Toxoplasma gondii is a threat for immunocompromized individuals, and no treatment is available for enhancing immunity against infection. Molecular adjuvants may improve the efficacy of DNA vaccine-induced T cell immunity. Here, we report that cocktailed DNA immunization with ROP5 and ROP18 boosted immune responses induced by a single DNA immunization with ROP5 or ROP18, but also that co-administration of molecular adjuvant IL-33 enhanced immune efficacy induced by this cocktailed DNA vaccination. These improved immune responses were characterized by higher Toxoplasma-specific IgG2a titers, Th1 responses associated with the production of IFN-γ, IL-2, IL-12, as well as cell-mediated activity with higher frequencies of CD8+ and CD4+ T cells. More importantly, this enhanced immunity has the ability to confer remarkable protection against a high dose lethal challenge of the T. gondii RH strain and thus against chronic infection with the T. gondii PRU strain. These data show that IL-33 is a promising immunoadjuvant to facilitate humoral as well as cellular immunity in a vaccine setting against T. gondii, and suggest that it should be evaluated in strategies against other apicomplexan parasites.
Immune response and protective effect against chronic Toxoplasma gondii infection induced by vaccination with a DNA vaccine encoding profilin