Leprosy: a model of immunological perturbation in chronic infection

T-Regulatory Cells in Erythema Nodosum Leprosum: An Immunohistochemical and Image Morphometric Study

ABSTRACT

Erythema nodosum leprosum (ENL) occurs as an immune-inflammatory complication of multibacillary leprosy (MBL), precipitated by an interaction between the host, bacilli, and the environment. This complication often causes significant morbidity due to systemic involvement and needs to be treated aggressively. T-regulatory cells (T-regs) are the immunomodulatory subset of T cells that are hypothesized to play a role in ENL. We have performed immunohistochemistry for FoxP3 (T-reg), CD3 (pan-T), CD4 (helper T), and CD8 (cytotoxic T) on 50 biopsy-proven cases of ENL along with 84 biopsy-proven cases of paucibacillary leprosy (PBL) (n = 49) and MBL (n = 35). Image morphometry was applied to objectively assess the relative preponderance of these subsets of T cells. The area fraction of T-regs showed a trend of reduction from PBL to MBL to ENL (P = 0.068), whereas the FoxP3:CD3 (T-reg: pan-T) ratio showed a significant reduction across these groups (P = 0.023). However, there was no significant difference of T-regs or FoxP3:CD3 ratio between MBL and ENL. The T-regs showed a significant positive correlation (P = 0.007) with the cytotoxic T cells in the skin biopsy. The presence of dermal eosinophils in ENL showed a trend association with the FoxP3:CD3 ratio (P = 0.05). Various histopathological parameters including epidermal spongiosis, dermal stromal edema, dermal ill-formed granuloma, and the presence of bacilli within the endothelium and vascular smooth muscle correlated with various T-cell subsets. Our study, one of the largest on this topic, objectively assessed the role of T-regs in the spectrum of leprosy. Nevertheless, the precipitation of ENL from MBL is probably not associated with the T-reg subset alone.

miRNome Expression Analysis Reveals New Players on Leprosy Immune Physiopathology

Leprosy remains as a public health problem and its physiopathology is still not fully understood. MicroRNAs (miRNA) are small RNA non-coding that can interfere with mRNA to regulate gene expression. A few studies using DNA chip microarrays have explored the expression of miRNA in leprosy patients using a predetermined set of genes as targets, providing interesting findings regarding the regulation of immune genes. However, using a predetermined set of genes restricted the possibility of finding new miRNAs that might be involved in different mechanisms of disease. Thus, we examined the miRNome of tuberculoid (TT) and lepromatous (LL) patients using both blood and lesional biopsies from classical leprosy patients (LP) who visited the Dr. Marcello Candia Reference Unit in Sanitary Dermatology in the State of Pará and compared them with healthy subjects. Using a set of tools to correlate significantly differentially expressed miRNAs with their gene targets, we identified possible interactions and networks of miRNAs that might be involved in leprosy immunophysiopathology. Using this approach, we showed that the leprosy miRNA profile in blood is distinct from that in lesional skin as well as that four main groups of genes are the targets of leprosy miRNA: (1) recognition and phagocytosis, with activation of immune effector cells, where the immunosuppressant profile of LL and immunoresponsive profile of TT are clearly affected by miRNA expression; (2) apoptosis, with supportive data for an antiapoptotic leprosy profile based on BCL2, MCL1, and CASP8 expression; (3) Schwann cells (SCs), demyelination and epithelial–mesenchymal transition (EMT), supporting a role for different developmental or differentiation gene families, such as Sox, Zeb, and Hox; and (4) loss of sensation and neuropathic pain, revealing that RHOA, ROCK1, SIGMAR1, and aquaporin-1 (AQP1) may be involved in the loss of sensation or leprosy pain, indicating possible new therapeutic targets. Additionally, AQP1 may also be involved in skin dryness and loss of elasticity, which are well known signs of leprosy but with unrecognized physiopathology. In sum, miRNA expression reveals new aspects of leprosy immunophysiopathology, especially on the regulation of the immune system, apoptosis, SC demyelination, EMT, and neuropathic pain.

A Systematic Review of Immunological Studies of Erythema Nodosum Leprosum

Erythema nodosum leprosum (ENL) is a painful inflammatory complication of leprosy occurring in 50% of lepromatous leprosy patients and 5-10% of borderline lepromatous patients. It is a significant cause of economic hardship, morbidity and mortality in leprosy patients. Our understanding of the causes of ENL is limited. We performed a systematic review of the published literature and critically evaluated the evidence for the role of neutrophils, immune complexes (ICs), T-cells, cytokines, and other immunological factors that could contribute to the development of ENL. Searches of the literature were performed in PubMed. Studies, independent of published date, using samples from patients with ENL were included. The search revealed more than 20,000 articles of which 146 eligible studies were included in this systematic review. The studies demonstrate that ENL may be associated with a neutrophilic infiltrate, but it is not clear whether it is an IC-mediated process or that the presence of ICs is an epiphenomenon. Increased levels of tumor necrosis factor-α and other pro-inflammatory cytokines support the role of this cytokine in the inflammatory phase of ENL but not necessarily the initiation. T-cell subsets appear to be important in ENL since multiple studies report an increased CD4⁺/CD8⁺ ratio in both skin and peripheral blood of patients with ENL. Microarray data have identified new molecules and whole pathophysiological pathways associated with ENL and provides new insights into the pathogenesis of ENL. Studies of ENL are often difficult to compare due to a lack of case definitions, treatment status, and timing of sampling as well as the use of different laboratory techniques. A standardized approach to some of these issues would be useful. ENL appears to be a complex interaction of various aspects of the immune system. Rigorous clinical descriptions of well-defined cohorts of patients and a systems biology approach using available technologies such as genomics, epigenomics, transcriptomics, and proteomics could yield greater understanding of the condition.

Complex Type 2 Reactions in Three Patients with Hansen's Disease from a Southern United States Clinic

In non-endemic countries, leprosy, or Hansen's disease (HD), remains rare and is often underrecognized. Consequently, the literature is currently lacking in clinical descriptions of leprosy complications in the United States. Immune-mediated inflammatory states known as reactions are common complications of HD. Type 1 reactions are typical of borderline cases and occur in 30% of patients and present as swelling and inflammation of existing skin lesions, neuritis, and nerve dysfunction. Type 2 reactions are systemic events that occur at the lepromatous end of the disease spectrum, and typical symptoms include fever, arthralgias, neuritis, and classic painful erythematous skin nodules known as erythema nodosum leprosum. We report three patients with lepromatous leprosy seen at a U.S. HD clinic with complicated type 2 reactions. The differences in presentations and clinical courses highlight the complexity of the disease and the need for increased awareness of unique manifestations of lepromatous leprosy in non-endemic areas.

Detection of high titres of Toxoplasma gondii antibodies in sera of patients with leprosy in Pakistan

Untreated and treated leprosy patients and their household contacts were screened for antibody to Toxoplasma gondii using antigen-coated latex particles. A significantly high level of seroprevalence (29.6%) was observed in the untreated leprosy patients compared to endemic controls (P < 0.01) with a mean reciprocal antibody titre of 20,007 +/- 3580 (n = 98) in seropositive patients. In treated patients seroprevalence dropped to 13.5%. Seroprevalence in a group of household contacts of leprosy patients was similar to that of control subjects from an endemic area but not exposed to leprosy (7.8% and 6.1% respectively), indicating that the increased seroprevalence in leprosy patients was not merely due to increased exposure related to socioeconomic factors. Antigenic cross-reactivity between T. gondii and Mycobacterium leprae antigens was ruled out by cross inhibition experiments carried out with soluble antigens from each of the organisms. We believe these antibodies may be induced by an increase in T. gondii load in leprosy due to a transient reactivation of latent T. gondii infections, as the antibodies in these leprosy patients were not associated with any sign of eye or lymphatic pathology related to toxoplasmosis.

Polyclonal B-cell activation in periodontitis

The evidence that periodontitis-associated bacteria contain potent PBA factors is very strong. Clearly, antibodies directed against non-oral antigens are produced in the inflamed periodontal lesion, and PBA appears to contribute to that production. It is also clear that B cells and plasma cells are the major cell types in the periodontal lesion. Furthermore, alterations in the regulation of B-cell responses to PBA factors are associated with severe periodontal disease. However, evidence demonstrating that activated B cells and plasma cells are directly involved in the pathogenic mechanisms leading to destruction of the periodontal support is still circumstantial. Polyclonal B-cell activation and potential pathways by which PBA-stimulated cells could be involved in periodontal destruction remain largely hypothetical. It appears that IL-1 is an important osteoclast-activating agent, and that LPS, which is a potent PBA factor in many systems, can elicit IL-1 production by B cells as well as by the monocyte/macrophage lineage. Recent data indicating that IL-1 is produced by numerous malignant B-cell lines lend support for the idea that B-cell IL-1 could be important in bone resorption. It is also likely that polyclonal activation may lead to production of autoantibody such as anti-type I and anti-type III collagens, and the destruction of self tissues through ADCC reactions, immune complex formation, and complement activation. Further research is needed to determine how the B cell/plasma cell may participate in tissue injury in periodontitis, and how the B-cell response to PBA factors is regulated.

[An increase in Hansen's disease in northeastern Brazil]

The epidemiological aspects of hanseniasis in Recife from 1960 to 1985 were studied. Clinical-epidemiological records of 3,923 leprosy patients reported to the Secretaria de Saúde do Estado de Pernambuco were reviewed. The cruce as well as the age, sex and type-specific detection rates were calculated. The way the cases were detected and the time elapsed between the appearance of the first symptoms and the disease was analysed. The analysis of the time trend during the observation period showed an increase in the detection rate with time, rising from 5.5 per 100,000 inhabitants in 1960 to 36.1 per 100,000 inhabitants in 1985. The higher frequency of the tuberculoid type of leprosy and the high percentage of patients under 15 might refleet the expansion of the disease in Recife. The decline and the stabilization in the time elapsed between the appearance of the disease and its detection, from 1979 onwards, indicates a more prompt detection and, as a consequence of that, that the rate of detection is approaching the incidence rate. From 1970 to 1985 the most common means of detecting cases of Hanseniasis was through dermatological consultation followed by disease notification. Only 14.2% of the cases were discovered through the surveillance of contacts. The analysis of the epidemiological and operational indicators suggest that the increase in the detection rate over the period from 1960 to 1985 was due both to expansion of the disease and improvement in control measures. The prevalence rate of Hanseniasis in Recife in December 1984 was 2.04 per 100,000 inhabitants; according to the WHO criteria Recife may be considered an area of high endemicity.

Bacterial cell wall-induced immunosuppression. Role of transforming growth factor beta

Group A streptococcal cell wall (SCW)-injected rats exhibit a profound immunosuppression that persists for months after the initial intraperitoneal injection of SCW. The goal of this study was to determine the mechanisms for the suppressed T lymphocyte proliferative responses in this experimental model of chronic inflammation. When spleen cell preparations were depleted of adherent cells, restoration of T cell proliferative responses to Con A and PHA occurred, implicating adherent macrophages in the regulation of immunosuppression. Furthermore, macrophages from SCW-treated animals, when cocultured with normal spleen cells in the presence of Con A or PHA, effectively inhibited the proliferative response. Supernatants from suppressed spleen cell cultures were found to inhibit normal T cell mitogenesis. Taken together, these results implicated a soluble macrophage-derived suppressor factor in the down regulation of T cell proliferation after exposure to SCW in vivo. Subsequent in vitro studies to identify this suppressor molecule(s) revealed the activity to be indistinguishable from the polypeptide transforming growth factor beta (TGF-beta). Furthermore, TGF-beta was identified by immunolocalization within the spleens of SCW-injected animals. The cells within the spleen that stained positively for TGF-beta were phagocytic cells that had ingested, and were presumably activated by, the SCW. These studies document that TGF-beta, previously shown to be a potent immunosuppressive agent in vitro, also effectively inhibits immune function in chronic inflammatory lesions in vivo.

Characterization of the anti-neural antibodies in the sera of leprosy patients

Sera from 43 leprosy patients were tested for antibodies that bound to normal human nerve. Thirty-eight percent showed positive staining as demonstrated by indirect immunofluorescence. Only 1 out of 30 control sera tested displayed similar staining. Western blots of myelin and neural intermediate filament (IF) proteins were tested with patient sera. Two of the anti-neural antibody (ANeAb)-positive leprosy sera bound to the P0 protein of PNS myelin. All 17 ANeAb-positive leprosy sera displayed 2 or more bands in the molecular weight range of Mr 45 000-55 000, when tested against IF proteins. One explanation for these findings is that leprosy patients produce antibodies to intermediate filament (IF) proteins released subsequent to the bacterial invasion of the peripheral nerves. The importance of these autoantibodies in the pathogenesis of leprosy is discussed.

Thymopentin treatment in patients with chemotherapy-resistant lepromatous leprosy

Leprosy is a chronic infectious disease caused by Mycobacterium leprae; it is chiefly involving the skin and peripheral nerves. In lepromatous leprosy there are widespread loose infiltrates with M. leprae multiplying extensively in the skin macrophages and Schwann cells of peripheral nerves. Such patients reveal a decrease of circulating T helper cells, which is still more pronounced in the cutaneous lesions. Due to the ever increasing bacterial resistance to classical dapsone and combined chemotherapy as well, an immunomodulatory approach seemed reasonable: Eight patients with long-lasting (5-40 years) disease who had become resistant to combined chemotherapy were treated with thymopentin, 50 mg s.c., 3 times weekly for 5 weeks and thereafter combined with dapsone and clofazimine for 5 months. During the trial a statistically significant increase in E-rosette-forming cells (p less than 0.05) was observed, along with a steady improvement of the bacterial status of the nasal mucus. Although the skin lesions did not disappear within the observation period of the study, it is important to realize that long-term improvement of such lesions is always initiated by clearance of bacilli from the nasal mucus, hence, thymopentin treatment appears to be a promising approach to chemotherapy-resistant lepromatous lepra.

Passive transfer of tuberculin sensitivity from anergic mice

Mice heavily infected with Mycobacterium bovis BCG rapidly became anergic to cutaneous injection with tuberculin. Evidence is presented suggesting that this anergy reflects an adaptive physiological change within the host in which antigen-reactive Thy-1.2+ cells become sequestered in central lymphoid tissues, with a concomitant reduction in the circulating pool. No evidence could be provided to support the suggestion that anergy was a consequence of an acquired immunosuppressive mechanism.

Demonstration of T lymphocytes in leprous granuloma using the acid alpha naphtyl acetate esterase activity. An attempt at quantitative analysis

In nine leprosy patients (1 TT, 1 BT, 4 BL and 3 LLp), esterase positive lymphocytes (T Lymphocytes) were studied in frozen sections of skin biopsies by alpha naphtyl acetate esterase pH 5.8 method (ANAE) Four patients had never been treated previously and five patients exhibited clinical and bacteriological evidence of relapse for inadequate therapy at first biopsy. There was an increase in ANAE (+) lymphocyte density in granulomas when second biopsies were done after efficient treatment, evaluated by bacillary index for the eight bacilliferous patients, and clinical improvement. The significance of T cells in granulomas is discussed.

Amyloidosis and the serum amyloid A protein response to muramyl dipeptide analogs and different mycobacterial species

Serum amyloid A protein (SAA) elevation accompanies induction of secondary amyloidosis in mice given Mycobacterium butyricum in Freund adjuvant. The synthesis of SAA by cultured hepatocytes is induced by a macrophage-derived mediator, which has been identified as interleukin 1. In these studies, SAA synthesis has been used as an index of macrophage activation to examine the in vivo response of mice to challenge with seven different mycobacteria and with synthetic analogs of the immunoadjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine [MDP(L-D)]. SAA synthesis was stimulated by administration (by the intraperitoneal route) of the mycobacteria dissolved in saline, with Mycobacterium vaccae being the most active and Mycobacterium leprae being the least stimulatory. MDP(L-D), which is the minimal structure (molecular weight, 492) able to substitute for mycobacteria in Freund adjuvant, stimulated SAA synthesis, whereas the MDP(D-D) isomer was inactive. The butyl ester of MDP, which induces no detectable pyrogenicity but retains adjuvanticity, required a 100-fold greater dosage than MDP(L-D) in stimulating SAA synthesis. Amyloidosis was detected histologically only when active SAA inducers MDP(L-D), M. vaccae, and M. butyricum, were administered in incomplete Freund adjuvant, with amyloid-enhancing factor. These studies demonstrated that SAA elevation was a sensitive in vivo marker of the capacity of antigens to stimulate macrophages to produce interleukin 1. A point of considerable relevance to the human use of MDP was the observation that repeated injections of the adjuvant MDP in saline did not induce secondary amyloidosis.

Immunoglobulin deposits in leprosy skin

An immunofluorescent study was carried out on skin biopsies from 12 leprosy patients who had been suffering from the disease for periods of one to 30 years; all were treated with dapsone and clofazimine at one stage. Skin biopsies made from reactive nodular lesions showed that all 12 had IgG deposits and seven had IgM deposits in the dermal-epidermal junction. No IgA, IgE, C3 and fibrinogen were found deposited in any biopsy. All patients had significantly raised levels of serum immunoglobulins and rheumatoid factor. Anti-epithelial (eight patients) and anti-nuclear (three patients) antibodies were also found. The possible role of autoantibodies in the present findings is discussed.

Deficit of interleukin 2 production associated with impaired T-cell proliferative responses in Mycobacterium lepraemurium infection

C57BL/6 and BALB/c mice were infected intravenously with 10(7) Mycobacterium lepraemurium (MLM). At various times after infection, spleen cells were tested for their capacity to proliferate in vitro in response to concanavalin A (ConA) and to allogeneic cells. The generation of alloreactive cytotoxic T lymphocytes was also studied. The mitogen- and allogeneic-cell-induced blastogenesis of splenocytes from MLM-infected C57BL/6 and BALB/c mice was shown to be depressed during infection. The maximal decrease occurred 6 months after infection. Conversely, no reduction in the ability to generate alloreactive cytotoxic T lymphocytes was observed even after 6 months of infection. At the same time, interleukin 2 (IL2) activity generated by ConA stimulation of infected splenocytes was measured in both strains. IL2 activity in the ConA-stimulated culture supernatants was decreased as early as 1 month after MLM inoculation as compared with supernatants from age-matched control mice. Thus, IL2 production by infected-mouse spleen cells was shown to decline earlier than their proliferative responses to ConA and to allogeneic cells. ConA-induced T-cell blasts from infected mice showed a reduced ability to proliferate when incubated with an IL2-containing reference supernatant from ConA-stimulated normal spleen cells. These data suggest that a defect in IL2 production and utilization might contribute to the impairment of T cell-mediated immunity observed in MLM-infected mice.

Immune reactions in tuberculous and chronic constrictive pericarditis. Clinical data and diagnostic significance of antimyocardial antibodies

Humoral immune reactions were analyzed in 12 patients with exudative tuberculous pericarditis, 10 patients with constrictive pericarditis due to former tuberculosis, 10 patients with viral pericarditis, 20 patients with pulmonary tuberculosis, and 98 healthy donors. Pericarditis occurred in 12.5% of the patients with tuberculosis, whereas the incidence of tuberculosis in the 149 patients with pericarditis was 8%. Repeated pericardial puncture and pericardial effusions of greater than 500 ml with impending cardiac tamponade had to be performed in 4 patients. Clinical data indicated probable myocardial involvement in 4 of 12 patients. Antimyolemmal antibodies, which are a muscle-specific subtype of antisarcolemmal antibodies, were found in all patients with exudative tuberculous pericarditis and viral perimyocarditis, in only 1 of 12 patients with constrictive pericarditis, and in no patients with pulmonary tuberculosis. Antifibrillary antibodies--primarily of the antimyosin type--were missed in patients with viral heart disease but were demonstrated in 75% of patients with tuberculous pericarditis. Only sera with complement-fixing antimyolemmal antibodies of the IgG type in titers greater than 1:40 induced cytolysis of vital adult heterologous cardiocytes isolated and enriched by silica sol gradient centrifugation. These findings suggest not only that antimyolemmal antibodies are diagnostic indicators of perimyocardial involvement in tuberculous pericarditis, but also that they may play a significant role in its pathogenesis.

Leprosy, an overview

Leprosy is both a public health problem and a model for host-parasite relationship. There is much progress in many areas, and in most, hurdles are not only scientific but also social and financial. The following are goals to reach: 1) progress of growth of M. leprae in animals (to be able to breed armadillos in captivity or to substitute them with other animals); 2) to develop methods for in vitro culture of M. leprae; 3) to obtain antigens from M. leprae and characterize them immunologically; 4) to achieve techniques for objective diagnosis of infection with M. leprae and of leprosy (these techniques will most likely be serologic); 5) to develop methods to direct and manipulate immune response. This should include a better definition of immunologically active cells, their characterization by reliable methods, and an understanding of their functions. Immune control mechanisms and ways to channel them should also be understood; and 6) to have better methods of treatment including flexible adaptable schedules. It will be clear that "solving" the problem of leprosy requires "solving" the social problems in developing countries, as well as unraveling the mystery of the precise control of immune response. As I pointed out, the problems that we face are basically similar to those of autoimmune disorders and of cancer immunology. Research in autoimmune diseases or cancer might provide answers to questions posed by leprosy. It may also be that research in leprosy could supply answers to questions concerning cancer and autoimmunity.

High incidence of IgG class of Epstein-Barr virus capsid antibody in Indian patients of lepromatous leprosy

Low levels of Epstein-Barr virus capsid (EBVC) antibody of the IgG class were detected in the sera of 19 of 23 (82.6%) lepromatous leprosy patients and six of 38 (16%) healthy controls. In contrast, heterophile antibody was found in only six of 43 (14%) lepromatous patients and three of 41 (7%) normal subjects. Overlap of the two types of antibody occurred only in one normal serum. It is inferred that the presence of EBVC antibody against an unbiquitous virus in lepromatous patients who often suffer from impairment of cell-mediated immunity might be due to past infection leading to persistence of the virus in their lymphoid cells and subsequent production of specific anti-viral antibody. Further, the striking finding of low incidence and titre of EBVC antibody in the normal Indian adults is consistent with the rarity of EB virus-associated disease, such as Burkitt's lymphoma, nasopharyngeal carcinoma and infectious mononucleosis in India.

Systemic Mycobacterium kansasii infection and regulation of the alloantigenic response

Specific-pathogen-free B6D2 F1 hybrid mice were infected intravenously with 10(7) to 10(8) viable Mycobacterium kansasii cells. The growth of the five test strains in vivo was correlated with the level of delayed hypersensitivity to a cytoplasmic protein antigen injected into the footpad. M. kansasii TMC no. 1201 and 1203 gave rise to persisting systemic infections with an early delayed hypersensitivity response (day 7) followed by a profound anergy to the cytoplasmic protein antigen injections. Strains 1204, 1214, and 1217 declined in viability relatively rapidly and failed to induce detectable levels of delayed hypersensitivity. Spleens harvested from mice infected 20 to 30 days earlier with 10(8) M. kansasii 1203 cells contained a T-cell subpopulation capable of suppressing mixed lymphocyte reactions between normal B6D2 and C3H(He) cells. On the other hand, splenic T-cells taken from M. kansasii 1214-infected mice enhanced, rather than suppressed, the indicator mixed lymphocyte reactions. The kinetics of stimulator-suppressor T-cell production within the spleens of the heavily infected mice differed as the two contrasting M. kansasii infections progressed. Such cellular interactions could well be responsible for the observed persistence of the systemic M. kansasii 1203 infection.

Selective suppression of granuloma formation and delayed hypersensitivity in rabbits

The relationship between dermal delayed hypersensitivity (DH) and granulomatous hypersensitivity was studied in rabbits sensitized with killed mycobacteria. Specific antigen challenge of sensitized animals resulted in extensive pulmonary granulomatous inflammation and induced suppression of both dermal DH and dermal granuloma formation. Whereas suppression of DH was concomitant with pulmonary granuloma formation, as is the case in a number of granulomatous diseases, a causal relationship between the two did not exist. Both DH and dermal granulomatous hypersensitivity were significantly suppressed whether or not the antigen challenge was of a granulomagenic (particulate) or nongranulomagenic (soluble) form. The data presented indicate that granulomatous hypersensitivity and DH are selectively suppressed with regard to different anatomical sites.