Evaluating the effect of the antiPCSK9 vaccine on systemic inflammation and oxidative stress in CFA-challenged albino mice
Authors: Momtazi-Borojeni A A , Banach M , Sahebkar A 
Published: November 2023

Abstract

Background
Besides effective lipid lowering therapy aimed to reduce LDL-C, one should always look at other risk factors that may essentially increase the risk of residual cardiovascular disease risk, including diabetes, thrombotic factors and inflammation.

Purpose
To find whether the antiPCSK9 vaccine can affect the serum C-reactive protein (CRP) and oxidative stress during acute systemic inflammation.

Methods
Male albino mice were randomly divided into three groups, including non-treated mice (the sham group), mice treated with Freund's complete adjuvant (CFA) (the CFA group), and vaccinated mice treated with CFA (the vaccine group). The vaccine group was subcutaneously immunized with the antiPCSK9 formulation, four times in bi-weekly intervals. To induce inflammation, all mice were subjected to the CFA challenge after the vaccination plan. To determine the efficacy of the antiPCSK9 vaccine in albino mice, plasma antiPCSK9 antibody titer, plasma PCSK9 concentration, and PCSK9/LDLR interaction were assayed. The serum level of high-sensitive CRP (hs-CRP) and oxidative stress status were evaluated by a mouse CRP ELISA kit and the pro-oxidant antioxidant balance (PAB) assay, respectively.

Results
Upon three boosters, the vaccine induced a high-titer IgG antiPCSK9 antibody in albino mice, which was accompanied with a significant reduction in the plasma level of the free PCSK9 (-24.7% and -28.5% compared with the sham and CFA group, respectively), and the inhibition of PCSK9/LDLR interaction (-27.8% and -29.4% compared with the sham and CFA group, respectively). In addition, the serum level of hs-CRP was significantly increased in the vaccine and CFA groups by 225% and 274%, respectively, when compared with the sham group; however, it was non-significantly decreased (-18%) in the vaccine group in comparison with the CFA group (Figure 1A). Moreover, the PAB values indicated that oxidative stress was significantly increased in the CFA group (by 72.7%) and the vaccine group (by 76%) when compared to the sham group; however, there was no significant difference in the PAB values between the vaccine and CFA groups (Figure 1B).

Conclusion
Our results indicate that, despite inducing the production of the functional antiPCSK9 antibodies, the antiPCSK9 vaccine failed to significantly reduce the serum hs-CRP and oxidative stress induced in the CFA-challenged albino mice.
Figure 1. The effect of the antiPCSK9 vaccine on (A) the serum level of hs-CRP in albino mice and (B) the serum PAB in albino mice. The sham group involved non-treated mice, the CFA group involved the CFA-treated mice, and the vaccine group involved mice who after vaccination were treated with the CFA. Pooling of samples was performed to obtain sufficient sample volume for assay, when needed. The PAB values were expressed in an arbitrary HK (Hamidi-Koliakos). Data are expressed as mean ±SD (10 mice per group). Statistical differences at a p-value &lt;0.05 were considered as significant.Figure 1.