Immunophenotyping of circulating T cells in a mucosal leishmaniasis patient coinfected with HIV

Complementary exams in the diagnosis of American tegumentary leishmaniasis

The diagnosis of American Tegumentary Leishmaniasis is a difficult but essential task when considering the high toxicity profile of the drugs available. Since the discovery of its etiologic agent, numerous diagnostic tests have been developed. None of the tests available today can be considered as the gold standard, since they do not add enough accuracy for the disease detection. Good epidemiological and clinical knowledge of the disease are fundamental precepts of the dermatology practice and precede the rational use of existing diagnostic tests. In this article we aim, through extensive literature review, to recall fundamental concepts of any diagnostic test. Subsequently, based on this information, we will weave important comments about the characteristics of existing diagnostic tests, including immunological tests such as Montenegro's skin test, serology and detection of parasites by direct examination, culture or histopathology. Finally we will discuss the new technologies and options for the diagnosis of Cutaneous Leishmaniasis. The molecular biology technique is considered a promising tool, promoting the rapid identification of the species involved. We also aim to educate dermatologists about a disease with high morbidity and assist in its difficult recognition.

PKDL and other dermal lesions in HIV co-infected patients with Leishmaniasis: review of clinical presentation in relation to immune responses

Background

Co-infection of leishmaniasis and HIV is increasingly reported. The clinical presentation of leishmaniasis is determined by the host immune response to the parasite; as a consequence, this presentation will be influenced by HIV-induced immunosuppression. As leishmaniasis commonly affects the skin, increasing immunosuppression changes the clinical presentation, such as in post-kala-azar dermal leishmaniasis (PKDL) and cutaneous leishmaniasis (CL); dermal lesions are also commonly reported in visceral leishmaniasis (VL) and HIV co-infection.

Methods

We reviewed the literature with regard to dermal manifestations in leishmaniasis and HIV co-infection, in three clinical syndromes, according to the primary presentation: PKDL, VL, or CL.

Results

A wide variety of descriptions of dermal leishmaniasis in HIV co-infection has been reported. Lesions are commonly described as florid, symmetrical, non-ulcerating, nodular lesions with atypical distribution and numerous parasites. Pre-existing, unrelated dermal lesions may become parasitized. Parasites lose their tropism and no longer exclusively cause VL or CL. PKDL in HIV co-infected patients is more common and more severe and is not restricted to Leishmania donovani. In VL, dermal lesions occur in up to 18% of patients and may present as (severe) localized cutaneous leishmaniasis, disseminated cutaneous leishmaniasis (DL) or diffuse cutaneous leishmaniasis (DCL); there may be an overlap with para-kala-azar dermal leishmaniasis. In CL, dissemination in the skin may occur resembling DL or DCL; subsequent spread to the viscera may follow. Mucosal lesions are commonly found in VL or CL and HIV co-infection. Classical mucocutaneous leishmaniasis is more severe. Immune reconstitution disease (IRD) is uncommon in HIV co-infected patients with leishmaniasis on antiretroviral treatment (ART).

Conclusion

With increasing immunosuppression, the clinical syndromes of CL, VL, and PKDL become more severe and may overlap. These syndromes may be best described as VL with disseminated cutaneous lesions (before, during, or after VL) and disseminated cutaneous leishmaniasis with or without visceralization.

Deception and manipulation: the arms of leishmania, a successful parasite

Leishmania spp. are intracellular parasitic protozoa responsible for a group of neglected tropical diseases, endemic in 98 countries around the world, called leishmaniasis. These parasites have a complex digenetic life cycle requiring a susceptible vertebrate host and a permissive insect vector, which allow their transmission. The clinical manifestations associated with leishmaniasis depend on complex interactions between the parasite and the host immune system. Consequently, leishmaniasis can be manifested as a self-healing cutaneous affliction or a visceral pathology, being the last one fatal in 85–90% of untreated cases. As a result of a long host–parasite co-evolutionary process, Leishmania spp. developed different immunomodulatory strategies that are essential for the establishment of infection. Only through deception and manipulation of the immune system, Leishmania spp. can complete its life cycle and survive. The understanding of the mechanisms associated with immune evasion and disease progression is essential for the development of novel therapies and vaccine approaches. Here, we revise how the parasite manipulates cell death and immune responses to survive and thrive in the shadow of the immune system.

Recent progress in host immunity to avian coccidiosis: IL-17 family cytokines as sentinels of the intestinal mucosa

The molecular and cellular mechanisms leading to immune protection against coccidiosis are complex and include multiple aspects of innate and adaptive immunities. Innate immunity is mediated by various subpopulations of immune cells that recognize pathogen associated molecular patterns (PAMPs) through their pattern recognition receptors (PRRs) leading to the secretion of soluble factors with diverse functions. Adaptive immunity, which is important in conferring protection against subsequent reinfections, involves subtypes of T and B lymphocytes that mediate antigen-specific immune responses. Recently, global gene expression microarray analysis has been used in an attempt to dissect this complex network of immune cells and molecules during avian coccidiosis. These new studies emphasized the uniqueness of the innate immune response to Eimeria infection, and directly led to the discovery of previously uncharacterized host genes and proteins whose expression levels were modulated following parasite infection. Among these is the IL-17 family of cytokines. This review highlights recent progress in IL-17 research in the context of host immunity to avian coccidiosis.

Immunopathogenesis of non-healing American cutaneous leishmaniasis and progressive visceral leishmaniasis

The outcomes of Leishmania infection are determined by host immune and nutrition status, parasite species, and co-infection with other pathogens. While subclinical infection and self-healing cutaneous leishmaniasis (CL) are common, uncontrolled parasite replication can lead to non-healing local lesions or visceral leishmaniasis (VL). It is known that infection control requires Th1-differentiation cytokines (IL-12, IL-18, and IL-27) and Th1 cell and macrophage activation. However, there is no generalized consensus for the mechanisms of host susceptibility. The recent studies on regulatory T cells and IL-17-producing cells help explain the effector T cell responses that occur independently of the known Th1/Th2 cell signaling pathways. This review focuses on the immunopathogenesis of non-healing American CL and progressive VL. We summarize recent evidence from human and animal studies that reveals the mechanisms of dysregulated, hyper-responses to Leishmania braziliensis, as well as the presence of disease-promoting or the absence of protective responses to Leishmania amazonensis and Leishmania donovani. We highlight immune-mediated parasite growth and immunopathogenesis, with an emphasis on the putative roles of IL-17 and its related cytokines as well as arginase. A better understanding of the quality and regulation of innate immunity and T cell responses triggered by Leishmania will aid in the rational control of pathology and the infection.