The aim of the study was to study a nanoliposomal anti-PCSK9 vaccine as a novel approach for cholesterol lowering via PCSK9 inhibition.

Material and methods:
An immunogenic peptide construct termed immunogenic fused PCSK9-tetanus (IFPT) was displayed on the surface of liposome nanoparticles (L-IFPT) and mixed into alum adjuvant (L-IFPTA+). The manufactured vaccine formulations IFPT, L-IFPT, L-IFPTA+, IFPTA+, and free nanoliposomes were subcutaneously injected four times with bi-weekly intervals in C57BL/6 mice on a severe atherogenic protocol.

Among the formulations, L-IFPTA+ vaccine was found to elicit the highest IgG response against PCSK9 peptide. The induced PCSK9 antibodies inhibited PCSK9-LDLR interaction through binding to PCSK9 in vaccinated mice. Liver low-density lipoprotein receptor (LDLR) protein was increased in vaccinated mice. L-IFPTA+, L-IFPT and IFPTA+ vaccines reduced total cholesterol by up to –38.13 ±3.8% (p = 0.006), –23 ±4.1% (p = 0.027) and –19.12 ±3% (p = 0.038), and low-density lipoprotein cholesterol (LDL-C) by up to –57 ±7.7% (p = 0.0003), –41.67 ±4.2% (p = 0.03) and –36.11 ±5% (p = 0.02) in hypercholesterolemic mice, respectively, versus control mice after 8 weeks. Long-term assessment indicated that the vaccine formulations could stimulate a long-lasting humoral immune response against PCSK9 peptide, which was associated with a marked reduction of total cholesterol in L-IFPTA+, L-IFPT and IFPTA+ vaccine groups by up to –82.5 ±7.3% (p = 0.002), –70.54 ±6.2% (p = 0.013) and –72.02 ±8.7% (p = 0.004), respectively, and LDL-C by up to –88.14 ±5.6% (p = 0.002), –55.92 ±8.3% (p = 0.003) and 54.81 ±9.3% (p = 0.003), respectively, versus the pre-vaccination time point adjusted to the control group. Anti-inflammatory Th2 cells and IL-4 cytokine were considerably increased in splenocytes of vaccinated mice.

L-IFPTA+ vaccine can induce long-lasting, functional and safe PCSK9-specific antibodies in hypercholesterolemic C57BL/6 mice, providing a long-term protective impact on dyslipidemia and atherosclerosis.