Development of vaccine for dyslipidemia targeted to a proprotein convertase subtilisin/kexin type 9 (PCSK9) epitope in mice

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates expression of low-density lipoprotein (LDL) receptors via receptor internalization and subsequent lysosomal degradation. Thus, an anti-PCSK9 antibody is well known as an anti-hyperlipidemia drug. Here, we aimed to develop vaccine for a long-term treatment of dyslipidemia targeted to PCSK9. In This study, we designed a peptide vaccine for mouse PCSK-9, which consisted of short peptides conjugated to keyhole limpet hemocyanin (KLH) as a carrier protein. Vaccines were administered to male apolipoprotein E (ApoE) deficient mice with adjuvants and significantly elicited an antibody response against PCSK9. The PCSK9 vaccines were administered to mice three times in 2-week intervals, and antibody titers and lipoprotein levels were evaluated up to 24 weeks after the first immunization to determine the therapeutic effect. Anti-PCSK9 antibody titers reached peak levels 6 weeks after the first immunization, and theses titers were maintained for up to 24 weeks. Decreased plasma levels of total cholesterol, very low-density lipoprotein (VLDL), and chylomicron (CM) were maintained for up to 24 weeks. Immunized mice exhibited a significant increase in cell-surface LDL receptor expression. Stimulation with KLH, but not PCSK9, induced the production of INF-gamma and interleukin-4 (IL-4), as determined with ELISPOT assays, thus indicating that PCSK9 vaccine did not elicit T-cell activation in our vaccine system. The present anti-PCSK9 vaccine induced long-lasting anti-PCSK9 antibody production and improved lipoprotein profiles. Thus, anti-PCSK9 vaccine could become a new option for the treatment of dyslipidemia as a long-acting therapy in future.