ T cells was increased, while the proportion of Vβ8⁺CD8⁺ T cells was decreased only in the spleens of mice challenged with SAg-producing S. aureus (p < 0.001). No such changes were measured in mice challenged with SAg non-producing S. aureus. Lungs, livers and kidneys from mice challenged with SAg-producing, but not SAg non-producing, S. aureus showed inflammatory changes. Overall, SAg-mediated systemic immune activation in wounds harboring S. aureus may have clinical implications.

Co-potentiation of antigen recognition: A mechanism to boost weak T cell responses and provide immunotherapy in vivo

Adaptive immunity is mediated by antigen receptors that can induce weak or strong immune responses depending on the nature of the antigen that is bound. In T lymphocytes, antigen recognition triggers signal transduction by clustering T cell receptor (TCR)/CD3 multiprotein complexes. In addition, it hypothesized that biophysical changes induced in TCR/CD3 that accompany receptor engagement may contribute to signal intensity. Nonclustering monovalent TCR/CD3 engagement is functionally inert despite the fact that it may induce changes in conformational arrangement or in the flexibility of receptor subunits. We report that the intrinsically inert monovalent engagement of TCR/CD3 can specifically enhance physiologic T cell responses to weak antigens in vitro and in vivo without stimulating antigen-unengaged T cells and without interrupting T cell responses to strong antigens, an effect that we term as "co-potentiation." We identified Mono-7D6-Fab, which biophysically altered TCR/CD3 when bound and functionally enhanced immune reactivity to several weak antigens in vitro, including a gp100-derived peptide associated with melanoma. In vivo, Mono-7D6-Fab induced T cell antigen-dependent therapeutic responses against melanoma lung metastases, an effect that synergized with other anti-melanoma immunotherapies to significantly improve outcome and survival. We conclude that Mono-7D6-Fab directly co-potentiated TCR/CD3 engagement by weak antigens and that such concept can be translated into an immunotherapeutic design. The co-potentiation principle may be applicable to other receptors that could be regulated by otherwise inert compounds whose latent potency is only invoked in concert with specific physiologic ligands.

Possible Role of Staphylococcal Enterotoxin B in the Pathogenesis of Autoimmune Diseases

As a member of superantigens (SAgs) produced by Staphylococcus aureus, staphylococcal enterotoxin B (SEB) is a exotoxin superantigen that can regulate the activity of immunomodulatory and pro-inflammatory cell types. In addition, SEB plays a critical role in the pathogenesis of autoimmune disorders either by initiating the autoimmune process or by inducing a relapse in an individual in clinical remission from an autoimmune disorder. SEB can directly activate T lymphocytes, leading to the release of cytokines, superoxides, or other mediators of inflammation either directly or indirectly, because of its unique ability to cross-link human major histocompatibility complex (MHC) class II and T cell receptors (TCR), forming a trimolecular complex. This review discusses the potential effects of SEB in the pathogenesis of autoimmune diseases such as multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis, and explores some updated therapeutic medications to neutralize SEB.

Superantigens produced by catheter-associated Staphylococcus aureus elicit systemic inflammatory disease in the absence of bacteremia

SAgs, produced by Staphylococcus aureus, play a major role in the pathogenesis of invasive staphylococcal diseases by inducing potent activation of the immune system. However, the role of SAgs, produced by S. aureus, associated with indwelling devices or tissues, are not known. Given the prevalence of device-associated infection with toxigenic S. aureus in clinical settings and the potency of SAgs, we hypothesized that continuous exposure to SAgs produced by catheter-associated S. aureus could have systemic consequences. To investigate these effects, we established a murine in vivo catheter colonization model. One centimeter long intravenous catheters were colonized with a clinical S. aureus isolate producing SAgs or isogenic S. aureus strains, capable or incapable of producing SAg. Catheters were subcutaneously implanted in age-matched HLA-DR3, B6, and AE(o) mice lacking MHC class II molecules and euthanized 7 d later. There was no evidence of systemic infection. However, in HLA-DR3 transgenic mice, which respond robustly to SSAgs, the SSAg-producing, but not the nonproducing strains, caused a transient increase in serum cytokine levels and a protracted expansion of splenic CD4(+) T cells expressing SSAg-reactive TCR Vβ8. Lungs, livers, and kidneys from these mice showed infiltration with CD4(+) and CD11b(+) cells. These findings were absent in B6 and AE(o) mice, which are known to respond poorly to SSAgs. Overall, our novel findings suggest that systemic immune activation elicited by SAgs, produced by S. aureus colonizing foreign bodies, could have clinical consequences in humans.

Systemic inflammatory response elicited by superantigen destabilizes T regulatory cells, rendering them ineffective during toxic shock syndrome

Life-threatening infections caused by Staphylococcus aureus, particularly the community-acquired methicillin-resistant strains of S. aureus, continue to pose serious problems. Greater virulence and increased pathogenicity of certain S. aureus strains are attributed to higher prevalence of exotoxins. Of these exotoxins, the superantigens (SAg) are likely most pathogenic because of their ability to rapidly and robustly activate the T cells even in extremely small quantities. Therefore, countering SAg-mediated T cell activation using T regulatory cells (Tregs) might be beneficial in diseases such as toxic shock syndrome (TSS). As the normal numbers of endogenous Tregs in a typical host are insufficient, we hypothesized that increasing the Treg numbers by administration of IL-2/anti-IL-2 Ab immune complexes (IL2C) or by adoptive transfer of ex vivo expanded Tregs might be more effective in countering SAg-mediated immune activation. HLA-DR3 transgenic mice that closely recapitulate human TSS were treated with IL2C to increase endogenous Tregs or received ex vivo expanded Tregs. Subsequently, they were challenged with SAg to induce TSS. Analyses of various parameters reflective of TSS (serum cytokine/chemokine levels, multiple organ pathology, and SAg-induced peripheral T cell expansion) indicated that increasing the Tregs failed to mitigate TSS. On the contrary, serum IFN-γ levels were increased in IL2C-treated mice. Exploration into the reasons behind the lack of protective effect of Tregs revealed IL-17 and IFN-γ-dependent loss of Tregs during TSS. In addition, significant upregulation of glucocorticoid-induced TNFR family-related receptor on conventional T cells during TSS could render them resistant to Treg-mediated suppression, contributing to failure of Treg-mediated immune regulation.

Plasmacytoid Dendritic Cells: Neglected Regulators of the Immune Response to Staphylococcus aureus

Plasmacytoid dendritic cells (pDC) are a rare subset of leukocytes equipped with Fcγ and Fcε receptors, which exert contrary effects on sensing of microbial nucleic acids by endosomal Toll-like receptors. In this article, we explain how pDC contribute to the immune response to Staphylococcus aureus. Under normal circumstances the pDC participates in the memory response to the pathogen: pDC activation is initiated by uptake of staphylococcal immune complexes with IgG or IgE. However, protein A-expressing S. aureus strains additionally trigger pDC activation in the absence of immunoglobulin. In this context, staphylococci exploit the pDC to induce antigen-independent differentiation of IL-10 producing plasmablasts, an elegant means to propagate immune evasion. We further discuss the role of type I interferons in infection with S. aureus and the implications of these findings for the development of immune based therapies and vaccination.

Late multiple organ surge in interferon-regulated target genes characterizes staphylococcal enterotoxin B lethality

Background

Bacterial superantigens are virulence factors that cause toxic shock syndrome. Here, the genome-wide, temporal response of mice to lethal intranasal staphylococcal enterotoxin B (SEB) challenge was investigated in six tissues.

Results

The earliest responses and largest number of affected genes occurred in peripheral blood mononuclear cells (PBMC), spleen, and lung tissues with the highest content of both T-cells and monocyte/macrophages, the direct cellular targets of SEB. In contrast, the response of liver, kidney, and heart was delayed and involved fewer genes, but revealed a dominant genetic program that was seen in all 6 tissues. Many of the 85 uniquely annotated transcripts participating in this shared genomic response have not been previously linked to SEB. Nine of the 85 genes were subsequently confirmed by RT-PCR in every tissue/organ at 24 h. These 85 transcripts, up-regulated in all tissues, annotated to the interferon (IFN)/antiviral-response and included genes belonging to the DNA/RNA sensing system, DNA damage repair, the immunoproteasome, and the ER/metabolic stress-response and apoptosis pathways. Overall, this shared program was identified as a type I and II interferon (IFN)-response and the promoters of these genes were highly enriched for IFN regulatory matrices. Several genes whose secreted products induce the IFN pathway were up-regulated at early time points in PBMCs, spleen, and/or lung. Furthermore, IFN regulatory factors including Irf1, Irf7 and Irf8, and Zbp1, a DNA sensor/transcription factor that can directly elicit an IFN innate immune response, participated in this host-wide SEB signature.

Conclusion

Global gene-expression changes across multiple organs implicated a host-wide IFN-response in SEB-induced death. Therapies aimed at IFN-associated innate immunity may improve outcome in toxic shock syndromes.

Update on staphylococcal superantigen-induced signaling pathways and therapeutic interventions

Staphylococcal enterotoxin B (SEB) and related bacterial toxins cause diseases in humans and laboratory animals ranging from food poisoning, acute lung injury to toxic shock. These superantigens bind directly to the major histocompatibility complex class II molecules on antigen-presenting cells and specific Vβ regions of T-cell receptors (TCR), resulting in rapid hyper-activation of the host immune system. In addition to TCR and co-stimulatory signals, proinflammatory mediators activate signaling pathways culminating in cell-stress response, activation of NFκB and mammalian target of rapamycin (mTOR). This article presents a concise review of superantigen-activated signaling pathways and focuses on the therapeutic challenges against bacterial superantigens.

Staphylococcal Enterotoxin B-specific monoclonal antibody 20B1 successfully treats diverse Staphylococcus aureus infections

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has become a major health threat in the United States. Staphylococcal enterotoxin B (SEB) is a potent superantigen that contributes to its virulence. High mortality and frequent failure of therapy despite available antibiotics have stimulated research efforts to develop adjunctive therapies.

METHODS

Treatment benefits of SEB-specific monoclonal antibody (mAb) 20B1 were investigated in mice in sepsis, superficial skin, and deep-tissue infection models.

RESULTS

Mice challenged with a SEB-producing MRSA strain developed fatal sepsis, extensive tissue skin infection, and abscess-forming deep-seeded thigh muscle infection. Animals preimmunized against SEB or treated passively with mAb 20B1 exhibited enhanced survival in the sepsis model, whereas decrease of bacterial burden was observed in the superficial skin and deep-tissue models. mAb 20B1 bound to SEB in the infected tissue and decreased abscess formation and proinflammatory cytokine levels, lymphocyte proliferation, and neutrophil recruitment.

CONCLUSIONS

mAb 20B1, an SEB-neutralizing mAb, is effective against MRSA infection. mAb 20B1 protects against lethal sepsis and reduces skin tissue invasion and deep-abscess formation. The mAb penetrates well into the abscess and binds to SEB. It affects the outcome of S. aureus infection by modulating the host's proinflammatory immune response.

The staphylococcal enterotoxin (SE) family: SEB and siblings

Staphylococcus aureus plays an important role in numerous human cases of food poisoning, soft tissue, and bone infections, as well as potentially lethal toxic shock. This common bacterium synthesizes various virulence factors that include staphylococcal enterotoxins (SEs). These protein toxins bind directly to major histocompatibility complex class II on antigen-presenting cells and specific Vβ regions of T-cell receptors, resulting in potentially life-threatening stimulation of the immune system. Picomolar concentrations of SEs ultimately elicit proinflammatory cytokines that can induce fever, hypotension, multi-organ failure, and lethal shock. Various in vitro and in vivo models have provided important tools for studying the biological effects of, as well as potential vaccines/therapeutics against, the SEs. This review succinctly presents known physical and biological properties of the SEs, including various intervention strategies. In particular, SEB will often be portrayed as per biodefense concerns dating back to the 1960s.