Highlights
- •PCSK9 inhibition is a pivotal approach for LDL cholesterol-lowering.
- •PCSK9 inhibition using monoclonal antibodies is short-term and not cost-effective.
- •We tested the efficacy of a nanoliposomal PCSK9-specific active vaccine.
- •The tested nanoliposomal vaccine induced humoral immunity against PCSK9 in BALB/c mice.
- •The tested vaccine was also safe and induced long-term generation of anti-PCSK9 antibodies.
Abstract
Background and aims
Proprotein convertase subtilisin kexin type 9 (PCSK9) is a liver secretory enzyme
that controls plasma low-density lipoprotein cholesterol (LDL-C) levels through modulation
of LDL receptor (LDLR). Inhibition of PCSK9 using monoclonal antibodies (mAbs) can
efficiently lower plasma LDL-C. However, the relatively short half-life of mAbs necessitates
frequent passive immunization, which is costly. These limitations can be circumvented
by active immunization. Here, we evaluated the long-term antiPCSK9 antibody generation
in BALB/c mice vaccinated with a nanoliposomal PCSK9-specific active vaccine.
Methods
Negatively charged nanoliposomes were used as a vaccine delivery system and prepared
via lipid-film hydration method. We constructed a peptide vaccine termed Immunogenic
Fused PCSK9-Tetanus (IFPT) by linking a short PCSK9 peptide (as B cell epitope) to
a tetanus peptide (as T cell epitope). The IFPT peptide was conjugated to the surface
of nanoliposome carriers using a DSPE-PEG- Maleimide (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimide(PEG)-2000]) linker. Nanoliposomal IFPT (L-IFPT) construct was formulated
with alum vaccine adjuvant (L-IFPTA+). To evaluate induction of antiPCSK9 antibody in vivo, BALB/c mice were subcutaneously inoculated four times in bi-weekly intervals with
prepared vaccine formulations, including L-IFPT, L-IFPTA+, IFPTA+, IFPT, and empty liposomes as negative control. The long-term efficacy of antiPCSK9
antibodies was evaluated over 48 weeks after prime inoculation. Specificity of generated
antiPCSK9 antibodies was assessed using ELISA method. To evaluate immunogenic safety,
production of IL-4 and IFN-γ, and population of CD8+ and CD4+ T cells in splenic cells isolated from the vaccinated mice were analyzed.
Results
The L-IFPTA+ vaccine was found to elicit the highest IgG antibody response against PCSK9 peptide
in the vaccinated mice, when compared with the other vaccine formulations. Antibody
titer analyses over 48 weeks post-prime vaccination revealed that the L-IFPTA+ vaccine was able to stimulate a long-lasting humoral immune response against PCSK9
peptide, and thereby decrease plasma PCSK9. Generated antibodies could specifically
target PCSK9 and thereby inhibit PCSK9-LDLR interaction. Analysis of splenic cells
showed that the population of anti-inflammatory CD4+ Th2 cells and production and secretion of IL-4 cytokine were increased in mice vaccinated
with the L-IFPTA+ vaccine, while population of inflammatory CD4+ Th1 cell and cytotoxic CD8+ T cells as well as production and secretion of IFN-γ were not altered.
Conclusions
The results indicate efficient activity of the tested nanoliposomal construct (L-IFPTA+) to induce humoral immune response against PCSK9 in BALB/c mice. L-IFPTA+ vaccine can induce immunogenic-safe and long-term generation of antiPCSK9 antibodies
in BALB/c mice.
Graphical abstract
Graphical Abstract
Keywords
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Article info
Publication history
Published online: February 13, 2019
Accepted:
February 5,
2019
Received in revised form:
January 17,
2019
Received:
November 13,
2018
Identification
Copyright
© 2019 Elsevier B.V. All rights reserved.
