Mecanismos de modulação da resposta imune de larvas de Toxocara canis em camundongos experimentalmente infectados

Abstract

Toxocariasis is considered one of the most prevalent helminth infections in the world, characterized by the migration and permanence of Toxocara canis larvae in different tissues of accidental hosts. Larvae release excretory-secretory substances (TES), which interact and modulate host immunity. The aim of this study was to evaluate the immune modulation in different tissues (splenocytes and mesenteric lymphoid nodes), mediated by infection with T. canis in the experimental mouse model (Balb/c). Through the indirect ELISA test, the profile and levels of immunoglobulins produced after infection with 100 T. canis L3 larvae were evaluated. Using qPCR, transcription levels of cytokines IL4, IL10, IL12 and YM1 protein (chitinase-like protein-3) were evaluated in splenocytes and mesenteric lymphoid nodules at 24 h, 48 h, 15 and 30 days after infection with T. canis. Infection with T. canis larvae generated a significant (p<0.05) level of total specific IgG at 15 days and 30 days post-infection (p.i). We observed significant levels (p<0.05) of IgG1, IgG2a, IgG2b and IgG3 with the same tendency of the observed response of total IgG. When evaluating the relative transcription of the genes, different levels of transcription were observed in relation to the tissue and the evaluated period. In splenocytes, the cytokine IL-4 and the YM1 gene showed higher levels of transcripts during the chronic phase, while the cytokine IL-10 showed higher levels during the acute phase of the infection. Cytokine IL-12 was present at basal levels both in the acute phase and in the chronic phase in splenocytes. In the mesenteric lymphoid nodules, the cytokines IL4, IL10, IL-12 and the YM1 gene showed significantly higher transcriptions (p<0.05) than the controls from 24 hours onwards (acute phase), decreasing levels over time studied, and IL-12 in the periods of 15 and 30 p.i (chronic phase) went to baseline levels. Higher levels of IL4, IL-10 and YM1 were detected during acute infection with T. canis. With the data obtained in this study, it can be suggested that the cytokines IL4, IL10, IL12 as well as the YM1 protein play a significant role in the immune response of Balb/c mice experimentally infected with Toxocara canis larvae. The predominantly Th2 response, with levels of IL4 transcription and regulatory response through IL10, suggest that they were responsible for the activation of immune system cells and, consequently, the transcription of the YM1 gene in splenocytes and mesenteric lymphoid nodules.