Interactions between HIV infection and leprosy: a paradox

Immunopathogenesis of immune reconstitution disease in HIV patients responding to antiretroviral therapy

PURPOSE OF REVIEW

The aim of this article is to review the most recent literature regarding the immunopathogenesis of pathogen-associated immune reconstitution disease and to discuss the role of immune activation and various effector molecules and cells such as macrophages, effector and regulatory T cells, and natural killer cells in immune reconstitution disease.

RECENT FINDINGS

Many HIV patients receiving antiretroviral treatment develop immune reconstitution disease, which is characterized by exaggerated inflammatory immune responses to replicating or dead pathogens. In the majority of these cases, immune reconstitution disease is associated with restoration of pathogen-specific cellular immune responses involving CD4 or CD8 effector T cells. The precise conditions that trigger immune reconstitution disease have not yet been identified. Immune reconstitution disease patients have overt immune activation, which may be due to poor homeostatic control after the fast initial immune recovery in patients receiving antiretroviral therapy. Poor homeostatic control in immune reconstitution disease patients may be linked to unbalanced restoration of effector and regulatory T cells.

SUMMARY

Although the precise mechanism of immune reconstitution disease is not well understood, it is probably related to rapid restoration of pathogen-specific immune responses and poor homeostatic control that promote exaggerated immunopathological responses, especially if viable pathogens or pathogen debris are present at high concentrations.

Immune reconstitution disease associated with mycobacterial infections

PURPOSE OF REVIEW

We review immune reconstitution disease associated with mycobacterial infections in patients receiving antiretroviral treatment. We draw particular attention to data relevant to resource-limited settings and focus predominantly on publications over the past year.

RECENT FINDINGS

Worldwide mycobacteria are the most important group of pathogens associated with immune reconstitution disease. In cohorts of patients with tuberculosis in high-income countries, up to one-third develop immune reconstitution disease compared with only 8-13% in current reports from resource-limited settings. We speculate on potential explanations for this difference. While most cases of tuberculosis immune reconstitution disease are self-limiting, deaths have been reported in South African and Thai cohorts. We discuss how risk and outcomes of tuberculosis immune reconstitution disease represent key variables regarding the optimum time to initiate antiretroviral treatment in tuberculosis patients. A new conceptual framework has been proposed regarding 'unmasking' of tuberculosis during antiretroviral treatment. Increasing numbers of cases of leprosy immune reconstitution disease and Bacillus Calmette-Guérin immune reconstitution disease have also been reported, mainly from resource-limited settings. Immune reconstitution disease associated with a variety of mycobacteria (tuberculous and nontuberculous) was common in a cohort of Thai children.

SUMMARY

Immune reconstitution disease associated with a range of mycobacteria constitutes a challenge to delivery of antiretroviral treatment worldwide. Data concerning the pathogenesis and management of all forms of mycobacterial immune reconstitution disease are lacking.

Immune reconstitution disease: recent developments and implications for antiretroviral treatment in resource-limited settings

PURPOSE OF REVIEW

We review literature published over the past 2 years regarding the immunopathogenesis, epidemiology, clinical spectrum and outcomes of immune reconstitution disease in patients receiving antiretroviral treatment. Particular attention is drawn to data relevant to resource-limited settings.

RECENT FINDINGS

In high-income countries, immune reconstitution disease occurs in association with a largely predictable spectrum of pathogens, including the herpesviruses, Mycobacterium tuberculosis and Mycobacterium avium complex, Cryptococcus neoformans and hepatitis viruses. Dermatological manifestations are most frequent. In resource-limited settings, patients accessing antiretroviral treatment programmes typically have advanced immunodeficiency, which increases risk of immune reconstitution disease. M. tuberculosis and C. neoformans have emerged as the key causes of morbidity and mortality associated with immune reconstitution disease. An increasing number of 'tropical' infections, including leprosy, schistosomiasis, strongyloidiasis, leishmaniasis, histoplasmosis and many nontuberculous mycobacteria, are also now recognised to provoke immune reconstitution disease but the overall spectrum and relative importance of these organisms remain to be defined. Better characterisation of immune reconstitution disease in these settings is needed to enable development of guidelines regarding prevention, diagnosis and management.

SUMMARY

While immune reconstitution disease in high-income countries has been clinically and epidemiologically well described, much remains to be learned in resource-limited settings in which immune reconstitution disease is emerging as a significant cause of morbidity and mortality.

Modified fine-needle aspiration technique for diagnosis of granulomatous skin lesions with special reference to leprosy and cutaneous tuberculosis

Skin infections are commonly assessed by slit skin or scrape methods. Fine-needle aspiration biopsy (FNAB) is highly effective especially with blanching of skin to ensure good yield and reduced bleeding. The aim of this study was to assess usefulness of cytology, especially modified FNAB technique, in diagnosis of leprosy and cutaneous tuberculosis and to identify specific cytological characteristics for diagnosis and classification. The study was conducted on 40 patients-25 cases of leprosy and 15 cases of cutaneous tuberculosis. Smears were prepared using modified FNAB technique, slit skin, and scrape methods (depending on type of lesion). Cytological diagnosis was confirmed by histopathology where the Ridley-Jopling system was used to classify cases of leprosy. A similar attempt was made for diagnosis and classification of leprosy on cytology. Diagnoses rendered by both modalities were compared to assess the efficacy of cytological examination. Cytological diagnosis was made in 23 cases of leprosy and 12 cases of cutaneous tuberculosis. The smears showed good cellularity. A broad division into tuberculoid and lepromatous leprosy could be made fairly accurately on cytology. Maximum agreement among clinical, cytological, and histopathological diagnosis was observed in cases of tuberculoid leprosy. Smears of cutaneous tuberculosis were characterized by epithelioid cell granulomas with caseation. Overall accuracy of diagnosis was 92% in leprosy and 80% in tuberculosis. FNAB is an inexpensive and accurate procedure for diagnosis of leprosy and cutaneous tuberculosis. The modified technique yields good results. However, clinical correlation, acid-fast staining, and culture are essential as they provide valuable supportive information.

Increased incidence of leprosy following HAART initiation: a manifestation of the immune reconstitution disease

A retrospective cohort study was conducted to determine whether the incidence of leprosy varied with the duration of antiretroviral therapy (ART). Between 1992 and 2006, seven cases of leprosy were observed. The incidence of leprosy in untreated patients was 0.7 per 1000 person-years, 13 per 1000 person-years in persons receiving HAART for more than 3 months and 0.9 per 1000 person-years for persons receiving HAART for more than 3 months. The adjusted hazard ratio was 18.5 (95% confidence interval, 1.6-217) with P = 0.02. In tropical areas where HAART is increasingly available, physicians should be aware of the possibility of incident leprosy shortly after HAART initiation.

Clinical and epidemiological study of leprosy cases in the University Hospital of Brasília: 20 years -- 1985 to 2005

Hansen's disease, also known as leprosy, is an infectious disease still prevalent in Brazil. It is a chronic illness with acute immunological phenomena known as leprosy reactions. In the Federal District of Brazil, the University Hospital of Brasília is the reference centre for leprosy care. The study aimed to characterize the clinical and epidemiological profile of Hansen's disease patients at the University Hospital of Brasília, by descriptive, retrospective analysis of 1,124 patients over the period from 1985 to 2005. The pattern of leprosy in this study demonstrated that type 2 leprosy reactions were common, especially in the lepromatous form and presented a direct correlation with the bacilloscopic index. The prevalence and frequency of severe complications, such as leprosy reactions, emphasize the importance of the ongoing study of leprosy and the need for continual improvement in the scope of knowledge concerning its treatment.

[Bacterial, mycobacterial and fungal opportunistic infections in HIV-infected immigrants: diagnosis and treatment]

The number of HIV infected immigrants has increased sharply in Spain. These patients are prone to contracting several different types of opportunistic infections, including bacterial, mycobacterial, fungal and parasitic infections. The present article provides an in-depth review of bacterial and fungal infections, with particular emphasis on those not endemic in our country.

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.

Immune cellular parameters of leprosy and human immunodeficiency virus-1 co-infected subjects

Leprosy and human immunodeficiency virus-1 (HIV-1) are examples of human infections where interactions between the pathogen and the host cellular immunity determine the clinical manifestations of disease. Hence, a significant immunopathological interaction between HIV-1 and leprosy might be expected. In the present study we explored several aspects of cellular immunity in patients co-infected with HIV-1 and Mycobacterium leprae. Twenty-eight individuals were studied, comprising four groups: healthy controls, HIV-1 and M. leprae co-infection, HIV-1 mono-infection, and M. leprae mono-infection. Subjects in the mono-infection and co-infection groups were matched as far as possible for bacillary load and HIV disease status, as appropriate. Peripheral blood mononuclear cells (PBMC) were analysed using six- and seven-colour flow cytometry to evaluate T-cell subpopulations and their activation status, dendritic cell (DC) distribution phenotypes and expression of IL-4 by T cells. The co-infected group exhibited lower CD4 : CD8 ratios, higher levels of CD8(+) T-cell activation, increased V delta : V delta 2 T cell ratios and decreased percentages of plasmacytoid DC, compared with HIV-1 mono-infected subjects. Across infected groups, IL-4 production by CD4(+) T lymphocytes was positively correlated with the percentage of effector memory CD4(+) T cells, suggesting antigenically driven differentiation of this population of T cells in both HIV-1 and M. leprae infections. Co-infection with M. leprae may exacerbate the immunopathology of HIV-1 disease. A T helper 2 (Th2) bias in the CD4(+) T-cell response was evident in both HIV-1 infection and leprosy, but no additive effect was apparent in co-infected patients.

HIV-M. leprae interaction: can HAART modify the course of leprosy?

It has been speculated that, as seen in tuberculosis, human immunodeficiency virus (HIV) and Mycobacterium leprae (M. leprae) co-infection may exacerbate the pathogenesis of leprosy lesions and/or lead to increased susceptibility to leprosy. However, to date, HIV infection has not appeared to increase susceptibility to leprosy. In contrast, initiation of antiretroviral treatment (ART) has been reported to be associated with anecdotal activation of M. leprae infection and exacerbation of existing leprosy lesions. To determine whether ART is associated with worsening of the manifestations of leprosy, a cohort of leprosy patients recruited between 1996 and 2006 at the Oswaldo Cruz Foundation (FIOCRUZ) Leprosy Outpatient Clinic in Rio de Janeiro, Brazil, was studied longitudinally. ART treatment of HIV/leprosy co-infection was associated with the tuberculoid type, paucibacillary disease, and lower bacillary loads. CD4 lymphocyte counts were higher among HIV/leprosy patients at the time of leprosy diagnosis, while viral loads were lower compared with the time of HIV diagnosis. The conclusion was that ART and immune reconstitution were critical factors driving the development and/or clinical appearance of leprosy lesions.

Immune reconstitution inflammatory syndrome in HIV-infected patients receiving antiretroviral therapy : pathogenesis, clinical manifestations and management

The use of antiretroviral therapy (ART) to treat HIV infection, by restoring CD4+ cell count and immune function, is associated with significant reductions in morbidity and mortality. Soon after ART initiation, there is a rapid phase of restoration of pathogen-specific immunity. In certain patients, this results in inflammatory responses that may result in clinical deterioration known as 'the immune reconstitution inflammatory syndrome' (IRIS). IRIS may be targeted at viable infective antigens, dead or dying infective antigens, host antigens, tumour antigens and other antigens, giving rise to a heterogeneous range of clinical manifestations. The commonest forms of IRIS are associated with mycobacterial infections, fungi and herpes viruses. In most patients, ART should be continued and treatment for the associated condition optimized, and there is anecdotal evidence for the use of corticosteroids in patients who are severely affected. In this review, we discuss research relating to pathogenesis, the range of clinical manifestations, treatment options and prevention issues.

[Immune reconstitution inflammatory syndrome (IRIS)]

Overwhelming immune reaction resulting in granulomatous inflammation after infection with opportunistic pathogens has been termed immune reconstitution inflammatory syndrome (IRIS). IRIS has mainly been described in patients with human immunodeficiency virus (HIV). However, IRIS is not restricted to HIV-patients and may occur in other infections and immunodeficiencies. In our clinic, we experienced a Whipple's disease patient with IRIS. IRIS occurs mainly after initiation of the highly active anti-retroviral therapy (HAART). Soon after HAART initiation, a marked inflammatory reaction can occur, triggered by restoration of pathogen-specific immunity. IRIS may be targeted by various infective antigens, dead or dying infective antigens, host antigens, tumor antigens and other antigens, giving rise to a heterogenous range of clinical manifestations. Treatment should be optimized for the associated condition and initiated immediately. Glucocorticoids should be used in patients who are severely affected by IRIS.

Towards understanding the pathology of erythema nodosum leprosum

Erythema nodosum leprosum (ENL) is an immune-mediated complication of leprosy presenting with inflammatory skin nodules and involvement of multiple organ systems, often running a protracted course. Immune complex production and deposition as well as complement activation have long been regarded as the principal aetiology of ENL. However, new data show that cell-mediated immunity is also important. We have performed a critical analysis of studies on the pathology of ENL. Our main findings are as follows. ENL is characterised by an inflammatory infiltrate of neutrophils with vasculitis and/or panniculitis. There is deposition of immune complexes and complement together with Mycobacterium leprae antigens in the skin. Changes in serum levels of Igs indicate a transient, localised immune response. The major T-cell subtype in ENL is the CD4 cell, in contrast to lepromatous leprosy where CD8 cells predominate. The cytokines TNFalpha and IL-6 are consistently found whilst IL-4 is low or absent in ENL lesions, indicating a T(H)1 type response. Keratinocyte 1a and intercellular adhesion molecule-1 (ICAM-1) have been shown to be present in the epidermis in ENL, which is evidence of a cell-mediated immune response. Co-stimulatory molecules such as B7-1 have also been studied but further work is needed to draw strong conclusions. We also highlight potential areas for future research.

Leprosy type 1 reactions and erythema nodosum leprosum

Leprosy reactions are a major cause of nerve damage and morbidity in a significant proportion of leprosy patients. Reactions are immunologically mediated and can occur even after successful completion of multi-drug therapy. This review focuses on the epidemiology, pathology and treatment of leprosy type 1 reactions, erythema nodosum leprosum and silent neuropathy.

Reação reversa atípica em paciente com hanseníase dimorfa co-infectado pelo HIV

A infecção pelo HIV não altera a história natural da hanseníase. Observa-se maior incidência de estados reacionais nos pacientes co-infectados, além de casos mais graves de neurite. Paciente soropositiva com hanseníase dimorfa tuberculóide manifestou reação reversa exuberante. Lesões cutâneas atípicas e raras surgiram após a introdução da terapia anti-retroviral que promoveu o início da recuperação imunológica com aumento de linfócitos T CD4+ e queda da carga viral. A restauração da imunidade celular nos pacientes soropositivos pode precipitar reações reversas, descritas recentemente como uma das manifestações da síndrome inflamatória de reconstituição imunológica associada à hanseníase.

Leprosy

Leprosy is a granulomatous disease affecting the skin and nerves caused by Mycobacterium leprae. It continues to be a significant public health problem. Despite multidrug therapy, immunologic reactions continue to occur, leading to disability and deformity due to neuropathy. It is important that dermatologists are aware of the neurologic as well as the skin manifestations of the condition so that nerve involvement can be identified and treated rapidly.

Two patients coinfected with Mycobacterium leprae and human immunodeficiency virus type 1 and naive for antiretroviral therapy who exhibited type 1 leprosy reactions mimicking the immune reconstitution inflammatory syndrome

Two case reports of patients with human immunodeficiency virus type 1 (HIV-1) infection who developed leprosy are presented. Both developed type 1 leprosy reactions in the absence of antiretroviral therapy. Reactions have been described for a number of HIV-1- and Mycobacterium leprae-coinfected patients and have been considered to be part of an immune reconstitution inflammatory syndrome (IRIS) since the reactions were usually linked to the administration of highly active antiretroviral therapy. The reports of our two patients suggest that the type 1 reactions in patients with leprosy and HIV may not always be an IRIS manifestation but may be akin to the classical reactional state described for the natural course of leprosy infection, which occurs in leprosy patients due to the fluctuations of the antimycobacterial immune response, whether they are coinfected with HIV or not.