Induction of Zika specific CD8 T cell responses in the placenta after heat shock protein gp96-Ig vaccination

Abstract

Abstract Heat shock protein (HSP) gp96 is a biological adjuvant that activates antigen-presenting cells and simultaneously delivers antigen specific peptides to MHC I for CD8 T cell activation. Here, we have transformed human embryonic kidney cell line (HEK-293) into powerful miniature osmotic pumps that continually secrete engineered form of gp96, gp96-Ig, along with its chaperoned antigens (ZIKV envelope immunogenic peptides) to induce ZIKV specific CD8+ cytotoxic T cell immune responses. B6 females were mated with B6 or BALB/c males and gestation day (GD) 0.5 was determined by the presence of vaginal plug. At GD 7.5 one million of irradiated 293-gp96-Ig secreting cells were injected subcutaneously (SC). Mice were followed up until the end of pregnancy (GD 19.5–21.5) or humanely euthanized 5 days after vaccination (GD 12.5). Frequency of CD8+ T cells was determent by flow cytometry, immunohistochemistry and antigen, ZIKV envelope specificity was confirmed by in vitro ZIKV peptide stimulation and by intracellular cytokine staining. We found that vaccinated mice have the same number of live-born pups as control mice without pathological changes in placenta or in fetus. This is the first finding that confirms the presence of gp96-Ig-ZIKV-induced CD8 T cells around arteries and larger blood vessels in the maternal part of the placenta, decidua. Furthermore, secreted gp96 vaccine induces very high frequency of ZIKV specific CD8 T cells in the maternal decidua (15%) without compromising placental or fetal viability. In summary, we have succeeded in generating vaccine that is expressing gp96-Ig and ZIKV envelope protein and also we confirmed that vaccination with secreted gp96-Ig-ZIKA is safe and induces CD8 T cell responses in maternal decidua.