Yoshihiro Eriguchi

Graft-versus-host disease disrupts intestinal microbial ecology by inhibiting Paneth cell production of α-defensins

Allogeneic hematopoietic stem cell transplantation (SCT) is a curative therapy for various hematologic disorders. Graft-versus-host disease (GVHD) and infections are the major complications of SCT, and their close relationship has been suggested. In this study, we evaluated a link between 2 complications in mouse models. The intestinal microbial communities are actively regulated by Paneth cells through their secretion of antimicrobial peptides, α-defensins. We discovered that Paneth cells are targeted by GVHD, resulting in marked reduction in the expression of α-defensins, which selectively kill noncommensals, while preserving commensals. Molecular profiling of intestinal microbial communities showed loss of physiologic diversity among the microflora and the overwhelming expansion of otherwise rare bacteria Escherichia coli, which caused septicemia. These changes occurred only in mice with GVHD, independently on conditioning-induced intestinal injury, and there was a significant correlation between alteration in the intestinal microbiota and GVHD severity. Oral administration of polymyxin B inhibited outgrowth of E coli and ameliorated GVHD. These results reveal the novel mechanism responsible for shift in the gut flora from commensals toward the widespread prevalence of pathogens and the previously unrecognized association between GVHD and infection after allogeneic SCT.

Clonal spread in Eastern Asia of ciprofloxacin-resistant Escherichia coli serogroup O25 strains, and associated virulence factors

A significant problem in the field of infectious diseases is the increase in fluoroquinolone (FQ)-resistant Escherichia coli. Although mutation of strains and clonal dissemination are supposed to be the cause of this increase, little is known about the prevalence of this organism. We investigated 219 FQ-resistant E. coli strains in Japan and nine Asian countries by serotyping and genotyping. Seventy-one strains (32.4%) were serogroup O25, which was prevalent in South Korea, China and Japan, especially in the southwest part of Japan. Aerobactin, a virulence factor in uropathogenic and avian pathogenic E. coli, was associated with the presence of FQ-resistant O25 strains of E. coli. Seven of the seventy-one FQ-resistant E. coli O25 had extended-spectrum beta-lactamase genes (six CTX-M-14 and one SHV-12), however, we were unable to find any E. coli O25-ST131 clone that produced CTX-M-15, which was previously reported to have emerged across continents. These data demonstrate that a clonal group of FQ-resistant and virulent E. coli recently became prevalent at least in East Asia and suggest that this might become a public health problem because the strains may acquire resistance to other antimicrobial agents.

Decreased secretion of Paneth cell α-defensins in graft-versus-host disease

Intestinal microbial ecology is actively regulated by Paneth cell‐derived antimicrobial peptides, α‐defensins. Graft‐versus‐host disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (SCT). We previously demonstrated that Paneth cells are targeted by GVHD, and their expression of antimicrobial peptide α‐defensins is impaired, leading to a loss of physiological diversity among the microflora and development of bloodstream infection. Herein, we evaluated whether fecal levels of α‐defensins could be surrogate marker of intestinal dysbiosis.

Combination therapy with micafungin and amphotericin B for invasive pulmonary aspergillosis in an immunocompromised mouse model

OBJECTIVES Antifungal monotherapy with polyenes, azoles or echinocandins is not always effective for invasive pulmonary aspergillosis (IPA). The main purpose of this study was to evaluate the efficacy of a combination of micafungin and amphotericin B for the primary treatment of IPA in an immunocompromised mouse model. METHODS Female ICR mice were used in all experiments. An immunosuppressive state was induced in mice by an intraperitoneal injection of cyclophosphamide. Mice were intratracheally inoculated with Aspergillus fumigatus conidia, treated with micafungin, amphotericin B or both for 7 days, and were tested for their survival 20 days after the Aspergillus inoculation. Fungal burden in lungs, serum galactomannan index (GMI) and histopathology of lungs, spleen and kidneys were also evaluated. RESULTS Combination therapy with micafungin and amphotericin B gave excellent survival of infected mice compared with monotherapy with micafungin or amphotericin B alone. Combined therapy reduced the fungal burden in the lungs and the serum GM levels compared with monotherapy or untreated controls, resulting in a significant histological improvement with disappearance of fungi in the lungs. CONCLUSIONS These findings suggest that combination therapy with micafungin and amphotericin B is more effective compared with monotherapy with either of them alone for IPA treatment.

Reciprocal Expression of Enteric Antimicrobial Proteins in Intestinal Graft-Versus-Host Disease

We recently demonstrated that expression of α-defensins, the major antimicrobial peptides produced by Paneth cells, was severely suppressed in mice with graft-versus-host disease (GVHD). In this study, we found that antibacterial lectin, regenerating islet-derived IIIγ (RegIIIγ) was upregulated in villous enterocytes, thus demonstrating the reciprocal control of enteric antimicrobial proteins in GVHD. Upregulation of RegIIIγ was mediated by a mechanism independent upon radiation-induced intestinal tract damage. MyD88-mediated signaling in intestinal epithelium was required for RegIIIγ upregulation in GVHD and antibiotic therapy downregulated RegIIIγ expression. These results suggest that MyD88-mediated sensing of the intestinal microbes disregulated in GVHD induces RegIIIγ upregulation in GVHD and argue a role for RegIIIγ in the pathogenesis of GVHD.

Evaluating the association between histological manifestations of cord colitis syndrome with GVHD

Cord colitis syndrome (CCS) is a recently proposed clinical entity characterized by a persistent diarrheal illness after cord blood transplantation (CBT), which is not caused by GVHD or CMV colitis. CCS is histologically characterized by chronic active colitis with granulomatous inflammation and Paneth cell metaplasia suggesting chronicity. However, the specificity of these pathological features to CCS remains to be validated. We conducted a retrospective study of 49 patients who had diarrhea and underwent diagnostic colonoscopy with biopsy following allogeneic hematopoietic SCT. None of the patients met the clinical criteria for CCS. Chronic active colitis with granulomatous inflammation and Paneth cell metaplasia was present in 12/33 (36%) patients with biopsy-proven GVHD, 4/6 (67%) patients with CMV colitis and 2/15 (13%) patients with nonspecific colitis. In patients with GVHD and/or CMV colitis, these pathological features were present in 4/8 (50%) patients after CBT and in 11/26 (42%) patients undergoing BMT or PBSCT. These results demonstrate that chronic active colitis with granuloma and Paneth cell metaplasia is not only a specific feature of CCS but also is present in GVHD and CMV colitis, irrespective of stem cell source.

Essential role of IFN-γ in T cell–associated intestinal inflammation

Paneth cells contribute to small intestinal homeostasis by secreting antimicrobial peptides and constituting the intestinal stem cell (ISC) niche. Certain T cell-mediated enteropathies are characterized by extensive Paneth cell depletion coincident with mucosal destruction and dysbiosis. In this study, mechanisms of intestinal crypt injury have been investigated by characterizing responses of mouse intestinal organoids (enteroids) in coculture with mouse T lymphocytes. Activated T cells induced enteroid damage, reduced Paneth cell and Lgr5+ ISC mRNA levels, and induced Paneth cell death through a caspase-3/7-dependent mechanism. IFN-γ mediated these effects, because IFN-γ receptor-null enteroids were unaffected by activated T cells. In mice, administration of IFN-γ induced enteropathy with crypt hyperplasia, villus shortening, Paneth cell depletion, and modified ISC marker expression. IFN-γ exacerbated radiation enteritis, which was ameliorated by treatment with a selective JAK1/2 inhibitor. Thus, IFN-γ induced Paneth cell death and impaired regeneration of small intestinal epithelium in vivo, suggesting that IFN-γ may be a useful target for treating defective mucosal regeneration in enteric inflammation.