Protective immunity against lethal anaphylactic reaction in Toxoplasma gondii -infected mice by DNA vaccination with T. gondii -derived heat shock protein 70 gene

Abstract Toxoplasma gondii -derived heat shock protein 70 ( T.g. HSP70) was proven to induce lethal anaphylactic reaction in T. gondii -infected mice through platelet-activating factor (PAF)-mediated, but not classical IgE-dependent, pathway via TLR4/MyD88 signal pathway. The effector cells generating PAF and causing T.g. HSP70-induced anaphylactic reaction were CD11b+ and CD11c+ cells, although the reaction was enhanced by marked IFN-γ production by CD11b+ , CD11c+ , CD4+ and CD8+ splenocytes. In the present study, the effects of T.g. HSP70 gene vaccine targeting peripheral dendritic cells were evaluated against T.g. HSP70-induced anaphylactic reaction in T. gondii -infected mice. C57BL/6 mice receiving T.g. HSP70 gene vaccine showed prolonged survival. Platelets of peripheral blood, which completely disappeared during the T.g. HSP70-induced anaphylactic reaction, were partially restored with the T.g. HSP70 gene vaccination. The T.g. HSP70-induced marked production of PAF and IFN-γ from splenocytes of infected mice during the T.g. HSP70-induced anaphylactic reaction was shown to decrease after the T.g. HSP70 gene vaccination. Thus, T.g. HSP70 gene vaccine induced protective immunity against T.g. HSP70-induced PAF-mediated lethal anaphylactic reaction in T. gondii -infected mice.