Leprosy as a model to understand cancer immunosurveillance and T cell anergy.

Leprosy is a disease caused by Mycobacterium leprae that presents on a spectrum of both clinical manifestations and T cell response. On one end of this spectrum, tuberculoid leprosy is a well-controlled disease, characterized by a cell-mediated immunity and immunosurveillance. On the opposite end of the spectrum, lepromatous leprosy is characterized by M. leprae proliferation and T cell anergy. Similar to progressive tumor cells, M. leprae escapes immunosurveillance in more severe forms of leprosy. The mechanisms by which M. leprae is able to evade the host immune response involve many, including the alterations of lipid droplets, microRNA, and Schwann cells, and involve the regulation of immune regulators, such as the negative checkpoint regulators CTLA-4, programmed death 1, and V-domain Ig suppressor of T cell activation-important targets in today's cancer immunotherapies. The means by which tumor cells become able to escape immunosurveillance through negative checkpoint regulators are evidenced by the successes of treatments, such as nivolumab and ipilimumab. Many parallels can be drawn between the immune responses seen in leprosy and cancer. Therefore, the understanding of how M. leprae encourages immune escape during proliferative disease states has potential to add to our understanding of cancer immunotherapy.

Pseudoepitheliomatous hyperplasia and transepidermal elimination in lepromatous leprosy: does T-cell plasticity play a role?

BACKGROUND: The longstanding concept of a Th1-Th2 dichotomy in leprosy, with Th1-predominant tuberculoid leprosy and Th2-predominant lepromatous leprosy (LL), has recently been challenged, and Cbl-b overexpression may emerge as an important factor in anergy and progression of LL. Moreover, Th17 and Th22 subsets have been identified as Th1-Th2 modulators in inflammatory skin diseases, most notably psoriasis, but their roles in leprosy have not yet been elucidated. The occurrence of pseudoepitheliomatous hyperplasia (PEH) with transepidermal elimination of mycobacteria in LL patients, which could theoretically be a portal for contact transmission, thus raises important immunological questions: Do Th17 and/or Th22 subsets mediate epidermal proliferation akin to Th1-driven psoriasis in supposedly Th2-predominant LL disease, and is the Th1-Th2 immunostat set systemically or locally? Furthermore, which microRNAs (miRs), signal transducers, and activators of transcription (STAT) proteins regulate this transition in leprosy, if any, and does differential Cb1-b expression play a role? OBSERVATION: A 71-year-old man presented with an infiltrative dermopathy characteristic of LL, as well as several hyperkeratotic plaques. Microscopic examination of the hyperkeratotic lesions demonstrated PEH with loss of the grenz zone and transepidermal elimination of acid-fast bacilli, whereas classic histopathologic features of LL were present at other sites. HYPOTHESES: We hypothesize that: Th17 and Th22 T-cell subsets act locally to induce T-cell plasticity in LL lesions, manifesting PEH; miR-181a is normal or increased in LL lesions with PEH compared to its expressional loss in classic LL lesions; miR-21 and STAT3 are increased in LL lesions with PEH, given their association with epithelial hyperproliferation; and Cbl-b is diminished in LL lesions with PEH compared to classic LL lesions. CONCLUSION: By understanding the factors that regulate T-cell and cytokine responses in leprosy, it should be possible to recognize these dynamic immunologic processes clinically and histopathologically and devise specific immunologic interventions.

Minocycline-induced hyperpigmentation in multibacillary leprosy.

Minocycline has been used in the treatment of leprosy since the demonstration of its efficacy in inhibiting Mycobacterium leprae growth in 1987. Hyperpigmentation, a well-documented adverse effect, classically shows 3 clinical and histological patterns: type I consists of blue-black pigmentation in areas of current or previous inflammation, type II consists of blue-gray pigmentation of normal skin, often seen on the legs, and type III consists of diffuse muddy-brown pigmentation accentuated on sun-exposed sites. Whereas type I hyperpigmentation stains positively for hemosiderin and type III hyperpigmentation stains positively for melanin, type II hyperpigmentation stains positively for both. We describe 2 patients with leprosy on minocycline therapy who developed multiple patches of blue-gray pigmentation within preexisting leprosy lesions. Biopsies from both patients demonstrated deposition of brownish-black pigment granules within the cytoplasm of foamy histiocytes that was highlighted by both Perls and Fontana-Masson stains. Given the clinical and histological findings in our patients, it is as yet unclear whether this coexistent type I clinical pattern and type II histopathologic pattern of pigmentation is unique to multibacillary leprosy. These findings provide support for the existence of additional subtypes of minocycline-induced hyperpigmentation that do not adhere to the classic 3-type model described.

Lessons of leprosy: the emergence of TH17 cytokines during type II reactions (ENL) is teaching us about T-cell plasticity.

BACKGROUND: Leprosy was the first disease classified according to the thymus derived T-cell in the 1960s and the first disease classified by the cytokine profile as intact interferon-γ (IFN-γ) and interleukin-2 (IL2) or TH1 (tuberculoid) and deficient IFN-γ and IL2 or TH2 (lepromatous), in the 1980s. OBJECTIVE: In the present study, we set out to explore the T helper 17 (TH17) lymphocyte subset, the hallmark of T-cell plasticity, in skin biopsies from patients with erythema nodosum leprosum (ENL) who were treated with thalidomide. METHOD: RNA was extracted from paraffin embedded tissue before and after thalidomide treatment of ENL and RT-PCR was performed. RESULTS: IL17A, the hallmark of TH17, was consistently seen before and after thalidomide treatment, confirming the TH17 subset to be involved in ENL and potentially up-regulated by thalidomide. CONCLUSION: A reduction in CD70, GARP, IDO, IL17B (IL-20), and IL17E (IL-25), coupled with increases in RORγT, ARNT, FoxP3, and IL17C (IL-21) following thalidomide treatment, opens the door to understanding the complexity of the immunomodulatory drug thalidomide, which can operate as an anti-inflammatory while simultaneously stimulating cell-mediated immunity (CMI). We conclude that TH17 is involved in the immunopathogenesis of ENL and that thalidomide suppresses inflammatory components of TH17, while enhancing other components of TH17 that are potentially involved in CMI.

Thalidomide and analogues: potential for immunomodulation of inflammatory and neoplastic dermatologic disorders.

Thalidomide and analogues are a class of immunomodulatory drugs or IMiDS. Thalidomide was initially approved by the U.S. Food and Drug Administation for treatment of erythema nodosum in leprosy and is now approved for multiple myeloma as well. A second generation IMiD, lenalidomide, is also approved for multiple myeloma and refractory myelodysplastic syndrome. Discovery of this class of drugs has been serendipitous and empirical, as the drug targets have been unknown. In this review, the authors integrate recent identification of drug targets of IMiDS, which include the inducible form of nitric oxide synthase (iNOS), Rho GTPase and caspase-1, with the developments in the understanding of the molecular biology of human inflammatory, infectious and neoplastic skin disorders. Because thalidomide reemerged through leprosy, the original disease classified by the T cell, the authors have also emphasized advances in the understanding of T-cell subsets in human skin disorders.

Lepromatous leprosy.

Lepromatous leprosy is a form of chronic granulomatous disease that is caused by infection with Mycobacterium leprae. Early involvement is marked by widespread, ill-defined, erythematous papules and plaques. With early intervention, leprosy is a curable disease; however, if not recognized and treated promptly, permanent sequelae and disability result. We present a patient with long-standing lepromatous leprosy who exhibits many of these sequelae.

The role of the armadillo and sooty mangabey monkey in human leprosy.

BACKGROUND: The armadillo was the first animal model of leprosy. Its role in the transmission of leprosy remains controversial. The sooty mangabey model of leprosy led to the discovery that rhesus monkeys were more susceptible to leprosy when coinfected with simian immunodeficiency virus (SIV), but that leprosy may play a protective role against acquired immunodeficiency syndrome (AIDS) mortality. Recently, molecular methods have been developed for leprosy and may help resolve the role of zoonoses in leprosy. OBSERVATIONS: The recent identification of a case of leprosy in a native-born American on the east coast of the USA and the identification of leprosy as an immunologic reconstitution inflammatory syndrome (IRIS) in human immunodeficiency virus (HIV)-positive cases raise the question of what role zoonoses may play in leprosy. CONCLUSIONS: Leprosy in armadillos and sooty mangabeys has been manipulated by human experimentation. In the case of the armadillo, further study, including molecular techniques, is required to elucidate the role of the armadillo as a zoonosis in human leprosy. Experimentation with the sooty mangabey led to the discovery of an interaction between SIV and leprosy in rhesus monkeys, and prompted the continued investigation of the relationship between HIV and leprosy.

Molecular origin of endemic leprosy in New York City.

We report an indigenous case of leprosy in New York City in an immunocompetent patient who was infected with a Mycobacterium leprae genotype that is consistent with an exogenous origin. Physicians in the eastern United States should be alerted that, although most patients who develop leprosy in the United States are foreign born, native-born Americans are also susceptible to the infection.

Identification of novel hsp65 RFLPs for Mycobacterium leprae.

Leprosy or Hansen's disease is a chronic infectious disease caused by an acid-fast bacillus, Mycobacterium leprae (M. leprae). The bacilli proliferate in macrophages infiltrating the skin and gain entry to the dermal nerves via the laminar surface of Schwann cells where they replicate. After entry, the Schwann cells proliferate and then die. Conclusive identification of M. leprae DNA in a sample can be obtained by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for the heat shock 65 gene (hsp65). Molecular epidemiology will make it possible to study the global distributions of M. leprae, explore the relationship between genotypes-incidence rates, mode of transmission, and the type of disease (tuberculoid vs. lepromatous). We amplified DNA using PCR for the hsp65 gene from 24 skin lesions from patients diagnosed with various types of leprosy. Fifteen out of 24 were positive for the hsp65 gene. Digestion with HaeIII-PAGE for the RFLP confirmation of the presence of M. leprae DNA showed the typical pattern in 5 out of 24 and 2 novel patterns in 10 out of 24 patients. We confirmed the presence of M. leprae DNA by sequencing the genes for gyraseA or B and folP, which contained only M. leprae specific single nucleotide polymorphisms (SNPs). Thus, we describe novel hsp65 RFLPs for M. leprae found in a high frequency making them ideal for future epidemiology and transmission studies.