Secreted heat shock protein gp96-Ig vaccine for malaria prophylaxis

Abstract

Abstract Proposed vaccine principle relies on secreted gp96-Ig chaperoning Plasmodium falciparum (Pf) AMA1 and PfCSP sporozoite proteins that are efficiently taken up and cross presented by activated DC via MHC I to CD8 CTL, thereby stimulating an avid, antigen specific, cytotoxic T cell response. The generation of a powerful, cytotoxic anti-sporozoite CD8 CTL response by the vaccine is expected to provide prophylactic immunity against malaria by killing infected liver cells, thereby preventing blood stage infection. We performed mouse immunogenicity experiments using 293-gp96-IgPfAMA1-PfCSP vaccine cells that produce gp96-Ig and express PfAMA1 and PfCSP. One million 293-gp96-IgPfAMA1-PfCSP cells were injected in B6 mice by intraperitoneal (IP), subcutaneous (SC), intramuscular (IM) and intradermal (ID) routes. Control mice received 293-gp96-Ig. Five days later, mice were sacrificed. Total spleen cells were cultured overnight in medium only or with pool of overlapping PfAMA1 and PfCSP peptides. Frequency of PfAMA1- and PfCSP-specific CD8 T cell responses in the spleen was measured by intracellular cytokine staining assay and analyzed by flow cytometry. We found that vaccine cells delivered by IP and SC routes induced the strongest PfAMA1- and PfCSP-specific immune response systemically (1.8±0.4% and 1.3±0.3% PfAMA1- and PfCSP-specific spleen CD8 T cells, respectively). In addition, after 293-gp96-IgPfAMA1-PfCSP vaccination frequency of liver-infiltrating CD8+ T cell was significantly increased (70% of all liver CD3+ cells were CD8+CD44+CD62L− T cells). Our findings are strongly supportive of the novel gp96-Ig malaria vaccine as unique systemic and liver-homing, sporozoite specific CD8 CTL vaccine strategy.