Aspectos protetores envolvidos na reinfecção por Ascaris suum em função do número de exposição e da dose da infecção na ascaridíase larval

Abstract

Human ascariasis is a neglected and cosmopolitan disease, affecting about 450 million people, making it the most prevalent geohelminthiasis in the world. In endemic areas, reinfection is recurrent due to the precarious conditions of basic sanitation and health education. In this scenario, the majority of adult individuals infected in these areas are exposed to the parasite multiple times, and have a low parasitic load. Despite the pulmonary immunological and physiological indications in studies with multiple exposures, further evaluations are necessary in order to provide more evidence on the biology of the interaction between Ascaris sp. and the host, therefore, it is necessary to compare single infections to different approaches to multiple infections and the impact on lung function in a murine model, focusing on the possible mechanisms that control protection against larval ascariasis. Thus, in order to combine parasitic protection with lower morbidity, the objective of the present study was to evaluate the impacts of Ascaris suum infection as a function of the number of exposures and the dose of infection in the protection of larval ascariasis. For this, BALB/c mice were divided into the following experimental groups: considering the number of exposures, one exposure - PI; two exposures - RI (2X) and three exposures - RI (3X), and considering the doses of infection, 25 eggs - RI (25); 250 eggs - RI (250) and 2,500 eggs - RI (3X), followed by challenge infection with 2.500 eggs. As main results obtained, we can highlight a reduction in the parasitic load of the reinfected groups when compared to the primoinfected ones, with the IR (3X) with greater protection. In compensation, the group and RI (250) showed a reduction in parasitic load close to that of RI (3X), however, this was combined with more mild inflammation, less tissue damage and physiological parameters similar to that of NI. Thus, among the reinfected groups, it was the one with the best prognosis. In addition, it was observed higher levels of total IgG and specific SIgA in the reinfected groups and that protection occurs depending on the number of exposure and the dose of infection, suggesting an important participation of the humoral response to the reduction and control of the parasitic load in the lungs of these animals.