Parasite Genotype Is a Major Predictor of Mortality from Visceral Leishmaniasis

Isolation and characterisation of Leishmania (Leishmania) infantum from cutaneous leishmaniasis patients in northeast Brazil

BACKGROUND

In Brazil, Leishmania (Leishmania) infantum is a widely distributed protozoan parasite. The human leishmaniasis caused by this species is often associated with visceral form. Tegumentary leishmaniasis (TL) cases due to L. (L.) infantum in the country are considered rare but may be underestimated. Although probably uncommon, these cases represent a new challenge to the prevention and control of leishmaniasis.

OBJECTIVES

Here, we describe two distinct cases of TL with atypical clinical presentations caused by L. (L.) infantum.

METHODS AND FINDINGS

Parasites were isolated from cutaneous lesions of the two patients and typed as L. (L.) infantum after sequencing of the ribosomal DNA internal transcribed spacer. The dermotropic L. (L.) infantum isolates were compared in terms of growth culture patterns, metacyclogenesis and in vitro infectivity in macrophages.

MAIN CONCLUSIONS

This study addresses the emergence of L. (L.) infantum as a causative agent of cutaneous disease in a visceral leishmaniasis hotspot located in northeast Brazil. The data presented provides novel information about the presence of dermotropic L. (L.) infantum in the country and demonstrates the infectivity potential of theses isolates.

Prognostic prediction models for clinical outcomes in patients diagnosed with visceral leishmaniasis: protocol for a systematic review

INTRODUCTION

Visceral leishmaniasis (VL) is a neglected tropical disease responsible for many thousands of preventable deaths each year. Symptomatic patients often struggle to access effective treatment, without which death is the norm. Risk prediction tools support clinical teams and policymakers in identifying high-risk patients who could benefit from more intensive management pathways. Investigators interested in using their clinical data for prognostic research should first identify currently available models that are candidates for validation and possible updating. Addressing these needs, we aim to identify, summarise and appraise the available models predicting clinical outcomes in VL patients.

METHODS AND ANALYSIS

We will include studies that have developed, validated or updated prognostic models predicting future clinical outcomes in patients diagnosed with VL. Systematic reviews and meta-analyses that include eligible studies are also considered for review. Conference abstracts and educational theses are excluded. Data extraction, appraisal and reporting will follow current methodological guidelines. Ovid Embase; Ovid MEDLINE; the Web of Science Core Collection, SciELO and LILACS are searched from database inception to 1 March 2023 using terms developed for the identification of prediction models, and with no language restriction. Screening, data extraction and risk of bias assessment will be performed in duplicate with discordance resolved by a third independent reviewer. Risk of bias will be assessed using the Prediction model Risk Of Bias ASsessment Tool (PROBAST). Tables and figures will compare and contrast key model information, including source data, participants, model development and performance measures, and risk of bias. We will consider the strengths, limitations and clinical applicability of the identified models.

ETHICS AND DISSEMINATION

Ethics approval is not required for this review. The systematic review and all accompanying data will be submitted to an open-access journal. Findings will also be disseminated through the research group's website (www.iddo.org/research-themes/visceral-leishmaniasis) and social media channels.

PROSPERO REGISTRATION NUMBER

CRD42023417226.

From Infection to Death: An Overview of the Pathogenesis of Visceral Leishmaniasis

Kala-azar, also known as visceral leishmaniasis (VL), is a disease caused by Leishmania infantum and L. donovani. Patients experience symptoms such as fever, weight loss, paleness, and enlarged liver and spleen. The disease also affects immunosuppressed individuals and has an overall mortality rate of up to 10%. This overview explores the literature on the pathogenesis of preclinical and clinical stages, including studies in vitro and in animal models, as well as complications and death. Asymptomatic infection can result in long-lasting immunity. VL develops in a minority of infected individuals when parasites overcome host defenses and multiply in tissues such as the spleen, liver, and bone marrow. Hepatosplenomegaly occurs due to hyperplasia, resulting from parasite proliferation. A systemic inflammation mediated by cytokines develops, triggering acute phase reactants from the liver. These cytokines can reach the brain, causing fever, cachexia and vomiting. Similar to sepsis, disseminated intravascular coagulation (DIC) occurs due to tissue factor overexpression. Anemia, hypergammaglobulinemia, and edema result from the acute phase response. A regulatory response and lymphocyte depletion increase the risk of bacterial superinfections, which, combined with DIC, are thought to cause death. Our understanding of VL's pathogenesis is limited, and further research is needed to elucidate the preclinical events and clinical manifestations in humans.

Role of Treg, Breg and other cytokine sets in host protection and immunopathology during human leishmaniasis: Are they potential valuable markers in clinical settings and vaccine evaluation?

Leishmaniasis is a vector-borne disease caused by obligate intracellular protozoan parasites that can infect humans and other mammals. Pro- and anti-inflammatory cytokines are important regulators of innate and specific responses in Leishmania infection. Resistance to leishmaniasis is related to T helper 1 (Th1) response with the production of pro-inflammatory cytokines: IL-12, IL-1β, IFN-γ, TNF-α, IL-2 leading to activation of macrophages and parasite killing. Instead, a more intense Th2 (IL-4, IL-5, IL-13), Treg (IL-10 and TGF-β) and Breg response (IL-10 and IL-35) are related to parasite persistence through the inhibition of macrophage activation, which promotes the escape from host immune system. Interestingly, a cytokine involved in the parasite killing in one form of leishmaniasis may be "pathogen friendly" in another form of the disease. To date, few studies are focusing on the role of Treg and Breg cytokines in human models of leishmaniasis; therefore, further investigations are needed to clarify their potential role in the diagnosis and prognosis of such protozoan infections, as well as in the development of vaccines against leishmaniasis. This review summarizes the current knowledge about the role of cytokines produced by Th1, Th2, Treg, and Breg cells involved in Leishmania disease progression and host protection. Some cytokines might play a role as diagnostic and prognostic clinical markers, or they could represent a novel approach leading to new anti-leishmaniasis therapies. Overall, advances in knowledge of the complex network of cytokines secreted by immune cells could help to better understand signaling pathways and host immune responses during Leishmania infection. This approach would allow these mediators to be used as therapeutic strategies against leishmaniasis.