Intestinal Epithelial Expression of MHCII Determines Severity of Chemical, T-Cell-Induced, and Infectious Colitis in Mice.

BACKGROUND & AIMS: Intestinal epithelial cells (IECs) provide a barrier that separates the mucosal immune system from the luminal microbiota. IECs constitutively express low levels of major histocompatibility complex (MHC) class II proteins, which are upregulated upon exposure to interferon gamma. We investigated the effects of deleting MHCII proteins specifically in mice with infectious, dextran sodium sulfate (DSS)-, and T-cell-induced colitis. METHODS: We disrupted the histocompatibility 2, class II antigen A, beta 1 gene (H2-Ab1) in IECs of C57BL/6 mice (I-AbΔIEC) or Rag1-/- mice (Rag1-/-I-AbΔIEC); we used I-AbWT mice as controls. Colitis was induced by administration of DSS, transfer of CD4+CD45RBhi T cells, or infection with Citrobacter rodentium. Colon tissues were collected and analyzed by histology, immunofluorescence, xMAP, and reverse-transcription polymerase chain reaction and organoids were generated. Microbiota (total and immunoglobulin [Ig]A-coated) in intestinal samples were analyzed by16S amplicon profiling. IgA+CD138+ plasma cells from Peyer's patches and lamina propria were analyzed by flow cytometry and IgA repertoire was determined by next-generation sequencing. RESULTS: Mice with IEC-specific loss of MHCII (I-AbΔIEC mice) developed less severe DSS- or T-cell transfer-induced colitis than control mice. Intestinal tissues from I-AbΔIEC mice had a lower proportion of IgA-coated bacteria compared with control mice, and a reduced luminal concentration of secretory IgA (SIgA) following infection with C rodentium. There was no significant difference in the mucosal IgA repertoire of I-AbΔIEC vs control mice, but opsonization of cultured C rodentium by SIgA isolated from I-AbΔIEC mice was 50% lower than that of SIgA from mAbWT mice. Fifty percent of I-AbΔIEC mice died after infection with C rodentium, compared with none of the control mice. We observed a transient but significant expansion of the pathogen in the feces of I-AbΔIEC mice compared with I-AbWT mice. CONCLUSIONS: In mice with DSS or T-cell-induced colitis, loss of MHCII from IECs reduces but does not eliminate mucosal inflammation. However, in mice with C rodentium-induced colitis, loss of MHCII reduces bacterial clearance by decreasing binding of IgA to commensal and pathogenic bacteria.

Secretion of the Shiga toxin B subunit (Stx1B) via an autotransporter protein optimizes the protective immune response to the antigen expressed in an attenuated E. coli (rEPEC E22Δler) vaccine strain.

We previously developed attenuated rabbit enteropathogenic E. coli (rEPEC) strains which are effective oral vaccines against their parent pathogens by deleting ler, a global regulator of virulence genes. To use these strains as orally administered vectors to deliver other antigens we incorporated the B subunit of shiga-like toxin 1(Stx1) into the passenger domain of the autotransporter EspP expressed on a plasmid. Native EspP enters the periplasm where its passenger domain is exported to the bacterial surface through an outer membrane channel formed by its translocator domain, then cleaved and secreted. Since antigen localization may determine immunogenicity, we engineered derivatives of EspP expressing Stx1B- passenger domain fusions: 1. in cytoplasm 2. in periplasm, 3. surface-attached or 4. secreted. To determine which construct was most immunogenic, rabbits were immunized with attenuated O103 E. coli strain (E22 Δler) alone or expressing Stx1B in each of the above four cellular locations. IgG responses to Stx1B, and toxin-neutralizing antibodies were measured. Animals were challenged with a virulent rabbit Enterohemorrhagic E. coli (EHEC) strain of a different serogroup (O15) than the vaccine strain expressing Stx1 (RDEC-H19) and their clinical course observed. IgG responses to Stx1B subunit were induced in all animals vaccinated with the strain secreting Stx1B, in some vaccinated with surface-expressed Stx1B, but in not animals immunized with periplasmic or cytoplasmic Stx1B. Robust protection was observed only in the group immunized with the vaccine secreting Stx1B. Taken together, our data suggest that secretion of Stx1B, or other antigens, via an autotransporter, may maximize the protective response to live attenuated oral vaccine strains.

Development of live attenuated bacterial vaccines targeting Escherichia coli heat-labile and heat-stable enterotoxins.

Enterotoxigenic Escherichia coli (ETEC), defined by the production of heat labile (LT) and/or heat stable (ST) toxins, are major causes of diarrhea in animals, children in developing countries and to travelers. No broadly protective ETEC vaccine is available, largely because of the difficulty in inducing immunity to the small ST molecule. To take advantage of the demonstration (Liu et al., 2011; Zhang et al., 2013, 2010) that genetically produced fusions of mutant ST with LT subunits can induce effective immunity against both toxins, we engineered a live attenuated vaccine vector strain of E. coli (ZCR533), expressing the immunogenic LT-ST fusions. To present the LT-ST fusions to the mucosal immune system, we used restriction-free cloning to incorporate them into the passenger domain of the autotransporter protein (EspP) expressed on a medium copy number plasmid. This versatile system permits expression of incorporated antigens in either surface-bound or secreted forms by the ZCR533 vector, for delivery to the mucosal inductive sites. Incorporation of the fusions into EspP plasmids was confirmed by PCR and DNA sequencing. Protein expression was confirmed by Western blot of whole cell lysates and culture supernatents using polyclonal antisera to LT. Expression of the surface-targeted fusion on the surface of ZCR533 was confirmed by immuno-fluorescent staining. These studies show that antigenic LT-ST fusions can be surface-expressed or secreted, by our attenuated E. coli ZCR533 vaccine vector via the EspP autotransporter. These constructs could serve as broadly protective vaccine candidates to protect against both LT- and ST-producing ETEC.

Sulfate-reducing bacteria impairs working memory in mice.

The ability of gut microbes to bi-directionally communicate with the brain and vice versa form the basis of the gut microbiome-central nervous system axis. It has been shown that inoculation with pathogenic gut bacteria alters the behavior of mice; however, it is not known whether or not non-pathogenic resident microbes have similar effects. In this study, we tested the hypothesis that the administration of sulfate-reducing bacteria (SRB), a specific group of resident gut bacteria that generate hydrogen sulfide (H2S), impair learning and memory performance in mice tested in an 8-arm radial maze and Morris water maze. We found that mice spent more time in the center of the maze when they were gavaged with live SRB as compared to mice given saline (control), lactulose+mannitol (L/M), or killed SRB. SRB-gavaged mice were also tested using the Morris water maze and were found to take longer to complete the test, spend more time further from the platform, and have a longer path length to reach the platform. This effect of SRB on maze performance was associated with a higher concentration of H2S in the small intestine and cecum. We conclude that SRB, a specific resident gut bacterial species, could impair cognitive function in mice.

Sensitive determination of BRAF copy number in clinical samples by pyrosequencing.

Pilocytic astrocytoma is the most frequently occurring brain tumor during childhood. It is classified as grade I by the World Health Organization and may rarely evolve into higher-grade tumors. Frequent genetic abnormalities documented in astrocytomas in children are gains on chromosomal arm 7q. Duplications at 7q34 lead to a fusion between genes KIAA1549 and BRAF resulting in constitutive activation of the BRAF kinase. The BRAF gene is located on chromosome 7q34 and a pseudogene has been identified on chromosome Xq13. We have developed a simple and sensitive pyrosequencing method for the determination of the BRAF copy number in clinical samples. The approach is based on the simultaneous amplification of a DNA fragment contained in exon 11 of BRAF and the respective pseudogene that is used as an internal control. Three different bases in the PCR product allow precise sequence assessment of products originating from the BRAF gene and the respective pseudogene and a calculation of gene copy numbers. After the calibration of the assay on 78 control DNA samples, 42 clinical PA samples were analyzed for variation in copy numbers by pyrosequencing and for fusion gene expression by reverse transcription-polymerase chain reaction. The results obtained from tumor DNA by the developed assay and the established reverse transcription-polymerase chain reaction assays show a high concordance. In summary, we have established a pyrosequencing-based assay allowing precise detection of BRAF copy numbers in DNA extracted from clinical samples.

Analysis of KIAA1549-BRAF fusion status in a case of rosette-forming glioneuronal tumor of the fourth ventricle (RGNT).

Rosette-forming glioneuronal tumors (RGNT) of the fourth ventricle are rare mixed glio-neuronal tumors included in the revised WHO classification of CNS tumors and show histopathological features similar to pilocytic astrocytomas. To evaluate at molecular level potential affinities between these tumors, we investigated a case of RGNT, arising in the cerebellum of a young patient, for the presence of transcriptional products originating from the KIAA1549-BRAF fusion. However, the analysis did not show any fusion. Further studies in larger RGNT case series are needed in order to demonstrate the possible presence of KIAA1549-BRAF fusion and better delineate its relationship with pilocytic astrocytomas.

Supratentorial primitive neuroectodermal tumors of the central nervous system in adults: molecular and histopathologic analysis of 12 cases.

Advances in understanding the molecular basis of primitive neuroectodermal tumors of the central nervous system (CNS-PNET) biology are critical to improve patient outcome. Recently, new data on their molecular features have been reported, suggesting that supratentorial PNET (s-PNET) in adult patients may represent a specific tumor entity among CNS-PNETs. In this study, we analyzed the clinicopathologic and molecular features of 12 cases of s-PNET in adult patients. The follow-up analysis showed that these tumors have an aggressive clinical behavior. At the histopathologic level, they resembled their pediatric counterpart, showing a variable spectrum of neuronal differentiation. These cases did not show astrocytic differentiation; therefore, they did not qualify for the differential diagnosis of glioblastoma variants. The tumors were also screened for mutation of TP53, IDH1, IDH2, and ß-catenin, using single strand conformation polymorphism-based and sequencing assays, and were analyzed for c-myc/N-myc gene copy numbers with a quantitative polymerase chain reaction-based method. The strand conformation polymorphism-based mutational analysis showed that 5 tumors harbored TP53 mutations. In 2 cases, a mutation at codon 132 of the IDH1 gene was also found. No mutations of the ß-catenin or IDH2 genes were identified. No cases presented c-myc or N-myc amplifications. Only 1 case presented overexpression of epidermal growth factor receptor. In conclusion, our data show a high incidence of TP53 mutations in this group of tumors and show, in comparison with pediatric s-PNET, the absence of amplification of the c-myc/N-myc genes, indicating that s-PNET in adult patients may represent a specific subset of tumors among CNS-PNETs.

A pyrosequencing-based assay for the rapid detection of IDH1 mutations in clinical samples.

Mutations of both the IDH1 and IDH2 (isocitratedehydrogenase enzyme 1 and 2) genes have recently been described in cases of human glioma. Since IDH1 mutations have been associated with better clinical outcome, they are suitable predictive markers for adult glioma patients. We have developed a pyrosequencing assay that allows both the sensitive and rapid detection of mutant IDH1 alleles in DNA extracted from formalin-fixed, paraffin-embedded tissues. PCR products that span exon 4 of IDH1 were used as a template for pyrosequencing. For validation, PCR products were additionally cloned and sequenced conventionally by Sanger sequencing. Sensitivity was measured by titration of wild-type and mutant sequences. PCR kinetic experiments were performed to investigate the influences of PCR cycle number on the accuracy of the assay. We found that a minimum of 5% of mutant IDH1 alleles can easily be detected with the pyrosequencing approach. So far, there are few data regarding IDH1 mutation status in high-grade gliomas of childhood. Therefore, we applied this assay to 47 pediatric high-grade glioma samples (age range 6 weeks to 23 years). Mutations were found in 5/14 astrocytoma III and in 6/33 glioblastomas. In conclusion, we have developed a pyrosequencing-based assay for the detection of mutations at the hotspot regions of IDH1 and provide proof for its applicability as a molecular diagnostic assay for clinical samples.

The cytotoxic activity of the total alkaloids isolated from different parts of Solanum pseudocapsicum.

The total alkaloid fractions of the methanolic extracts of the leaves, ripe fruits, roots, seeds and stem of Solanum pseudocapsicum were subjected to in-vitro cytotoxicity, short-term toxicity and long-term survival studies. All the five fractions exhibited potent activity. The total alkaloid fraction of leaves was found to be the most potent. The HT-29 cell line was the most sensitive to the fractions. The cytotoxic concentration (CTC(50)) values for all these fractions ranged between 0.39-0.91, 0.68-2.8, 0.92-3.56, 4.05-8.2, 3.28-5.65 and 0.95-5.55 microg/ml, respectively for HT-29, RD-228, A-549, HEp-2, B(16)F(10) and Vero cell lines. In short-term toxicity studies, the fractions showed 50% viability at 93-128 microg/ml for DLA cells and 141-189 microg/ml for human lymphocytes. In the long-term survival studies on the cell lines RD-228, HEp-2 and Vero, cells retained their regenerative capacities at concentrations below 8 microg/ml. The total alkaloids of the plant, especially from the leaves merit further investigations to identify the active constituents in animal models.