Antibody and cytokine responses to house dust mite allergens and Toxoplasma gondii antigens in atopic and non-atopic Brazilian subjects

Abstract

According to hygiene hypothesis, a lower exposure to infection is associated with increased prevalence of allergic diseases. This study aimed to investigate the association between atopy and Toxoplasma gondii (Tg) infection by analyzing the antibody and cytokine responses to house dust mite allergens and T. gondii antigens in Brazilian subjects. 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 markers (positive ELISA-IgG to T. gondii). Tg-seropositive individuals presented lower allergenic sensitization (37%) to mite allergens than Tg-seronegative subjects (54%). A significant association was found between atopy and negative serology to T. gondii (OR: 2.0; 95% CI: 1.23–3.26; P<0.05). Proliferative responses and cytokine production after antigenic stimulation showed predominant synthesis of Th1-cytokines as IFN-γ 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. Levels of IL-10, IL-13, IL-17, and TGF-β were not able to discriminate the groups. Hence, a negative association between atopy and infection by T. gondii was demonstrated for the first time in Brazilian subjects, focusing on the antibody and cytokine responses and indicating that the immunomodulation induced by the parasite may play a protective role in the development of allergic diseases.

Potential immunomodulatory effects of latent toxoplasmosis in humans

“…Possibly, the Toxoplasma -positive men (with decreased counts of leukocytes, B-cells, NK cells and monocytes) are protected against allergies and therefore were not enrolled in our study, while the women (with increased counts of total leukocytes, NK-cells and monocytes) have higher probability of allergies and immunopathological diseases. Decreased frequency of Toxoplasma -positive subjects in patients with atopic disease has already reported in several studies [32-34]. It must be remind, however, the low frequency of Toxoplasma infected men as well as the statistically significant associations between the Toxoplasma infection and the cell counts were observed mostly in subjects with immunodeficiencies (D.89.9) not in patients with allergies (J.30.1-4) in our study.…”

Toxoplasma gondii protects from IgE sensitization and induces Th1/Th2 immune profile

“…The most common aeroallergen worldwide is Dermatophagoides pteronyssinus . It is considered a significant source of inhaled allergens, inducing airway allergen sensitization in genetically predisposed individuals . In the present study, we hypothesize that T gondii infection may be regulating allergic sensitization.…”

“…Exposure to pathogens transmitted by orofecal route or foodborne transmission, such as Toxoplasma gondii , has been shown to protect against the development of autoimmune and allergic diseases in experimental animal models . Some evidence in support of this hypothesis has been observed in human populations . However, the results obtained so far by different research groups are inconsistent .…”

Parasites and allergy: Observations from Brazil

“…Another protozoan parasite, T. gondii , has been extensively studied with respect to allergic sensitization in both murine models and humans . Inverse associations have been observed in Brazilian populations between seropositivity for T. gondii and atopy (measured as both SPT and serum IgE to aeroallergens) .…”

“…Another protozoan parasite, T. gondii , has been extensively studied with respect to allergic sensitization in both murine models and humans . Inverse associations have been observed in Brazilian populations between seropositivity for T. gondii and atopy (measured as both SPT and serum IgE to aeroallergens) . Although the mechanism whereby this modulation occurs is not well understood, data from murine models have shown that allergic inflammation can be suppressed by treating animals with Toxoplasma extract or derived proteins …”