Regulatory T cells in erythema nodosum leprosum maintain anti-inflammatory function.

BACKGROUND: The numbers of circulating regulatory T cells (Tregs) are increased in lepromatous leprosy (LL) but reduced in erythema nodosum leprosum (ENL), the inflammatory complication of LL. It is unclear whether the suppressive function of Tregs is intact in both these conditions. METHODS: A longitudinal study recruited participants at ALERT Hospital, Ethiopia. Peripheral blood samples were obtained before and after 24 weeks of prednisolone treatment for ENL and multidrug therapy (MDT) for participants with LL. We evaluated the suppressive function of Tregs in the peripheral blood mononuclear cells (PBMCs) of participants with LL and ENL by analysis of TNFα, IFNγ and IL-10 responses to Mycobacterium leprae (M. leprae) stimulation before and after depletion of CD25+ cells. RESULTS: 30 LL participants with ENL and 30 LL participants without ENL were recruited. The depletion of CD25+ cells from PBMCs was associated with enhanced TNFα and IFNγ responses to M. leprae stimulation before and after 24 weeks treatment of LL with MDT and of ENL with prednisolone. The addition of autologous CD25+ cells to CD25+ depleted PBMCs abolished these responses. In both non-reactional LL and ENL groups mitogen (PHA)-induced TNFα and IFNγ responses were not affected by depletion of CD25+ cells either before or after treatment. Depleting CD25+ cells did not affect the IL-10 response to M. leprae before and after 24 weeks of MDT in participants with LL. However, depletion of CD25+ cells was associated with an enhanced IL-10 response on stimulation with M. leprae in untreated participants with ENL and reduced IL-10 responses in treated individuals with ENL. The enhanced IL-10 in untreated ENL and the reduced IL-10 response in prednisolone treated individuals with ENL was abolished by addition of autologous CD25+ cells. CONCLUSION: The findings support the hypothesis that the impaired cell-mediated immune response in individuals with LL is M. leprae antigen specific and the unresponsiveness can be reversed by depleting CD25+ cells. Our results suggest that the suppressive function of Tregs in ENL is intact despite ENL being associated with reduced numbers of Tregs. The lack of difference in IL-10 response in control PBMCs and CD25+ depleted PBMCs in individuals with LL and the increased IL-10 response following the depletion of CD25+ cells in individuals with untreated ENL suggest that the mechanism of immune regulation by Tregs in leprosy appears independent of IL-10 or that other cells may be responsible for IL-10 production in leprosy. The present findings highlight mechanisms of T cell regulation in LL and ENL and provide insights into the control of peripheral immune tolerance, identifying Tregs as a potential therapeutic target.

The effects of prednisolone treatment on serological responses and lipid profiles in Ethiopian leprosy patients with Erythema Nodosum Leprosum reactions.

BACKGROUND: Erythema nodosum leprosum (ENL) is a systemic inflammatory complication occurring mainly in patients with lepromatous leprosy (LL) and borderline lepromatous leprosy (BL). Prednisolone is widely used for treatment of ENL reactions. However, it has been reported that prolonged treatment with prednisolone increases the risk for prednisolone-induced complications such as osteoporosis, diabetes, cataract and arteriosclerosis. It has been speculated that perhaps these complications result from lipid profile alterations by prednisolone. The effects of extended prednisolone treatment on lipid profiles in ENL patients have not been studied in leprosy patients with ENL reactions. Therefore, in this study we conducted a case-control study to investigate the changes in lipid profiles and serological responses in Ethiopian patients with ENL reaction after prednisolone treatment. METHODS: A prospective matched case-control study was employed to recruit 30 patients with ENL and 30 non-reactional LL patient controls at ALERT Hospital, Ethiopia. Blood samples were obtained from each patient with ENL reaction before and after prednisolone treatment as well as from LL controls. The serological host responses to PGL-1, LAM and Ag85 M. leprae antigens were measured by ELISA. Total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL) and low density lipoprotein (LDL) were measured by spectrophotometric method. RESULTS: The host antibody response to M. leprae PGL-1, LAM and Ag85 antigens were significantly reduced in patients with ENL reactions compared to LL controls after treatment. Comparison between patients with acute and chronic ENL showed that host-response to PGL-1 was significantly reduced in chronic ENL after prednisolone treatment. Untreated patients with ENL reactions had low lipid concentration compared to LL controls. However, after treatment, both groups had comparable lipid profiles except for LDL, which was significantly higher in patients with ENL reaction. Comparison within the ENL group before and after treatment showed that prednisolone significantly increased LDL and HDL levels in ENL patients and this was more prominent in chronic ENL than in acute patients with ENL. CONCLUSION: The significantly increased prednisolone-induced LDL and TG levels, particularly in patients with chronic ENL reactions, is a concern in the use of prednisolone for extended periods in ENL patients. The findings highlight the importance of monitoring lipid profiles during treatment of patients to minimize the long-term risk of prednisolone-induced complications.

Complement C1q expression in Erythema nodosum leprosum.

Complement C1q is a soluble protein capable of initiating components of the classical pathway in host defence system. In earlier qualitative studies, C1q has been implicated in the pathogenesis of Erythema Nodosum Leprosum (ENL). However, little is known about the role of this complement in ENL reaction. In the present study we described the protein level of C1q production and its gene expression in the peripheral blood and skin biopsies in patients with ENL reaction and lepromatous leprosy (LL) patient controls before and after treatment. Thirty untreated patients with ENL reaction and 30 non-reactional LL patient controls were recruited at ALERT Hospital, Ethiopia. Peripheral blood and skin biopsies were obtained from each patient before and after treatment. The level of circulating C1q in the plasma was determined by enzyme-linked immunosorbent assay. The mRNA expression of the three C1q components, C1qA, C1qB, and C1qC in the peripheral blood and skin biopsies was determined by qPCR. Circulating C1q in the peripheral blood of untreated ENL patients was significantly decreased compared to LL patient controls. Untreated ENL patients had increased C1q gene expression in the peripheral blood compared to LL controls. Similarly, C1qA and C1qC gene expression were substantially increased in the skin biopsies of untreated ENL patients compared to LL controls. However, after treatment none of these genes show significant difference in both groups. In conclusion, while circulating C1q is inversely correlated with active ENL reactions, its gene expression is directly correlated with ENL. The decreased circulating C1q may suggest the utilization of C1q in immune-complex formation in these patients. Therefore, C1q could be a potential diagnostic marker for active ENL reactions as well as for monitoring ENL treatment.

The Effects of Prednisolone Treatment on Cytokine Expression in Patients with Erythema Nodosum Leprosum Reactions.

Erythema nodosum leprosum (ENL) is a systemic inflammatory complication occurring mainly in patients with lepromatous leprosy (LL) and borderline lepromatous leprosy. Prednisolone is widely used for treatment of ENL reactions but clinical improvement varies. However, there is little good in vivo data as to the effect of prednisolone treatment on the pro-inflammatory cytokines in patients with ENL reactions. As a result, treatment and management of reactional and post-reactional episodes of ENL often pose a therapeutic challenge. We investigated the effect of prednisolone treatment on the inflammatory cytokines TNF, IFN-γ, IL-1ß, IL-6, and IL-17 and the regulatory cytokines IL-10 and TGF-ß in the skin lesion and blood of patients with ENL and compared with non-reactional LL patient controls. A case-control study was employed to recruit 30 patients with ENL and 30 non-reactional LL patient controls at ALERT Hospital, Ethiopia. Blood and skin biopsy samples were obtained from each patient before and after prednisolone treatment. Peripheral blood mononuclear cells from patients with ENL cases and LL controls were cultured with M. leprae whole-cell sonicates (MLWCS), phytohemagglutinin or no stimulation for 6 days. The supernatants were assessed with the enzyme-linked immunosorbent assay for inflammatory and regulatory cytokines. For cytokine gene expression, mRNA was isolated from whole blood and skin lesions and then reverse transcribed into cDNA. The mRNA gene expression was quantified on a Light Cycler using real-time PCR assays specific to TNF, IFN-γ, IL-ß, TGF-ß, IL-17A, IL-6, IL-8, and IL-10. The ex vivo production of the cytokines: TNF, IFN-γ, IL-1ß, and IL-17A was significantly increased in untreated patients with ENL. However, IL-10 production was significantly lower in untreated patients with ENL and significantly increased after treatment. The ex vivo production of IL-6 and IL-8 in patients with ENL did not show statistically significant differences before and after prednisolone treatment. The mRNA expression in blood and skin lesion for TNF, IFN-γ, IL-1ß, IL-6, and IL-17A significantly reduced in patients with ENL after treatment, while mRNA expression for IL-10 and TGF-ß was significantly increased both in blood and skin lesion after treatment. This is the first study examining the effect of prednisolone on the kinetics of inflammatory and regulatory cytokines in patients with ENL reactions before and after prednisolone treatment. Our findings suggest that prednisolone modulates the pro-inflammatory cytokines studied here either directly or through suppression of the immune cells producing these inflammatory cytokines.

Increased activated memory B-cells in the peripheral blood of patients with erythema nodosum leprosum reactions.

B-cells, in addition to antibody secretion, have emerged increasingly as effector and immunoregulatory cells in several chronic inflammatory diseases. Although Erythema Nodosum Leprosum (ENL) is an inflammatory complication of leprosy, the role of B- cell subsets has never been studied in this patient group. Therefore, it would be interesting to examine the contribution of B-cells in the pathogenesis of ENL. A case-control study design was used to recruit 30 untreated patients with ENL and 30 non-reactional lepromatous leprosy (LL) patient controls at ALERT Hospital, Ethiopia. Peripheral blood samples were obtained before, during and after treatment from each patient. Peripheral blood mononuclear cells (PBMCs) were isolated and used for immunophenotyping of B- cell subsets by flow cytometry. The kinetics of B-cells in patients with ENL before, during and after Prednisolone treatment of ENL was compared with LL patient controls as well as within ENL group. Total B-cells, mature B-cells and resting memory B-cells were not significantly different between patients with ENL reactions and LL controls before treatment. Interestingly, while the percentage of naive B-cells was significantly lower in untreated ENL patients than in LL patient controls, the percentage of activated memory B-cells was significantly higher in these untreated ENL patients than in LL controls. On the other hand, the percentage of tissue-like memory B-cells was considerably low in untreated ENL patients compared to LL controls. It appears that the lower frequency of tissue-like memory B-cells in untreated ENL could promote the B-cell/T-cell interaction in these patients through downregulation of inhibitory molecules unlike in LL patients. Conversely, the increased production of activated memory B-cells in ENL patients could imply the scale up of immune activation through antigen presentation to T-cells. However, the generation and differential function of these memory B-cells need further investigation. The finding of increased percentage of activated memory B-cells in untreated patients with ENL reactions suggests the association of these cells with the ENL pathology. The mechanism by which inflammatory reactions like ENL affecting these memory cells and contributing to the disease pathology is an interesting area to be explored for and could lead to the development of novel and highly efficacious drug for ENL treatment.

New Insight into the Pathogenesis of Erythema Nodosum Leprosum: The Role of Activated Memory T-Cells.

Memory T-cells, particularly, effector memory T cells are implicated in the pathogenesis of inflammatory diseases and may contribute to tissue injury and disease progression. Although erythema nodosum leprosum (ENL) is an inflammatory complication of leprosy, the role of memory T cell subsets has never been studied in this patient group. The aim of this study was at investigate the kinetics of memory T cell subsets in patients with ENL before and after prednisolone treatment. A case-control study design was used to recruit 35 untreated patients with ENL and 25 non-reactional lepromatous leprosy (LL) patient controls at ALERT Hospital, Ethiopia. Venous blood samples were obtained before, during, and after treatment from each patient. Peripheral blood mononuclear cells (PBMCs) were isolated and used for immunophenotyping of T cell activation and memory T-cell subsets by flow cytometry. The kinetics of these immune cells in patients with ENL before and after treatment were compared with LL patient controls as well as within ENL cases at different time points. The median percentage of CD3+, CD4+, and CD8+ T-cells expressing activated T-cells were significantly higher in the PBMCs from patients with ENL than from LL patient controls before treatment. The median percentage of central and activated memory T-cells was significantly increased in patients with ENL compared to LL patient controls before treatment. Interestingly, patients with ENL had a lower percentage of naïve T cells (27.7%) compared to LL patient controls (59.5%) (P < 0.0001) before treatment. However, after prednisolone treatment, patients with ENL had a higher median percentage of naïve T-cells (43.0%) than LL controls (33.0%) (P < 0.001). The median percentage of activated T-cells (effector memory and effector T-cells) was significantly increased in patients with ENL (59.2%) before treatment compared to after treatment with prednisolone (33.9%) (P < 0.005). This is the first work which has shown T-cell activation and the different subsets of memory T cells in untreated patients with ENL. Consequently, this study delineates the role of T-cell activation in the pathogenesis of ENL reaction and challenges the long-standing dogma of immune complex as a sole etiology of ENL reaction.

T-cell regulation in Erythema Nodosum Leprosum.

Leprosy is a disease caused by Mycobacterium leprae where the clinical spectrum correlates with the patient immune response. Erythema Nodosum Leprosum (ENL) is an immune-mediated inflammatory complication, which causes significant morbidity in affected leprosy patients. The underlying cause of ENL is not conclusively known. However, immune-complexes and cell-mediated immunity have been suggested in the pathogenesis of ENL. The aim of this study was to investigate the regulatory T-cells in patients with ENL. Forty-six untreated patients with ENL and 31 non-reactional lepromatous leprosy (LL) patient controls visiting ALERT Hospital, Ethiopia were enrolled to the study. Blood samples were obtained before, during and after prednisolone treatment of ENL cases. Peripheral blood mononuclear cells (PBMCs) were isolated and used for immunophenotyping of regulatory T-cells by flow cytometry. Five markers: CD3, CD4 or CD8, CD25, CD27 and FoxP3 were used to define CD4+ and CD8+ regulatory T-cells. Clinical and histopathological data were obtained as supplementary information. All patients had been followed for 28 weeks. Patients with ENL reactions had a lower percentage of CD4+ regulatory T-cells (1.7%) than LL patient controls (3.8%) at diagnosis of ENL before treatment. After treatment, the percentage of CD4+regulatory T-cells was not significantly different between the two groups. The percentage of CD8+ regulatory T-cells was not significantly different in ENL and LL controls before and after treatment. Furthermore, patients with ENL had higher percentage of CD4+ T-ells and CD4+/CD8+ T-cells ratio than LL patient controls before treatment. The expression of CD25 on CD4+ and CD8+ T-cells was not significantly different in ENL and LL controls suggesting that CD25 expression is not associated with ENL reactions while FoxP3 expression on CD4+ T-cells was significantly lower in patients with ENL than in LL controls. We also found that prednisolone treatment of patients with ENL reactions suppresses CD4+ T-cell but not CD8+ T-cell frequencies. Hence, ENL is associated with lower levels of T regulatory cells and higher CD4+/CD8+ T-cell ratio. We suggest that this loss of regulation is one of the causes of ENL.

Clinico-pathological features of erythema nodosum leprosum: A case-control study at ALERT hospital, Ethiopia.

BACKGROUND: Leprosy reactions are a significant cause of morbidity in leprosy population. Erythema nodosum leprosum (ENL) is an immunological complication affecting approximately 50% of patients with lepromatous leprosy (LL) and 10% of borderline lepromatous (BL) leprosy. ENL is associated with clinical features such as skin lesions, neuritis, arthritis, dactylitis, eye inflammation, osteitis, orchitis, lymphadenitis and nephritis. ENL is treated mainly with corticosteroids and corticosteroids are often required for extended periods of time which may lead to serious adverse effects. High mortality rate and increased morbidity associated with corticosteroid treatment of ENL has been reported. For improved and evidence-based treatment of ENL, documenting the systems affected by ENL is important. We report here the clinical features of ENL in a cohort of patients with acute ENL who were recruited for a clinico-pathological study before and after prednisolone treatment. MATERIALS AND METHODS: A case-control study was performed at ALERT hospital, Ethiopia. Forty-six LL patients with ENL and 31 non-reactional LL matched controls were enrolled to the study and followed for 28 weeks. Clinical features were systematically documented at three visits (before, during and after predinsolone treatment of ENL cases) using a specifically designed form. Skin biopsy samples were obtained from each patient before and after treatment and used for histopathological investigations to supplement the clinical data. RESULTS: Pain was the most common symptom reported (98%) by patients with ENL. Eighty percent of them had reported skin pain and more than 70% had nerve and joint pain at enrolment. About 40% of the patients developed chronic ENL. Most individuals 95.7% had nodular skin lesions. Over half of patients with ENL had old nerve function impairment (NFI) while 13% had new NFI at enrolment. Facial and limb oedema were present in 60% patients. Regarding pathological findings before treatment, dermal neutrophilic infiltration was noted in 58.8% of patients with ENL compared to 14.3% in LL controls. Only 14.7% patients with ENL had evidence of vasculitis at enrolment. CONCLUSION: In our study, painful nodular skin lesions were present in all ENL patients. Only 58% patients had dermal polymorphonuclear cell infiltration showing that not all clinically confirmed ENL cases have neutrophilic infiltration in lesions. Very few patients had histological evidence of vasculitis. Many patients developed chronic ENL and these patients require inpatient corticosteroid treatment for extended periods which challenges the health service facility in resource poor settings, as well as the patient's quality of life.

Host Immune Responses Differ between M. africanum- and M. tuberculosis-Infected Patients following Standard Anti-tuberculosis Treatment.

Epidemiological differences exist between Mycobacterium africanum (Maf)- and Mycobacterium tuberculosis (Mtb)-infected patients, but to date, contributing host factors have not been characterised. We analysed clinical outcomes, as well as soluble markers and gene expression profiles in unstimulated, and ESAT6/CFP-10-, whole-Maf- and Mtb-stimulated blood samples of 26 Maf- and 49 Mtb-HIV-negative tuberculosis patients before, and after 2 and 6 months of anti-tuberculosis therapy. Before treatment, both groups had similar clinical parameters, but differed in few cytokines concentration and gene expression profiles. Following treatment the body mass index, skinfold thickness and chest X-ray scores showed greater improvement in the Mtb- compared to Maf-infected patients, after adjusting for age, sex and ethnicity (p = 0.02; 0.04 and 0.007, respectively). In addition, in unstimulated blood, IL-12p70, IL12A and TLR9 were significantly higher in Maf-infected patients, while IL-15, IL-8 and MIP-1α were higher in Mtb-infected patients. Overnight stimulation with ESAT-6/CFP-10 induced significantly higher levels of IFN-γ and TNF-α production, as well as gene expression of CCL4, IL1B and TLR4 in Mtb- compared to Maf-infected patients. Our study confirms differences in clinical features and immune genes expression and concentration of proteins associated with inflammatory processes between Mtb- and Maf-infected patients following anti-tuberculosis treatment These findings have public health implications for treatment regimens, and biomarkers for tuberculosis diagnosis and susceptibility.

Identification of serological biomarkers of infection, disease progression and treatment efficacy for leprosy

Although leprosy is curable with drug treatment, the identification of biomarkers of infection, disease progression and treatment efficacy would greatly help to reduce the overall prevalence of the disease. Reliable biomarkers would also reduce the incidence of grade-2 disability by ensuring that those who are most at risk are diagnosed and treated early or offered repeated treatments in the case of relapse. In this study, we examined the reactivity of sera from lepromatous and tuberculoid leprosy patients (LPs) against a panel of 12 recombinant Mycobacterium leprae proteins and found that six proteins were strongly recognised by multibacillary (MB) patients, while only three were consistently recognised by paucibacillary patients. To better understand the dynamics of patient antibody responses during and after drug therapy, we measured antibody titres to four recombinant proteins, phenolic glycolipid-I and lipoarabinomannan at baseline and up to two years after diagnosis to investigate the temporal changes in the antibody titres. Reactivity patterns to individual antigens and decreases in antibody titres were patient-specific. Antibody titres to proteins declined more rapidly vs. those to carbohydrate and glycolipid antigens. Compared to baseline values, increases in antibody titres were observed during reactional episodes in one individual. Additionally, antibody responses against a subset of antigens that provided a good prognostic indicator of disease progression were analysed in 51 household contacts of MB index cases for up to two years. Although the majority of these contacts showed no change or exhibited decreases in antibody titres, seven individuals developed higher titres towards one or more of these antigens and one individual with progressively higher titres was diagnosed with borderline lepromatous leprosy 19 months after enrolment. The results of this study indicate that antibody titres to specific M. leprae antigens can be used to monitor treatment efficacy in LPs and assess disease progression in those most at risk for developing this disease.

New biomarkers with relevance to leprosy diagnosis applicable in areas hyperendemic for leprosy.

Leprosy is not eradicable with currently available diagnostics or interventions, as evidenced by its stable incidence. Early diagnosis of Mycobacterium leprae infection should therefore be emphasized in leprosy research. It remains challenging to develop tests based on immunological biomarkers that distinguish individuals controlling bacterial replication from those developing disease. To identify biomarkers for field-applicable diagnostics, we determined cytokines/chemokines induced by M. leprae proteins in blood of leprosy patients and endemic controls (EC) from high leprosy-prevalence areas (Bangladesh, Brazil, Ethiopia) and from South Korea, where leprosy is not endemic anymore. M. leprae-sonicate-induced IFN-γ was similar for all groups, excluding M. leprae/IFN-γ as a diagnostic readout. By contrast, ML2478 and ML0840 induced high IFN-γ concentrations in Bangladeshi EC, which were completely absent for South Korean controls. Importantly, ML2478/IFN-γ could indicate distinct degrees of M. leprae exposure, and thereby the risk of infection and transmission, in different parts of Brazilian and Ethiopian cities. Notwithstanding these discriminatory responses, M. leprae proteins did not distinguish patients from EC in one leprosy-endemic area based on IFN-γ. Analyses of additional cytokines/chemokines showed that M. leprae and ML2478 induced significantly higher concentrations of MCP-1, MIP-1ß, and IL-1ß in patients compared with EC, whereas IFN-inducible protein-10, like IFN-γ, differed between EC from areas with dissimilar leprosy prevalence. This study identifies M. leprae-unique Ags, particularly ML2478, as biomarker tools to measure M. leprae exposure using IFN-γ or IFN-inducible protein-10, and also shows that MCP-1, MIP-1ß, and IL-1ß can potentially distinguish pathogenic immune responses from those induced during asymptomatic exposure to M. leprae.

Identification of serological biomarkers of infection, disease progression and treatment efficacy for leprosy.

Although leprosy is curable with drug treatment, the identification of biomarkers of infection, disease progression and treatment efficacy would greatly help to reduce the overall prevalence of the disease. Reliable biomarkers would also reduce the incidence of grade-2 disability by ensuring that those who are most at risk are diagnosed and treated early or offered repeated treatments in the case of relapse. In this study, we examined the reactivity of sera from lepromatous and tuberculoid leprosy patients (LPs) against a panel of 12 recombinant Mycobacterium leprae proteins and found that six proteins were strongly recognised by multibacillary (MB) patients, while only three were consistently recognised by paucibacillary patients. To better understand the dynamics of patient antibody responses during and after drug therapy, we measured antibody titres to four recombinant proteins, phenolic glycolipid-I and lipoarabinomannan at baseline and up to two years after diagnosis to investigate the temporal changes in the antibody titres. Reactivity patterns to individual antigens and decreases in antibody titres were patient-specific. Antibody titres to proteins declined more rapidly vs. those to carbohydrate and glycolipid antigens. Compared to baseline values, increases in antibody titres were observed during reactional episodes in one individual. Additionally, antibody responses against a subset of antigens that provided a good prognostic indicator of disease progression were analysed in 51 household contacts of MB index cases for up to two years. Although the majority of these contacts showed no change or exhibited decreases in antibody titres, seven individuals developed higher titres towards one or more of these antigens and one individual with progressively higher titres was diagnosed with borderline lepromatous leprosy 19 months after enrolment. The results of this study indicate that antibody titres to specific M. leprae antigens can be used to monitor treatment efficacy in LPs and assess disease progression in those most at risk for developing this disease.

Informe de la sexta reunión del consorcio (iniciativa para técnicas diagnósticas y epidemiológicas para la lepra) ideal celebrada en Beijing, China, del 23-25 agosto de 2010 / No disponible

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Analysis of antibody responses to Mycobacterium leprae phenolic glycolipid I, lipoarabinomannan, and recombinant proteins to define disease subtype-specific antigenic profiles in leprosy.

A simple serodiagnostic test based on the Mycobacterium leprae-specific phenolic glycolipid I(PGL-I), for individuals with leprosy is nearly universally positive in leprosy patients with high bacillary loads but cannot be used as a stand-alone diagnostic test for the entire spectrum of the disease process. For patients with early infection with no detectable acid-fast bacilli in lesions or with low or no antibody titer to PGL-I, as in those at the tuberculoid end of the disease spectrum, this diagnostic approach has limited usefulness. To identify additional M. leprae antigens that might enhance the serological detection of these individuals, we have examined the reactivity patterns of patient sera to PGL-I, lipoarabinomannan (LAM), and six recombinant M. leprae proteins (ML1877, ML0841, ML2028, ML2038, ML0380, and ML0050) by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). Overall, the responses to ML2028 (Ag85B) and ML2038 (bacterioferritin) were consistently high in both multibacillary and paucibacillary groups and weak or absent in endemic controls, while responses to other antigens showed considerable variability, from strongly positive to completely negative. This analysis has given a clearer understanding of some of the differences in the antibody responses between individuals at opposite ends of the disease spectrum, as well as illustrating the heterogeneity of antibody responses toward protein, carbohydrate, and glycolipid antigens within a clinical group. Correlating these response patterns with a particular disease state could allow for a more critical assessment of the form of disease within the leprosy spectrum and could lead to better patient management.

Presidential address: the role of research networks in tackling major challenges in international health.

One pressing challenge in the fields of international health and tropical medicine is how to achieve the Millennium Development Goals by 2015. Changes in how research is conducted are, however, contributing to progress in reaching these targets. Increasingly researchers from different institutions, countries and even continents are working together through research consortia. These consortia can be focused around research questions such as developing new TB vaccines, designed to deliver capacity building, promote advocacy, or to maintain efforts directed at threatened research areas such as leprosy research. Researchers connected through consortia can provide robust answers to research questions, removing duplication of effort, within a stimulating environment for discussion and development of research ideas. Another advantage is that south-south research links may be strengthened, which is of increasing relevance as the balance of power and money is moving south, providing new opportunities for the African continent. However, there are disadvantages as well as advantages to consortia. Having too many connections can immobilise researchers in a web of meetings, teleconferences, and reports, reducing the time for original innovative ideas. Learned societies, such as the Royal Society of Tropical Medicine and Hygiene provide their own networks and connections and allow the bigger issues of international health and development to be discussed in a multidisciplinary environment.

From genome-based in silico predictions to ex vivo verification of leprosy diagnosis.

The detection of hundreds of thousands of new cases of leprosy every year suggests that transmission of Mycobacterium leprae infection still continues. Unfortunately, tools for identification of asymptomatic disease and/or early-stage M. leprae infection (likely sources of transmission) are lacking. The recent identification of M. leprae-unique genes has allowed the analysis of human T-cell responses to novel M. leprae antigens. Antigens with the most-promising diagnostic potential were tested for their ability to induce cytokine secretion by using peripheral blood mononuclear cells from leprosy patients and controls in five different areas where leprosy is endemic; 246 individuals from Brazil, Nepal, Bangladesh, Pakistan, and Ethiopia were analyzed for gamma interferon responses to five recombinant proteins (ML1989, ML1990, ML2283, ML2346, and ML2567) and 22 synthetic peptides. Of these, the M. leprae-unique protein ML1989 was the most frequently recognized and ML2283 the most specific for M. leprae infection/exposure, as only a limited number of tuberculosis patients responded to this antigen. However, all proteins were recognized by a significant number of controls in areas of endemicity. T-cell responses correlated with in vitro response to M. leprae, suggesting that healthy controls in areas where leprosy is endemic are exposed to M. leprae. Importantly, 50% of the healthy household contacts and 59% of the controls in areas of endemicity had no detectable immunoglobulin M antibodies to M. leprae-specific PGL-I but responded in T-cell assays to >or=1 M. leprae protein. T-cell responses specific for leprosy patients and healthy household contacts were observed for ML2283- and ML0126-derived peptides, indicating that M. leprae peptides hold potential as diagnostic tools. Future work should concentrate on the development of a sensitive and field-friendly assay and identification of additional peptides and proteins that can induce M. leprae-specific T-cell responses.

Comparison of IFN-gamma responses to mycobacterial antigens as markers of response to BCG vaccination.

An increase in interferon-gamma (IFN-gamma) production to Mycobacterium tuberculosis purified protein derivative (Mtb PPD), as measured in the cultured diluted whole blood assay, is one indicator of a protective immune response to BCG vaccine. We have explored the potential for this assay to be improved by measuring IFN-gamma responses to more defined antigens of M. tuberculosis (short-term and mid-term culture filtrates, ESAT-6, 38 kDa), Mycobacterium bovis (MPB70), M. bovis BCG (Antigen 85) and Mycobacterium leprae (35 kDa), in UK teenagers before and 1 year after BCG vaccination (or no vaccination as controls). There was a significant increase in response to the culture filtrates post-vaccination, but this was no greater than that to Mtb PPD. Many teenagers responded to the purified antigens, in particular to Antigen 85, prior to vaccination, and BCG vaccination could only augment this pre-existing response to a limited extent; prior exposure to environmental mycobacteria can thus induce cross-reactive responses to antigens which complicate interpretation of in vitro assays of vaccine response. In contrast, ESAT-6 was recognised by only one teenager prior to vaccination, and, as expected, responses were not boosted by BCG. We therefore conclude that Mtb PPD is the antigen preparation of choice for assessing the immunogenicity of BCG vaccination.