Response of human leukocytes after stimulation with excreted-secreted toxocara canis larval antigens

Background: Specific immunotherapy by administration of allergen extracts has been successfully used in asthma, allergic rhinitis and for venom. The identification of molecules which could be used as adjuvants in anti-allergy immunotherapeutic preparations is highly desirable. Anti-allergy immunotherapy has been associated with the induction of regulatory T cells. Helminths possibly downmodulate immune responses to airborne allergens, indirectly, through the stimulation of a regulatory network. 

Methods: In this study, it was investigated whether excreted-secreted Toxocara canis larval antigens (TES) (native) could elicit recall immune responses that could potentially inhibit a Th2 response, in nine allergic and ten non-allergic individuals' peripheral blood mononuclear cells (PBMC). PBMC were cultivated in vitro in the presence or absence of these extracts at 37 °C and 5% CO2 during 48 and 120 hours and their supernatants were evaluated for cytokine production (TGF-β, IL-10, IL-12, IFN-γ, IL-6, TNF-α, IL-5 IL13 and IL-17). 

Results: The antigen induced cytokine production in all PBMC preparations. Stimulation of the production of Treg cytokines (TGF-β and/or IL-10), accompanied or not by stimulation of cytokines production associated with the Th1 response (IL-12 and IFN-γ), but without stimulation of Th2 cytokines (IL-5 and IL-13) and IL-17, by antigen TES, was seen with 6 out of 10 allergic patients' PBMC. 

Conclusions: The results indicate that antigen TES induce Treg with or without Th1 immune responses. Searches of molecules, in this extract, which specifically induce this profile is suggested.