Seiji Arihiro

HELIGMOSOMOIDES POLYGYRUS INFECTION CAN INHIBIT COLITIS THROUGH DIRECT INTERACTION WITH INNATE IMMUNITY

Less developed countries have a low incidence of immunological diseases like inflammatory bowel disease (IBD), perhaps prevented by the high prevalence of helminth infections in their populations. In the Rag IL-10−/− T cell transfer model of colitis, Heligmosomoides polygyrus, an intestinal helminth, prevents and reverses intestinal inflammation. This model of colitis was used to explore the importance of innate immunity in H. polygyrus protection from IBD. Rag mice briefly exposed to H. polygyrus before reconstitution with IL-10−/− colitogenic T cells are protected from colitis. Exposure to H. polygyrus before introduction of IL-10−/− and OT2 T cells reduced the capacity of the intestinal mucosa to make IFN-γ and IL-17 after either anti-CD3 mAb or OVA stimulation. This depressed cytokine response was evident even in the absence of colitis, suggesting that the downmodulation in proinflammatory cytokine secretion was not just secondary to improvement in intestinal inflammation. Following H. polygyrus infection, dendritic cells (DCs) from the lamina propria of Rag mice displayed decreased expression of CD80 and CD86, and heightened expression of plasmacytoid dendritic cell Ag-1 and CD40. They were also less responsive to lamina proprias, producing less IL-12p40 and IL-10. Also diminished was their capacity to present OVA to OT2 T cells. These experiments infer that H. polygyrus does not require direct interactions with T or B cells to render animals resistant to colitis. DCs have an important role in driving both murine and human IBD. Data suggest that phenotypic alternations in mucosal DC function are part of the regulatory process.

Immunotherapy for colorectal cancer

The incidence of colorectal cancer (CRC) is on the rise, and the prognosis for patients with recurrent or metastatic disease is extremely poor. Although chemotherapy and radiation therapy can improve survival rates, it is imperative to integrate alternative strategies such as immunotherapy to improve outcomes for patients with advanced CRC. In this review, we will discuss the effect of immunotherapy for inducing cytotoxic T lymphocytes and the major immunotherapeutic approaches for CRC that are currently in clinical trials, including peptide vaccines, dendritic cell-based cancer vaccines, whole tumor cell vaccines, viral vector-based cancer vaccines, adoptive cell transfer therapy, antibody-based cancer immunotherapy, and cytokine therapy. The possibility of combination therapies will also be discussed along with the challenges presented by tumor escape mechanisms.

Control of NOD2 and Rip2 dependent innate immune activation by GEF-H1

Background: Genetic variants of nucleotide‐binding oligomerization domain 2 (NOD2) lead to aberrant microbial recognition and can cause chronic inflammatory diseases in patients with Crohns disease (CD). Methods: We utilized gene‐specific siRNA mediated knockdown and expression of guanine nucleotide exchange factor H1 (GEF‐H1) in wildtype, Rip2‐, and Nod2‐deficient macrophages, HCT‐116 and HEK 293 cells to determine the role of GEF‐H1 in NOD2 and Rip2‐mediated NF‐&kgr;B‐dependent induction of proinflammatory cytokine expression. Confocal microscopy was used to determine subcellular distribution of GEF‐H1, Rip2, and NOD2. Results: We identified GEF‐H1 as an unexpected component of innate immune regulation during microbial pattern recognition by NOD2. Surprisingly, GEF‐H1‐mediated the activation of Rip2 during signaling by NOD2, but not in the presence of the 3020insC variant of NOD2 associated with CD. GEF‐H1 functioned downstream of NOD2 as part of Rip2‐containing signaling complexes and was responsible for phosphorylation of Rip2 by Src tyrosine kinase. Rip2 variants lacking the tyrosine target of GEF‐H1‐mediated phosphorylation were unable to mediate NF‐&kgr;B activation in Rip2‐deficient macrophages and failed to transduce NOD2 signaling. GEF‐H1 is required downstream of NOD2 as part of Rip2‐containing signaling complexes for the activation of innate immune responses. Conclusions: GEF‐H1 connects tyrosine kinase function to NOD‐like receptor signaling and is fundamental to the regulation of microbial recognition by ubiquitous innate immune mechanisms mediated by Rip2 kinase. (Inflamm Bowel Dis 2011;)

Fusions between dendritic cells and whole tumor cells as anticancer vaccines

Various strategies have been developed to deliver tumor-associated antigens (TAAs) to dendritic cells (DCs). Among these, the fusion of DCs and whole cancer cells can process a broad array of TAAs, including hitherto unidentified molecules, and present them in complex with MHC Class I and II molecules and in the context of co-stimulatory signals. DC-cancer cell fusions have been shown to stimulate potent antitumor immune responses in animal models. In early clinical trials, however, the antitumor effects of DC-cancer cell fusions are not as vigorous as in preclinical settings. This mini-review summarizes recent advances in anticancer vaccines based on DC-cancer cell fusions.

Clinical usefulness of diffusion-weighted MR imaging for detection of pancreatic cancer: comparison with enhanced multidetector-row CT

PurposeThe aim of this study was to compare diffusion-weighted magnetic resonance imaging (DWI) and multidetector-row computed tomography (MDCT) for detection of primary pancreatic cancer by reviewing images of patients at high risk for pancreatic cancer with main pancreatic duct (MPD) dilatation shown by magnetic resonance cholangiopancreatography (MRCP).MethodsFrom October 2007 to September 2009, 83 patients who had undergone both DWI and MDCT with MPD dilatation were identified and were reviewed by four readers (2 radiologists and 2 gastroenterology fellows). Diagnostic performance in pancreatic cancer detection was evaluated with 95% confidence intervals. Statistically significant differences in the detection of pancreatic cancer between DWI and MDCT were compared by receiver operating characteristics and the confidence of the diagnosis by the paired t test.ResultsThirty-two of 83 patients were diagnosed with primary pancreatic cancer by histological evaluation of 15 surgical and 2 endoscopic ultrasound-guided fine needle aspiration samples, and by the clinical course for 15 lesions. Overall average accuracies of pancreatic cancer detection by the four readers were 84% with DWI and 86% with MDCT.ConclusionPerformance of DWI and MDCT was equivocal for detection of pancreatic cancer in a high-risk population with MPD dilatation. The combination of MRCP and DWI for detection of pancreatic cancer allowed identification of a high-risk population and tumor detection with a single imaging modality with no need for contrast medium.

Dendritic/pancreatic carcinoma fusions for clinical use: Comparative functional analysis of healthy- versus patient-derived fusions.

Fetal calf serum (FCS)-independent pancreatic cancer cells were established in plasma protein fraction (PPF)-supplemented medium that is an agent of good manufacturing practice (GMP) grade. Dendritic cells (DCs) were activated with the Toll-like receptor agonist, penicillin-inactivated Streptococcus pyogenes (OK-432) that is also a GMP grade agent. Therefore, sufficient amounts of FCS-independent fusions were successfully generated with decreased potential hazards of FCS. The FCS-independent fusions expressed tumor-associated antigens, HLA-DR, costimulatory molecules, IL-12, and IL-10. Stimulation of T cells with fusions from healthy donors resulted in proliferation of T cells with high expression levels of perforin/granzyme B and IFN-gamma and efficient induction of antigen-specific cytotoxic T lymphocytes (CTLs). Selection and expansion of T-cell clones were confirmed by TCR Vbeta analysis. However, fusions from patients with metastatic pancreatic cancer induced increased expression levels of TGF-beta1 in CD4+ CD25high T cells and low levels of CTLs with decreased IFN-gamma production.

Combined TLR2/4-Activated Dendritic/Tumor Cell Fusions Induce Augmented Cytotoxic T Lymphocytes

Induction of antitumor immunity by dendritic cell (DC)-tumor fusion cells (DC/tumor) can be modulated by their activation status. In this study, to address optimal status of DC/tumor to induce efficient antigen-specific cytotoxic T lymphocytes (CTLs), we have created various types of DC/tumor: 1) un-activated DC/tumor; 2) penicillin-killed Streptococcus pyogenes (OK-432; TLR4 agonist)-activated DC/tumor; 3) protein-bound polysaccharides isolated from Coriolus versicolor (PSK; TLR2 agonist)-activated DC/tumor; and 4) Combined OK-432- and PSK-activated DC/tumor. Moreover, we assessed the effects of TGF-β1 derived from DC/tumor on the induction of MUC1-specific CTLs. Combined TLR2- and TLR4-activated DC/tumor overcame immune-suppressive effect of TGF-β1 in comparison to those single activated or un-activated DC/tumor as demonstrated by: 1) up-regulation of MHC class II and CD86 expression on DC/tumor; 2) increased fusion efficiency; 3) increased production of fusions derived IL-12p70; 4) activation of CD4+ and CD8+ T cells that produce high levels of IFN-γ; 5) augmented induction of CTL activity specific for MUC1; and 6) superior efficacy in inhibiting CD4+CD25+Foxp3+ T cell generation. However, DC/tumor-derived TGF-β1 reduced the efficacy of DC/tumor vaccine in vitro. Incorporating combined TLRs-activation and TGF-β1-blockade of DC/tumor may enhance the effectiveness of DC/tumor-based cancer vaccines and have the potential applicability to the field of adoptive immunotherapy.

Endoscopic features of colorectal serrated lesions using image-enhanced endoscopy with pathological analysis.

Objective To clarify of the features of sessile serrated adenoma/polyp (SSA/P) observed with image-enhanced endoscopy using immunohistochemical staining. Materials and methods Twenty-five hyperplastic polyps (HP) and 46 SSA/P were studied with autofluorescence imaging (AFI) and magnifying endoscopy with narrow-band imaging (ME-NBI). AFI color change, capillary dilatation, existence of a mucous layer on the tumor surface, and pit dilatation under ME-NBI were examined retrospectively. Immunohistochemical staining was performed with the proliferation-associated antigen MIB-1 (Ki-67). Results Using AFI, a magenta color was observed in 32% of HP and 44% of SSA/P. With NBI observation, capillary dilatation was observed in 4% of HP and 11% of SSA/P, a mucous cap was observed in 60% of HP and 94% of SSA/P, and pit dilatation was observed in 28% of HP and 80% of SSA/P. When magenta color, capillary dilatation, mucous cap, and pit dilatation were used for the differential diagnosis of SSA/P from HP, the sensitivity, specificity, and accuracy were 43, 68, and 52% for AFI, respectively, 10, 96, and, 41% for capillary dilatation, respectively, 94, 40, and 75% for mucous cap, respectively, and 80, 72, and 78% for pit dilatation, respectively. Compared with HP, MIB-1-positive cells were more frequently distributed in the gland’s intermediate zone in SSA/P. Conclusion The biological malignant potential of SSA/P could be higher compared with HP as suggested by the MIB-1 stain. Therefore, endoscopic differentiation of SSA/P from HP is important, and the findings of a mucous cap and dilatated pit might be helpful for the differentiation of SSA/P from HP.

Small Molecule Tyrosine Kinase Inhibitors for the Treatment of Intestinal Inflammation

Background: We developed a series of dendritic cell autoimmune modulators (DCAMs) based on small molecule Flt3 receptor tyrosine kinase inhibitors (TKIs) for the inhibition of intestinal inflammation and oral delivery. Methods: DCAMs were administered orally during and after induction of dextran sodium sulfate (DSS)‐induced colitis. Dendritic cell recruitment and inflammatory responses were determined in the mucosal immune system during acute intestinal inflammatory responses and mucosal recovery. Bone marrow‐derived macrophages were utilized to define the mechanisms by which DCAMs can modify responses to microbial signals. Results: Oral doses of DCAMs prevented severe weight loss and mucosal inflammation associated with DSS colitis in mice. The presence of DCAMs increased the number of CD11c+PDCA1+ dendritic cells, induced interleukin (IL)‐10 expression, and reduced inflammatory cytokine expression in the mucosal immune system. Surprisingly, DCAMs regulated innate immune responses in macrophages resulting in the inhibition of tumor necrosis factor alpha (TNF‐&agr;) production and the induction of IL‐10 expression during Toll‐like receptor‐mediated signaling. Conclusions: We identified two new imidazoacridinone derivatives that protect mice from severe colitis and promote mucosal recovery by enhancing protective cytokine production while inhibiting proinflammatory stimuli during microbial recognition. These compounds are promising candidates for further development into potent orally available drugs for the prevention of colitis and promotion of mucosal recovery.

Strategies to improve the immunogenicity of anticancer vaccines based on dendritic cell/malignant cell fusions.

The rationale for fusing dendritic cells (DCs) with whole tumor cells to generate anticancer vaccines resides in the fact that the former operate as potent antigen-presenting cells, whereas the latter express a constellation of tumor-associated antigens (TAAs). Although the administration of DC/malignant cell fusions to cancer patients is safe and this immunotherapeutic intervention triggers efficient tumor-specific T-cell responses in vitro, a limited number of objective clinical responses to DC/cancer cell fusions has been reported thus far. This review discusses novel approaches to improve the immunogenicity of DC/malignant cell fusions as anticancer vaccines.