Konstantinos A. Papadakis

LDL-cholesterol concentrations: a genome-wide association study

Summary Background LDL cholesterol has a causal role in the development of cardiovascular disease. Improved understanding of the biological mechanisms that underlie the metabolism and regulation of LDL cholesterol might help to identify novel therapeutic targets. We therefore did a genome-wide association study of LDL-cholesterol concentrations. Methods We used genome-wide association data from up to 11 685 participants with measures of circulating LDL-cholesterol concentrations across five studies, including data for 293 461 autosomal single nucleotide polymorphisms (SNPs) with a minor allele frequency of 5% or more that passed our quality control criteria. We also used data from a second genome-wide array in up to 4337 participants from three of these five studies, with data for 290 140 SNPs. We did replication studies in two independent populations consisting of up to 4979 participants. Statistical approaches, including meta-analysis and linkage disequilibrium plots, were used to refine association signals; we analysed pooled data from all seven populations to determine the effect of each SNP on variations in circulating LDL-cholesterol concentrations. Findings In our initial scan, we found two SNPs (rs599839 [p=1·7×10−15] and rs4970834 [p=3·0×10−11]) that showed genome-wide statistical association with LDL cholesterol at chromosomal locus 1p13.3. The second genome screen found a third statistically associated SNP at the same locus (rs646776 [p=4·3×10−9]). Meta-analysis of data from all studies showed an association of SNPs rs599839 (combined p=1·2×10−33) and rs646776 (p=4·8×10−20) with LDL-cholesterol concentrations. SNPs rs599839 and rs646776 both explained around 1% of the variation in circulating LDL-cholesterol concentrations and were associated with about 15% of an SD change in LDL cholesterol per allele, assuming an SD of 1 mmol/L. Interpretation We found evidence for a novel locus for LDL cholesterol on chromosome 1p13.3. These results potentially provide insight into the biological mechanisms that underlie the regulation of LDL cholesterol and might help in the discovery of novel therapeutic targets for cardiovascular disease.

The Role of Thymus-Expressed Chemokine and Its Receptor CCR9 on Lymphocytes in the Regional Specialization of the Mucosal Immune System

Chemokines play an important role in the migration of leukocytes at sites of inflammation, and some constitutively expressed chemokines may direct lymphocyte trafficking within lymphoid organs and peripheral tissues. Thymus-expressed chemokine (TECK or Ckβ-15/CCL25), which signals through the chemokine receptor CCR9, is constitutively expressed in the thymus and small intestine but not colon, and chemoattracts a small fraction of PBLs that coexpress the integrin α4β7. Here we show that TECK is expressed in the human small bowel but not colon by endothelial cells and a subset of cells in intestinal crypts and lamina propria. CCR9 is expressed in the majority of freshly isolated small bowel lamina propria mononuclear cells (LPMC) and at significantly higher levels compared with colonic LPMC or PBL. TECK was selectively chemotactic for small bowel but not colonic LPMC in vitro. The TECK-induced chemotaxis was sensitive to pertussis toxin and partially inhibited by Abs to CCR9. TECK attracts predominantly the T cell fraction of small bowel LPMC, whereas sorted CD3+CCR9+ and CD3+CCR9− lymphocytes produce similar Th1 or Th2 cytokines at the single cell level. Collectively, our data suggest that the selective expression of TECK in the small bowel underlie the homing of CCR9+ intestinal memory T cells to the small bowel rather than to the colon. This regional specialization implies a segregation of small intestinal from colonic immune responses.

Initial experience with wireless capsule enteroscopy in the diagnosis and management of inflammatory bowel disease

BACKGROUND AND AIMS Wireless capsule enteroscopy (WCE) offers the potential to directly visualize the entire small bowel and identify superficial lesions not detected by traditional endoscopy and radiography. The aim of this study is to assess the clinical utility of WCE in the evaluation of patients with known or suspected inflammatory bowel disease (IBD). METHODS Fifty patients with ongoing symptoms underwent Given M2A endoscopic capsule examinations. Indications included: (1) evaluation for small-bowel involvement in patients with IBD with isolated colitis (n = 22), (2) determination of the extent of small-bowel disease in patients with Crohns disease (CD; n = 20), and (3) workup of suspected IBD (n = 8). Outcome measures were classified as diagnostic when multiple ulcerations were present, suspicious when </=3 ulcerations were seen, and nonspecific or normal. RESULTS WCE findings were diagnostic for CD in 20 patients and suspicious for small-bowel CD in 10 patients. Seventeen of 20 patients with diagnostic WCE findings improved with increased IBD-directed medical therapy, as did 7 of 10 patients with suspicious study results. WCE was normal or showed nonspecific findings in the remaining 20 patients. Notably, identification of small-bowel lesions in 5 patients with a previous history of isolated colitis resulted in a change in diagnosis to CD after confirmatory ileoscopy with biopsy. CONCLUSIONS Results of this preliminary study suggest that WCE is a novel and potentially clinically useful method of directly visualizing and diagnosing small-bowel lesions in patients with IBD that can be missed by traditional endoscopic and radiological procedures.

Patients with Inflammatory Bowel Disease are at Risk for Vaccine-Preventable Illnesses

BACKGROUND:Patients with chronic, immune-mediated conditions such as inflammatory bowel disease (IBD) are often treated with long-term immunosuppressive therapies, potentially increasing their risk of developing an infection. Empiric data suggest that vaccines are underutilized in immunocompromised patients, despite published guidelines recommending their use. We aimed to assess exposure risk and immunization status among patients receiving care in an IBD specialty clinic.METHODS:Patients completed a self-administered, pretested, structured questionnaire during a routine visit for the management of IBD. Survey questions related to medical and immunization histories, and exposures to known risk factors for influenza, pneumococcus, viral hepatitis, and varicella. Additionally, in a subgroup of patients who agreed to donate a sample of blood, immune status to hepatitis A (HAV), hepatitis B (HBV), and varicella was determined.RESULTS:Two hundred four patients were asked to participate in the study; 169 completed surveys and comprised the study population. Mean age was 35 yr (range 13–75 yr). One hundred forty-six respondents (86%) reported current or prior use of immunosuppressive medications. Only 45% of respondents recalled tetanus immunization within the past 10 yr, 41 (28%) reported regularly receiving flu shots, and 13 (9%) reported having received pneumococcal vaccine. The most common reasons for nonimmunization with influenza included lack of awareness (49%) and concern for side effects (18%). Responses indicated that 75 (44%) patients were at risk for HBV but only 47 (28%) had been vaccinated against the infection; of patients with previous HBV vaccination, only three of nine (33%) had measurable antibodies against hepatitis B surface antigen.CONCLUSIONS:Immunization against selected vaccine-preventable illnesses was uncommon in patients with IBD, despite the presence of significant risk factors. Efforts to improve immunization status among patients with IBD and other chronic, immune-mediated conditions are needed.

Outcome of cytomegalovirus infections in patients with inflammatory bowel disease

OBJECTIVE: The aim of this study was to determine the outcome of cytomegalovirus (CMV) infections complicating the course of inflammatory bowel disease (IBD). METHODS: The records and clinical courses were reviewed for all IBD patients who were evaluated at the IBD Center of the Cedars-Sinai Medical Center and who developed CMV infection. RESULTS: Ten patients with severe, medically refractory IBD (five ulcerative colitis, three Crohn’s colitis, and two indeterminate colitis) developed CMV infection. All but two were hospitalized with exacerbation of their underlying disease and were receiving immunosuppressive treatment with steroids, thiopurines, and/or cyclosporine at the time CMV infection was recognized. Eight patients had documented colonic CMV (one had concurrent upper GI tract involvement), one developed interstitial CMV and Pneumocystis carinii pneumonia, and one developed primary CMV mononucleosis. Prompt treatment with ganciclovir and withdrawal of immunosuppressive treatment resulted in gradual improvement and induction of remission of the underlying IBD in five patients. The patient with concomitant CMV and P. carinii pneumonitis died. In two patients, treatment with ganciclovir did not alter the clinical course of their IBD, and one of them underwent colectomy. In one patient CMV was found on the resected colonic specimen. One patient with primary CMV infection responded also to ganciclovir treatment. CONCLUSIONS: CMV infection may aggravate the course of seemingly refractory IBD in patients who either fail to respond or experience worsening of symptoms despite immunosuppressive therapy. Expedient evaluation, prompt treatment intervention with ganciclovir, and withdrawal of immunosuppressive treatment may avoid complications and mortality. This regimen leads to improvement of the underlying IBD in most patients.

Safety and Efficacy of Adalimumab (D2E7) in Crohn's Disease Patients with an Attenuated Response to Infliximab

OBJECTIVES:Although infliximab is highly effective in the treatment of Crohns disease (CD), attenuated response to infliximab may develop over time in a subgroup of patients. The aim of our study was to examine the safety and efficacy of adalimumab (D2E7), a fully humanized anti-TNF-α Ab, in CD patients who had experienced an attenuated response to infliximab.METHODS:Fifteen patients with active CD who experienced an attenuated response to infliximab were treated with adalimumab over a 6-month period. Patients, received a loading dose of 80 mg subcutaneously followed by 40 mg every 2 wk. The clinical response to adalimumab was classified as complete response, partial response, or nonresponse.RESULTS:Two patients received the loading dose of adalimumab but did not have adequate follow-up evaluations. Of the remaining 13 patients, 7 (54%) had a complete response, 4 (31%) had a partial response, and 2 (15%) were nonresponders. In six patients, the maintenance dose was increased in order to maintain clinical response. Eight of 11 (73%) patients on concurrent corticosteroids were able to discontinue or significantly decrease the dose of the steroids. Adalimumab was well tolerated without signs or symptoms of allergic reaction except in two patients who developed an injection site reaction.CONCLUSIONS:Our preliminary data suggest that adalimumab may be a safe and effective therapy for patients with CD who have experienced an attenuated response to infliximab.

High incidence of anergy in inflammatory bowel disease patients limits the usefulness of PPD screening before infliximab therapy.

BACKGROUND & AIMS Reports of tuberculosis (TB) in patients administered infliximab prompted the Food and Drug Administration to recommend that all patients being considered for this therapy be evaluated for the risk for latent TB infection by means of a tuberculin skin test (TST). The aim of this study is to evaluate the utility of a TST as an adequate screen for TB exposure in patients with inflammatory bowel disease (IBD). METHODS Eighty-two consecutive patients with IBD (Crohns disease, 70 patients; ulcerative colitis, 4 patients; indeterminate colitis, 8 patients) seen at Cedars-Sinai Medical Center IBD Center (Los Angeles, CA) being treated with or considered for infliximab therapy underwent a standard intradermal purified protein derivative (PPD) TST before or between infusions of infliximab. One or more control antigens (Candida, tetanus, and/or mumps) were concurrently placed on 69 of these patients. Skin tests were read for induration at 48-72 hours after placement, and results were recorded. RESULTS None of 82 patients had a positive PPD TST result. Overall, 71% of patients (49 of 69 patients) with controls placed failed to react to any antigen. Eighty-three percent of patients (40 of 48 patients) who were administered corticosteroids and/or immunosuppressive medications, not including infliximab, for at least 1 month were anergic compared with 43% of patients (9 of 21 patients; P < 0.002) who were not administered those medications. CONCLUSIONS Given the high prevalence of anergy, a negative TST result in patients with IBD administered infliximab is an unreliable indicator for TB exposure. Evaluation for TB risks should include not only a TST, but also a detailed history of travel, TB exposures, and such symptoms as chronic cough and weight loss, and a chest radiograph should be considered.

Expression and functional characterization of FOXP3+CD4+ regulatory T cells in ulcerative colitis†

Background CD4+CD25+ regulatory T cells (TR) can prevent or treat experimental murine colitis but little is known about their potential role in human inflammatory bowel disease (IBD). FOXP3 is a transcription factor that plays a critical role in the development and function of CD4+CD25+ TR. The aim of this study was to examine the presence and functional characteristics of TR cells in colonic lymphoid tissues in patients with ulcerative colitis (UC). Methods FOXP3 expression was assessed by flow cytometry, immunohistochemistry, and reverse‐transcriptase polymerase chain reaction (RT‐PCR). Functional characterization of CD4+CD25+ cells was analyzed by suppression of proliferation and secretion of cytokines by cocultured effector CD4+CD25− T cells. Results FOXP3+CD4+ T cells are increased in the lamina propria (LP) of inflamed and noninflamed areas of UC colon compared to normal colon. CD4+CD25+ T cells in UC mesenteric lymph nodes (MLN) express FOXP3 mRNA and protein and suppress the proliferation of autologous MLN CD4+CD25− T cells. The suppressor activity of MLN CD4+CD25+ T cells is cell contact‐dependent but cytokine‐independent. In addition, CD4+CD25+ T cells potently suppress the production of both Th1 (IFN‐&ggr;, IL‐2) and Th2 (IL‐5, IL‐13) cytokines by cocultured CD4+CD25− T cells. FOXP3+ cells localized in the T‐cell‐rich areas of MLN and occasionally present in the follicles. Conclusions There is an expansion of FOXP3+CD4+ T cells in mucosal lymphoid tissues in UC. CD4+CD25+ isolated from UC MLN express FOXP3 and display features of TR cells in spite of active mucosal inflammation. These data suggest that their suppressor activity may be abrogated in vivo or they are unable to counterbalance the chronic mucosal inflammation in UC. (Inflamm Bowel Dis 2007)

TL1A Synergizes with IL-12 and IL-18 to Enhance IFN-γ Production in Human T Cells and NK Cells

TL1A, a recently described TNF-like cytokine that interacts with DR3, costimulates T cells and augments anti-CD3 plus anti-CD28 IFN-γ production. In the current study we show that TL1A or an agonistic anti-DR3 mAb synergize with IL-12/IL-18 to augment IFN-γ production in human peripheral blood T cells and NK cells. TL1A also enhanced IFN-γ production by IL-12/IL-18 stimulated CD56+ T cells. When expressed as fold change, the synergistic effect of TL1A on cytokine-induced IFN-γ production was more pronounced on CD4+ and CD8+ T cells than on CD56+ T cells or NK cells. Intracellular cytokine staining showed that TL1A significantly enhanced both the percentage and the mean fluorescence intensity of IFN-γ-producing T cells in response to IL-12/IL-18. The combination of IL-12 and IL-18 markedly up-regulated DR3 expression in NK cells, whereas it had minimal effect in T cells. Our data suggest that TL1A/DR3 pathway plays an important role in the augmentation of cytokine-induced IFN-γ production in T cells and that DR3 expression is differentially regulated by IL-12/IL-18 in T cells and NK cells.

A pilot study of adalimumab in infliximab‐allergic patients

The anti-TNF-&agr; antibody infliximab (Remicade) is highly effective in the treatment of Crohns disease. A subset of patients experience allergic reactions as a result of antibodies to infliximab (ATIs). The purpose of the current study is to describe the safety and efficacy of adalimumab (Humira) in patients previously allergic or intolerant to infliximab. Adalimumab is an anti-TNF-&agr; agent containing only human peptide sequences. Seven patients have been treated with adalimumab who had experienced immediate- or delayed-hypersensitivity reactions to infliximab and one with infliximab-induced lupus. Except for injection site discomfort, adalimumab was well tolerated without signs or symptoms of allergic reactions. One patient who had previously received pooled human immunoglobulin developed a pruritic rash after each dose of adalimumab. Patients with active disease who had previously experienced a robust response to infliximab responded to adalimumab as reflected by an improvement in Harvey-Bradshaw index and inflammatory markers. Based on these preliminary data, adalimumab may be a safe and effective substitute for infliximab-allergic patients. Individuals who have been exposed to human antibodies may be sensitized to other human antibodies such as adalimumab.