Diana N. J. Lockwood

Comparative genomic and phylogeographic analysis of Mycobacterium leprae.

Reductive evolution and massive pseudogene formation have shaped the 3.31-Mb genome of Mycobacterium leprae, an unculturable obligate pathogen that causes leprosy in humans. The complete genome sequence of M. leprae strain Br4923 from Brazil was obtained by conventional methods (6× coverage), and Illumina resequencing technology was used to obtain the sequences of strains Thai53 (38× coverage) and NHDP63 (46× coverage) from Thailand and the United States, respectively. Whole-genome comparisons with the previously sequenced TN strain from India revealed that the four strains share 99.995% sequence identity and differ only in 215 polymorphic sites, mainly SNPs, and by 5 pseudogenes. Sixteen interrelated SNP subtypes were defined by genotyping both extant and extinct strains of M. leprae from around the world. The 16 SNP subtypes showed a strong geographical association that reflects the migration patterns of early humans and trade routes, with the Silk Road linking Europe to China having contributed to the spread of leprosy.

Leprosy now: epidemiology, progress, challenges, and research gaps

Leprosy continues to be a challenge to health worldwide, with about 250,000 new cases being detected every year. Despite widespread implementation of effective multidrug therapy, leprosy has not been eliminated. A third of newly diagnosed patients have nerve damage and might develop disabilities, although the proportion varies according to several factors, including level of self-care. Women who develop leprosy continue to be especially disadvantaged, with rates of late diagnosis and disability remaining high in this subgroup. Leprosy was not a specified disease in the Millennium Development Goals, but improvements in the other areas they cover, such as education and levels of poverty, will help leprosy patients and services. We review data and make recommendations for research on diagnosis, treatment, and prevention, such as further use of molecular analysis of the Mycobacterium leprae genome, implementation of BCG vaccination, and administration of chemoprophylaxis to household contacts. We also suggest development of tools for early diagnosis and detection of infection and nerve damage, and formulation of strategies to manage the chronic complications of leprosy, such as immune-mediated reactions and neuropathy.

Leprosy: too complex a disease for a simple elimination paradigm

Can leprosy be eliminated? This paper considers the question against the background of the WHO programme to eliminate leprosy. In 1991 the World Health Assembly set a target of eliminating leprosy as a public health problem by 2000. Elimination was defined as reaching a prevalence of < 1 case per 10 000 people. The elimination programme has been successful in delivering highly effective antibiotic therapy worldwide. However, despite this advance, new-case detection rates remain stable in countries with the highest rates of endemic leprosy, such as Brazil and India. This suggests that infection has not been adequately controlled by antibiotics alone. Leprosy is perhaps more appropriately classed as a chronic stable disease than as an acute infectious disease responsive to elimination strategies. In many countries activities to control and treat leprosy are being integrated into the general health-care system. This reduces the stigma associated with leprosy. However, leprosy causes long-term immunological complications, disability and deformity. The health-care activities of treating and preventing disabilities need to be provided in an integrated setting. Detecting new cases and monitoring disability caused by leprosy will be a challenge. One solution is to implement long-term surveillance in selected countries with the highest rates of endemic disease so that an accurate estimate of the burden of leprosy can be determined. It is also critical that broad-based research into this challenging disease continues until the problems are truly solved.

Treatment of visceral leishmaniasis

The available treatment options for visceral leishmaniasis (VL) have problems relating to efficacy, adverse effects and cost, making treatment a complex issue. We review the evidence relating to the different methods of treatment in relation to - efficacy and toxicity of the drugs in different areas of the world; ability to monitor side effects, length of treatment; ability of patients to pay for and stay safe during treatment, ability of the healthcare services to give intramuscular, intravenous or oral therapy; the sex and child-bearing potential of the patient and the immune status of the patient. The high mortality of untreated/ poorly treated VL infection makes the decisions paramount, but a unified and coordinated response by each area is likely to be more effective and informative to future policies than an ad hoc response. For patients in resource-rich countries, liposomal amphotericin B appears to be the optimal treatment. In South Asia, miltefosine is being used; the combination of single dose liposomal amphotericin B and short course miltefosine looks encouraging but has the problem of potential reproductive toxicities in females. In Africa, the evidence to switch from SSG is not yet compelling. The need to monitor and plan for evolving drug failure, secondary to leishmania parasite resistance, is paramount. With a few drugs the options may be limited; however, we await key ongoing trials in both Africa and India to explore the effects of combination treatment. If safe and reliable combinations are revealed by the ongoing studies, it is far from clear as to whether this will avoid leishmania parasite resistance. The development of new drugs to add to the armamentarium is paramount. Lessons can be learnt from the management of diseases such as tuberculosis and malaria in terms of planning the switch to combination treatment. As important as establishing the best choice for specific antileishmanial agent is ensuring treatment centers, which can best manage the problems encountered during treatment, specifically malnutrition, bleeding, intercurrent infections, drug side effects and detecting and treating underlying immunosuppression.

Interactions between HIV infection and leprosy: a paradox

Early in the HIV epidemic it was feared that the disease would undermine leprosy control, as has occurred with tuberculosis. It was predicted that patients with leprosy and HIV coinfection would have an increased risk of lepromatous disease and a faster clinical evolution, and that the leprosy would be more difficult to treat. None of these concerns have materialised and the interaction between HIV and Mycobacterium leprae seems to be far more subtle than that between HIV and tuberculosis. We review the epidemiological, clinical, and pathological data relating to leprosy/HIV coinfection. The published epidemiological data are limited in quality but show neither an increased HIV prevalence among leprosy cases nor an alteration in clinical spectrum of leprosy among coinfected patients. Some data suggest that immune-mediated reactions that complicate leprosy occur at a higher frequency in coinfected patients. Leprosy has now been reported presenting as immune reconstitution disease among patients commencing highly active antiretroviral treatment. Histopathological observations reveal a normal spectrum of appearances in biopsies of leprosy lesions from coinfected patients, even among those with advanced immunodeficiency. These observations suggest that cell-mediated immune responses to M leprae are preserved at the site of disease despite evidence that these responses are abrogated systemically, by contrast with tuberculosis, in which the host granulomatous response is impaired by HIV coinfection. We speculate that this paradox may relate to differences between the activation state and rates of cell turnover within leprosy and tuberculosis granulomas that differentially affect the susceptibility of the granulomas to HIV. The interactions between leprosy and HIV have been little studied and further research on the clinical, pathological, and management aspects of this coinfection is warranted.

Tumour necrosis factor‐alpha (TNF‐α) synthesis is associated with the skin and peripheral nerve pathology of leprosy reversal reactions

Leprosy may be complicated by episodes of increased cell‐mediated immunity towards Mycobacterium leprae (reversal reactions) which result in severe local immunopathology in skin lesions and peripheral nerves. Using in situ hybridization and MoAb techniques we have demonstrated TNF‐α mRNA and TNF‐α protein in macrophages infiltrating leprosy skin and peripheral nerve. Levels of TNF‐α mRNA are significantly increased in reactional skin and nerve, particularly in borderline tuberculoid patients. TNF‐α mRNA and TNF‐α protein levels are higher in reactional nerves then reactional skin. In both reactional skin and nerve TNF‐α mRNA is more abundant than TNF‐α protein; this may reflect the rapid turnover of TNF‐α protein in an immunologically dynamic situation, such as is seen in reversal reaction. Our findings emphasize the importance of documenting both mRNA and protein production when assessing the role of cytokines in pathology. The leprosy reversal reaction may be regarded as a useful model of tissue immunopathology in which TNF‐α is generated as part of the host response to infection, but also produces local tissue damage.

Leprosy elimination-a virtual phenomenon or a reality?

Why are evidence based policies not guiding the World Health Organizations leprosy elimination campaign, asks Diana Lockwood Leprosy is an infectious disease but it has many features in common with neurodegenerative disorders. It results in a chronic neurological illness, which is progressive unless treated; frequently produces long term disability; and is associated with high levels of stigma. As it has a known infective agent, Mycobacterium leprae , there is the possibility of disease control. Multidrug treatment with the antibiotic combination rifampicin, dapsone, and clofazimine is highly effective in curing infection, with relapse rates of 1%.1 It was hoped that having effective antibiotics would permit disease control and thus the concept of leprosy elimination developed. “Leprosy elimination by the year 2000” was first proposed in 1986 and at the 44th World Health Assembly in 1991 modified by the addendum “as a public health problem,” defined as less than one case per 10 000 population.2 The leprosy elimination campaign has had some notable successes but also illustrates the epidemiological, medical, and political problems of the elimination concept. #### Summary points Leprosy is a leading cause of neurological disability The World Health Organizations leprosy elimination campaign has treated 11 million patients, but case numbers are still rising in the major countries where leprosy is endemic New methods for diagnosis and treatment proposed by the WHO risk missing disease and undertreating patients, and an opportunity for implementing evidence based policies may be missed Leprosy is a complex mycobacterial disease whose manifestations and complications are determined by the immune response. Many patients experience immune mediated nerve damage, which may occur before, during, or after treatment. Recent field based cohort studies have shown that at diagnosis many patients already have established nerve damage; rates vary from 20% in Bangladesh to 56% in Ethiopia, 3 4 and these …

Borderline Tuberculoid Leprosy: An Immune Reconstitution Phenomenon in a Human Immunodeficiency Virus–Infected Person

Two months after starting highly active antiretroviral treatment (HAART), an individual with human immunodeficiency virus type 1 (HIV-1) infection and profound CD4+ T lymphocytopenia developed several erythematous plaques on his face, which were due to borderline tuberculoid leprosy with reversal reaction. The temporal association between the development of these lesions and changes in blood CD4+ lymphocyte count and plasma HIV-1 load observed during HAART strongly suggests that the presentation of leprosy resulted from immune reconstitution.

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.

Immunohistochemical Analysis of Cellular Infiltrate and Gamma Interferon, Interleukin-12, and Inducible Nitric Oxide Synthase Expression in Leprosy Type 1 (Reversal) Reactions before and during Prednisolone Treatment

ABSTRACT The effects of prednisolone treatment on the cellularity and cytokine (gamma interferon, interleukin-12, and inducible nitric oxide synthase) profiles of leprosy skin type 1 (reversal) reactions were studied using immunohistochemistry. Skin biopsies were taken from 15 patients with leprosy type 1 (reversal) reactions at days 0, 7, 28, and 180 after the start of steroid treatment. Prednisolone treatment had little effect at day 7, but by day 28 significant decreases were found in cytokine levels. Some patients maintained cytokine production at days 28 and 180. These results illustrate the strong Th1 profile of type 1 reactional lesions, the slow response to steroid therapy, and continuing activity at 180 days.