Immunization with cytolethal distending toxin B produces autoantibodies to vinculin and small bowel bacterial changes in a rat model of postinfectious irritable bowel syndrome

Tracking Anti-cytolethal Distending Toxin B and Anti-vinculin Over Time and Their Roles in Symptoms

BACKGROUND AND AIMS

Antibodies targeting bacterial cytolethal distending toxin subunit B (CdtB) and vinculin are diagnostic of post-infection irritable bowel syndrome (IBS). In this study, we explored the temporal behavior of anti-CdtB and anti-vinculin antibodies and potential relationships to IBS symptoms. The potential impacts of antibody reduction therapies were also assessed.

METHODS

A retrospective chart review of 417 IBS patients who had been tested for anti-CdtB and anti-vinculin antibodies was performed. Anti-vinculin and anti-CdtB antibody levels, time to normalization of antibody levels, and IBS symptoms' burdens and changes were assessed. Use of antibody-depleting therapies (intravenous immunoglobulin [IVIG] or plasmapheresis exchange [PLEX]) vs. usual management was also recorded.

RESULTS

158 subjects (38.5%) were positive for either anti-CdtB or anti-vinculin. In subjects with multiple tests (total N = 38), normalization of anti-vinculin levels over time correlated with improvements in IBS symptoms (p = 0.020). Plasmapheresis (PLEX) or intravenous immunoglobulins (IVIG) treatments were associated with greater antibody normalization than usual management (p = 0.046).

CONCLUSIONS

Anti-CdtB and anti-vinculin antibodies are common in post-infection IBS, and anti-vinculin levels may correlate with severity of IBS symptoms.

Vinculin: A new target for the diagnosis and treatment of disease

Vinculin, a crucial adhesion plaque protein, plays a significant role in cell morphology and tissue development. Dysregulation of focal adhesion proteins has been linked to numerous diseases, including cardiovascular conditions, gastrointestinal disorders, and cancer. Recent studies increasingly highlight vinculin's involvement in the progression of these diseases; however, a comprehensive review remains lacking. Therefore, an in-depth and timely review is essential to consolidate the latest findings on vinculin's role in disease mechanisms. This study aims to examine how vinculin coordinates a complex network of signaling pathways across various pathological contexts.

Diversity of Campylobacter spp. circulating in a rhesus macaque (Macaca mulatta) breeding colony using culture and molecular methods

Campylobacter jejuni and Campylobacter coli represent the leading causes of bacterial gastroenteritis in humans, and infections can produce post-infectious irritable bowel syndrome (PI-IBS). Rhesus macaques (Macaca mulatta) (RM) are similarly susceptible to acute campylobacteriosis and represent a potential model of PI-IBS. We characterized the Campylobacter species circulating in an RM breeding colony using culture, qPCR, and whole genome sequencing (WGS). We also compared the C. jejuni and C. coli prevalence in RM as detected with qPCR versus culture and identified risk factors for bacteria presence and intestinal disease. Culture of 275 samples yielded C. coli (103) and C. jejuni (8), of which 21.6% were resistant to quinolones and 3.6% were resistant to macrolides. Multidrug-resistant isolates were obtained exclusively from animals exhibiting diarrhea or with histologically confirmed chronic enterocolitis. WGS revealed a non-clonal population of Campylobacter spp. Genotypic predictions of resistance were excellent except for aminoglycosides. All sequenced isolates contained genes for all subunits of cytolethal distending toxin. qPCR detected a prevalence of 45.9% for C. coli and 29.6% for C. jejuni. The quantity of either bacteria was significantly higher (P < 0.05) in animals with intestinal disease compared to healthy animals, though only young age was significantly associated with the presence of Campylobacter sp. or intestinal disease. Significantly more C. jejuni positive animals were detected with qPCR than with culture. These results provide a comprehensive characterization of Campylobacter spp. circulating in a breeding colony of RM in the United States and suggest that qPCR is superior for the detection of C. jejuni in RM.

IMPORTANCE

Gastrointestinal disease is one of the most common reasons for hospitalization in non-human primate colonies and accounts for over one-third of non-research related euthanasia. In rhesus macaques, this manifests as both acute diarrhea and chronic enterocolitis (CE), a syndrome of chronic diarrhea resulting in poor weight gain or weight loss which is minimally responsive to treatment. Campylobacter spp. are major causes of acute enterocolitis in rhesus macaques and may predispose individuals to the development of CE, similar to post-infectious irritable bowel syndrome in humans. Despite these concerns, there are few studies characterizing Campylobacter in rhesus macaque colonies, in particular utilizing whole genome sequencing and assessing findings with respect to the health status of the host. Our findings provide insight into Campylobacter strains circulating in rhesus macaque colonies, which can improve clinical monitoring, assist in treatment decisions, and provide new avenues of investigation into campylobacteriosis as a catalyst for CE.

Low dose rifaximin combined with N-acetylcysteine is superior to rifaximin alone in a rat model of IBS-D: a randomized trial

Rifaximin is FDA-approved for treatment of irritable bowel syndrome with diarrhea (IBS-D), but poor solubility may limit its efficacy against microbes in the mucus layer, e.g. Escherichia coli. Here we evaluate adding the mucolytic N-acetylcysteine (NAC) to improve rifaximin efficacy. In a resazurin checkerboard assay, combining rifaximin with NAC had significant synergistic effects in reducing E. coli levels. The optimal rifaximin + NAC combination was then tested in a validated rat model of IBS-D (induced by cytolethal distending toxin [CdtB] inoculation). Rats were inoculated with vehicle and treated with placebo (Control-PBS) or rifaximin + NAC (Control-Rif + NAC, safety), or inoculated with CdtB and treated with placebo (CdtB-PBS), rifaximin (CdtB-Rifaximin), or rifaximin + NAC (CdtB-Rif + NAC) for 10 days. CdtB-inoculated rats (CdtB-PBS) developed wide variability in stool consistency (P = 0.0014) vs. controls (Control-PBS). Stool variability normalized in rats treated with rifaximin + NAC (CdtB-Rif + NAC) but not rifaximin alone (CdtB-Rifaximin). Small bowel bacterial levels were elevated in CdtB-PBS rats but normalized in CdtB-Rif + NAC but not CdtB-Rifaximin rats. E. coli and Desulfovibrio spp levels (each associated with different IBS-D microtypes) were also elevated in CdtB-inoculated (CdtB-PBS) but normalized in CdtB-Rif + NAC rats. Cytokine levels normalized only in CdtB-Rif + NAC rats, in a manner predicted to be associated with reduced diarrhea driven by reduced E. coli. These findings suggest that combining rifaximin with NAC may improve the percentage of IBS-D patients responding to treatment.

Campylobacter jejuni virulence factors: update on emerging issues and trends

Campylobacter jejuni is a very common cause of gastroenteritis, and is frequently transmitted to humans through contaminated food products or water. Importantly, C. jejuni infections have a range of short- and long-term sequelae such as irritable bowel syndrome and Guillain Barre syndrome. C. jejuni triggers disease by employing a range of molecular strategies which enable it to colonise the gut, invade the epithelium, persist intracellularly and avoid detection by the host immune response. The objective of this review is to explore and summarise recent advances in the understanding of the C. jejuni molecular factors involved in colonisation, invasion of cells, collective quorum sensing-mediated behaviours and persistence. Understanding the mechanisms that underpin the pathogenicity of C. jejuni will enable future development of effective preventative approaches and vaccines against this pathogen.

Cytolethal distending toxin B inoculation leads to distinct gut microtypes and IBS-D-like microRNA-mediated gene expression changes in a rodent model

Diarrhea-predominant irritable bowel syndrome (IBS-D), associated with increased intestinal permeability, inflammation, and small intestinal bacterial overgrowth, can be triggered by acute gastroenteritis. Cytolethal distending toxin B (CdtB) is produced by gastroenteritis-causing pathogens and may underlie IBS-D development, through molecular mimicry with vinculin. Here, we examine the effects of exposure to CdtB alone on gut microbiome composition, host intestinal gene expression, and IBS-D-like phenotypes in a rat model. CdtB-inoculated rats exhibited increased anti-CdtB levels, which correlated with increased stool wet weights, pro-inflammatory cytokines (TNFα, IL2) and predicted microbial metabolic pathways including inflammatory responses, TNF responses, and diarrhea. Three distinct ileal microbiome profiles (microtypes) were identified in CdtB-inoculated rats. The first microtype (most like controls) had altered relative abundance (RA) of genera Bifidobacterium, Lactococcus, and Rothia. The second had lower microbial diversity, higher Escherichia-Shigella RA, higher absolute E. coli abundance, and altered host ileal tissue expression of immune-response and TNF-response genes compared to controls. The third microtype had higher microbial diversity, higher RA of hydrogen sulfide (H2S)-producer Desulfovibrio, and increased expression of H2S-associated pain/serotonin response genes. All CdtB-inoculated rats exhibited decreased ileal expression of cell junction component mRNAs, including vinculin-associated proteins. Significantly, cluster-specific microRNA-mRNA interactions controlling intestinal permeability, visceral hypersensitivity/pain, and gastrointestinal motility genes, including several previously associated with IBS were seen. These findings demonstrate that exposure to CdtB toxin alone results in IBS-like phenotypes including inflammation and diarrhea-like stool, decreased expression of intestinal barrier components, and altered ileal microtypes that influenced changes in microRNA-modulated gene expression and predicted metabolic pathways consistent with specific IBS-D symptoms.

Carriage of CdtB Encoding Campylobacter spp., Salmonella enterica, and Yersinia entercolitica in Patients with Gastroenteritis and Irritable Bowel Syndrome

INTRODUCTION

Cytolethal distending toxin (Cdt) is one of the bacterial toxins that present in a variety of gram-negative human pathogens, such as E. coli, Salmonella spp., and Campylobacter spp. CDT is composed of three subunits encoded by three adjacent genes, including cdtA, cdtB, and cdtC. cdtB has been shown to have toxic activity and cause DNA damage in host cells. Despite its presence in different bacterial species, the role of CdtB in acute and chronic infections, such as gastroenteritis and irritable bowel syndrome (IBS), is unclear. To analyze this correlation, we studied the prevalence of cdtB among different enteropathogenic bacteria in patients with gastroenteritis and IBS compared with healthy people.

MATERIALS AND METHODS

In this cross-sectional descriptive study, 230 stool samples were collected from patients with gastroenteritis, IBS, and healthy people. The presence of CdtB encoding bacteria, including Escherichia coli, Campylobacter spp., Yersinia entercolitica, Providencia alkalifacience, and Salmonella enterica, was examined by polymerase chain reaction using genus-specific primers.

RESULTS

Out of 230 stool samples, CdtB encoding Campylobacter spp. were found in 34.6% (52/150), 6.25% (5/80), and 4% (2/50) of the patients with gastroenteritis, IBS, and the control group, respectively. Carriage of CdtB encoding Salmonella enterica was characterized among 5.3% (8/150) of the patients with gastroenteritis and 17.5% (14/80) of the IBS patients. Although none of the patients carried CdtB encoding E. coli and Providencia spp., cdtB of Y. enterocolitica was detected in one of the patients with gastroenteritis (0.6%). Statistical analysis showed significant correlation between infection with CdtB encoding Campylobacter spp. and IBS-D subtype. No significant correlation was found between infection with CdtB encoding bacteria and other clinical and demographic data.

CONCLUSION

Our results confirmed a relatively higher frequency of CdtB encoding bacteria in the intestine of patients with gastroenteritis and those with IBS compared with healthy individuals. Regarding the frequency of CdtB encoding Salmonella and Campylobacter bacteria, it was proposed that infection with these enteropathogens could be considered a risk factor for the development or progression of IBS among Iranian patients. Further studies are needed to establish this involvement.

Small Intestinal Bacterial Overgrowth-Pathophysiology and Its Implications for Definition and Management

The concept of small intestinal bacterial overgrowth (SIBO) arose in the context of maldigestion and malabsorption among patients with obvious risk factors that permitted the small bowel to be colonized by potentially injurious colonic microbiota. Such colonization resulted in clinical signs, symptoms, and laboratory abnormalities that were explicable within a coherent pathophysiological framework. Coincident with advances in medical science, diagnostic testing evolved from small bowel culture to breath tests and on to next-generation, culture-independent microbial analytics. The advent and ready availability of breath tests generated a dramatic expansion in both the rate of diagnosis of SIBO and the range of associated gastrointestinal and nongastrointestinal clinical scenarios. However, issues with the specificity of these same breath tests have clouded their interpretation and aroused some skepticism regarding the role of SIBO in this expanded clinical repertoire. Furthermore, the pathophysiological plausibility that underpins SIBO as a cause of maldigestion/malabsorption is lacking in regard to its purported role in irritable bowel syndrome, for example. One hopes that the application of an ever-expanding armamentarium of modern molecular microbiology to the human small intestinal microbiome in both health and disease will ultimately resolve this impasse and provide an objective basis for the diagnosis of SIBO.

Diarrhea, Dysbiosis, Dysfunction, and the Disastrous Global Health Consequences: Piecing the Puzzle Together

The burden of diarrheal infections globally, including the chronic health consequences, is an important problem. Herein we describe a recent paper published by the Journal and describe how it fits within and advances our knowledge in this area.

Small Intestine Bacterial Overgrowth in Bangladeshi Infants Is Associated With Growth Stunting in a Longitudinal Cohort

INTRODUCTION

Small intestine bacterial overgrowth (SIBO) is common in children from low-income countries and has been cross-sectionally associated with growth stunting. We sought to determine whether SIBO was associated with poor growth and neurodevelopmental in a longitudinal analysis.

METHODS

We measured SIBO by glucose hydrogen breath test (GHBT) at 18, 52, 78, and 104 weeks of life in a prospective longitudinal birth cohort of Bangladeshi children. Sociodemographic information and measures of enteric inflammation were analyzed as covariates. Diarrheal samples were tested for enteropathogens using polymerase chain reaction. Regression models were created using standardized mean GHBT area under the H2 curve (AUC) to determine associations with linear growth and cognitive, language, and motor scores on the Bayley-III Scales of Infant and Toddler Development at 2 years. We also investigated associations between GHBT AUC and enteropathogen exposure.

RESULTS

A 1-ppm increase in standardized mean GHBT AUC was associated with a 0.01-SD decrease in length-for-age Z score (P = 0.03) and a 0.11-point decrease in Bayley language score (P = 0.05) at 2 years of age in adjusted analysis. Enteroaggregative Escherichia coli, Enteropathogenic Escherichia coli, Giardia, and Enterocytozoon bieneusi were associated with increased GHBT AUC, whereas Clostridium difficile, norovirus GI, sapovirus, rotavirus, and Cryptosporidium were associated with decreased GHBT AUC. None were consistent across all 4 time points.

DISCUSSION

SIBO in the first 2 years of life is associated with growth stunting and decreased language ability in Bangladeshi infants and may represent a modifiable risk factor in poor growth and neurodevelopment in low-income countries.

Anti-vinculin autoantibodies in systemic sclerosis: a step toward a novel biomarker?

Gastrointestinal (GI) disease is common in systemic sclerosis, and novel biomarkers are needed to identify and monitor these patients. Dr. Suliman and colleagues identify anti-vinculin autoantibodies in a subset of systemic sclerosis patients which associate with GI symptom severity, although more work is needed to determine their clinical utility.