Comparative analysis of biological aspects of Leishmania infantum strains

Abstract

Leishmania infantum infantum (LII) is one of the species that causes visceral leishmaniasis (VL) in the Old World, while L. infantum chagasi (LIC) is present in the New World. Few studies address biological differences or the behavior of these strains during infection. These parasites live inside cells of their hosts, continuously evading microbicidal mechanisms and modulating the immune responses of these cells. One of the mechanisms used by these protozoa involves the L-arginine metabolism. Understanding the differences between Leishmania species and establishing an improved murine model for study of leishmaniasis are matters of extreme importance. Thereby, the objectives of this work were to analyze the biological and molecular differences between two Leishmania infantum strains (LII and LIC) and the degree of susceptibility to infection of mice with different genetic backgrounds. The infectivity in vivo and in vitro of LII and LIC strains was evaluated in BALB/c and Swiss Webster mice, as well the NOS and ARG activities. The LII strain was more infective than the LIC strain both in vivo and in vitro. In animals infected by the LII and LIC strains, differences in NOS and ARG activities occurred. In vitro, promastigotes of LII isolated from BALB/c and Swiss Webster mice showed higher ARG activity than LIC promastigotes during the growth curve. However, no difference was observed in intracellular NO production by promastigotes of these strains. The ARG gene sequences were compared, and those of both strains were identical. However, despite the similarity, the strains showed different expression levels of this gene. It can be concluded that although L. chagasi strains are considered identical to L. infantum strains from a molecular point of view, these strains have different biological behavior.

Pathophysiology of Leishmaniasis

“…To classified as the reservoir species, two conditions be met: firstly, it must host a significant number of parasites that can be efficiently transmitted during feeding, and secondly, the infection in these species must be relatively harmless or show no symptoms, in order to ensure survival of reservoir. Among mammals, blood and the skin and provide favorable circumstances for the parasite to multiply [41].…”

“…After bite by the sand fly, promastigotes, are outside cells, are take in by host's macrophages. Inside macrophages, it changing into the amastigotes [41].…”

Pleiotropic Effect of Hormone Insulin-Like Growth Factor-I in Immune Response and Pathogenesis in Leishmaniases

“…Further, in L. infantum- infected BALB/c and Swiss Webster mice, in the presence of spleen and liver cells producing high NO levels but with low arginase activity, the parasites continue multiplying within the host cells [ 86 ]. In vitro, L. infantum survives in the presence of high amounts of NO added in the culture medium [ 87 ].…”

Avaliação da evolução da infecção experimental in vitro e in vivo em hamster, Mesocricetus auratus, causada por Leishmania (L.) infantum chagasi isoladas de pacientes com leishmaniose visceral humana e leishmaniose cutânea atípica no município de Amapala

“…Após infecção, os mecanismos de ativação do macrófago são marcados por uma cascata de reações que culminam com a produção de intermediários reativos de oxigênio, de óxido nítrico e produção de citocinas relacionadas ao mecanismo de ativação da resposta imune (BALESTIERI et al, 2002;LIEW et al, 1990). Tem sido relatada uma associação entre maior índice de infecção e menor produção de óxido nítrico por macrófagos infectados com diferentes cepas de Leishmania (CAMPOS et al, 2008;FERREIRA-PAES et al, 2020). Porém, em nosso estudo não observamos associação na produção de NO e o índice de infecção em macrófagos peritoneais de hamster infectados com as diferentes cepas isoladas de casos de LCNU e LV.…”