Addiction of anti-CD28 antibodies restores PBMC proliferation and IFN-gamma production in lepromatous leprosy patients

In search of biomarkers for leprosy by unraveling the host immune response to Mycobacterium leprae

Mycobacterium leprae, the causative agent of leprosy, is still actively transmitted in endemic areas reflected by the fairly stable number of new cases detected each year. Recognizing the signs and symptoms of leprosy is challenging, especially at an early stage. Improved diagnostic tools, based on sensitive and specific biomarkers, that facilitate diagnosis of leprosy are therefore urgently needed. In this review, we address the challenges that leprosy biomarker research is facing by reviewing cell types reported to be involved in host immunity to M leprae. These cell types can be associated with different possible fates of M leprae infection being either protective immunity, or pathogenic immune responses inducing nerve damage. Unraveling these responses will facilitate the search for biomarkers. Implications for further studies to disentangle the complex interplay between host responses that lead to leprosy disease are discussed, providing leads for the identification of new biomarkers to improve leprosy diagnostics.

Immunological biomarkers of subclinical infection in household contacts of leprosy patients

Hansen's disease (or leprosy) still persists as a serious public health issue. Its diagnosis is based primarily on the detection of clinical signs that are characteristic of the disease. Studies have pointed to the selection of a set of serological and cellular biomarkers of subclinical infection that result in an efficient diagnosis. The aim of this study was compare index cases and their household contacts to identify differentially expressed biomarkers of immune response in leprosy that could provide reliable evidence of subclinical infection in household contacts. The study population consisted of index cases with multibacillary form (IC, n = 13) and their household contacts (HC, n = 14). Serum cytokines and chemokines were quantified using the cytometric beads array (CBA) system. The humoral response was assessed by ELISA test. Flow cytometry was used to characterize the cellular immune response. Monocyte and CD4 + T lymphocytes frequency was significantly higher in IC. Both CD4+ and CD8 + T lymphocytes had a reduced CD25 expression in HC. The immunoglobulin (Ig)M profile anti- NDO-HSA, LID-1, and NDOLID antigens was significantly higher in IC. This study points to the monocyte and CD4+ lymphocyte frequency, as well as specific IgM profile, as predictors of subclinical infection in the household contacts.

Abnormalities in intracellular processing and expression of interferon-gamma receptor in adherent cells from lepromatous leprosy patients

Peripheral blood mononuclear cells in lepromatous leprosy (LL) patients produce low levels of interferon-gamma (IFN-gamma) and interleukin-12 (IL-12), and these cells exhibit partial or complete deficiency in the IL-12 receptor. The behavior of the IFN-gamma receptor (IFN-gamma R) has not been described in cells from people with leprosy. We found higher levels of mRNA for IFN-gamma R1 and IFN-gamma R2 in adherent cells stimulated with IFN-gamma and Mycobacterium leprae membrane proteins from LL patients compared with healthy subjects. Flow cytometry showed no significant difference in IFN-gamma R1 expression between LL patients and healthy subjects. Immunoblotting detected only the mature glycosylated form of the 61-67 kDa IFN-gamma R2 protein in healthy subjects. In contrast, cells from LL patients showed three different expression patterns: (1) the immature deglycosylated form of the 34.8 kDa IFN-gamma R2 protein, (2) the mature glycosylated 61-67 kDa form, and (3) both forms. Our data indicate the existence of abnormalities in the intracellular processing and protein expression of the IFN-gamma R in response to specific stimuli such as IFN-gamma and M. leprae membrane proteins in adherent cells of LL patients.

On Cell Signalling Mechanism of Mycobaterium Leprae Soluble Antigen (MLSA) in Jurkat T Cells

We investigated the role of Mycobaterium leprae soluble antigen (MLSA) in the modulation of calcium signalling, phosphorylation of mitogen-activated protein (MAP) kinases and IL-2 mRNA expression in human Jurkat T cells. We observed that MLSA induced an increase in free intracellular calcium concentrations, [Ca2+]i, via opening CRAC (Ca2+-release activated- Ca2+) channels. Furthermore, MLSA failed to potentiate both thapsigargin- and anti-CD3 antibodies-induced capacitative calcium influx in Jurkat T cells. We observed that MLSA failed to affect the degree of phosphorylation of two MAP kinases, i.e., ERK1/ERK2, stimulated by anti-CD3 antibodies alone or phorbol 12-myristate 13-acetate (PMA) alone. In order to mimic co-stimulation of T cells, we stimulated them by both PMA and anti-CD3 antibodies. MLSA significantly curtailed the phosphorylation of ERK1/ERK2, stimulated by both PMA and anti-CD3 antibodies in Jurkat T cells. Also MLSA was found to reduce the transcription of IL-2 gene in PMA plus anti-CD3 antibodies-activated Jurkat T cells. Our finding demonstrates that Ca2+ influx via CRAC channels, inhibition of ERK1/ERK2 phosphorylation and IL-2 gene transcription may be implicated in immunosuppressive effects of MLSA antigen.

Electrochemical antigen-retrieval of formaldehyde fixed and paraffin-embeddedarchived leprosy skin biopsies

While formaldehyde fixation preserves tissue morphology, it often hinders immunodetection of antigens in paraffin-embedded tissue because the antigens are masked. Antigen unmasking can be achieved with treatments such as microwave irradiation but they often lead to excessive tissue damage. Therefore, an electrochemical antigen-retrieval method (EAR) was devised in which an alternating electric current is passed through the tissue in a chamber containing an electrolyte buffer. The results obtained with this method were compared to those after microwave irradiation using archived samples of formaldehyde-fixed and paraffin-embedded lepromatous leprosy skin. The efficacy of the two unmasking procedures was assessed by the immunodetectability of several marker antigens using 24 antibodies. Fifteen antibodies that were directed against transmembrane proteins (CD), and the remaining 9 against cytokeratins 18.6 and 19, laminin, vimentin, S100a, BCG, Ulex europaeus lectin, PCNA, and P21ras. Simple and double immunohistochemistry was performed using the universal ENVISION and LSAB + AP detection systems. After unmasking with the EAR method, immunoreactivity was clearly detected with 22 of the 24 antibodies in single labeling reactions. They include the critical antigens CD3 and CD4 for identifying the T lymphocyte lineages. In contrast, only 20 of the antibodies reacted after microwave irradiation. After double immunolabeling, immunoreactivity was quantitatively similar with both methods. However, the EAR unmasking produced a stronger labeling reaction. Thus, with double labeling immunohistochemistry, EAR made it possible to use higher antibody dilutions and shorter incubation times. Heat damage was also prevented. In conclusion, EAR treatment produces better staining results than microwave irradiation treatment.

Expression of costimulatory molecules (CD80, CD86, CD28, CD152), accessory molecules (TCR αβ, TCR γδ) and T cell lineage molecules (CD4+, CD8+) in PBMC of leprosy patients using Mycobacterium leprae antigen (MLCWA) with murabutide and T cell peptide of Trat protein

In leprosy, cell-mediated immunity (CMI) is more significant than humoral response to eliminate intracellular pathogen. T cell defect is a common feature in lepromatous leprosy (LL) patients as compared to tuberculoid type (TT) patients. For efficient initiation of CD4+, T cell response requires T cell receptor (TCR) activation and costimulation provided by molecules on antigen-presenting cells (APC) and their counter receptors on T cells. In our previous study, the defective T cell function in LL patients was restored to a proliferating state with the release of TH1 type cytokines using mycobacterial antigen(s) with two immunomodulators (Murabutide (MDP-BE) and T cell epitope of Trat protein of Escherichia coli) by presenting the antigen in particulate form in vitro to PBMC derived from leprosy patients. This observation prompted us to study the expression of the costimulatory molecules (CD80, CD86, CD28, CD152), other accessory molecules (TCR alphabeta/gammadelta) and T cell lineage molecules (CD4+ and CD8+) during constitutive and activated state of peripheral blood mononuclear cells (PBMC) derived from normal and leprosy individuals using different formulations of Mycobacterium leprae total cell wall antigen (MLCWA), Trat and MDP-BE using flow cytometric analysis. An increased surface expression of CD80, CD86 and CD28 but decreased CD152 expression was observed when PBMC of normal, BT/TT (tuberculoid) and BL/LL (lepromatous) patients were stimulated in vitro with MLCWA+MDP-BE+Trat peptide using liposomal mode of antigen delivery, while opposite results were obtained with the antigen alone. Antibody inhibition study using antihuman CD80 or CD86 completely abolished the T cell lymphoproliferation, thereby reconfirming the importance of these costimulatory molecules during T cell activation/differentiation. Though the liposome-entrapped antigen formulation has no effect on expression of alphabeta/gammadelta T cell receptor, the constitutive levels of TCR gammadelta were high in lepromatous patients. Thus, TCR bearing gammadelta appears to have a negligible regulatory role in peripheral blood of leprosy patients. The percentage of cells positive for CD4+ are increased in inducible state in all the three groups, while CD8+-positive cells were decreased in LL patients, thereby reconfirming the fact that priming of CD4+ cells are necessary for producing final effector functions. Lastly, intracellular cytokine staining experiment indicated that CD4+ cells are the major producers of IFN-gamma but not NK cells. The study highlights the reversal of T cell anergy especially in lepromatous patients through the modulation of costimulatory molecule expression under the influence of Th1 cytokines, i.e., IL-2 and IFNgamma.