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The discovery points the way to a search for novel treatments for the disease as well as casting light on a key mechanism involved in other diseases.

The mechanism involves Leishmania, macrophages and a virus that lives endosymbiotically in the parasite and is known as the Leishmania RNA virus (LRV). According to a study published in the journal iScience, the parasite inhibits activation of caspase-11 via LRV-induced autophagy.

Caspases are a family of enzymes that play essential roles in programmed cell death and the innate immune system. LRV, therefore, prevents defense cells from blocking progression of the disease.

Infectious and not contagious, leishmaniasis is considered endemic to some regions of Brazil. The mucocutaneous form of the disease, caused in the Neotropics by species such as L. guyanensis and L. braziliensis, is characterized by skin lesions that affect the mucous membranes of the nose, mouth and throat. In severe cases, it can lead to cartilage and bone erosion and cause deformations. Some 20,000 cases of tegumental leishmaniasis, which includes the cutaneous and mucocutaneous forms, are reported each year in Brazil.

The study showing how LRV blocks caspase-11 via autophagy was part of the Ph.D. research of Renan V. H. de Carvalho, with Dario Zamboni as thesis advisor. Zamboni is a professor in the Department of Cellular and Molecular Biology and Pathogenic Bioagents at the University of São Paulo's Ribeirão Preto Medical School (FMRP-USP) in Brazil.

Using macrophages and mice, we discovered that LRV inhibits activation of caspase-11 by Leishmania, and this extends our understanding of the mechanisms used by the virus to exacerbate the disease." Dario Zamboni, Professor in Department of Cellular and Molecular Biology and Pathogenic Bioagents University of São Paulo's Ribeirão Preto Medical School

The study, which belongs to a series already published by the group,…

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