Prostate speci c antigen (PSA) and prostatic acid phosphatase (PAP) have been considered as immunotherapeutic antigens for prostate cancer. The use of a single antigenic agent is unlikely to be effective in eliciting immunotherapeutic responses due to the heterogeneous and multifocal nature of prostate cancer. Thus, multiple antigens have been combined to enhance their anti-cancer effects. In the current study, PSA and PAP were fused to the crystallizable region (Fc region) of immunoglobulin G1 and tagged with KDEL, the endoplasmic reticulum (ER) retention signal motif, to generate PSA-FcK and PAP-FcK, respectively, and were transiently co-expressed in Nicotiana benthamiana. Western blot analysis con rmed the co-expression of PSA-FcK and PAP-FcK (PSA-FcK+PAP-FcK) with a 1:3 ratio in the coin ltrated plants. PSA-FcK, PAP-FcK, and PSA-FcK+PAP-FcK proteins were successfully puri ed from N. benthamiana by protein A a nity chromatography. ELISA showed that anti-PAP and anti-PSA antibodies successfully detected PAP-FcK and PSA-FcK, respectively, and both detected PSA-FcK+PAP-FcK. Surface plasmon resonance (SPR) analysis con rmed the binding a nity of the plant-derived Fc fusion proteins to FcγRI/CD64. Furthermore, we also con rmed that mice injected with PSA-FcK+PAP-FcK produced both PSA and PAP-speci c IgGs, demonstrating their immunogenicity. This study suggested that the transient plant expression system can be applied to produce the dual-antigen Fc fusion protein (PSA-FcK+PAP-FcK) for prostate cancer immunotherapy.
Key MessagePAP-FcK and PSA-FcK prostate cancer antigenic proteins transiently co-expressed in plant induce their speci c humoral immune responses in mice.