Protection against Mycobacterium leprae infection by the ID83/GLA-SE and ID93/GLA-SE vaccines developed for tuberculosis.

Despite the dramatic reduction in the number of leprosy cases worldwide in the 1990s, transmission of the causative agent, Mycobacterium leprae, is still occurring, and new cases continue to appear. New strategies are required in the pursuit of leprosy elimination. The cross-application of vaccines in development for tuberculosis may lead to tools applicable to elimination of leprosy. In this report, we demonstrate that the chimeric fusion proteins ID83 and ID93, developed as antigens for tuberculosis (TB) vaccine candidates, elicited gamma interferon (IFN-γ) responses from both TB and paucibacillary (PB) leprosy patients and from healthy household contacts of multibacillary (MB) patients (HHC) but not from nonexposed healthy controls. Immunization of mice with either protein formulated with a Toll-like receptor 4 ligand (TLR4L)-containing adjuvant (glucopyranosyl lipid adjuvant in a stable emulsion [GLA-SE]) stimulated antigen-specific IFN-γ secretion from pluripotent Th1 cells. When immunized mice were experimentally infected with M. leprae, both cellular infiltration into the local lymph node and bacterial growth at the site were reduced relative to those of unimmunized mice. Thus, the use of the Mycobacterium tuberculosis candidate vaccines ID83/GLA-SE and ID93/GLA-SE may confer cross-protection against M. leprae infection. Our data suggest these vaccines could potentially be used as an additional control measure for leprosy.

Development and pre-clinical assessment of a 73 kD chimeric fusion protein as a defined sub-unit vaccine for leprosy.

Despite the advances toward the elimination of leprosy through widespread provision of multi-drug therapy to registered patients over the last 2 decades, new case detection rates have stabilized and leprosy remains endemic in a number of localized regions. A vaccine could overcome the inherent limitations of the drug treatment program by providing protection in individuals who are not already harboring the Mycobacterium leprae bacilli at the time of administration and effectively interrupt the transmission cycle over a wider timespan. In this report we present data validating the production of 73f, a chimeric fusion protein incorporating the M. leprae antigens ML2028, ML2346 and ML2044. The 73f protein was recognized by IgG in multibacillary (MB) leprosy patient sera and stimulated IFNγ production within whole blood assays of paucibacillary (PB) leprosy patient and healthy household contacts of MB patients (HHC). When formulated with a TLR4L-containing adjuvant (GLA-SE), 73f stimulated a strong and pluripotent Th1 response that inhibited M. leprae-induced inflammation in mice. We are using these data to develop new vaccine initiatives for the continued and long-term control of leprosy.

Genetic and immunological evidence implicates interleukin 6 as a susceptibility gene for leprosy type 2 reaction.

In leprosy, type 1 reaction (T1R) and type 2 reaction (T2R) are major causes of nerve injury and permanent disabilities. A previous study on plasma levels of 27 cytokines in patients with T1R or T2R and controls with nonreactional leprosy identified the gene for interleukin 6 (IL-6) as a candidate for genetic analysis. Two nested case-control studies were built from a cohort of 409 patients with leprosy from central Brazil, monitored for T1R and T2R. There was evidence for association between T2R and IL-6 tag single-nucleotide polymorphisms rs2069832 (P = .002), rs2069840 (P = .03), and rs2069845 (P = .04), with information on the entire IL-6 locus, as well as functional IL-6 variant rs1800795 (P = .005). Moreover, IL-6 plasma levels in patients with T2R correlated with IL-6 genotypes (P = .04). No association was found between IL-6 variants and T1R. Identifying genetic predictive factors for leprosy reactions may have a major impact on preventive strategies.

Potential plasma markers of Type 1 and Type 2 leprosy reactions: a preliminary report.

BACKGROUND: The clinical management of leprosy Type 1 (T1R) and Type 2 (T2R) reactions pose challenges mainly because they can cause severe nerve injury and disability. No laboratory test or marker is available for the diagnosis or prognosis of leprosy reactions. This study simultaneously screened plasma factors to identify circulating biomarkers associated with leprosy T1R and T2R among patients recruited in Goiania, Central Brazil. METHODS: A nested case-control study evaluated T1R (n = 10) and TR2 (n = 10) compared to leprosy patients without reactions (n = 29), matched by sex and age-group (+/- 5 years) and histopathological classification. Multiplex bead based technique provided profiles of 27 plasma factors including 16 pro inflammatory cytokines: tumor necrosis factor-alpha (TNF-alpha), Interferon-gamma (IFN-gamma), interleukin (IL)- IL12p70, IL2, IL17, IL1 beta, IL6, IL15, IL5, IL8, macrophage inflammatory protein (MIP)-1 alpha (MIP1alpha), 1 beta (MIP1beta), regulated upon activation normal T-cell expressed and secreted (RANTES), monocyte chemoattractrant protein 1 (MCP1), CC-chemokine 11 (CCL11/Eotaxin), CXC-chemokine 10 (CXCL10/IP10); 4 anti inflammatory interleukins: IL4, IL10, IL13, IL1Ralpha and 7 growth factors: IL7, IL9, granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), platelet-derived growth factor BB (PDGF BB), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF). RESULTS: Elevations of plasma CXCL10 (P = 0.004) and IL6 (p = 0.013) were observed in T1R patients compared to controls without reaction. IL6 (p = 0.05), IL7 (p = 0.039), and PDGF-BB (p = 0.041) were elevated in T2R. RANTES and GMCSF were excluded due to values above and below detection limit respectively in all samples. CONCLUSION: Potential biomarkers of T1R identified were CXCL10 and IL6 whereas IL7, PDGF-BB and IL6, may be laboratory markers of TR2. Additional studies on these biomarkers may help understand the immunopathologic mechanisms of leprosy reactions and indicate their usefulness for the diagnosis and for the clinical management of these events.

Antigen-specific T-cell responses of leprosy patients.

The identification of human T-cell antigens of Mycobacterium leprae could improve treatment and help to disrupt the transmission of leprosy by directing diagnosis and vaccine programs. This study screened a panel of M. leprae recombinant proteins for T-cell recall responses, measured by gamma interferon (IFN-gamma) production, among leprosy patients. After initial studies using peripheral blood mononuclear cells from leprosy patients, we transitioned our studies to simple whole-blood assays (WBA), which are more applicable in field or clinical settings. T-cell responses generated in WBA using blood from individuals in Goiânia, Brazil, demonstrated that several M. leprae antigens (ML0276, ML0840, ML1623, ML2044, and 46f) elicited >0.5 IU/ml IFN-gamma, and these proteins were classified as immunogenic and leprosy specific. Several of these individual antigens were recognized by cells from >60% of Brazilian paucibacillary (PB) leprosy patients, and ML0276, ML0840, ML1623, and 46f complemented each other such that 82% of PB patients had strong (>1.25 IU/ml IFN-gamma) responses to at least one of these proteins. These proteins were also recognized by cells from a significant proportion of the household contacts of multibacillary leprosy patients, but in contrast, few responses were observed in active tuberculosis patients or healthy control groups from areas of endemicity. Our results indicate several potential candidate antigens which may be useful for either leprosy diagnosis or vaccination and demonstrate the utility of leprosy WBA that can be applied broadly in clinical or field settings.