Widespread intradermal accumulation of mononuclear leukocytes in lepromatous leprosy patients treated systemically with recombinant interferon gamma

Interferon- and infectious diseases: Lessons and prospects

Infectious diseases continue to claim many lives. Prevention of morbidity and mortality from these diseases would benefit not just from new medicines and vaccines but also from a better understanding of what constitutes protective immunity. Among the major immune signals that mobilize host defense against infection is interferon-γ (IFN-γ), a protein secreted by lymphocytes. Forty years ago, IFN-γ was identified as a macrophage-activating factor, and, in recent years, there has been a resurgent interest in IFN-γ biology and its role in human defense. Here we assess the current understanding of IFN-γ, revisit its designation as an "interferon," and weigh its prospects as a therapeutic against globally pervasive microbial pathogens.

Susceptibility and resistance in leprosy: Studies in the mouse model

Leprosy is a chronic granulomatous infectious disease caused by the pathogen, Mycobacterium leprae, and the more recently discovered, M. lepromatosis. Described in 1873, M. leprae was among the first microorganisms to be proposed as a cause of a human infectious disease. As an obligate intracellular bacterium, it has still not thus far been reproducibly cultivated in axenic medium or cell cultures. Shepard's mouse footpad assay, therefore, was truly a breakthrough in leprosy research. The generation of immunosuppressed and genetically engineered mice, along with advances in molecular and cellular techniques, has since offered more tools for the study of the M. leprae–induced granuloma. While far from perfect, these new mouse models have provided insights into the immunoregulatory mechanisms responsible for the spectrum of this complex disease.

A journey in science: promise, purpose, privilege

Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research; and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed, and treated. In this volume, the first Cerami Award Monograph, by Carl Nathan, MD, chairman of the Department of Microbiology and Immunology at Weill Cornell Medical College, reflects towering genius and soaring inspiration.

A single intradermal injection of IFN-γ induces an inflammatory state in both non-lesional psoriatic and healthy skin

Psoriasis is a chronic, debilitating, immune-mediated inflammatory skin disease. As IFN-γ is involved in many cellular processes, including activation of dendritic cells (DCs), antigen processing and presentation, cell adhesion and trafficking, and cytokine and chemokine production, IFN-γ-producing Th1 cells were proposed to be integral to the pathogenesis of psoriasis. Recently, IFN-γ was shown to enhance IL-23 and IL-1 production by DCs and subsequently induce Th17 cells, which are important contributors to the inflammatory cascade in psoriatic lesions. To determine whether IFN-γ indeed induces the pathways expressed in psoriatic lesions, a single intradermal injection of IFN-γ was administered to an area of clinically normal, non-lesional (NL) skin of psoriasis patients and biopsies were collected 24 hours later. Although there were no visible changes in the skin, IFN-γ induced many molecular and histological features characteristic of psoriatic lesions. IFN-γ increased a number of differentially expressed genes in the skin, including many chemokines concomitant with an influx of T cells and inflammatory DCs. Furthermore, inflammatory DC products tumor necrosis factor (TNF), inducible nitric oxide synthase, IL-23, and TNF-related apoptosis-inducing ligand were present in IFN-γ-treated skin. Thus, IFN-γ, which is significantly elevated in NL skin compared with healthy skin, appears to be a key pathogenic cytokine that can induce many features of the inflammatory cascade of psoriasis.

A single intradermal injection of IFN-γ induces an inflammatory state in both non-lesional psoriatic and healthy skin

Psoriasis is a chronic, debilitating, immune-mediated inflammatory skin disease. As IFN-γ is involved in many cellular processes, including activation of dendritic cells (DCs), antigen processing and presentation, cell adhesion and trafficking, and cytokine and chemokine production, IFN-γ-producing Th1 cells were proposed to be integral to the pathogenesis of psoriasis. Recently, IFN-γ was shown to enhance IL-23 and IL-1 production by DCs and subsequently induce Th17 cells, which are important contributors to the inflammatory cascade in psoriatic lesions. To determine whether IFN-γ indeed induces the pathways expressed in psoriatic lesions, a single intradermal injection of IFN-γ was administered to an area of clinically normal, non-lesional (NL) skin of psoriasis patients and biopsies were collected 24 hours later. Although there were no visible changes in the skin, IFN-γ induced many molecular and histological features characteristic of psoriatic lesions. IFN-γ increased a number of differentially expressed genes in the skin, including many chemokines concomitant with an influx of T cells and inflammatory DCs. Furthermore, inflammatory DC products tumor necrosis factor (TNF), inducible nitric oxide synthase, IL-23, and TNF-related apoptosis-inducing ligand were present in IFN-γ-treated skin. Thus, IFN-γ, which is significantly elevated in NL skin compared with healthy skin, appears to be a key pathogenic cytokine that can induce many features of the inflammatory cascade of psoriasis.

Long-term culture of multibacillary leprosy macrophages isolated from skin lesions: a new model to study Mycobacterium leprae-human cell interaction

BACKGROUND

Leprosy is characterized by a disease spectrum having two polar clinical forms dependent on the presence or not of cell-mediated immunity. In the tuberculoid forms, granuloma-activated macrophages kill Mycobacterium leprae in conjunction with a Th1 response while, in multibacillary (MB) lesions, M. leprae nonactivated macrophages infiltrate the nerves and internal organs together with a Th2 response. The functional properties and activation pathways of macrophages isolated from patients with MB leprosy remain only partially understood.

OBJECTIVES

To establish an ex vivo methodology capable of evaluating the activation pathways, grade and fate of cultured macrophages isolated from MB lesions.

METHODS

Skin biopsies from patients with borderline tuberculoid, bordeline lepromatous and lepromatous leprosy (LL) were characterized by immunohistochemistry and transcriptional analysis. To isolate inflammatory cells, a portion of the samples was submitted to enzymatic digestion. These same cells, maintained in culture for a minimum 7-day period, were characterized morphologically and via flow cytometry at different culture time points. Cytokine [interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-10] mRNA levels were quantified by real-time polymerase chain reaction and protein secretion in the culture supernatants was measured by enzyme-linked immunosorbent assay and the nitric oxide levels by Griess reagent.

RESULTS

RNA expression in tuberculoid and MB lesions showed the profile expected of characteristic Th1 and Th2 responses, respectively. The inflammatory cells in all biopsies were successfully isolated. Although the number of cells varied between biopsies, it was highest in LL biopsies. The frequency of isolated CD14+ and CD3+ cells measured by flow cytometry correlated with the percentages of macrophages and lymphocytes in the lesions. Throughout the culture period, CD68+ macrophages showed morphological changes. A progressive increase in cell number and reduction of infected cells were perceptible in the cultures. In contrast to the biopsies, TNF-alpha, IFN-gamma and IL-10 expression in the tuberculoid and MB leprosy cells in 24-h culture and the cytokine levels in the supernatants did not differ significantly. During the culture period, cytokine expression in the MB cells progressively declined, whereas, from days 1 to 7, nitrite levels progressively increased. After day 40, the remaining macrophages were able to ingest fluorescein isothiocyanate-labelled M. leprae. These data need to be confirmed.

CONCLUSIONS

This study confirmed the feasibility of obtaining ex vivo macrophages from leprosy lesions and keeping them in long-term culture. This procedure may open new pathways to studying the interaction between M. leprae and human macrophages, which might, in turn, lead to the development of therapeutic tools capable of overcoming the specific anergy found in patients with MB leprosy.

An in vitro model for the lepromatous leprosy granuloma: fate of Mycobacterium leprae from target macrophages after interaction with normal and activated effector macrophages

The lepromatous leprosy granuloma is a dynamic entity requiring a steady influx of macrophages (Mphi) for its maintenance. We have developed an in vitro model to study the fate of Mycobacterium leprae in a LL lesion, with and without immunotherapeutic intervention. Target cells, consisting of granuloma Mphi harvested from the footpads of M. leprae-infected athymic nu/nu mice, were cocultured with normal or IFN-gamma-activated (ACT) effector Mphi. The bacilli were recovered and assessed for viability by radiorespirometry. M. leprae recovered from target Mphi possessed high metabolic activity, indicating a viable state in this uncultivable organism. M. leprae recovered from target Mphi incubated with normal effector Mphi exhibited significantly higher metabolism. In contrast, bacilli recovered from target Mphi cocultured with ACT effector Mphi displayed a markedly decreased metabolic activity. Inhibition by ACT Mphi required an E:T ratio of at least 5:1, a coculture incubation period of 3-5 days, and the production of reactive nitrogen intermediates, but not reactive oxygen intermediates. Neither IFN-gamma nor TNF-alpha were required during the cocultivation period. However, cell-to-cell contact between the target and effector Mphi was necessary for augmentation of M. leprae metabolism by normal effector Mphi as well as for inhibition of M. leprae by ACT effector Mphi. Conventional fluorescence microscopy and confocal fluorescence microscopy revealed that the bacilli from the target Mphi were acquired by the effector Mphi. Thus, the state of Mphi infiltrating the granuloma may markedly affect the viability of M. leprae residing in Mphi in the lepromatous lesion.

Immunochemotherapy with interferon-gamma and multidrug therapy for multibacillary leprosy

Treatment for multibacillary leprosy is presently performed with a multidrug therapy (MDT) scheme maintained for 2 years. Leprosy treatment however can benefit from the reduction of length. The lack of interferon-gamma (IFN-gamma) production by lepromatous leprosy (LL) patients' lymphocytes lead us to use this cytokine in the treatment of multibacillary leprosy associated with MDT in the treatment of multibacillary leprosy, and monitor several clinical and immunological parameters during the course of treatment. A total of 20 multibacillary leprosy patients were evaluated, 10 treated with MDT alone, and 10 treated with MDT + 10 daily doses of 2 x 10(6) international units (IU) of recombinant human IFN-gamma/m2 followed by 10 daily doses of 10(7) IU IFN-gamma/m2, intramuscularly, during the first 20 days of MDT. IFN-gamma was well tolerated and did not cause any increase in the rate of leprosy reactions development during treatment. Decrease of bacillary load, fall of anti-Mycobacterium leprae IgG serum antibodies, changes of histological pattern, as well as changes in lymphocyte proliferation assay in response to mitogens (PHA or PWM), M. leprae antigen or PPD was similar in both groups of patients. Among several soluble immunological markers measured before and 30 days after beginning of treatment, levels of soluble IL-2R receptor increased in patients treated with MDT plus IFN-gamma whereas decreased in patients treated with MDT alone. Soluble ICAM-1 levels decreased in the MDT group but did not change in the MDT + IFN-gamma treated patients. Soluble CD4 and soluble CD8 markers did not change significantly in either group of patients. Neopterin, a marker of macrophage activation, increased in all but one patient treated with MDT + IFN-gamma but in none treated with MDT alone, indicating that IFN-gamma was active in vivo. Our findings indicate that despite being able to promote macrophage activation in multibacillary leprosy patients a short course of systemically administered IFN-gamma is not able to change the clinical course of a long standing disease such as leprosy.

Reproductive effects of chronic administration of murine interferon-gamma

Daily subcutaneous doses of 0.02, 0.2, or 2 mg/kg/d of recombinant murine interferon-gamma (rmuIFN-gamma) were given to mice on postnatal days 8 through 60 to determine effects on maturation, behavioral/ functional development, and reproductive capacity. Male mice receiving 2 mg/kg/d rmuIFN-gamma had delayed sexual maturation, reduced epididymal and testes weights, reduced sperm count and concentration, and sperm abnormalities (crimped flagellum). Mating performance and fertility were also reduced in the absence of altered histopathology of the testes. Males given 0.2 and 2 mg/kg/d had swelling and ulcerative dermatitis around the urogenital area, which were observed after sexual contact and attributed to a bacterial infection. Motor activity (time spent in movement) was decreased in all mice receiving 2 mg/kg/d. No microscopic changes observed in any organs were attributed to rmuIFN-gamma administration.

Contribution of alpha/beta and gamma/delta T lymphocytes to immunity against Mycobacterium bovis bacillus Calmette Guérin: studies with T cell receptor-deficient mutant mice

Mutant mice with defined T cell deficiencies were infected with Mycobacterium bovis bacillus Calmette Guérin (BCG) and the relative contribution of alpha/beta T cells and gamma/delta T cells to the host immune response was assessed. Recombinase activating gene (RAG-1)-/- mutants as well as T cell receptor (TcR) beta-/-, but not TcR-delta-/-, mutants succumbed to M. bovis BCG infection and failed to develop granulomatous lesions. Antigen-induced IFN-gamma production by spleen cells in vitro was abrogated in RAG-1-/- mutants and markedly diminished in TcR-beta-/- and TcR-delta-/- mice. Reconstitution experiments suggest that both alpha/beta and gamma/delta T cells are essential for antigen-specific IFN-gamma secretion. Our data formally prove the crucial role of alpha/beta T cells and reveal accessory functions of gamma/delta T cells in optimum immunity against M. bovis BCG.

Interferon-gamma and host antimicrobial defense: current and future clinical applications

In the 1980s, substantive experimental data and emerging clinical results suggested that interferon-gamma (IFN-gamma), a T-cell-derived lymphokine with broad macrophage-activating effects, had considerable potential in the treatment of nonviral infections as a host defense-enhancing antimicrobial agent. During the past 6 years, the breadth of the experimental activity with IFN-gamma against nonviral pathogens has been expanded still further, and pilot studies and formal clinical trials using IFN-gamma have been undertaken in the treatment of patients both at risk for and with active infections. Thus far, IFN-gamma has been approved for use as prophylaxis in patients with chronic granulomatous disease. However, IFN-gamma also appears effective as adjunctive therapy for at least one disseminated intracellular infection (visceral leishmaniasis), and in conjunction with conventional therapy, may benefit patients with certain forms of cutaneous leishmaniasis, disseminated Mycobacterium avium complex infection, and lepromatous leprosy. Despite a rationale for its use, IFN-gamma has not yet been tested in tuberculosis or fungal or common bacterial infections nor sufficiently examined in the prevention and/or treatment of the opportunistic infections related to acquired immunodeficiency syndrome. IFN-gamma remains a promising host defense-enhancing cytokine with still unexplored clinical potential.

The role of cytokines in mycobacterial infection

Mycobacterial infections are a major cause of morbidity and mortality worldwide. The pathogenesis of infection and the mechanisms for the development of protective immunity are poorly known, but cytokines appear to play an important role in the modulation of the immune response. Evidence exists for the role of tumor necrosis factor (TNF-alpha), granulocyte macrophage colony stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) in the host defense against mycobacteria. In this article we discuss recent findings about the role of cytokines in leprosy, tuberculosis and Mycobacterium avium infection, using in vitro and in vivo human and murine data.

IFN-gamma, IL-6 and IL-4 modulate M. leprae- or PPD-specific cytotoxic T cells in leprosy patients

Specific cytotoxic T cells against intracellular pathogens may be generated in vitro. On the other hand it is well known that cytokines can regulate almost every aspect of immune function. The aim of this study was to evaluate the effect of some cytokines on the generation of cytotoxic T cells with specificity for Mycobacterium leprae- or PPD-pulsed autologous macrophages from leprosy patients and normal controls. Peripheral blood mononuclear cells from M. bovis BCG-immunized controls or from leprosy patients were stimulated with antigen, in the presence or absence of cytokines, for 7 days. These were used as effector cells in a 4-h [51Cr]-release assay. Our results show that development of cytotoxic T cells may be enhanced by gamma-IFN, IL-6 or the combination of IL-6 and IL-2. Addition of IL-2 or TNF-alpha alone did not modify the generation of cytotoxic activity. IL-4 down-regulated the cytotoxic response and gamma-IFN was able to counteract this effect. Hence, the generation of specific cytotoxic T cells can be modulated by cytokines. Whether this cytotoxic mechanism contributes to protection or tissue damage in M. leprae infection remains to be determined.

Interferon-gamma and resistance to bacterial infections

Since its initial description as an antiviral, it has become clear that Interferon-gamma (IFN-gamma) has potent immunoregulatory and cell growth regulatory activities. As a result of these additional activities, it is now apparent that IFN-gamma plays a major role in regulation of bacterial infections. IFN-gamma can be both induced by bacteria and bacterial products; endogenous IFN-gamma production has been shown to play a protective role in the natural host response to several bacterial infections; and administration of exogenous IFN-gamma is effective in the prevention and treatment of bacterial infections in numerous animal model systems. Although it is now clear that IFN-gamma plays a role in regulation of bacterial infections, the mechanisms of its anti-bacterial effects in vivo remain to be established due to the pleiotropic nature of IFN-gamma activity.

Lepromatous leprosy treated with recombinant interferon gamma: cutaneous histologic changes

We report on the histologic changes occurring in single cutaneous lesions, from six active lepromatous patients, 1 week following the administration of three daily intradermal injections, 35 micrograms each, of recombinant interferon gamma (rIFN-gamma). Except for a strong induration at the injection site, rIFN-gamma produced no adverse systemic reactions and was able to promote a remarkable influx of T-lymphocytes, mononuclear phagocytes with large nuclei, nonvacuolated cytoplasm, and reduced lysozyme reactivity. Furthermore, despite no clear-cut reduction of mycobacterial dermal burden, bacilli showed a clear increase in the granular appearance. Present findings provide a basis for further elucidation of rIFN-gamma as an additional tool for leprosy treatment.

Prolonged treatment with recombinant interferon gamma induces erythema nodosum leprosum in lepromatous leprosy patients

10 patients with borderline and lepromatous leprosy were selected for a prolonged trial with recombinant interferon gamma (rIFN-gamma). Patients received 30 micrograms intradermally for six injections over a 9-d period, and then either 100 micrograms intradermally every 1 mo for 10 mo or every 2 wk for 5 mo (total, 1.2 mg). Erythema nodosum leprosum (ENL) was induced in 60% of the patients within 6-7 mo, as compared with an incidence of 15% per year with multiple drug therapy alone. The mean whole-body reduction in bacterial index over the first 6 mo was 0.9 log units. Cutaneous induration at the intradermal injection sites of greater than or equal to 15 mm predicted the development of a subsequent reactional state. Monocytes obtained from patients receiving the lymphokine demonstrated an increased respiratory burst and a 2.5-5.1-fold increase in tumor necrosis factor alpha (TNF-alpha) secretion in response to agonists. Patients in ENL had an even higher release of TNF-alpha from monocytes as well as high levels of TNF-alpha in the plasma (mean, 2,000 pg/ml). Thalidomide therapy was required to treat the systemic manifestations of ENL. Control of toxic symptoms with thalidomide was associated with a 50-80% reduction in agonist-stimulated monocyte TNF-alpha secretion. IFN-gamma enhanced the monocyte release of TNF-alpha by 3-7.5-fold (agonist dependent) when added to patient's cells in vitro, and this could be suppressed by the in vitro addition of 10 micrograms/ml of thalidomide.

Preferential increase of IL-2R+ CD4+ T cells and CD45RB- CD4+ T cells in the central nervous system in experimental allergic encephalomyelitis

We examined lymphocytes isolated from the spinal cord (SC), peripheral blood (PB) and lymph nodes (LN) draining the immunization site of Lewis rats with acute experimental allergic encephalomyelitis (EAE). Cells were analysed for T cell subset markers CD4 (mAb W3/25) and CD8 (mAb OX8), for IL-2R (mAb OX39), and for high molecular mass leukocyte common antigen (LCA, CD45RB) expression (mAb OX22). T cells expressing high (CD45RB+) or low (CD45RB-) molecular mass LCA are of different maturational stages and/or separate lineages. CD4+ T cells were more predominant in SC than in PB and LN; CD8+ T cells were scarce in SC but common in PB and LN. Activated CD4+ T cells (IL-2R+) were common in the SC and LN but infrequent in blood. CD4+ T cells that were CD45RB+ were scarce in the SC. In contrast, the majority of CD4+ T cells in the PB and LN were CD45RB+. The preferential accumulation of IL-2R+ CD4+ T cells and of CD45RB- CD4+ T cells in the central nervous system (CNS) indicates that a selective mechanism directs cell egress into CNS lesions in EAE.

Cytokines in clinical cancer therapy

Cytokines have been of much interest in clinical cancer therapy research over the past decade. One important advance during the past year has been the clear demonstration, in large prospective randomized studies, that granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor reduce the neutropenia-related morbidity of cancer therapy.

An immunogenetic view of delayed type hypersensitivity

This review, the third in the series on cellular immune reactivity to tubercle bacilli in the centenary year of Koch's classical paper describing this phenomenon and its possible implications, represents an immunogenetic point of view. In fact this will be quite a broad point of view by an immunogeneticist who is not hampered by specific knowledge on therapy or prevention of tuberculosis. In this respect I probably do not differ very much from Robert Koch 100 years ago! An important difference, however, is that we think we now understand a great deal of the cellular and molecular basis of the immunological phenomena observed by Koch. Immunogenetics has contributed considerably to our current understanding and I will try to review that contribution here. Because thus far my main research interest has been in another mycobacterium, namely Mycobacterium leprae, I will use M. leprae and leprosy as an example to illustrate some ideas. The message of this review is that there is a reason for optimism: the knowledge recently gained by cellular and molecular immunologists as well as immunogeneticists has straightforward implications for the rational development of subunit vaccines and immunotherapeutic strategies.

Role of T-cell subsets in bacterial infections

Classic functional partitioning of T-cell subsets is being questioned: in many bacterial and protozoan infections, CD8 T cells play a role in protection; two types of CD4 T helper cells have been characterized, one protective, the other exacerbating disease; finally, gamma delta T cells have been implicated in the host response to certain bacteria. Moreover, evidence is accumulating that, in addition to T-cell helper functions, cytolytic T-cell functions participate in antibacterial immunity.

Leprosy and cell-mediated immunity

The intradermal injection of the purified protein derivative of tuberculin into lepromatous leprosy patients leads to a local cell-mediated immune response and to the extensive destruction of Mycobacterium leprae. This local response also occurs after intradermal injection of recombinant human interleukin-2; when administered over an 8-day period interleukin-2 evokes a systemic cell-mediated immune response and a reduction in the bacillary burden.