Multiple cytokines for the detection of Mycobacterium tuberculosis infection in children with tuberculosis

SETTING

Interferon-gamma (IFN-γ) release assays (IGRAs) play an important role in the diagnosis of Mycobacterium tuberculosis infection. However, in children with tuberculosis (TB), some studies have shown increased frequencies of false-negative or indeterminate IGRA results.

OBJECTIVE

To analyse the spectrum of different cytokines to improve the diagnostic accuracy of IGRAs in latent tuberculous infection (LTBI) and active TB.

DESIGN

We performed multiplex cytokine expression analysis of QuantiFERON® Gold In-Tube supernatants in children with active TB (n = 21) and disease-free contacts with (n = 15) and without LTBI (n = 12), to determine the sensitivity and specificity of the modified tests.

RESULTS

Of 21 initial cytokines analysed, IFN-γ and six other candidates (interleukin [IL] 2, inducible protein 10 [IP-10], IL-13, IL-1α, tumour necrosis factor alpha [TNF-α] and granulocyte-macrophage colony-stimulating factor [GM-CSF]) were significantly more elevated in children with TB and those with LTBI than in the non-infected controls. Sensitivity and specificity were similar for IFN-γ and IL-2, but lower for the remaining candidates. Notably, a subset of candidates, including IP-10, showed M. tuberculosis antigen-induced specific expression in non-infected children. None of the candidates showed differences in expression between children with TB and those with LTBI.

CONCLUSIONS

Our results did not suggest that alternative IGRA cytokines can distinguish between children with active TB and those with LTBI. IFN-γ and IL-2 showed comparable capacity in diagnosing M. tuberculosis infection in our study groups.

[Dysphagia and dyspnea after laparoscopic fundoplication]

Intrathoracic gastric herniation after laparoscopic antireflux surgery is a rare but well known phenomenon. It may occur during the early and late postoperative period. We report on a patient with early onset of dysphagia after surgery due to a tight wrap. Subsequent vomiting and dysphagia increased due to a gastric herniation. After gastroscopy and bougienage, tension pneumothorax developed. The context and relationships are illustrated and discussed referring to the current literature.

A stepwise approach to the laboratory diagnosis of Buruli ulcer disease

OBJECTIVE

In view of technical and financial limitations in areas of endemicity, the current practice and recommendations for the laboratory diagnosis of Buruli ulcer disease (BUD) may have to be reconsidered. We reviewed diagnostic results in order to explore options for a modified, more practicable, cost-effective and timely approach to the laboratory diagnosis of BUD.

METHODS

Diagnostic specimens from 161 clinically diagnosed BUD patients from four different treatment centres in Ghana were subjected to laboratory analysis. The positivity rates of the laboratory assays were compared.

RESULTS

The number of laboratory-confirmed clinically diagnosed BUD cases with one positive confirmative test was 20% higher than that with two positive confirmative tests. The specificity of microscopy (MIC) and PCR was 96.6% and 100%, respectively. Subsequent analysis of specimens from surgically excised pre-ulcerative tissue-by-tissue MIC and tissue PCR rendered 65% laboratory-confirmed BUD cases. Subsequent analysis of diagnostic swabs from ulcerative lesions by swab smear MIC and swab PCR rendered 70% of laboratory-confirmed BUD cases.

CONCLUSIONS

The specificity of the diagnostic tests used in this study suggests that one positive diagnostic test may be considered sufficient for the laboratory confirmation of BUD. Subsequent application of different diagnostic tests rendered a laboratory confirmation of 65% pre-ulcerative and of 70% ulcerative lesions. Implementation of a stepwise, subsequent analysis of diagnostic specimens will result in considerable cost saving compared with simultaneous testing of specimens by several diagnostic assays.

External quality assurance for the laboratory diagnosis of Buruli ulcer disease in Ghana

OBJECTIVE

To assure the quality of the laboratory diagnosis of Buruli ulcer disease; microscopy and PCR were subjected to external quality assurance (EQA).

METHODS

Slides were read by test laboratory staff, followed by blinded re-reading by the controller. Parallel testing of PCR specimens was carried out at the local and external reference laboratory. Slides and PCR specimens with discordant results were subjected to a second reading/testing by the controller to determine the final result. For training purposes, slides and PCR specimens with discrepant results were subsequently re-read/re-tested under supervision at the test laboratory.

RESULTS

Microscopy. First reading: concordance rate 82.9%, discordance rate 17.1%, percentage false negatives 27.1% (sensitivity 72.9%), percentage false positives 10.1% (specificity 89.9%). Second reading: concordance rate 97.9%, discordance rate 2.1%, percentage false negatives 4.2% (sensitivity 95.8%), percentage false positives 0.6% (specificity 99.4%). PCR. First testing: concordance rate 87.9%, discordance rate 12.1%, percentage false negatives 8.2% (sensitivity 91.8%), percentage false positives 19.1% (specificity 80.9%). Second testing: concordance rate 96.2%, discordance rate 3.8%, percentage false negatives 4.7% (sensitivity 95.3%), percentage false-positives 2.1% (specificity 97.9%).

CONCLUSIONS

EQA identified deficiencies in the laboratory performance. Corrective action consisted in on-site training and reduced the number of false-negative and false-positive microscopy and PCR results.

Suppression of Mcl-1 via RNA interference sensitizes human hepatocellular carcinoma cells towards apoptosis induction

Background

Hepatocelluar carcinoma (HCC) is one of the most common cancers worldwide and a major cause of cancer-related mortality. HCC is highly resistant to currently available chemotherapeutic drugs. Defects in apoptosis signaling contribute to this resistance. Myeloid cell leukemia-1 (Mcl-1) is an anti-apoptotic member of the Bcl-2 protein family which interferes with mitochondrial activation. In a previous study we have shown that Mcl-1 is highly expressed in tissues of human HCC. In this study, we manipulated expression of the Mcl-1 protein in HCC cells by RNA interference and analyzed its impact on apoptosis sensitivity of HCC cells in vitro.

Methods

RNA interference was performed by transfecting siRNA to specifically knock down Mcl-1 expression in HCC cells. Mcl-1 expression was measured by quantitative real-time PCR and Western blot. Induction of apoptosis and caspase activity after treatment with chemotherapeutic drugs and different targeted therapies were measured by flow cytometry and fluorometric analysis, respectively.

Results

Here we demonstrate that Mcl-1 expressing HCC cell lines show low sensitivity towards treatment with a panel of chemotherapeutic drugs. However, treatment with the anthracycline derivative epirubicin resulted in comparatively high apoptosis rates in HCC cells. Inhibition of the kinase PI3K significantly increased apoptosis induction by chemotherapy. RNA interference efficiently downregulated Mcl-1 expression in HCC cells. Mcl-1 downregulation sensitized HCC cells to different chemotherapeutic agents. Sensitization was accompanied by profound activation of caspase-3 and -9. In addition, Mcl-1 downregulation also increased apoptosis rates after treatment with PI3K inhibitors and, to a lower extent, after treatment with mTOR, Raf I and VEGF/PDGF kinase inhibitors. TRAIL-induced apoptosis did not markedly respond to Mcl-1 knockdown. Additionally, knockdown of Mcl-1 efficiently enhanced apoptosis sensitivity towards combined treatment modalities: Mcl-1 knockdown significantly augmented apoptosis sensitivity of HCC cells towards chemotherapy combined with PI3K inhibition.

Conclusion

Our data suggest that specific downregulation of Mcl-1 by RNA interference is a promising approach to sensitize HCC cells towards chemotherapy and molecularly targeted therapies.

Interaction of natural killer cells with Trypanosoma cruzi-infected fibroblasts

The protozoan parasite Trypanosoma cruzi circulates in the blood as trypomastigotes and invades a variety of cells to multiply intracellularly as amastigotes. The acute phase triggers an immune response that restricts the proliferation of the parasite. However, parasites are able to persist in different tissues causing the pathology of Chagas' disease. Natural killer (NK) cells play an important role in innate resistance to a variety of pathogens. In the present study we demonstrate that NK cells trigger trypanocidal mechanisms in infected L929 cells that are critically dependent on inducible nitric oxide (NO) synthase (iNOS) induction which is, to a major degree, triggered by interferon (IFN)-gamma provided by NK cells. This work provides a more detailed analysis of how NK cells as a part of the innate immune system participate in the control of parasites that reside intracellularly in fibroblast-like L929 cells.

Cyclooxygenase-2 Inhibition Induces Apoptosis Signaling via Death Receptors and Mitochondria in Hepatocellular Carcinoma

Inhibition of cyclooxygenase (COX)-2 elicits chemopreventive and therapeutic effects in solid tumors that are coupled with the induction of apoptosis in tumor cells. We investigated the mechanisms by which COX-2 inhibition induces apoptosis in hepatocellular carcinoma (HCC) cells. COX-2 inhibition triggered expression of the CD95, tumor necrosis factor (TNF)-R, and TNF-related apoptosis-inducing ligand (TRAIL)-R1 and TRAIL-R2 death receptors. Addition of the respective specific ligands further increased apoptosis, indicating that COX-2 inhibition induced the expression of functional death receptors. Overexpression of a dominant-negative Fas-associated death domain mutant reduced COX-2 inhibitor-mediated apoptosis. Furthermore, our findings showed a link between COX-2 inhibition and the mitochondrial apoptosis pathway. COX-2 inhibition led to a rapid down-regulation of myeloid cell leukemia-1 (Mcl-1), an antiapoptotic member of the Bcl-2 family, followed by translocation of Bax to mitochondria and cytochrome c release from mitochondria. Consequently, overexpression of Mcl-1 led to inhibition of COX-2 inhibitor-mediated apoptosis. Furthermore, blocking endogenous Mcl-1 function using a small-interfering RNA approach enhanced COX-2 inhibitor-mediated apoptosis. It is of clinical importance that celecoxib acted synergistically with chemotherapeutic drugs in the induction of apoptosis in HCC cells. The clinical relevance of these results is further substantiated by the finding that COX-2 inhibitors did not sensitize primary human hepatocytes toward chemotherapy-induced apoptosis. In conclusion, COX-2 inhibition engages different apoptosis pathways in HCC cells stimulating death receptor signaling, activation of caspases, and apoptosis originating from mitochondria.

Histone deacetylase inhibition by valproic acid down-regulates c-FLIP/CASH and sensitizes hepatoma cells towards CD95- and TRAIL receptor-mediated apoptosis and chemotherapy

Hepatocellular carcinoma (HCC) is highly resistant to chemotherapy, leading to a poor prognosis of advanced disease. Inhibitors of histone deacetylase (HDACi) induce re-differentiation in tumor cells and thereby re-establish sensitivity towards apoptotic stimuli. HDACi are entering the clinical stage of tumor treatment, and several substances are currently being tested in clinical trials to prove their efficacy in the treatment of leukemias and solid tumors. In this study, we investigated the impact of the HDACi valproic acid (VA) on TRAIL- and CD95-mediated apoptosis in hepatoma cells, as well as its sensitizing effect on a chemotherapeutic agent. Treatment of HepG2 cells with VA increased sensitivity to CD95-mediated apoptosis (4% apoptosis vs. 42%), and treatment with epirubicin (74% vs. 90% viability). Caspase-3 activity was significantly enhanced in cells treated with VA plus anti-CD95 antibodies compared to cells treated with antibodies alone. In parallel, VA strongly augmented the effect of TNF-related apoptosis-inducing ligand (TRAIL or Apo2 ligand) on HepG2 cells (10% vs. 58% apoptosis). VA induced down-regulation of cellular FLICE-inhibitory protein (c-FLIP/CASH, also known as Casper/iFLICE/FLAME-1/CLARP/MRIT/usurpin), providing a possible molecular mechanism underlying the increased sensitivity towards cell death-mediated apoptosis. HDAC inhibitors are a promising class for the treatment of leukemias. In addition, among other class members, VA deserves further evaluation as a treatment option for patients with advanced HCC.

Mcl-1 is an anti-apoptotic factor for human hepatocellular carcinoma

Defects in apoptosis signaling in hepatocytes contribute to tumorigenesis in hepatocellular carcinoma (HCC). In addition, treatment with chemotherapeutic drugs is often ineffective in HCC patients due to the apoptosis resistance of cancer cells. Anti-apoptotic members of the Bcl-2 family, including myeloid cell leukemia-1 (Mcl-1), which regulate intrinsic apoptosis induction at the mito-chondrial level, are often overexpressed in human cancer, and are implicated with disease grade and prognosis. Yet, little is known about the role of Mcl-1 in HCC. In this study, we analyzed the relevance of Mcl-1 expression for the apop-tosis resistance of human HCC. Mcl-1 protein expression was considerably enhanced in human HCC tissue compared to adjacent non-tumor tissue. In addition, Mcl-1 was prominently expressed in various HCC cell lines. Mcl-1 basal expression is dependent on a functional phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway; treatment of the cells with a specific PI3 kinase inhibitor led to both decreased Mcl-1 expression and a sensitization towards chemotherapeutic drug-induced apoptosis. Furthermore, the hepatocyte growth factor and epidermal growth factor induced Mcl-1 expression in an Akt- and ERK-dependent manner. Finally, specific upregulation of Mcl-1 in HCC cells inhibited chemotherapeutic drug-induced apoptosis. Our data suggest that Mcl-1 is an important factor for the apoptosis resistance of human HCC, and constitutes an interesting target for HCC therapy.

Mcl-1 is an anti-apoptotic factor for human hepatocellular carcinoma

Defects in apoptosis signaling in hepatocytes contribute to tumorigenesis in hepatocellular carcinoma (HCC). In addition, treatment with chemotherapeutic drugs is often ineffective in HCC patients due to the apoptosis resistance of cancer cells. Anti-apoptotic members of the Bcl-2 family, including myeloid cell leukemia-1 (Mcl-1), which regulate intrinsic apoptosis induction at the mito-chondrial level, are often overexpressed in human cancer, and are implicated with disease grade and prognosis. Yet, little is known about the role of Mcl-1 in HCC. In this study, we analyzed the relevance of Mcl-1 expression for the apop-tosis resistance of human HCC. Mcl-1 protein expression was considerably enhanced in human HCC tissue compared to adjacent non-tumor tissue. In addition, Mcl-1 was prominently expressed in various HCC cell lines. Mcl-1 basal expression is dependent on a functional phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway; treatment of the cells with a specific PI3 kinase inhibitor led to both decreased Mcl-1 expression and a sensitization towards chemotherapeutic drug-induced apoptosis. Furthermore, the hepatocyte growth factor and epidermal growth factor induced Mcl-1 expression in an Akt- and ERK-dependent manner. Finally, specific upregulation of Mcl-1 in HCC cells inhibited chemotherapeutic drug-induced apoptosis. Our data suggest that Mcl-1 is an important factor for the apoptosis resistance of human HCC, and constitutes an interesting target for HCC therapy.

Post-surgical assessment of excised tissue from patients with Buruli ulcer disease: progression of infection in macroscopically healthy tissue

OBJECTIVE

The current standard of treatment of Buruli ulcer disease (BUD) is surgical excision of lesions. Excision size is determined macroscopically assuming the complete removal of all infected tissue. However, dissemination of infection beyond the excision margins into apparently healthy tissue, possibly associated with recurrences, cannot be excluded in this way. To assess the central to peripheral progression of Mycobacterium ulcerans infection and the mycobacterial infiltration of excision margins, excised tissue was examined for signs of infection.

METHODS

20 BUD lesions were excised in general anaesthesia including all necrotic and subcutaneous adipose tissue down to the fascia and at an average of 40 mm into the macroscopically unaffected tissue beyond the border of the lesion. Tissue samples were subjected to PCR and histopathology.

RESULTS

Although the bacillary load decreased from central to peripheral, M. ulcerans infection was detected throughout all examined tissue specimens including the peripheral segments as well as excision margins of all patients. During the post-operative hospitalization period (averaging 2 months) no local recurrences were observed.

CONCLUSION

Available data suggest a correlation of surgical techniques with local recurrences. The results of this study indicate the unnoticed early progression of mycobacterial infection into macroscopically healthy tissue. Thus, the removal of all infected tissue cannot always be verified visually by the surgeon. Provided that long-term follow up of patients with positive excision margins will establish the clinical relevance of these findings, on-site laboratory assessment of excised tissue in combination with follow up may contribute to reduce recurrence rates.

Bilateral thoracic extraadrenal myelolipoma

Myelolipoma commonly occurs in the adrenal gland and is composed of both adipose tissue and normal hematopoietic elements. Extraadrenal myelolipoma may occur in the retroperitoneum, stomach, liver, lung, and in 3% of cases even in the mediastinum. We present a 65-year-old female patient with unspecific clinical symptoms. Routine chest roentgenograms revealed bilateral widening of the posterior mediastinum. Computed tomography showed bilateral, paravertebral lesions of 4.5 and 6.5 cm in diameter, respectively. After surgical removal, bilateral thoracic myelolipoma was pathomorphologically diagnosed. The imaging differential diagnosis of bilateral solid lesions in the posterior mediastinum including lymph node metastases, lymphomas, neurogenic tumors and extramedullary hematopoietic tumors is discussed.

Dry-reagent-based PCR as a novel tool for laboratory confirmation of clinically diagnosed Mycobacterium ulcerans-associated disease in areas in the tropics where M. ulcerans is endemic

After tuberculosis and leprosy, Buruli ulcer (BU), caused by Mycobacterium ulcerans, is the third most common mycobacterial disease in immunocompetent humans. The disease occurs in tropical countries, with foci in West Africa, Central Africa, and the western Pacific. BU is defined as an infectious disease involving the skin and the subcutaneous adipose tissue characterized by a painless nodule, papule, plaque, or edema, evolving into a painless ulcer with undermined edges and often leading to invalidating sequelae. Due to the fundamental lack of understanding of modes of transmission, disease control in endemic countries is limited to early case detection through improved active surveillance and surgical treatment. The laboratory confirmation of BU is complicated by the absence of a diagnostic "gold standard." Therefore, misclassification and delayed diagnosis of BU may occur frequently, causing a considerable socioeconomic impact in terms of treatment costs due to prolonged hospitalization. In order to respond to the urgent need to develop reliable tools for early case detection and to overcome technical difficulties accompanying the implementation of diagnostic PCR procedures in tropical countries, a dry-reagent-based PCR formulation for the detection of M. ulcerans in diagnostic specimens has been developed at the Bernhard Nocht Institute for Tropical Medicine. Following technical and clinical validation, the assay has been successfully installed and field tested at the Kumasi Centre for Collaborative Research in Tropical Medicine, Kumasi, Ghana. Preliminary results show an excellent diagnostic sensitivity of >95%.

[Global warming and spread of infectious diseases]

At the end of the twentieth century, tropical infectious diseases increased despite earlier successes of eradication campaigns. As a global warming of 1.4-5.8 degrees C is anticipated to occur by 2100, mainly the vector-borne tropical diseases that are particularly sensitive to climate are expected to spread. Although biological reasons seemingly support this hypothesis, ecological and socioeconomic factors have in the past proven to be stronger driving forces for the spread of infectious disease than climate.

CTLA-4 regulates the murine immune response to Trypanosoma cruzi infection

Infection with Trypanosoma cruzi causes a profound suppression of T cell responsiveness to polyclonal or antigenic stimuli. In this study, we quantified expression of the negative T cell regulatory molecule CTLA-4 in T. cruzi infected mice and analysed its influence on the immune suppression. Levels of splenic CTLA-4 expression were highest around day 10 after infection, reaching 5% in resistant B6D2F1 mice, but exceeding 10% of CD4(+) T cells in C57BL/6 mice that were susceptible to mortal disease. The proliferative response of explanted splenocytes to CD3-mediated stimulation was strongly suppressed in both the susceptible and the resistant strains. Blockade of CTLA-4 in vitro with a monoclonal antibody affected neither proliferative response nor cytokine production (IFN-gamma, IL-4 and IL-2) by splenic T cells from infected C57BL/6 mice. Treatment of mice with anti-CTLA-4 antibody on the day of infection decreased IFN-gamma production and reduced mortality by about 50%. We conclude that high CTLA-4 expression is a hallmark of severe disease in murine T. cruzi infection, and that CTLA-4 has a regulative influence at the early stages during priming of the immune reaction to the parasite, augmenting a strong Th1-biased response.

[Renin-angiotensin system: molecular biology]

Renin-angiotensin system (RAS) have been extensively studied in last few decades. RAS regulates blood pressure, water and electrolytes balance. The disorders in function of RAS may play a potential role in development of some complex diseases like: hypertension, myocardial infarction, stroke, nephropathies and renal failure, chronic obstruction pulmonary disease and many more. RAS may take part in formation and progression of these diseases. In this work we focus on molecular biology of RAS and polymorphisms of RAS genes.

Enhanced activation of CD83-positive T cells

CD83 is a marker molecule for mature dendritic cells (DCs) but is also substantially expressed on activated T cells in humans and mice. Its function is unknown, but CD83 knockout mice show an impaired thymic maturation of CD4-positive cells and soluble CD83 inhibits partially antigen-specific responses in vitro pointing to a role of CD83 in the immune system. Here we show that CD83-positive T cells produce strongly increased amounts of interferon-gamma and interleukin-2. In contrast, constitutive expression of CD83 on DCs alters neither the activation of DCs following addition of lipopolysaccharide nor the ability to present antigenic peptides. Thus, the expression of CD83 on T cells has direct functional consequences for tuning the activation threshold.

Murine susceptibility to Chagas' disease maps to chromosomes 5 and 17

Chagas' disease is caused by the protozoan parasite Trypanosoma cruzi and commonly modelled in inbred mice. Susceptibility of mouse strains to experimental infection varies considerably. We quantified parasite tissue burdens in resistant and susceptible strains by real time PCR and applied a backcross strategy to map the genomic loci linked to susceptibility in inbred mice. Resistant B6D2F1 mice were backcrossed with susceptible C57BL/6 mice, and 46 of a total 192 offspring died after infection. Their genomes were scanned with microsatellite markers. One region on chromosome 17 was significantly linked to susceptibility, while another on chromosome 5 was suggestive of linkage.

'Ignorance' of antigen-specific murine CD4+ and CD8+ T cells is overruled by lipopolysaccharide and leads to specific induction of IFN-gamma

Lipopolysaccharide (LPS) can activate human and murine T cells in vivo and in vitro. Here we analysed the effects of LPS on T cells with defined specificities in T-cell receptor (TCR)-transgenic systems. LPS rapidly induced high amounts of interferon (IFN)-gamma in a subpopulation of purified T cells from DO11.10 (OVA323-339/H2-Ad) and OT-1 (OVA257-264/H2-Kb) mice when coincubated with antigen-pulsed peritoneal exudate cells (PECs). LPS induced IFN-gamma in T cell cultures even when the number of antigenic major histocompatibility complex (MHC) class-I complexes was too small to stimulate the T cells. LPS, thus, overruled the unresponsiveness of the otherwise 'antigen-ignorant' T cells. The release of IFN-gamma strictly correlates with the PECs' ability to produce interleukin (IL)-12. In contrast to the induction of IFN-gamma, antigen-specific IL-2 secretion and proliferation of T cells were rather decreased in the presence of LPS. Only very few IFN-gamma-secreting natural killer (NK) cells and natural killer T (NKT) cells in the given experimental system could be detected using intracellular fluorescence-activated cell sorter (FACS) staining. Taken together, our results indicate that LPS has the potential to activate quiescent T cells and to specifically induce IFN-gamma in CD4 and CD8 T cells. This may have direct consequences for the activation of autoreactive T cells following bacterial infections.

Call to consolidate achievements for onchocerciasis and lymphatic filariasis control

The Bernhard Nocht Institute for Tropical Medicine and the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases held an international conference to review recent achievements in research and control of onchocerciasis and lymphatic filariasis on 19-23 September 2001 in Hamburg, Germany.

Downregulation of p56(lck) tyrosine kinase activity in T cells of squirrel monkeys (Saimiri sciureus) correlates with the nontransforming and apathogenic properties of herpesvirus saimiri in its natural host

Herpesvirus saimiri is capable of transforming T lymphocytes of various primate species to stable growth in culture. The interaction of the T-cellular tyrosine kinase p56(lck) with the transformation-associated viral protein Tip has been shown before to activate the kinase and provides one model for the T-cell-specific transformation by herpesvirus saimiri subgroup C strains. In contrast to other primate species, squirrel monkeys (Saimiri sciureus) are naturally infected with the virus without signs of lymphoma or other disease. Although the endogenous virus was regularly recovered from peripheral blood cells from squirrel monkeys, we observed that the T cells lost the virus genomes in culture. Superinfection with virus strain C488 did not induce growth transformation, in contrast to parallel experiments with T cells of other primate species. Surprisingly, p56(lck) was enzymatically inactive in primary T-cell lines derived from different squirrel monkeys, although the T cells reacted appropriately to stimulatory signals. The cDNA sequence revealed minor point mutations only, and transfections in COS-7 cells demonstrated that the S. sciureus lck gene codes for a functional enzyme. In S. sciureus, the tyrosine kinase p56(lck) was not activated after T-cell stimulation and enzymatic activity could not be induced by Tip of herpesvirus saimiri C488. However, the suppression of p56(lck) was partially released after administration of the phosphatase inhibitor pervanadate. This argues for unique species-specific conditions in T cells of S. sciureus which may interfere with the transforming activity and pathogenicity of herpesvirus saimiri subgroup C strains in their natural host.

Increased expression of CTLA-4 (CD152) by T and B lymphocytes in Wegener's granulomatosis

CTLA-4 (CD152) is a surface molecule of activated T cells with sequence homology to CD28. Both molecules bind to the same ligands, B7.1 (CD80) and B7.2 (CD86) but have antagonistic functions. While CD28 is an important costimulator, CTLA-4 has an essential inhibitory function in maintaining the homeostasis of the immune system. Furthermore, CTLA-4 has a role in inducing a Th1 response and suppressing Th2 cytokines, an effect which is antagonized by CD28. Many autoimmune diseases are characterized by an overwhelming production of Th1 cytokines. Recently, the predominance of the Th1 cytokine pattern has been directly observed in the granulomatous inflammation of patients with Wegener's granulomatosis. The balance between CD28 and CTLA-4 expression by T lymphocytes could be a factor in the pathogenesis of autoimmune diseases. Down regulation of CD28 predominantly on CD8+ T cells has been described in Wegner's granulomatosis; however, analysis of CTLA-4 is complicated by its low expression levels. Here we have used potent signal enhancement to study CTLA-4 on PBMC in patients with Wegener's granulomatosis (n = 25) in comparison with healthy controls (n = 19). Expression levels of CTLA-4 were significantly increased selectively on CD4+ and possibly also on CD4-/CD8- T cells in Wegener's granulomatosis. High CTLA-4 expression by T lymphocytes was associated with more severe disease. In contrast, after stimulation with the mitogen PHA, CTLA-4 levels were strongly increased on T cells from controls but in T cells from Wegener's granulomatosis patients this response was severely impaired. Interestingly, while CTLA-4 was seen exclusively on T cells in control individuals, about half of the Wegener's patients showed CTLA-4 expression by a fraction of peripheral B lymphocytes. CTLA-4 positive B cells in the periphery were associated with less acute disease.

Heat shock proteins as "danger signals": eukaryotic Hsp60 enhances and accelerates antigen-specific IFN-gamma production in T cells

The heat shock proteins (HSP) gp96, Hsp70 and Hsp60 activate professional antigen-presenting cells (APC) to secrete proinflammatory cytokines and to express costimulatory molecules. Here, we analyze the impact of Hsp60 as a hypothetical danger signal on the antigen-specific activation of T cells derived from DO11.10 TCR-transgenic mice. The release of IFN-gamma, induced by the antigenic OVA(323-339)-peptide, is increased and accelerated dramatically by the addition of Hsp60 to ex vivo purified populations of T cells and peritoneal macrophages (PEC), while the antigen-specific IL-2 production or proliferation of the T cells remain unchanged. In contrast, "effector" T cells, undergoing secondary stimulation, displayed almost unchanged activation kinetics in the presence of Hsp60. The presence of Hsp60 induces IFN-gamma and up-regulation of CD69 in T cell/PEC cocultures even in the absence of antigenic peptide and this induction of IFN-gamma is strictly dependent on the ability of the macrophages to produce IL-12. Taken together, our data strongly suggest that the presence of eukaryotic mitochondrial Hsp60 allows antigen-specific IFN-gamma secretion under conditions when an antigenic stimulus alone is not sufficient to activate T cells.

Heat shock proteins as "danger signals": eukaryotic Hsp60 enhances and accelerates antigen-specific IFN-gamma production in T cells

The heat shock proteins (HSP) gp96, Hsp70 and Hsp60 activate professional antigen-presenting cells (APC) to secrete proinflammatory cytokines and to express costimulatory molecules. Here, we analyze the impact of Hsp60 as a hypothetical danger signal on the antigen-specific activation of T cells derived from DO11.10 TCR-transgenic mice. The release of IFN-gamma, induced by the antigenic OVA(323-339)-peptide, is increased and accelerated dramatically by the addition of Hsp60 to ex vivo purified populations of T cells and peritoneal macrophages (PEC), while the antigen-specific IL-2 production or proliferation of the T cells remain unchanged. In contrast, "effector" T cells, undergoing secondary stimulation, displayed almost unchanged activation kinetics in the presence of Hsp60. The presence of Hsp60 induces IFN-gamma and up-regulation of CD69 in T cell/PEC cocultures even in the absence of antigenic peptide and this induction of IFN-gamma is strictly dependent on the ability of the macrophages to produce IL-12. Taken together, our data strongly suggest that the presence of eukaryotic mitochondrial Hsp60 allows antigen-specific IFN-gamma secretion under conditions when an antigenic stimulus alone is not sufficient to activate T cells.

Fusion proteins of B7.1 and a carcinoembryonic antigen (CEA)-specific antibody fragment opsonize CEA-expressing tumor cells and coactivate T-cell immunity

Genetic engineering can be used to generate antigen-specific molecules for improved tumor immunotherapy. We have constructed genes coding for fusion proteins consisting of a high-affinity antibody single-chain antibody fragment (scFv) specific for the human carcinoembryonic antigen (CEA) and the costimulation domain of the murine B7.1 molecule (mB7.1) linked to the antibody moiety by an IgG3 peptide linker. The hybrid genes were constructed in 2 orientations, one with the scFv located N-terminal to mB7.1 and one vice versa. Soluble proteins were expressed by CHO cells, purified using anti-idiotype-affinity chromatography and characterized by tumor-cell binding and costimulation activity. When tumor cells expressing CEA on the cell membrane were opsonized with the CEA-specific costimulators, both fusion proteins specifically stimulated murine T-cell preparations to proliferate in a similar manner. Our data suggest that "costimulation coating" of tumor cells may be a suitable approach for activation of a sustained cellular antitumor response. It also provides the opportunity to increase tumor immunogenicity using easily generated soluble fusion proteins that advantageously link biological functions of both the humoral and the cellular arm of the specific immune system.

Fusion proteins of B7.1 and a carcinoembryonic antigen (CEA)-specific antibody fragment opsonize CEA-expressing tumor cells and coactivate T-cell immunity

Genetic engineering can be used to generate antigen-specific molecules for improved tumor immunotherapy. We have constructed genes coding for fusion proteins consisting of a high-affinity antibody single-chain antibody fragment (scFv) specific for the human carcinoembryonic antigen (CEA) and the costimulation domain of the murine B7.1 molecule (mB7.1) linked to the antibody moiety by an IgG3 peptide linker. The hybrid genes were constructed in 2 orientations, one with the scFv located N-terminal to mB7.1 and one vice versa. Soluble proteins were expressed by CHO cells, purified using anti-idiotype-affinity chromatography and characterized by tumor-cell binding and costimulation activity. When tumor cells expressing CEA on the cell membrane were opsonized with the CEA-specific costimulators, both fusion proteins specifically stimulated murine T-cell preparations to proliferate in a similar manner. Our data suggest that "costimulation coating" of tumor cells may be a suitable approach for activation of a sustained cellular antitumor response. It also provides the opportunity to increase tumor immunogenicity using easily generated soluble fusion proteins that advantageously link biological functions of both the humoral and the cellular arm of the specific immune system.

Depletion of wolbachia endobacteria in Onchocerca volvulus by doxycycline and microfilaridermia after ivermectin treatment

Ivermectin is the drug used for mass chemotherapy of onchocerciasis within the WHO African Programme for Onchocerciasis Control. This approach aims to eliminate the disease as a public health problem but using one dose per year may not completely interrupt transmission since it does not suppress microfilaridermia thoroughly enough. Here we show that additional treatment with doxycycline, previously shown to sterilise adult female worms for a few months by depletion of symbiotic wolbachia endobacteria, significantly enhances ivermectin-induced suppression of microfilaridermia, rendering anti-wolbachia treatment a promising basis for blocking transmission by a drug-based approach.

Interleukin-4 is essential for the control of microfilariae in murine infection with the filaria Litomosoides sigmodontis

Litomosoides sigmodontis is the only filaria which develops from infective larvae into microfilaria-producing adults in immunocompetent laboratory mice. In this study we report that interleukin-4 knockout (IL-4 KO) mice have an up to 100-fold-higher and a significantly prolonged microfilaremia compared to wild-type BALB/c mice, as well as 20 times more microfilariae in the thoracic cavity, the site of infection. While worm development and adult worm persistence were equivalent in IL-4 KO and wild-type mice, the fertility and length of adult female worms in IL-4 KO mice was clearly enhanced. The high susceptibility to microfilariae in IL-4 KO mice required the presence of adult worms in a full infection cycle since microfilariae loads did not differ much between IL-4 KO and wild-type mice when purified microfilariae were injected into mice. In addition, we found that eosinophilia was diminished and immunoglobulin E (IgE) was absent in IL-4 KO mice. IgE, however, does not seem to be the essential factor for microfilarial containment since microfilaremia was not elevated in B-cell KO mice. In conclusion, IL-4 is shown for the first time to be essential for the control of microfilarial loads but not of adult worm loads in a fully permissive murine filarial infection. IL-4 dependent effector pathways seem to operate on adult worms rather than directly on microfilariae.

Stage-dependent role of nitric oxide in control of Trypanosoma cruzi infection

Trypanosoma cruzi, the causative agent of Chagas' disease, is known to be susceptible to nitric oxide (NO)-dependent killing by gamma interferon-activated macrophages. Mice deficient for inducible nitric oxide synthase (iNOS) are highly susceptible to T. cruzi, and inhibition of iNOS from the beginning of infection was reported to lead to an increase in trypomastigotes in the blood and to high mortality. In the present study, we investigated whether NO production is essential for the control of T. cruzi in all phases of the infection. BALB/c mice were treated at different time intervals after T. cruzi infection with an iNOS inhibitor, aminoguanidine or L-N6-(1-iminoethyl)-lysine (L-NIL). Treatment initiated with the beginning of the infection resulted in 100% mortality by day 16 postinfection (p.i.). If treatment was started later during the acute phase at the peak of parasitemia (day 20 p.i.), all the mice survived. Parasitemia was cleared and tissue amastigotes became undetectable in these mice even in the presence of the iNOS inhibitor L-NIL. Inhibition of iNOS in the chronic phase of the infection, i.e., from day 60 to day 120 p.i., with L-NIL did not result in a reappearance of parasitemia. These data suggest that while NO is essential for T. cruzi control in the early phase of acute infection, it is dispensable in the late acute and chronic phase, revealing a fundamental difference in control mechanisms compared to those in infections by other members of the order Kinetoplastida, e.g., Leishmania major.

Basic streptococcal superantigens (SPEX/SMEZ or SPEC) are responsible for the mitogenic activity of the so-called mitogenic factor (MF)

The mitogenic factor (MF) of group A streptococci has been reported to be a superantigen stimulating human T cells carrying Vbeta2, 4 and 8 and has been designated streptococcal pyrogenic exotoxin F (SPEF). MF was also shown to possess DNase activity. Here we have purified MF from culture supernatants of different Streptococcus pyogenes strains. Surprisingly, the MF preparations from different strains showed different Vbeta specificities depending on the expression of SPEC or SMEZ3 by the producing strain. Their mitogenic activity decreased upon further purification. In addition, the mitogenic activity could be only neutralized by antibodies against the basic streptococcal superantigens SPEC or SPEX (SMEZ3) but not by antibodies against MF itself although the latter were able to neutralize completely the DNase activity of MF. We found that streptodornase type B (SDB) was expressed in two molecular forms (SDBI and SDBII), differing only by one additional N-terminal arginine at SDBI. MF was found identical to the enzyme SDBII but is devoid of superantigenic properties and should no longer be called a superantigen or a pyrogenic exotoxin.

Lack of interferon-γ confers impaired neutrophil granulocyte function and imparts prolonged survival of adult filarial worms in murine filariasis

We investigated the role of IFN-gamma in host defense during murine filariasis. Using the fully permissive infection of BALB/c mice with the rodent filaria Litomosoides sigmodontis, we show that interferon (IFN)-gamma is essential for encapsulation of adult filarial worms in inflammatory nodules and for normal worm clearance. IFN-gamma knockout (KO) mice had only one third of the nodules of wild-type mice but displayed a more than twofold increase in worm burden and increased microfilaremia. Neutrophil granulocytes, but not macrophages or eosinophils, appear to directly control worm load and nodule formation. Neutrophils, which we showed earlier to be essential for the encapsulation process in the thoracic cavity, where the worms reside, were diminished at this location in IFN-gamma KO compared to wild-type mice; they also displayed strongly reduced chemotactic and phagocytic activity compared to neutrophils of controls. This argues for a distinct defect in neutrophil activation accounting for the low formation of inflammatory nodules. Tumor necrosis factor-alpha, a major neutrophil-activating cytokine expressed by macrophages in the thoracic cavity around the worms, was highly induced in wild-type but absent in KO mice. Diminished activation of neutrophils seems to be a general hallmark of IFN-gamma KO mice, since neutrophils from uninfected KO mice also showed a reduction in chemotactic and phagocytic activity when induced by casein. In conclusion, these data are the first to define an IFN-gamma-dependent immune effector mechanism in murine filarial infection, i.e. neutrophil-mediated control of the adult worm load.

The Bernhard Nocht Institute: 100 years of tropical medicine in Hamburg

The Bernhard Nocht Institute (BNI) is a four months younger and much smaller sibling of the Instituto Oswaldo Cruz. It was founded on 1 October 1900 as an Institut für Schiffs- und Tropenkrankheiten (Institute for Maritime and Tropical Diseases) and was later named after its founder and first director Bernhard Nocht. Today it is the Germany's largest institution for research in tropical medicine. It is a government institution affiliated to the Federal Ministry of Health of Germany and the Department of Health of the State of Hamburg. As the center for research in tropical medicine in Germany the BNI is dedicated to research, training and patient care in the area of human infectious diseases, which are of particular relevance in the tropics. It is the primary mission of the BNI to develop means to the control of these diseases. Secondary missions are to provide expertise for regional and national authorities and to directly and indirectly improve the health care for national and regional citizens in regard to diseases of the tropics.

IL-5 is essential for vaccine-induced protection and for resolution of primary infection in murine filariasis

The pathways conferring immunity to human filariases are not well known, in part because human-pathogenic filariae do not complete a full life cycle in laboratory mice. We have used the only fully permissive infection of mice with filariae, i.e., infection of BALB/c mice with the rodent filarial nematode Litomosoides sigmodontis. Our previous results showed that worm development is inversely correlated with Th2 cytokine production and eosinophilia. The scope of the present study was to directly elucidate the role of interleukin-5 (IL-5) and eosinophils in controlling the development of L. sigmodonitis after vaccination and in primary infection. BALB/c mice immunized with irradiated third-stage larvae (L3) were confirmed to have elevated IL-5 levels as well as high subcutaneous eosinophilia and to attack and reduce incoming larvae within the first 2 days, resulting in 70% reduction of worm load. Treatment of vaccinated mice with anti-IL-5 antibody (TRFK-5) suppressed both blood and tissue eosinophilia and completely abolished protection. This demonstrates, for the first time in a fully permissive filarial infection, that IL-5 is essential for protection induced by irradiated L3 larvae. In contrast, in primary-infected mice, anti-IL-5 treatment did not modify filarial infection within the 1st month, most likely because during primary infection IL-5-dependent mechanisms such as subcutaneous eosinophilia are induced too late to disturb worm establishment. However, there is a role for IL-5 late in primary infection where neutrophil-dependent worm encapsulation is also under the control of IL-5.