Associação negativa entre atopia e toxoplasmose em seres humanos

Abstract

According to hygiene hypothesis, a lower exposure to infection is associated with the increase in allergic disease prevalence. This study aimed to investigate the association between atopy and Toxoplasma gondii (Tg) infection by analyzing the humoral and cellular immune responses in Tg-seropositive and -seronegative, atopic and non-atopic patients. A total of 275 individuals were assessed and divided into atopics (n=129) and non-atopics (n=146) based on markers of allergy (positive skin prick test and ELISA-IgE to mite allergens) or Tg-seropositive (n=116) and Tg-seronegative (n=159) groups according to infection serological markers (positive ELISA-IgG to T. gondii). Tg-seropositive individuals presented lower allergenic sensitization (37%) to Dermatophagoides pteronyssinus (Dp) and Dermatophagoides farinae (Df) mite than Tg-seronegative subjects (54%). The odds ratio (OR) of belonging to an atopic group with positive serology to T. gondii was 0.50 (95% CI: 0.31-0.81; p<0.05) while the association between atopy and negative serology to T. gondii resulted in OR of 2.0 (95% CI, 1.23-3.26; p<0.05). Cellular immune response evaluated by proliferative responses and cytokine production after antigenic or allergenic stimulation showed predominant synthesis of Th1-cytokines as IFN-&#947; in Tg-seropositive patients, whether atopics or non-atopics. Conversely, Th2-cytokines as IL-5 prevailed in atopics compared to non-atopics, regardless the seropositivity to T. gondii. Response of regulatory cytokines, such as IL-10, was evidenced in all groups, markedly after stimulation with the Df allergen. Hence, the negative association between atopy and T. gondii infection was evidenced, indicating that the presence of parasite infection can influence negatively in the induction of allergenic sensitization rather than the manifestation of allergic symptoms, reinforcing the protective role of this infection in the development of allergic diseases.