Systematic review: Whipple's disease (Tropheryma whipplei infection) and its unmasking by tumour necrosis factor inhibitors

BACKGROUND

The classical form of Whipple's disease (WD), clinically characterised by arthropathy, diarrhoea and weight loss, is rare. Recently, other more frequent forms of Tropheryma whipplei infection have been recognised. The clinical spectrum includes an acute, self-limiting disease in children, localised forms affecting cardiac valves or the central nervous system without intestinal symptoms, and asymptomatic carriage of T. whipplei which is found in around 4% of Europeans. Genomic analysis has shown that T. whipplei represents a host-dependent or opportunistic bacterium. It has been reported that the clinical course of T. whipplei infection may be influenced by medical immunosuppression.

AIM

To identify associations between immunomodulatory treatment and the clinical course of T. whipplei infection.

METHODS

A PubMed literature search was performed and 19 studies reporting on immunosuppression, particularly therapy with tumour necrosis factor inhibitors (TNFI) prior to the diagnosis in 41 patients with Whipple?s disease, were evaluated.

RESULTS

As arthritis may precede the diagnosis of WD by many years, a relevant percentage (up to 50% in some reports) of patients are treated with immunomodulatory drugs or with TNFI. Many publications report on a complicated Whipple?s disease course or T. whipplei endocarditis following medical immunosuppression, particularly after TNFI. Standard diagnostic tests such as periodic acid-Schiff stain used to diagnose Whipple?s disease often fail in patients who are pre-treated by TNFI.

CONCLUSIONS

In cases of doubt, Whipple?s disease should be excluded before therapy with TNFI. The fact that immunosuppressive therapy contributes to the progression of T. whipplei infection expands our pathogenetic view of this clinical entity.

Non-alcoholic steatohepatitis occurs in celiac disease and is associated with cellular stress

BACKGROUND AND AIMS

Liver and gut not only share alimentary but also immunological features. Major histocompatibility complex class I-related chains A and B (MIC A/B) function as indicators for cellular stress. These so called stress-induced ligands are suggested to play an important role in the progression of non-alcoholic fatty liver disease (NAFLD) and are a prominent feature of celiac disease (CD).

PATIENTS AND METHODS

In the present study, 24 patients with celiac disease and 20 patients with non-alcoholic steatohepatitis (NASH) were included. Liver enzymes, serum cell death markers (M30, M65), MIC B and expression of adiponectin were determined.

RESULTS

Mean patient age was 42 years (18 - 69) for CD and 49 years (33 - 68) for the NASH group. ALT and AST values were lower in CD compared to NASH patients. While serum cell death markers were higher in NASH, the predominant type of cell death in CD was apoptosis. Also, expression of MIC B was significantly up-regulated in CD patients as compared to NASH patients. Adiponectin values were significantly lower in NASH compared to CD patients.

CONCLUSION

Stress-induced ligands and apoptosis are induced in CD. Prospective studies need to determine the exact role of cellular stress and apoptosis in the gut-liver axis and the clinical implications to screen for NAFLD in CD patients.

Perioperative adjuvant therapy with infliximab in complicated anal Crohn's disease

PURPOSE

Infliximab may represent an adjuvant to surgical therapy in patients with severe anal Crohn's disease as it has been shown to affect rapid remissions in a proportion of cases.

PATIENTS AND METHODS

Nineteen patients underwent infliximab therapy 5 mg/kg perioperatively to scheduled anal reconstructive surgery for complicated fistulising anal Crohn's disease.

RESULTS

One adverse event was recorded (generalised exanthema with subsequent resolution). Eight patients showed complete clinical remission refusing further surgery. One of the eight relapsed during follow-up and was continued on infliximab. Surgery consisted of advancement flaps. It was successful at first attempt in nine of the remaining 11 patients (82%). Operative fistula closure remained unsuccessful in two patients. Overall, 16 of 19 patients (84%) with advanced anal Crohn's disease had a favourable outcome.

CONCLUSION

The use of infliximab as adjuvant to surgery in this series of patients with complicated anal Crohn's disease was safe. Although the data is uncontrolled a positive effect of infliximab on the outcome of surgery may be postulated since our results compare favourably with other studies.

Interleukin-18 is increased only in a minority of patients with active Crohn's disease

BACKGROUND AND AIMS

It has been suggested that Crohn's Disease (CD) is associated with an elevated T helper 1 response as manifested by increased production of interleukin-18 (IL-18). Local concentrations of neutralizing IL-18 binding proteins (IL-18 bp) may counteract biological functions of mature IL-18 in mucosal inflammation. Therefore, we investigated the IL-18/IL-18 bp system in a large group of patients with active inflammatory bowel disease (IBD) to identify patients that could respond theoretically to IL-18 neutralizing treatment strategies.

PATIENT/METHODS

IL-18 and IL-18 bp messenger RNA (mRNA) expression in colonic mucosa from patients with active CD (n = 72), active ulcerative colitis (UC; n = 32), and non-IBD controls (infectious colitis or diverticulitis; n = 19) and normal, non-diseased controls (n = 20) were measured by reverse-transcribed real-time polymerase chain reaction. Mature IL-18 protein and IL-18 bp expression in inflamed mucosa were assessed by Western blotting.

RESULTS/FINDINGS

Although IL-18 mRNA was increased in some patients with CD, the increase was not statistically significant. Densitometric evaluation of IL-18/alpha-actin ratio in patients with active CD (n = 20) and patients with UC (n = 10) demonstrated an increased ratio of IL-18 protein in CD when compared to UC (1.04 vs 0.72 [median]). On closer inspections, only 7/20 CD patients had an increased IL-18 protein expression in inflamed areas compared to noninflamed mucosa.

INTERPRETATION/CONCLUSION

IL-18 expression in active CD is heterogeneous, only a minority of patients expresses elevated levels. Further treatment strategies targeting IL-18 expression in active CD should be concentrated on this subgroup of patients.

[Whipple's disease]

Whipple's disease is a rare infectious disorder affecting mostly middle aged men. The causative organism, Tropheryma whipplei, recently has been cultivated and phylogenetically identified as an actinomycete. The rareness of the disease despite the ubiquitous occurence of T. whipplei presumably is related to a predisposing defect in cellular immunity. The diagnosis usually can be established by small bowel biopsy, but is frequently delayed due to protean clinical manifestations. The initiation of antibiotic treatment in most cases results in clinical remission, however, a significant number of patients is refractory to antimicrobial therapy or has a relapsing course.

Current Concepts of Immunopathogenesis, Diagnosis and Therapy in Whipples Disease

Whipple's disease (WD) is a rare chronic infectious disorder caused by the rod- shaped bacterium Tropheryma whipplei. The disorder is characterized clinically by arthralgia, abdominal pain, diarrhea, malabsorbtion and progressive weight loss. Other important sites of infection include the heart (resulting in the clinical picture of endocarditis and heart failure) and the central nervous system (CNS) (manifestations include confusion, memory loss, focal cranial nerve signs, nystagmus and ophtalmoplegia). The bacterium is presumed to be ubiquitously present. A defect in cellular immune response may predispose patients for an infection with T. whipplei and this might explain the rarity of the disorder despite the ubiquitous bacterial presence. The presumed immunological defect is likely to be quite specific for T. whipplei, since patients are not generally affected by other infections. Decreased production of Interleukin(IL)-12, IL-2 and Interferon (IFN)-g accompanied by an increased secretion of IL-4 are the main features of this defective immunological response. The finding of periodic acid-Schiff (PAS)-positive macrophages in the lamina propria of tissue samples obtained by duodenal biopsy usually establishes the diagnosis. The PAS-positive inclusions represent the remnants of the bacteria. Attempts to isolate the causative agent were unsuccessful for nearby 100 years after the first recognition of the disease. In the year 2000, the bacterium was finally successfully grown on a human fibroblast cell line. Untreated WD patients suffer from a chronic progressive disorder which possibly leads to death. Most patients show a fast clinical improvement to antibiotic therapy, but clinical relapses are described frequently. There is a number of patients, unable to eradicate the bacterium even after several antibiotic treatments and patients with CNS disease, in both of whom alternative therapy strategies are necessary.

Decreased levels of interleukin-12p40 in the serum of patients with Whipple's disease

BACKGROUND

An impaired production of interleukin (IL)-12 and T cell interferon-gamma (IFN-gamma) of in vitro stimulated monocytes has been discussed as a pathogenic factor in Whipple's disease (WD). It is unclear whether this defect of cellular immunity is translated to the humoral immune system and to serum correlates.

METHODS

We analyzed the serum of 40 patients with Whipple's disease in various degrees of disease activity by sandwich enzyme-linked immunosorbent assay for differences in cytokine and cell adhesion molecule concentrations compared with age- and sex-matched controls.

RESULTS

We observed a highly significant reduction of IL-12p40 levels (patients, 0.18+/-0.05 ng/ml (mean+/-SEM); controls, 3.19+/-0.39 ng/ml; p<0.01) in all stages of disease activity, whereas the concentration of IL-12p70 was comparable with controls. Furthermore, we observed a slight decrease in tumour necrosis factor alpha (TNF-alpha) concentrations in the serum of patients (patients, 6.36+/-0.90 pg/ml; controls, 10.5+/-1.23 pg/ml; p<0,05). The levels of other cytokines such as IFN-gamma, IL-2, IL-13 and transforming growth factor beta, as well as soluble cell adhesion molecules lymphocyte function-associated antigen 3 and intercellular adhesion molecule 1, were not significantly different compared with controls. Levels of immunoglobulin G2 (IgG2) measured in the serum of WD patients were below normal in 24 of 29 patients and were even below the 95% confidence interval in 10 patients.

CONCLUSION

Our data demonstrate a persistent defect of the cellular immune response with decreased serum concentrations of IL-12p40 and TNF-alpha and decreased IgG2 levels in a large group of WD patients. These data support as in vivo finding the results obtained in previous investigations with stimulated monocytes/lymphocytes. The isolated decrease in IL-12p40 may hint at possible defects in the IL-12/IFN-gamma promoter system.

Progress, problems, and perspectives in diagnosis and treatment of Whipple's disease

Whipple's disease is a rare chronic infectious disorder first described in 1907 by G.H. Whipple. The disorder is caused by the newly identified bacterium Tropheryma whipplei and there is evidence that altered immune functions play a role in the manifestation of the disease. The organ systems mostly affected are the joints and the gut, and in the further course often also the heart, lung, brain, and eyes. The intestinal involvement occurs with abdominal pain and diarrhea, which leads to weight loss, malnutrition, and anemia. In some cases the infection spreads to the central nervous system, which may lead to loss of memory, confusion, or disturbances in gait. In the last few years, several steps towards an improved diagnosis of the disease and characterization of the causative bacterium have been made. While untreated disease may be lethal, treatment is often able to eradicate the organism. At present, therapy is based on observations in small patient groups and personal experience. There are different antibiotic therapy regimens often starting with intravenous application for 2 weeks followed by oral medication for 1 year. The first clinical therapy study is ongoing.

An interleukin 12 p40-IgG2b fusion protein abrogates T cell mediated inflammation: anti-inflammatory activity in Crohn's disease and experimental colitis in vivo

BACKGROUND AND AIMS

Interleukin-12 (IL-12), a p35/p40 heterodimer, plays a pivotal role in the immune response in Crohn's disease (CD). Since IL-12 p40 dimers act as IL-12 antagonists, we assayed p40 dimer proteins to modulate chronic intestinal inflammation.

METHODS

We generated a fusion protein consisting of the IL-12(p40) subunit fused to the constant region of IgG2b. IL-12(p40)-IgG2b was tested in a murine 2,4,6,-trinitrobenzene sulphonic acid (TNBS) colitis model and in lamina propria mononuclear cells (LPMNC) from patients with CD in vitro.

RESULTS

Dimeric IL-12(p40)-IgG2b fusion protein bound specifically to the IL-12 receptor. In concentrations <10(-7) M, it acted as an IL-12 antagonist as it inhibited interferon gamma (IFN-gamma) secretion, suppressed proliferation, and increased apoptosis of LPMNC from patients with CD. However, in concentrations >10(-6) M, IL-12(p40)-IgG2b increased IFN-gamma secretion and lymphocyte proliferation thereby acting as an IL-12 agonist. In TNBS colitic mice, IL-12(p40)-IgG2b decreased mortality (10% v 68%), prevented body weight loss, reduced tumour necrosis factor alpha, and increased IL-10 secretion.

CONCLUSIONS

The IL-12(p40)-IgG2b fusion protein has dichotomic properties as a specific IL-12 antagonist and selective repressor of mucosal inflammation at low concentration and as an IL-12 agonist at high concentration.

Increased expression of interleukin-12 receptor beta(2) on lamina propria mononuclear cells of patients with active Crohn's disease

BACKGROUND AND AIMS

Since interleukin-12 is pathogenetically involved in Crohn's disease (CD) but not in ulcerative colitis (UC), expression and mechanisms of induction of interleukin-12 receptor (IL-12R) subunits beta(1) and beta(2) were analyzed in lamina propria mononuclear cells (LPMNC) of patients with CD and UC.

PATIENTS AND METHODS

LPMNC from patients with CD ( n=17), UC ( n=14), and controls ( n=19) were isolated by standard techniques. IL-12R beta(1) and IL-12R beta(2) transcripts were semiquantified by RT-PCR, and expression of IL-12R beta(2) chain was characterized by flow cytometry. LPMNC were activated by cross-linking with anti-CD3 antibodies and B7-1 costimulation.

RESULTS

IL-12R beta(1) and IL-12R beta(2) transcript concentrations were higher in inflamed specimens than in noninflamed segments of patients with CD but not in UC. Increased percentage of mucosal CD4(+)/IL-12R beta(2)(+) cells was observed in active CD, but not UC. In vitro stimulation of LPMNC with anti-CD3 antibodies resulted in an increase in IL-12R beta(1) transcripts irrespective of B7-1 mediated costimulation (84% and 95%, respectively). However, increased expression of IL-12R beta(2) mRNA (110%) was detected only after B7-1 costimulation.

CONCLUSION

Our data indicate that increased mucosal expression of IL-12R beta(2) on LPMNC in CD but not in UC may be the result of B7-1 costimulation. Modulation or inhibition of IL-12R beta(2) expression on LPMNC could provide a selective therapeutic approach in CD.

The diagnosis and treatment of Whipple's disease

Whipple's disease is a rare, chronic, and systemic infectious disease caused by the ubiquitously occurring bacterium Tropheryma whippelii. For two reasons, the disease represents a good example for documenting the input of modern molecular-based techniques into pathogenetic, diagnostic, and therapeutic concepts in clinical medicine. First, the unidentified and uncultivable causative organism has been characterized by novel molecular-genetic techniques. Second, in contrast to other chronic inflammatory disorders, clinical manifestations of T. whippelii infection seem to be based on reduced T-cell helper type 1 (TH1) activity. These findings have led to an improved pathophysiologic understanding of the disease and to new aspects in treatment strategies that are discussed in this paper.

Antigen-induced mucosal T cell activation is followed by Th1 T cell suppression in continuously fed ovalbumin TCR-transgenic mice

We investigated kinetics and dose-dependent features of mucosal and peripheral immune responses following oral antigen application in a TCR-transgenic mouse model. Ovalbumin (OVA) TCR-transgenic mice were fed OVA at different doses (5-250 mg) and various frequencies (one to seven times, or continuous feeding). Low- and medium-dose (10, 100 mg) OVA feeding resulted in priming of immune responses, i.e. increased antigen-specific proliferation as well as IL-2, IL-4 and IFN-gamma secretion upon in vitro restimulation in Peyer's patches and spleen. Immune responses were suppressed with doses of one or three times 250 mg OVA feeding in the spleen. However, only the highest OVA feeding doses (7x250 mg OVA) or continuous feeding (5 mg daily in the drinking water over a 12-week period) actively suppressed immune responses and were associated with production of TGF-beta and IL-10 in the spleen and Peyer's patches. Thus, the cell population generated by continuous antigen feeding was characterized by production of suppressive cytokines and seems to be based on a counter-regulation with Th1 cytokines. These data further define the regulation of suppressive immune functions following antigen feeding in the periphery and the mucosal immune system.

Antigen-induced mucosal T cell activation is followed by Th1 T cell suppression in continuously fed ovalbumin TCR-transgenic mice

We investigated kinetics and dose-dependent features of mucosal and peripheral immune responses following oral antigen application in a TCR-transgenic mouse model. Ovalbumin (OVA) TCR-transgenic mice were fed OVA at different doses (5-250 mg) and various frequencies (one to seven times, or continuous feeding). Low- and medium-dose (10, 100 mg) OVA feeding resulted in priming of immune responses, i.e. increased antigen-specific proliferation as well as IL-2, IL-4 and IFN-gamma secretion upon in vitro restimulation in Peyer's patches and spleen. Immune responses were suppressed with doses of one or three times 250 mg OVA feeding in the spleen. However, only the highest OVA feeding doses (7x250 mg OVA) or continuous feeding (5 mg daily in the drinking water over a 12-week period) actively suppressed immune responses and were associated with production of TGF-beta and IL-10 in the spleen and Peyer's patches. Thus, the cell population generated by continuous antigen feeding was characterized by production of suppressive cytokines and seems to be based on a counter-regulation with Th1 cytokines. These data further define the regulation of suppressive immune functions following antigen feeding in the periphery and the mucosal immune system.

Anti-interleukin 12 treatment regulates apoptosis of Th1 T cells in experimental colitis in mice

BACKGROUND & AIMS

Trinitrobenzene sulfonic acid (TNBS)-induced colitis is a T-helper 1 (Th1) T cell-mediated inflammation that is rapidly reversed by administration of anti-interleukin (IL) 12. This study sought to define the mechanism of this curative effect.

METHODS

Cells and tissue from mice with TNBS colitis receiving treatment with anticytokines were analyzed for phenotype, cytokine production, and apoptosis.

RESULTS

In initial studies, we found that treatment of mice with TNBS-induced colitis with anti-IL-12 was more effective than with anti-interferon (IFN)-gamma, and that anti-IL-12 led to complete normalization of IFN-gamma production by lamina propria T cells ex vivo, whereas anti-IFN-gamma did not. These data suggesting that anti-IL-12 leads to reversal of colitis by elimination of the Th1 T cells were substantiated by studies showing that anti-IL-12 treatment led to increased numbers of apoptotic cells in the lamina propria and spleen by both TUNEL staining of tissues and dispersed spleen cell populations. Finally, we found that the observed apoptosis was mediated by the Fas pathway because (1) MRL/MpJ-lpr(fas) mice lacking Fas function develop colitis that responds poorly to treatment with anti-IL-12; and (2) SJL/J mice with TNBS colitis that received Fas-Fc to block the Fas pathway were resistant to anti-IL-12 treatment.

CONCLUSIONS

These studies show that a main mechanism of action of anti-IL-12 in TNBS-induced colitis is the induction of Fas-mediated apoptosis of the Th1 T cells, causing inflammation.

Extinction of IL-12 signaling promotes Fas-mediated apoptosis of antigen-specific T cells

In previous studies we have shown that peripheral tolerance achieved by high dose feeding of OVA to intact OVA-TCR transgenic mice was enhanced when endogenous IL-12 was neutralized simultaneously. To generalize this phenomenon, in the present study we investigated the tolerogenic mechanisms underlying the blockade of IL-12 signaling following oral and systemic Ag delivery. We found that the numbers of Ag-specific T cells in several lymphoid organs were significantly reduced due to T cell apoptosis following oral OVA or systemic OVA administration when combined with anti-IL-12 injection, but there was no decrease in T cell numbers for OVA-fed, OVA-injected, or anti-IL-12 alone-treated mice compared with those in untreated control mice. In addition, mostly Fas+ T cells were subject to apoptotic deletion in the OVA- plus anti-IL-12-treated groups, and an enhanced cell death of T cells upon OVA restimulation in vitro could be partially reversed by blockade of the Fas/Fas ligand interaction. Finally, in a murine model of superantigen-driven T cell expansion and deletion, we observed no deletional effects of anti-IL-12 treatment on CD4+ cells in Fas-deficient (MRL/lpr) mice, but did find these effects in MRL wild-type mice. In summary, our data suggest that in the course of Ag-induced cell proliferation of Th1 cells, signaling through IL-12 is required to prevent an induction of Fas-mediated apoptosis. Thus, the use of anti-IL-12 may be potentially useful in modulating peripheral immune responses by promotion of Fas-mediated cell death.

[Mechanisms and applications of oral tolerance]

The term oral tolerance (OT) describes the antigen-specific suppression of immune responses following the feeding of the antigen. While some common features with other forms of induction of systemic tolerance have been disclosed, OT can be distinguished by certain immunologic characteristics. Thus, work in experimental animal models revealed the importance of intestinal antigen processing, especially antigen processing in the Peyer's patches, in inducing OT. It has become clear that suppressive T cell cytokines derived from mucosal sites play a major role in mediating OT. The variation of the dose of fed antigen and the modulation of the cytokine milieu both have influences on the underlying immunologic mechanisms active suppression, clonal anergy and clonal deletion following oral antigen uptake. In several animal models of autoimmunity the disease activity can be suppressed by feeding oral autoantigen. Based on these results, recent clinical studies have begun to explore OT as a means to treat autoimmune disorders such as multiple sclerosis, rheumatoid arthritis and diabetes.

Murine model of oral tolerance. Induction of Fas-mediated apoptosis by blockade of interleukin-12

We explored the immunological mechanisms underlying the development of oral tolerance with the use of ovalbumin (OVA) T-cell receptor (TCR)-transgenic mice. Feeding high doses of OVA induced tolerance in the peripheral lymphoid tissues, and the degree of peripheral tolerance was enhanced when antigen feeding was combined with systemic administration of antibodies to interleukin-12 (anti-IL-12). Using the TUNEL technique by which apoptotic cells can be specifically identified, we found evidence that peripheral clonal deletion occurs in OVA-TCR transgenic mice in vivo after oral antigen delivery and treatment with anti-IL-12, but only to a minor degree after antigen feeding alone. The mechanism that accounts for the dramatic loss of peripheral cells is Fas-mediated, since > 90% of antigen-specific Fas+ T cells were lost. In addition, antagonizing Fas but not TNF reversed the phenomenon when cells were stimulated in vitro. These findings suggest that IL-12 negatively regulates apoptosis, a major mechanism of peripheral tolerance. A combination of oral antigen feeding and administration of anti-IL-12 may thus be useful in the treatment of autoimmune diseases and may be a potent means to modulate peripheral tolerance.

Factors involved in the differentiation of TGF-beta-producing cells from naive CD4+ T cells: IL-4 and IFN-gamma have opposing effects, while TGF-beta positively regulates its own production

TGF-beta has been shown to play a central role in regulating inflammatory responses; thus, understanding the factors involved in the generation of TGF-beta-producing cells could lead to interventions that are useful in effecting disease progression. In initial studies, the capacity of naive CD4+ T cells from TCR transgenic (Tg) mice to produce TGF-beta following primary and secondary stimulation was assessed. TGF-beta, IL-4, or IFN-gamma production could not be detected from highly purified naive CD4+/lymphocyte endothelial cell adhesion molecule (LECAM)-1high cells following primary stimulation for 36 h with plate-bound anti-CD3, anti-CD28, and IL-2. This population was subsequently used to study the differentiation of TGF-beta-producing CD4+ T cells. In further studies, naive CD4+/LECAM-1high cells from TCR transgenic mice of both the BALB/c and B10.A backgrounds were stimulated with T-depleted spleen cells (TDS) and specific peptide in the presence of various cytokines and/or cytokine antagonists for 5 days, restimulated, and TGF-beta, IL-4, and IFN-gamma production were measured. Priming conditions favoring high IL-4 production and/or low IFN-gamma production greatly enhanced TGF-beta production in secondary cultures. Furthermore, the presence of IL-10 in cultures was associated with an increase in TGF-beta production following restimulation. The importance of IL-4 and IFN-gamma in regulating TGF-beta production was confirmed in studies showing that cells from IFN-gamma(-/-) mice produced more TGF-beta, while cells from IL-4(-/-) mice produced less TGF-beta compared with wild-type controls. Finally, the addition of exogenous TGF-beta to priming cultures significantly enhanced the production of TGF-beta upon restimulation, demonstrating that TGF-beta has a role in self-regulating its own production.

Oral tolerance

Oral tolerance is the immunologic mechanism by which the mucosal immune system maintains unresponsiveness to the myriad of antigens in the mucosal environment which might otherwise induce untoward immune responses. Recent studies have shown that it is mediated by several distinct, yet interacting mechanisms including the generation of suppressive T cells producing antigen nonspecific cytokines and the induction of clonal deletion and/or anergy. In this review of oral tolerance, we discuss these mechanisms in detail and show how oral tolerance or lack thereof may explain the occurrence of mucosal inflammation. In addition, we discuss how induction of oral tolerance can be used to treat autoimmune states.

Defects of monocyte interleukin 12 production and humoral immunity in Whipple's disease

BACKGROUND & AIMS

Whipple's disease (WD) is a systemic infection in which the causative bacteria typically accumulate within macrophages. The aim of this study was to test whether this macrophage dysfunction is the cause or result of previously shown T-cell defects.

METHODS

In vitro production of interleukin (IL)-12, IL-10, tumor necrosis factor alpha, interferon gamma (IFN-gamma), and transforming growth factor beta (TGF-beta) from purified monocytes and peripheral blood mononuclear cells, cytokine expression on duodenal biopsy specimens, and serum cytokine and immunoglobulin (Ig) levels were tested in 9 patients with WD.

RESULTS

Reduced monocyte IL-12 production and decreased IFN-gamma secretion by peripheral blood mononuclear cells in vitro were found, as well as reduced immunohistological staining for IL-12 and IFN-gamma, but no decrease in other cytokines in patients with WD. A similar but less severe defect in 2 relatives with WD argued for a genetic basis of this abnormality. Serum IgG2, an IFN-gamma-dependent Ig subclass, and serum TGF-beta levels were reduced in patients with WD.

CONCLUSIONS

The described monocyte defects in WD may result in a secondary reduction of IFN-gamma production and IgG2 serum levels. This provides a rationale for additive immunotherapy in patients with antibiotic-refractory WD.

Regulation of interleukin-12 by complement receptor 3 signaling

Complement receptor type 3 (CR3, CD11b/CD18) serves as a receptor for a number of endogenous ligands and infectious organisms, and is involved in adhesion and host defense functions. Here, we report that signaling via CR3 plays an important role in regulating production of interleukin-12 (IL-12), a key mediator of cell-mediated immunity (CMI). We demonstrate with a variety of stimuli a dose-dependent, specific downregulation of IL-12 secretion by human monocytes in vitro after exposure to antibodies to CR3 (anti-CD11b and anti-CD18), as well as to the natural CR3 ligands, iC3b, and Histoplasma capsulatum. CR3 antibodies also suppressed interferon-gamma (IFN-gamma) production in cultures of human peripheral blood mononuclear cells (PBMC). We determined that one mechanism by which CR3 antibodies may suppress IL-12 production is by the inhibition of IFN-gamma-induced tyrosine phosphorylation. Finally, in a murine model of IL-12-dependent septic shock, we provide evidence that administration of CR3 antibodies leads to suppression of IL-12 and IFN-gamma in vivo. Our studies thus define a novel role for CR3 in regulating CMI functions via IL-12.

Regulation of transforming growth factor-beta production by interleukin-12

The induction of peripheral tolerance following oral antigen administration in several autoimmune disease and conventional animal models correlates with the production of transforming growth factor-beta (TGF-beta) and T helper type 2 (Th2) cytokines. The factors regulating TGF-beta production and its relation to the Th2 response, however, have not been defined. We demonstrate that the systemic administration of antibodies to interleukin (IL)-12 to ovalbumin (OVA)-T cell receptor (TCR) transgenic mice fed high doses of OVA, followed by systemic OVA challenge, substantially enhances TGF-beta, but not IL-4 production by peripheral T cells. Furthermore, we demonstrate in an in vitro T cell differentiation model that naive (CD4+/Mel-14hi) OVA-TCR-T cells stimulated with OVA-pulsed dendritic cells (DC) produce four- to fivefold higher amounts of TGF-beta when cultured with anti-IL-12 or anti-interferon-gamma (IFN-gamma). In this in vitro system, IL-4 was not required for TGF-beta production by T cells; however, it appeared to enhance levels of TGF-beta by promoting the growth of TGF-beta-producing cells. Our findings demonstrate that IL-12 and IFN-gamma are important negative regulators of TGF-beta production both in vivo and in vitro, and that their modulation may be of benefit for the treatment of autoimmune disorders.

Reciprocal IFN-gamma and TGF-beta responses regulate the occurrence of mucosal inflammation

The above new findings concerning the immunological mechanisms governing mucosa, immune responses and oral tolerance in TCR-transgenic mice, as well as those operative in mice with experimental colitis, greatly expand our understanding of the processes that normally control mucosal inflammation and possibly other types of inflammation as well (Fig. 1). They indicate that, in the nondiseased mouse, ingested proteins evoke a Th1-cell (IFN-gamma) response in the mucosal follicles that is quickly counter-regulated by induction of T-cell anergy/deletion, if this Th1-cell response is inhibited (experimentally by anti-IL-12), TGF beta-producing cells appear, and these are capable of active immune suppression. This reciprocal relationship between IFN-gamma production and TGF-beta production is further supported in mouse models of mucosal inflammation. Thus, in the TNBS-colitis model, there is direct stimulation of the immune cells in the lamina propria as a result of diffuse haptenization of mucosal proteins, which leads to a massive Th1-cell response capable of overwhelming any suppressive counter-regulatory mechanisms normally generated in the PPs. This highly polarized Th1-cell response is controlled only by direct abrogation of IL-12 production with exogenous administration of anti-IL-12, or with indirect inhibition of this response via induction of oral tolerance and accompanying production of TGF-beta (Refs 6-8). The data obtained from this model are consistent with those obtained with another model of intestinal inflammation--inflammation in severe combined immunodeficiency (SCID) mice following lymphoid repletion with CD45Rbhi (naive) T cells. In this model, inflammation is again mediated by Th1 cells and is prevented by co-repletion with CD45Rbhi (memory) T cells, which appear to work by secreting TGF-beta (Refs 9, 10). Thus, a common feature of the various experimental models of intestinal inflammation studied to date is the Yin-Yang relationship of IFN-gamma and TGF-beta, with the former being proinflammatory and the latter anti-inflammatory. Is the IFN-gamma TGF-beta dichotomy that is evident both in the normal state and in models of inflammation simply a reflection of an underlying Th1 Th2 dichotomy? The answer to this important question is not yet known. Thus, while it is clear from the in vitro studies already discussed that IL-12 and/or IFN-gamma inhibit TGF-beta production, the role of IL-4 in this process is more elusive. These in vitro studies indicate that IL-4 is not required for TGF-beta production, a finding that is consistent with studies in which the transfer of CD45Rbhi, T cells from IL-4-/- mice protected SCID mice from colitis induced by CD45Rbhi T cells. However, the addition of IL-4 to in vitro cultures containing anti-IL-12 augmented TGF-beta production, most probably by IL-4 acting as a growth factor for TGF-beta-producing cells rather than as an inducing factor (T. Marth et al., unpublished). Obviously, more work will be necessary to resolve this issue. Finally, it should be noted that the above considerations apply to human inflammatory diseases of the gastrointestinal tract, such as Crohn's disease. Recently, it has been shown that T cells extracted from Crohn's disease tissues manifest skewed Th1-cell responses. The hypothesis can therefore be put forward that this disease results from a dysregulated Th1-cell response to ubiquitous mucosal antigens that is not appropriately controlled by normal counter-regulatory mechanisms. Interventions that artificially bring the excessive Th1-cell response back into balance, such as administration of IL-12 antagonists, should therefore find a central place in the treatment of the disease.

High dose oral tolerance in ovalbumin TCR-transgenic mice: systemic neutralization of IL-12 augments TGF-beta secretion and T cell apoptosis

The immune response to oral Ag administration, including the development of oral tolerance, was explored with the use of OVA TCR-transgenic mice. Feeding high doses of OVA enhanced IFN-gamma production in the Peyer's patches, but induced tolerance in the peripheral lymphoid tissues marked by suppressed proliferative and cytokine responses. Systemic administration of Abs to IL-12 (anti-IL-12) simultaneous with Ag feeding modestly enhanced the degree of tolerance in the peripheral lymphoid tissues, as shown by increased suppression of proliferative responses after in vitro restimulation, and secondary responses in the popliteal lymph nodes following in vivo challenge and in vitro restimulation. Systemic anti-IL-12 treatment was associated with augmented TGF-beta production and T cell apoptosis in both Peyer's patches and peripheral lymphoid tissues. Cell mixing studies and proliferation assays in the presence of anti-TGF-beta provided evidence that the increased suppression of responses induced by anti-IL-12 was due primarily to the secretion of TGF-beta. These findings suggest that IL-12 negatively regulates two of the main mechanisms of oral tolerance, TGF-beta production and clonal deletion via apoptosis. in addition, they suggest that the combination of oral Ag feeding and systemic anti-IL-12 administration may be of benefit in the treatment of autoimmune diseases.

High dose oral tolerance in ovalbumin TCR-transgenic mice: systemic neutralization of IL-12 augments TGF-beta secretion and T cell apoptosis

The immune response to oral Ag administration, including the development of oral tolerance, was explored with the use of OVA TCR-transgenic mice. Feeding high doses of OVA enhanced IFN-gamma production in the Peyer's patches, but induced tolerance in the peripheral lymphoid tissues marked by suppressed proliferative and cytokine responses. Systemic administration of Abs to IL-12 (anti-IL-12) simultaneous with Ag feeding modestly enhanced the degree of tolerance in the peripheral lymphoid tissues, as shown by increased suppression of proliferative responses after in vitro restimulation, and secondary responses in the popliteal lymph nodes following in vivo challenge and in vitro restimulation. Systemic anti-IL-12 treatment was associated with augmented TGF-beta production and T cell apoptosis in both Peyer's patches and peripheral lymphoid tissues. Cell mixing studies and proliferation assays in the presence of anti-TGF-beta provided evidence that the increased suppression of responses induced by anti-IL-12 was due primarily to the secretion of TGF-beta. These findings suggest that IL-12 negatively regulates two of the main mechanisms of oral tolerance, TGF-beta production and clonal deletion via apoptosis. in addition, they suggest that the combination of oral Ag feeding and systemic anti-IL-12 administration may be of benefit in the treatment of autoimmune diseases.

[Gastric hamartoma and thyroid gland carcinoma with follicular and neuroendocrine differentiation in Cowden syndrome]

A 40-year old male patient presented with a history of subtotal strumectomy, excision of multiple cutaneous lesions at the upper trunk and gastrointestinal polyposis of unknown origin. The patient was admitted for weight loss and intermittent diarrhea. Physical examination revealed craniomegaly, papillomatosis of the oral mucosa and epigastric tenderness. Endoscopically, multiple polyps were seen in the stomach, the duodenum, the terminal ileum, the distal colon and the rectum. Histologically, these lesions were classified as hamartomatous and hyperplastic polyps. In the punctate of the relapsed nodular goitre, neoplastic follicular cells were found. These findings led to the diagnosis of Cowden's disease. A complete thyroidectomy was performed. The histology verified a follicular thyroid carcinoma and showed a combined expression of thyroglobulin and of the neuroendocrine marker synaptophysin (appr. 50% of all tumor cells). Chromogranin A (a neuroendocrine tumor marker) was also elevated in the serum of the patient. Postoperatively, a radioiodine therapy was performed and the clinical condition of the patient has improved ever since. The presented case of Cowden's disease is the first male patient with thyroid carcinoma. Early consideration of Cowden's disease is substantial as multiple malignant neoplasms may occur in this disorder in increased incidence.

Whipple's disease

Whipple's disease (WD) is a rare systemic disease caused by infection with the recently identified actinomycetes, Tropheryma whippelii. The disorder affects mostly middle-aged men, and the major clinical features are weight loss, arthropathy, and diarrhea; other symptoms, caused by systemic infection, are not infrequent. The diagnosis is usually established by duodenal biopsy, which shows the pathognomonic periodic acid Schiff-positive infiltrates in the lamina propria. In addition, RT-polymerase chain reaction of tissue specimens can be used to verify the presence of T whippelii. In most cases, patients can be successfully treated by prolonged administration of antimicrobials, such as trimethoprim-sulfamethoxazole. The unusual chronic-relapsing course of the disease, the predisposition of middle-aged, HLA-B27-positive men for WD, and other characteristics of the disease imply that host factors are involved in the etiopathogenesis of WD. Indeed, it has been shown that patients with WD have suppressed delayed-type hypersensitivity responses in vivo and decreased in vitro T-cell responses, eg, to phytohemagglutinin and concanavalin A. In addition, serum-suppressor factors and shifts in T-cell subpopulations have been found. Perhaps most importantly, WD macrophages have a decreased ability to degrade intracellular microorganisms and patients have reduced numbers of circulating cells expressing CD11b, a cell adhesion and complement receptor molecule on macrophages involved in the activation of intracellular killing of pathogens. Most of those immunologic alterations also occur in patients with longstanding clinical remission, suggesting that this subtle host-defense defect plays an important role in disease pathogenesis.

Persistent reduction of complement receptor 3 alpha-chain expressing mononuclear blood cells and transient inhibitory serum factors in Whipple's disease

Several small studies have indicated an impaired cell mediated immune response as a possible cause for the delayed elimination of the bacteria in Whipple's disease. A specific defect, however, has not been defined. We examined the expression of cell surface molecules and mitogenic responses of peripheral blood mononuclear cells in 27 patients with Whipple's disease at different disease stages by indirect immunofluorescence and by measurement of [3H]thymidine incorporation, respectively. E-rosette formation and cutaneous reaction to seven recall antigens were determined. Matched healthy donors served as controls. We found a significantly reduced number of cells expressing the complement receptor 3 alpha-chain (= CD11b) in all patients. In florid disease, the number of activated cells (in particular CD58 positive cells) was increased and CD4/CD8 ratios were diminished. Proliferation to phytohemagglutinin and to sheep red blood cells was reduced at all stages of the disease. Serum of control persons reversed this decreased responsiveness especially in patients with active disease. Skin reaction was hypoergic in all patients. Determination of CD58 positive cells increased in patients with active disease may be useful to define the activity of the disease and the duration necessary for treatment. Transient inhibiting serum activities may impair the CD2/CD58 interaction. The reduction of cells expressing CD11b, the decreased proliferation, and the cutaneous hypoergy indicate a persisting defect of cell mediated immunity in vivo and in vitro. These defects may contribute to the impaired ability of patients with Whipple's disease to eliminate bacteria.

An evaluation of antimicrobial treatment for Whipple's Disease. Tetracycline versus trimethoprim-sulfamethoxazole

Whipple's disease is a multisystemic disorder in which almost all organ systems can be invaded by rod-shaped bacteria. Without extended antimicrobial therapy, its course is lethal. Empirically, treatment consists of tetracyclines given for one to two years. Trimethoprim-sulfamethoxazole, a compound that crosses the blood-brain barrier, has been suggested as an alternative when patients were observed with progressive cerebral involvement. There has never been a formal evaluation of the selection of antibiotics for the treatment of Whipple's disease. In the present nonrandomized, partially retrospective study, we compared the result of two treatment regimens in 30 patients, all examined personally. Twenty-two patients were treated with tetracycline and eight patients with trimethoprim-sulfamethoxazole. In five patients, therapy with tetracycline was changed to another antimicrobial agent because of treatment failure or drug intolerance. The main treatment measure was disappearance of the clinical symptoms such as weight loss, arthritis, malabsorption, fever, edema, central nervous system manifestations, lymphadenopathy, and congestive heart failure. Drug intolerance requiring a change of medication was also considered a treatment failure. We found that trimethoprim-sulfamethoxazole induced complete clinical remission in 12 of 13 treatment cycles, tetracycline in 13 of 22 treatment cycles (P < 0.05; mean difference 33%; 95% confidence interval 8% to 58%). Trimethoprim-sulfamethoxazole was also more efficacious than tetracycline in the treatment of cerebral Whipple's disease. However, trimethoprim-sulfamethoxazole did not prevent cerebral manifestations in all cases. The only deaths due to Whipple's disease occurred in patients with cerebral involvement. It is concluded that treatment with trimethoprim-sulfamethoxazole was significantly superior to that with tetracycline in inducing clinical remission of Whipple's disease.(ABSTRACT TRUNCATED AT 250 WORDS)