A Therapeutic Peptide Vaccine Against PCSK9

The role of PCSK9 in heart failure and other cardiovascular diseases-mechanisms of action beyond its effect on LDL cholesterol

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a protein that regulates low-density lipoprotein (LDL) cholesterol metabolism by binding to the hepatic LDL receptor (LDLR), ultimately leading to its lysosomal degradation and an increase in LDL cholesterol (LDLc) levels. Treatment strategies have been developed based on blocking PCSK9 with specific antibodies (alirocumab, evolocumab) and on blocking its production with small regulatory RNA (siRNA) (inclisiran). Clinical trials evaluating these drugs have confirmed their high efficacy in reducing serum LDLc levels and improving the prognosis in patients with atherosclerotic cardiovascular diseases. Most studies have focused on the action of PCSK9 on LDLRs and the subsequent increase in LDLc concentrations. Increasing evidence suggests that the adverse cardiovascular effects of PCSK9, particularly its atherosclerotic effects on the vascular wall, may also result from mechanisms independent of its effects on lipid metabolism. PCSK9 induces the expression of pro-inflammatory cytokines contributing to inflammation within the vascular wall and promotes apoptosis, pyroptosis, and ferroptosis of cardiomyocytes and is thus involved in the development and progression of heart failure. The elimination of PCSK9 may, therefore, not only be a treatment for hypercholesterolaemia but also for atherosclerosis and other cardiovascular diseases. The mechanisms of action of PCSK9 in the cardiovascular system are not yet fully understood. This article reviews the current understanding of the mechanisms of PCSK9 action in the cardiovascular system and its contribution to cardiovascular diseases. Knowledge of these mechanisms may contribute to the wider use of PCSK9 inhibitors in the treatment of cardiovascular diseases.

Cholesterol reduction by immunization with a PCSK9 mimic

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a plasma protein that controls cholesterol homeostasis. Here, we design a human PCSK9 mimic, named HIT01, with no consecutive 9-residue stretch in common with any human protein as a potential heart attack vaccine. Murine immunizations with HIT01 reduce low-density lipoprotein (LDL) and cholesterol levels by 40% and 30%, respectively. Immunization of cynomolgus macaques with HIT01-K21Q-R218E, a cleavage-resistant variant, elicits high-titer PCSK9-directed antibody responses and significantly reduces serum levels of cholesterol 2 weeks after each immunization. However, HIT01-K21Q-R218E immunizations also increase serum PCSK9 levels by up to 5-fold, likely due to PCSK9-binding antibodies altering the half-life of PCSK9. While vaccination with a PCSK9 mimic can induce antibodies that block interactions of PCSK9 with the LDL receptor, PCSK9-binding antibodies appear to alter homeostatic levels of PCSK9, thereby confounding its vaccine impact. Our results nevertheless suggest a mechanism for increasing the half-life of soluble regulatory factors by vaccination.

Development of a PCSK9-targeted nanoparticle vaccine to effectively decrease the hypercholesterolemia

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the low-density lipoprotein receptor (LDLR) and mediates its internalization and degradation, resulting in an increase in LDL cholesterol levels. Recently, PCSK9 emerged as a therapeutic target for hypercholesterolemia and atherosclerosis. In this study, we develop a PCSK9 nanoparticle (NP) vaccine by covalently conjugating the catalytic domain (aa 153-aa 454, D374Y) of PCSK9 to self-assembled 24-mer ferritin NPs. We demonstrate that the PCSK9 NP vaccine effectively induces interfering antibodies against PCSK9 and reduces serum lipids levels in both a high-fat diet-induced hypercholesterolemia model and an adeno-associated virus-hPCSK9D374Y-induced hypercholesterolemia model. Additionally, the vaccine significantly reduces plaque lesion areas in the aorta and macrophages infiltration in an atherosclerosis mouse model. Furthermore, we discover that the vaccine's efficacy relied on T follicular help cells and LDLR. Overall, these findings suggest that the PCSK9 NP vaccine holds promise as an effective treatment for hypercholesterolemia and atherosclerosis.

Vaccine Targeting Alpha 1D-Adrenergic Receptor Improved Metabolic Syndrome in Mice

PURPOSE

Metabolic syndrome (MetS) is a complex chronic disease that includes obesity and hypertension, with rising evidence demonstrating that sympathetic nervous system (SNS) activation plays a key role. Our team designed a therapeutic vaccine called ADRQβ-004 targeting the α1D-adrenergic receptor (α1D-AR). This study was performed to investigate whether the ADRQβ-004 vaccine improves MetS by modulating SNS activity.

METHODS

C57BL/6N mice were fed a high-fat diet (HFD) and Nω-nitro-L-arginine methyl ester (L-NAME) combination diet for 18 weeks to elicit MetS. The MetS mice were subcutaneously immunized with the ADRQβ-004 vaccine four times to evaluate the therapeutic efficacy in obesity and hypertension and other associated abnormalities related to MetS by conducting echocardiographic, histological, and biochemical analyses.

RESULTS

The ADRQβ-004 vaccine induced strong antibody production and maintained a high anti-ADR-004 antibody titer in MetS mice. The ADRQβ-004 vaccine improved obesity (P < 0.001) and decreased systolic blood pressure (P < 0.001). Improvements in dysregulated glucose homeostasis and dyslipidemia resulting from the ADRQβ-004 vaccine were also confirmed. Furthermore, the ADRQβ-004 vaccine attenuated cardiovascular functional (P = 0.015) and structural changes (P < 0.001), decreased fat accumulation (P = 0.012) and inflammation (P = 0.050) in the epididymal white adipose tissue, and alleviated hepatic steatosis (P = 0.043) involved in MetS. Moreover, the ADRQβ-004 vaccine improved systematic and visceral organs SNS activities in the MetS.

CONCLUSION

This study demonstrated for the first time that the ADRQβ-004 vaccine targeting α1D-AR improved obesity, hypertension, dyslipidemia, and dysglycemia, and further reduced end-organ damage, which may provide new motivation for MetS research.

Whether and Why Do We Need a Vaccine Against Atherosclerosis? Can We Expect It Anytime Soon?

PURPOSE OF REVIEW

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of premature death. Lipid disorders, particularly elevated serum low-density lipoprotein cholesterol (LDL-C), contribute significantly to ASCVD. The risk of developing ASCVD is influenced by the duration of exposure to elevated LDL-C concentrations (cholesterol-years concept). Implementing lipid-lowering treatments based on the principles of "the earlier the better," "the lower the better," and "the longer the better" has been shown to reduce cardiovascular risk and significantly extend lifespan. Despite the availability of numerous lipid-lowering drugs, achieving satisfactory control of lipid disorders remains very challenging. Therefore, there is a need for novel approaches to improve treatment adherence.

RECENT FINDINGS

One promising solution under investigation is the development of an anti-PCSK9 vaccine, which could be administered annually to provide long-term control over LDL-C concentrations. Experimental studies and the sole clinical trial conducted thus far have demonstrated that the anti-PCSK9 vaccine induces a durable immune response associated with lipid-lowering and anti-atherosclerotic effects. Furthermore, it has exhibited good tolerability and a satisfactory safety profile. However, we still need data from phase 2, 3, and cardiovascular outcome trial to confirm its safety and efficacy and add value in the armamentarium of available and perspective lipid-lowering drugs. This article highlights the significance of developing an anti-PCSK9 vaccine and provides an overview of the current knowledge on various anti-PCSK9 vaccines.

Advances in Pharmacological Approaches for Managing Hypercholesterolemia: A Comprehensive Overview of Novel Treatments

Hypercholesterolemia plays a crucial role in the formation of lipid plaques, particularly with elevated low-density lipoprotein (LDL-C) levels, which are linked to increased risks of cardiovascular disease, cerebrovascular disease, and peripheral arterial disease. Controlling blood cholesterol values, specifically reducing LDL-C, is widely recognized as a key modifiable risk factor for decreasing the morbidity and mortality associated with cardiovascular diseases. Historically, statins, by inhibiting the enzyme β-hydroxy β-methylglutaryl-coenzyme A (HMG)-CoA reductase, have been among the most effective drugs. However, newer non-statin agents have since been introduced into hypercholesterolemia therapy, providing a viable alternative with a favorable cost-benefit ratio. This paper aims to delve into the latest therapies, shedding light on their mechanisms of action and therapeutic benefits.

VXX-401, a novel anti-PCSK9 vaccine, reduces LDL-C in cynomolgus monkeys

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of disease burden in the world and is highly correlated with chronic elevations of LDL-C. LDL-C-lowering drugs, such as statins or monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9), are known to reduce the risk of cardiovascular diseases; however, statins are associated with limited efficacy and poor adherence to treatment, whereas PCSK9 inhibitors are only prescribed to a "high-risk" patient population or those who have failed other therapies. Based on the proven efficacy and safety profile of existing monoclonal antibodies, we have developed a peptide-based vaccine against PCSK9, VXX-401, as an alternative option to treat hypercholesterolemia and prevent ASCVD. VXX-401 is designed to trigger a safe humoral immune response against PCSK9, resulting in the production of endogenous antibodies and a subsequent 30-40% reduction in blood LDL-C. In this article, VXX-401 demonstrates robust immunogenicity and sustained serum LDL-C-lowering effects in nonhuman primates. In addition, antibodies induced by VXX-401 bind to human PCSK9 with high affinity and block the inhibitory effect of PCSK9 on LDL-C uptake in a hepatic cell model. A repeat-dose toxicity study conducted in nonhuman primates under good laboratory practices toxicity indicated a suitable safety and tolerability profile, with injection site reactions being the main findings. As a promising safe and effective LDL-C-lowering therapy, VXX-401 may represent a broadly accessible and convenient option to treat hypercholesterolemia and prevent ASCVD.

New Biological Therapies for Low-Density Lipoprotein Cholesterol

Depressed low-density lipoprotein cholesterol concentration protects against atherosclerotic cardiovascular disease. Natural hypocholesterolemia states can have a monogenic etiology, caused by pathogenic loss of function variants in the PCSK9, ANGPTL3, MTTP, or APOB genes. In this focused review, we discuss development and clinical use of several new therapeutics that inhibit these gene products to target elevated levels of low-density lipoprotein cholesterol. In particular, inhibitors of proprotein convertase subtilisin kexin type 9 (PCSK9) have notably affected clinical practice, followed recently by inhibition of angiopoietin-like 3 (ANGPTL3). Currently used in the clinic are alirocumab and evolocumab, two anti-PCSK9 monoclonal antibodies, inclisiran, a small interfering RNA that prevents PCSK9 translation, evinacumab, an anti-ANGPTL3 monoclonal antibody, and lomitapide, a small-molecule inhibitor of microsomal triglyceride transfer protein. Additional therapies are in preclinical or clinical trial stages of development. These consist of other monoclonal antibodies, antisense oligonucleotides, small-molecule inhibitors, mimetic peptides, adnectins, vaccines, and gene-editing therapies. Vaccines and gene-editing therapies in particular hold great potential to confer active long-term attenuation or provide single-treatment life-long knock-down of PCSK9 or ANGPTL3 activity. Biologic therapies inspired by monogenic hypocholesterolemia states are becoming valuable tools to help protect against atherosclerotic cardiovascular disease.

A virus-like particle-based bivalent PCSK9 vaccine lowers LDL-cholesterol levels in non-human primates

Elevated low-density lipoprotein cholesterol (LDL-C) is an important risk factor in the development of atherosclerotic cardiovascular disease (ASCVD). Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of LDL-C metabolism, have emerged as promising approaches for reducing elevated LDL-C levels. Here, we evaluated the cholesterol-lowering efficacy of virus-like particle (VLP) based vaccines that target epitopes found within the LDL receptor (LDL-R) binding domain of PCSK9. In both mice and non-human primates, a bivalent VLP vaccine targeting two distinct epitopes on PCSK9 elicited strong and durable antibody responses and lowered cholesterol levels. In macaques, a VLP vaccine targeting a single PCSK9 epitope was only effective at lowering LDL-C levels in combination with statins, whereas immunization with the bivalent vaccine lowered LDL-C without requiring statin co-administration. These data highlight the efficacy of an alternative, vaccine-based approach for lowering LDL-C.

Novel and future lipid-modulating therapies for the prevention of cardiovascular disease

Lowering the levels of LDL cholesterol in the plasma has been shown to reduce the risk of atherosclerotic cardiovascular disease (ASCVD). Several other lipoproteins, such as triglyceride-rich lipoproteins, HDL and lipoprotein(a) are associated with atherosclerosis and ASCVD, with strong evidence supporting causality for some. In this Review, we discuss novel and upcoming therapeutic strategies targeting different pathways in lipid metabolism to potentially attenuate the risk of cardiovascular events. Key proteins involved in lipoprotein metabolism, such as PCSK9, angiopoietin-related protein 3, cholesteryl ester transfer protein and apolipoprotein(a), have been identified as viable targets for therapeutic intervention through observational and genetic studies. These proteins can be targeted using a variety of approaches, such as protein inhibition or interference, inhibition of translation at the mRNA level (with the use of antisense oligonucleotides or small interfering RNA), and the introduction of loss-of-function mutations through base editing. These novel and upcoming strategies are complementary to and could work synergistically with existing therapies, or in some cases could potentially replace therapies, offering unprecedented opportunities to prevent ASCVD. Moreover, a major challenge in the prevention and treatment of non-communicable diseases is how to achieve safe, long-lasting reductions in causal exposures. This challenge might be overcome with approaches such as small interfering RNAs or genome editing, which shows how far the field has advanced from when the burden of achieving this goal was placed upon patients through rigorous adherence to daily small-molecule drug regimens.

Two decades of vaccine development against atherosclerosis

Atherosclerosis is an immune-mediated chronic inflammatory disease that leads to the development of fatty plaques in the arterial walls, ultimately increasing the risk of thrombosis, stroke, and myocardial infarction. The immune response in this complex disease is both atheroprotective and pro-atherogenic, involving both innate and adaptive immunity. Current treatments include the adjustment of lifestyle factors, cholesterol-lowering drugs such as statins, and immunotherapy, whereas vaccine development has received comparatively little attention. In this review, we discuss the potential of antigen-specific vaccination as a preventative approach based on more than 20 years of research and innovation. Vaccination targets include proteins that are more abundant in atherosclerotic patients, such as oxidized low-density lipoprotein (LDL), apolipoprotein B-100, proprotein convertase subtilisin/kexin type-9 serine protease (PCSK9), cholesteryl ester transfer protein (CETP), and heat shock proteins HSP60 and HSP65. Immunization with such proteins or their peptide epitopes has been shown to induce T-cell activation, produce antigen-specific antibodies, reduce the size of atherosclerotic lesions, and/or reduce serum cholesterol levels. Vaccination against atherosclerosis therefore offers a new strategy to address the burden on healthcare systems caused by cardiovascular disease, the leading cause of death worldwide.

A Virus-like particle-based bivalent PCSK9 vaccine lowers LDL-cholesterol levels in Non-Human Primates

Elevated low-density lipoprotein cholesterol (LDL-C) is an important risk factor in the development of atherosclerotic cardiovascular disease (ASCVD). Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of LDL-C metabolism, have emerged as promising approaches for reducing elevated LDL-C levels. Here, we evaluated the cholesterol lowering efficacy of virus-like particle (VLP) based vaccines that target epitopes found within the LDL receptor (LDL-R) binding domain of PCSK9. In both mice and non-human primates, a bivalent VLP vaccine targeting two distinct epitopes on PCSK9 elicited strong and durable antibody responses and lowered cholesterol levels. In macaques, a VLP vaccine targeting a single PCSK9 epitope was only effective at lowering LDL-C levels in combination with statins, whereas immunization with the bivalent vaccine lowered LDL-C without requiring statin co-administration. These data highlight the efficacy of an alternative, vaccine-based approach for lowering LDL-C.

A novel vaccine targeting β1-adrenergic receptor

Beta-blockers are widely used in the treatment of hypertension, heart failure and ischemic heart disease. However, unstandardized medication results in diverse clinical outcomes in patients. The main causes are unattained optimal doses, insufficient follow-up and patients' poor adherence. To improve the medication inadequacy, our team developed a novel therapeutic vaccine targeting β1-adrenergic receptor (β1-AR). The β1-AR vaccine named ABRQβ-006 was prepared by chemical conjugation of a screened β1-AR peptide with Qβ virus like particle (VLP). The antihypertensive, anti-remodeling and cardio-protective effects of β1-AR vaccine were evaluated in different animal models. The ABRQβ-006 vaccine was immunogenic that induced high titers of antibodies against β1-AR epitope peptide. In the NG-nitro-L-arginine methyl ester (L-NAME) + Sprague Dawley (SD) hypertension model, ABRQβ-006 lowered systolic blood pressure about 10 mmHg and attenuated vascular remodeling, myocardial hypertrophy and perivascular fibrosis. In the pressure-overload transverse aortic constriction (TAC) model, ABRQβ-006 significantly improved cardiac function, decreased myocardial hypertrophy, perivascular fibrosis and vascular remodeling. In the myocardial infarction (MI) model, ABRQβ-006 effectively improved cardiac remodeling, reduced cardiac fibrosis and inflammatory infiltration, which was superior to metoprolol. Moreover, no significant immune-mediated damage was observed in immunized animals. The ABRQβ-006 vaccine targeting β1-AR showed the effects on hypertension and heart rate control, myocardial remodeling inhibition and cardiac function protection. These effects could be differentiated in different types of diseases with diverse pathogenesis. ABRQβ-006 could be a novel and promising method for the treatment of hypertension and heart failure with different etiologies.

Preclinical toxicity assessment of a peptide-based antiPCSK9 vaccine in healthy mice

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a novel cholesterol-lowering treatment for decreasing the risk of atherosclerosis. We have previously shown that active immunization using the antiPCSK9 vaccine could decrease hypercholesterolemia and impede the development of atherosclerotic lesions in the experimental model of atherosclerosis. Here, we evaluated the toxicity of the vaccine in healthy mice.

METHODS

Forty male and female albino mice were divided into 4 experimental groups, including vaccine female (10 mice) and male (10 mice) groups receiving the antiPCSK9 vaccine as well as the corresponding control female (10 mice) and male (10 mice) groups receiving the phosphate buffer. Vaccination was planned based on 4 subcutaneous injections of the vaccine formulation (10 µg/mouse) in bi-weekly intervals. The toxicity study was performed by the subacute protocol, 28 days after the last vaccine injection. To this end, the plasma levels of lipid indexes, urea, creatinine, AST, ALT, ALP, and fasting plasma glucose (FPG), as well as the CBC test were measured. To evaluate histopathological alterations, various tissues including the heart, liver, kidney, spleen, and brain were studied using hematoxylin & eosin (H&E) staining by an expert pathologist. The severity of damage to the tissue was considered based on the standard classification; grade 1 as light damage, grade 2 as moderate damage, grade 3 as near intense damage, and grade 4 as intense damage.

RESULTS

The results showed non-significant changes of total cholesterol, LDL-C, triglyceride, HDL-C, FBS, creatinine, urea, AST, ALP, ALT, and PAB in the vaccinated mice when compared with control mice. The CBS test indicated that there were no significant changes in the levels of WBC, RBC, HGB, HCT, MCH, MCHC, PLT, LYM, NEUT, MCV, RDW-S, PDW, and MPV in the vaccinated mice when compared with control mice. Evaluating histopathological alterations in various tissues indicated no significant adverse effects in vaccinated mice when compared to control mice.

CONCLUSION

The findings of the present study indicate that antiPCSK9 is safe and exerts no adverse effects on the function of different organs and blood levels of cellular and biochemical biomarkers in healthy mice.

A cVLP-Based Vaccine Displaying Full-Length PCSK9 Elicits a Higher Reduction in Plasma PCSK9 Than Similar Peptide-Based cVLP Vaccines

Administration of PCSK9-specific monoclonal antibodies, as well as peptide-based PCSK9 vaccines, can lower plasma LDL cholesterol by blocking PCSK9. However, these treatments also cause an increase in plasma PCSK9 levels, presumably due to the formation of immune complexes. Here, we utilize a versatile capsid virus-like particle (cVLP)-based vaccine platform to deliver both full-length (FL) PCSK9 and PCSK9-derived peptide antigens, to investigate whether induction of a broader polyclonal anti-PCSK9 antibody response would mediate more efficient clearance of plasma PCSK9. This head-to-head immunization study reveals a significantly increased capacity of the FL PCSK9 cVLP vaccine to opsonize and clear plasma PCSK9. These findings may have implications for the design of PCSK9 and other vaccines that should effectively mediate opsonization and immune clearance of target antigens.

Recent Update on the Development of PCSK9 Inhibitors for Hypercholesterolemia Treatment

The proprotein convertase subtilisin/kexin-type 9 (PCSK9) binds to low-density lipoprotein receptors (LDLR), thereby trafficking them to lysosomes upon endocytosis and enhancing intracellular degradation to prevent their recycling. As a result, the levels of circulating LDL cholesterol (LDL-C) increase, which is a prominent risk factor for developing atherosclerotic cardiovascular diseases (ASCVD). Thus, PCSK9 has become a promising therapeutic target that offers a fertile testing ground for new drug modalities to regulate plasma LDL-C levels to prevent ASCVD. In this review, we have discussed the role of PCSK9 in lipid metabolism and briefly summarized the current clinical status of modalities targeting PCSK9. In particular, a detailed overview of peptide-based PCSK9 inhibitors is presented, which emphasizes their structural features and design, therapeutic effects on patients, and preclinical cardiovascular disease (CVD) models, along with PCSK9 modulation mechanisms. As a promising alternative to monoclonal antibodies (mAbs) for managing LDL-C, anti-PCSK9 peptides are emerging as a prospective next generation therapy.

Development of therapeutic vaccines for the treatment of diseases

Vaccines are one of the most effective medical interventions to combat newly emerging and re-emerging diseases. Prophylactic vaccines against rabies, measles, etc., have excellent effectiveness in preventing viral infection and associated diseases. However, the host immune response is unable to inhibit virus replication or eradicate established diseases in most infected people. Therapeutic vaccines, expressing specific endogenous or exogenous antigens, mainly induce or boost cell-mediated immunity via provoking cytotoxic T cells or elicit humoral immunity via activating B cells to produce specific antibodies. The ultimate aim of a therapeutic vaccine is to reshape the host immunity for eradicating a disease and establishing lasting memory. Therefore, therapeutic vaccines have been developed for the treatment of some infectious diseases and chronic noncommunicable diseases. Various technological strategies have been implemented for the development of therapeutic vaccines, including molecular-based vaccines (peptide/protein, DNA and mRNA vaccines), vector-based vaccines (bacterial vector vaccines, viral vector vaccines and yeast-based vaccines) and cell-based vaccines (dendritic cell vaccines and genetically modified cell vaccines) as well as combinatorial approaches. This review mainly summarizes therapeutic vaccine-induced immunity and describes the development and status of multiple types of therapeutic vaccines against infectious diseases, such as those caused by HPV, HBV, HIV, HCV, and SARS-CoV-2, and chronic noncommunicable diseases, including cancer, hypertension, Alzheimer's disease, amyotrophic lateral sclerosis, diabetes, and dyslipidemia, that have been evaluated in recent preclinical and clinical studies.

Current progress in the development of prophylactic and therapeutic vaccines

Vaccines are essential public health tools and play an important role in reducing the burden of infectious diseases in the population. Emerging infectious diseases and outbreaks pose new challenges for vaccine development, requiring the rapid design and production of safe and effective vaccines against diseases with limited resources. Here, we focus on the development of vaccines in broad fields ranging from conventional prophylactic vaccines against infectious diseases to therapeutic vaccines against chronic diseases and cancer providing a comprehensive overview of recent advances in eight different vaccine forms (live attenuated vaccines, inactivated vaccines, polysaccharide and polysaccharide conjugate vaccines, recombinant subunit vaccines, virus-like particle and nanoparticle vaccines, polypeptide vaccines, DNA vaccines, and mRNA vaccines) and the therapeutic vaccines against five solid tumors (lung cancer breast cancer colorectal cancer liver cancer and gastric cancer), three infectious diseases (human immunodeficiency virus, hepatitis B virus and human papillomavirus-induced diseases) and three common chronic diseases (hypertension, diabetes mellitus and dyslipidemia). We aim to provide new insights into vaccine technologies, platforms, applications and understanding of potential next-generation preventive and therapeutic vaccine technologies paving the way for the vaccines design in the future.

A single-dose Qβ VLP vaccine against S100A9 protein reduces atherosclerosis in a preclinical model

The standard therapy for cardiovascular disease (CVD) is the administration of statins to reduce plasma cholesterol levels, but this requires lifelong treatment. We developed a CVD vaccine candidate that targets the pro-inflammatory mediator calprotectin by eliciting antibodies against the S100A9 protein. The vaccine, based on bacteriophage Qβ virus-like particles (VLPs) displaying S100A9 peptide epitopes, was formulated as a slow-release PLGA:VLP implant by hot-melt extrusion. The single-dose implant elicited S100A9-specific antibody titers comparable to a three-dose injection schedule with soluble VLPs. In an animal model of CVD (ApoE-/- mice fed on a high-fat diet), the implant reduced serum levels of calprotectin, IL-1β, IL-6 and MCP-1, resulting in less severe aortic lesions. This novel implant was therefore able to attenuate atherosclerosis over a sustained period and offers a novel and promising strategy to replace the repetitive administration of statins for the treatment of CVD.

The Multifaceted Biology of PCSK9

This article reviews the discovery of PCSK9, its structure-function characteristics, and its presently known and proposed novel biological functions. The major critical function of PCSK9 deduced from human and mouse studies, as well as cellular and structural analyses, is its role in increasing the levels of circulating low-density lipoprotein (LDL)-cholesterol (LDLc), via its ability to enhance the sorting and escort of the cell surface LDL receptor (LDLR) to lysosomes. This implicates the binding of the catalytic domain of PCSK9 to the EGF-A domain of the LDLR. This also requires the presence of the C-terminal Cys/His-rich domain, its binding to the secreted cytosolic cyclase associated protein 1, and possibly another membrane-bound "protein X". Curiously, in PCSK9-deficient mice, an alternative to the downregulation of the surface levels of the LDLR by PCSK9 is taking place in the liver of female mice in a 17β-estradiol-dependent manner by still an unknown mechanism. Recent studies have extended our understanding of the biological functions of PCSK9, namely its implication in septic shock, vascular inflammation, viral infections (Dengue; SARS-CoV-2) or immune checkpoint modulation in cancer via the regulation of the cell surface levels of the T-cell receptor and MHC-I, which govern the antitumoral activity of CD8+ T cells. Because PCSK9 inhibition may be advantageous in these processes, the availability of injectable safe PCSK9 inhibitors that reduces by 50% to 60% LDLc above the effect of statins is highly valuable. Indeed, injectable PCSK9 monoclonal antibody or small interfering RNA could be added to current immunotherapies in cancer/metastasis.

Targeted Strategy in Lipid-Lowering Therapy

Dyslipidemia is characterized by a diminished lipid profile, including increased level of total cholesterol and low-density lipoprotein cholesterol (LDL-c) and reduced level of high-density lipoprotein cholesterol (HDL-c). Lipid-lowering agents represent an efficient tool for the prevention or reduction of progression of atherosclerosis, coronary heart diseases and metabolic syndrome. Statins, ezetimibe, and recently proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are the most effective and used drugs in clinical lipid-lowering therapy. These drugs are mainly aimed to lower cholesterol levels by different mechanisms of actions. Statins, the agents of the first-line therapy—known as 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors—suppress the liver cholesterol synthesis. Ezetimibe as the second-line therapy can decrease cholesterol by inhibiting cholesterol absorption. Finally, the PCSK9 inhibitors act as an inducer of LDL excretion. In spite of their beneficial lipid-lowering properties, many patients suffer from their serious side effects, route of administration, or unsatisfactory physicochemical characteristics. Clinical demand for dose reduction and the improvement of bioavailability as well as pharmacodynamic and pharmacokinetic profile has resulted in the development of a new targeted therapy that includes nanoparticle carriers, emulsions or vaccination often associated with another more subtle form of administration. Targeted therapy aims to exert a more potent drug profile with lipid-lowering properties either alone or in mutual combination to potentiate their beneficial effects. This review describes the most effective lipid-lowering drugs, their favorable and adverse effects, as well as targeted therapy and alternative treatments to help reduce or prevent atherosclerotic processes and cardiovascular events.

Updated Understanding of the Crosstalk Between Glucose/Insulin and Cholesterol Metabolism

Glucose and cholesterol engage in almost all human physiological activities. As the primary energy substance, glucose can be assimilated and converted into diverse essential substances, including cholesterol. Cholesterol is mainly derived from de novo biosynthesis and the intestinal absorption of diets. It is evidenced that glucose/insulin promotes cholesterol biosynthesis and uptake, which have been targeted by several drugs for lipid-lowering, e.g., bempedoic acid, statins, ezetimibe, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. Inversely, these lipid-lowering drugs may also interfere with glucose metabolism. This review would briefly summarize the mechanisms of glucose/insulin-stimulated cholesterol biosynthesis and uptake, and discuss the effect and mechanisms of lipid-lowering drugs and genetic mutations on glucose homeostasis, aiming to help better understand the intricate relationship between glucose and cholesterol metabolism.

Insight into the Evolving Role of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is the last discovered member of the family of proprotein convertases (PCs), mainly synthetized in hepatic cells. This serine protease plays a pivotal role in the reduction of the number of low-density lipoprotein receptors (LDLRs) on the surface of hepatocytes, which leads to an increase in the level of cholesterol in the blood. This mechanism and the fact that gain of function (GOF) mutations in PCSK9 are responsible for causing familial hypercholesterolemia whereas loss-of-function (LOF) mutations are associated with hypocholesterolemia, prompted the invention of drugs that block PCSK9 action. The high efficiency of PCSK9 inhibitors (e.g., alirocumab, evolocumab) in decreasing cardiovascular risk, pleiotropic effects of other lipid-lowering drugs (e.g., statins) and the multifunctional character of other proprotein convertases, were the cause for proceeding studies on functions of PCSK9 beyond cholesterol metabolism. In this article, we summarize the current knowledge on the roles that PCSK9 plays in different tissues and perspectives for its clinical use.

Identification of dominant conformational epitopes from the whole structure of the proprotein convertase subtilisin/kexin type 9

Proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of LDLR, has emerged as an important target for the treatment of hypercholesterolemic cardiovascular disease, and monoclonal antibodies alirocumab and evolocumab against it have been widely used in clinical practice. The vaccine research of PCSK9 is considered a promising option for the long-term treatment and prevention of cardiovascular disease, but progress has been slow. The selection of safe and effective epitopes is one of the key steps in vaccine development. In this study, we designed a phage display library of cascaded peptides for affinity screening with two antibody drugs, and found that the two peptides PC3 and PS6, which are adjacent to each other in protein spatial structure, both have superior binding activity to the screening antibodies. We performed in vitro recombination design on the dominant sequences, and obtained recombinant sequences that can respond to the dominant conformational epitope of PCSK9, which provides a meaningful reference for epitope selection in subsequent PCSK9 vaccine development.

Cholesterol Lowering Biotechnological Strategies: From Monoclonal Antibodies to Antisense Therapies. A Pre-Clinical Perspective Review

In recent years, the increase in available genetic information and a better understanding of the genetic bases of dyslipidemias has led to the identification of potential new avenues for therapies. Additionally, the development of new technologies has presented the key for developing novel therapeutic strategies targeting not only proteins (e.g., the monoclonal antibodies and vaccines) but also the transcripts (from antisense oligonucleotides (ASOs) to small interfering RNAs) or the genomic sequence (gene therapies). These pharmacological advances have led to successful therapeutic improvements, particularly in the cardiovascular arena because we are now able to treat rare, genetically driven, and previously untreatable conditions (e.g, familial hypertriglyceridemia or hyperchylomicronemia). In this review, the pre-clinical pharmacological development of the major biotechnological cholesterol lowering advances were discussed, describing facts, gaps, potential future steps forward, and therapeutic opportunities.

PCSK9 inhibition-based therapeutic approaches: an immunotherapy perspective

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors (PCSK9-I) are novel therapeutic tools to decrease cardiovascular risk. These agents work by lowering the low-density lipoprotein cholesterol (LDL-C) in hypercholesterolemic patients who are statin resistant/intolerant. Current clinically approved and investigational PCSK9-I act generally by blocking PCSK9 activity in the plasma or suppressing its expression or secretion by hepatocytes. The most widely investigated method is the disruption of PCSK9/LDL receptor (LDLR) interaction by fully-humanized monoclonal antibodies (mAbs), evolocumab and alirocumab, which have been approved for the therapy of hypercholesterolemia and atherosclerotic cardiovascular disease (CVD). Besides, a small interfering RNA called inclisiran, which specifically suppresses PCSK9 expression in hepatocytes, is as effective as mAbs but with administration twice a year. Because of the high costs of such therapeutic approaches, several other PCSK9-I have been surveyed, including peptide-based anti-PCSK9 vaccines and small oral anti-PCSK9 molecules, which are under investigation in preclinical and phase I clinical studies. Interestingly, anti-PCSK9 vaccination has been found to serve as a more widely feasible and more cost-effective therapeutic tool over mAb PCSK9-I for managing hypercholesterolemia. The present review will discuss LDL-lowering and cardioprotective effects of PCSK9-I, mainly immunotherapy-based inhibitors including mAbs and vaccines, in preclinical and clinical studies.

Optimizing the synthesis and purification of MS2 virus like particles

Introducing bacteriophage MS2 virus-like particles (VLPs) as gene and drug delivery tools increases the demand for optimizing their production and purification procedure. PEG precipitation method is used efficiently to purify VLPs, while the effects of pH and different electrolytes on the stability, size, and homogeneity of purified MS2 VLPs, and the encapsulated RNA sequences remained to be elucidated. In this regard, a vector, capable of producing VLP with an shRNA packed inside was prepared. The resulting VLPs in different buffers/solutions were assessed for their size, polydispersity index, and ability to protect the enclosed shRNA. We report that among Tris, HEPES, and PBS, with or without NaNO3, and also NaNO3 alone in different pH and ionic concentrations, the 100 mM NaNO3-Tris buffer with pH:8 can be used as a new and optimal MS2 VLP production buffer, capable of inhibiting the VLPs aggregation. These VLPs show a size range of 27-30 nm and suitable homogeneity with minimum 12-month stability at 4 °C. Moreover, the resulting MS2 VLPs were highly efficient and stable for at least 48 h in conditions similar to in vivo. These features of MS2 VLPs produced in the newly introduced buffer make them an appropriate candidate for therapeutic agents' delivery.

Trivalent Subunit Vaccine Candidates for COVID-19 and Their Delivery Devices

The COVID-19 pandemic highlights the need for platform technologies enabling rapid development of vaccines for emerging viral diseases. The current vaccines target the SARS-CoV-2 spike (S) protein and thus far have shown tremendous efficacy. However, the need for cold-chain distribution, a prime-boost administration schedule, and the emergence of variants of concern (VOCs) call for diligence in novel SARS-CoV-2 vaccine approaches. We studied 13 peptide epitopes from SARS-CoV-2 and identified three neutralizing epitopes that are highly conserved among the VOCs. Monovalent and trivalent COVID-19 vaccine candidates were formulated by chemical conjugation of the peptide epitopes to cowpea mosaic virus (CPMV) nanoparticles and virus-like particles (VLPs) derived from bacteriophage Qβ. Efficacy of this approach was validated first using soluble vaccine candidates as solo or trivalent mixtures and subcutaneous prime-boost injection. The high thermal stability of our vaccine candidates allowed for formulation into single-dose injectable slow-release polymer implants, manufactured by melt extrusion, as well as microneedle (MN) patches, obtained through casting into micromolds, for prime-boost self-administration. Immunization of mice yielded high titers of antibodies against the target epitope and S protein, and data confirms that antibodies block receptor binding and neutralize SARS-CoV and SARS-CoV-2 against infection of human cells. We present a nanotechnology vaccine platform that is stable outside the cold-chain and can be formulated into delivery devices enabling single administration or self-administration. CPMV or Qβ VLPs could be stockpiled, and epitopes exchanged to target new mutants or emergent diseases as the need arises.

A single-dose, implant-based, trivalent virus-like particle vaccine against "cholesterol checkpoint" proteins

Cardiovascular disease is the number one cause of death globally. Lowering cholesterol levels in plasma is the mainstay therapy; however lifelong treatment and adverse effects call for improved therapeutic interventions. We developed a trivalent vaccine candidate targeting proprotein convertase subtilisin/kexin-9 (PCSK9), apolipoprotein B (ApoB), and cholesteryl ester transfer protein (CETP). Vaccine candidates were developed using bacteriophage Qβ-based virus-like particles (VLPs) displaying antigens of PCKS9, ApoB, and CETP, respectively. Vaccine candidate mixtures were formulated as slow-release PLGA:VLP implants using hot-melt extrusion. The delivery of the trivalent vaccine candidate via the implant produced antibodies against the cholesterol checkpoint proteins at levels comparable to a three-dose injection schedule with soluble mixtures. The reduction in PCSK9 and ApoB levels in plasma, inhibition of CETP (in vitro), and total plasma cholesterol decrease was achieved. All-together, we present a platform technology for a single-dose multi-target vaccination platform targeting cholesterol checkpoint proteins.

Pre-Clinical Evaluation of the Nanoliposomal antiPCSK9 Vaccine in Healthy Non-Human Primates

BACKGROUND

Our previous studies showed the safe preventive and therapeutic effects of immunization using the nanoliposomal antiPCSK9 vaccine called "Liposomal Immunogenic Fused PCSK9-Tetanus plus Alum adjuvant" (L-IFPTA), in mouse models of atherosclerosis. Here we aimed to ascertain the immunogenicity and safety of the L-IFPTA vaccine in a pre-clinical study in healthy non-human primates.

METHODS

Five male rhesus macaque monkeys were subcutaneously immunized with the L-IFPTA vaccine, four times with bi-weekly intervals. To evaluate immunogenicity, the plasma antiPCSK9 antibody in immunized monkeys was detected and quantified using the ELISA method. The functionality of the induced antiPCSK9 antibodies was determined by the PCSK9/LDLR in vitro binding assay kit. The safety of the vaccine was tested using the evaluation of several major circulating indicators including plasma lipid alterations, inflammatory biomarkers and organ injury biomarkers.

RESULTS

The resultant data indicated that the L-IFPTA vaccine significantly and highly induced the generation of functional and safe antiPCSK9 antibodies in immunized monkeys. Plasma levels of specific biomarkers indicating organ performance including creatinine, urea, uric acid, bilirubin, ALP, AS, ALT and TSH were not significantly altered. After immunization in healthy monkeys, non-prespecified endpoints (plasma levels of TC, LDL-C, VLDL-C and TG) were non-significantly reduced by 11.6 ± 36%; 16 ± 28%; 22 ± 53% and 24 ± 51%, respectively, while HDL-C was slightly increased by 2 ± 64%. There were also no significant changes in plasma levels of pro- and anti-inflammatory biomarkers.

CONCLUSION

The L-IFPTA vaccine could efficiently stimulate the host humoral immune response to produce active antibodies that inhibit plasma PCSK9 while not provoking systemic inflammation and not adversely affecting organ performance.

The emerging landscape of peptide-based inhibitors of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a clinically validated target for treating cardiovascular disease (CVD) due to its involvement in cholesterol metabolism. Although approved monoclonal antibodies (alirocumab and evolocumab) that inhibit PCSK9 function are very effective in lowering cholesterol, their limitations, including high treatment costs, have so far prohibited widespread use. Accordingly, there is great interest in alternative drug modalities to antibodies. Like antibodies, peptides are valuable therapeutics due to their high target potency and specificity. Furthermore, being smaller than antibodies means they have access to more drug administration options, are less likely to induce adverse immunogenic responses, and are better suited to affordable production. This review surveys the current peptide-based landscape aimed towards PCSK9 inhibition, covering pre-clinical to patented drug candidates and comparing them to current cholesterol lowering therapeutics. Classes of peptides reported to be inhibitors include nature-inspired disulfide-rich peptides, combinatorially derived cyclic peptides, and peptidomimetics. Their functional activities have been validated in biophysical and cellular assays, and in some cases pre-clinical mouse models. Recent efforts report peptides with potent sub-nanomolar binding affinities to PCSK9, which highlights their potential to achieve antibody-like potency. Studies are beginning to address pharmacokinetic properties of PCSK9-targeting peptides in more detail. We conclude by highlighting opportunities to investigate their biological effects in pre-clinical models of cardiovascular disease. The anticipation concerning the PCSK9-targeting peptide landscape is accelerating and it seems likely that a peptide-based therapeutic for treating PCSK9-mediated hypercholesterolemia may be clinically available in the near future.

Increased Valency Improves Inhibitory Activity of Peptides Targeting Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9)

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a clinically validated target for treating hypercholesterolemia. Peptide-based PCSK9 inhibitors have attracted pharmaceutical interest, but the effect of multivalency on bioactivity is poorly understood. Here we designed bivalent and tetravalent dendrimers, decorated with the PCSK9 inhibitory peptides Pep2-8[RRG] or P9-38, to study relationships between peptide binding affinity, peptide valency, and PCSK9 inhibition. Increased valency resulted in improved PCSK9 inhibition for both peptides, with activity improvements of up to 100-fold achieved for the P9-38-decorated dendrimers compared to monomeric P9-38 in in vitro competition binding assays. Furthermore, the P9-38-decorated dendrimers showed improved potency at restoring functional low-density lipoprotein (LDL) receptor levels and internalizing LDL in the presence of PCSK9, demonstrating significant cell-based activity at picomolar concentrations. This study demonstrates the potential of increasing valency as a strategy for increasing the efficacy of peptide-based PCSK9 therapeutics.

The role of proteomics in defining autoimmunity

INTRODUCTION

Proteomics, i.e. the study of the set of proteins produced in a cell, tissue, organism, or biological entity, has made possible analyses and contextual comparisons of proteomes/proteins and biological functions among the most disparate entities, from viruses to the human being. In this way, proteomic scrutiny of tumor-associated proteins, autoantigens, and pathogen antigens offers the tools for fighting cancer, autoimmunity, and infections.

AREAS COVERED

Comparative proteomics and immunoproteomics, the new scientific disciplines generated by proteomics, are the main themes of the present review that describes how comparative analyses of pathogen and human proteomes led to re-modulate the molecular mimicry concept of the pre-proteomic era. I.e. before proteomics, molecular mimicry - the sharing of peptide sequences between two biological entities - was considered as intrinsically endowed with immunologic properties and was related to cross-reactivity. Proteomics allowed to redefine such an assumption using physicochemical parameters according to which frequency and hydrophobicity preferentially confer an immunologic potential to shared peptide sequences.

EXPERT OPINION

Proteomics is outlining peptide platforms to be used for the diagnostics and management of human diseases. A Molecular Medicine targeted to obtain healing without paying the price for adverse events is on the horizon. The next step is to take up the challenge and operate the paradigm shift that the current proteomic era requires.

Pleiotropic Effects of PCSK-9 Inhibitors

Proprotein convertase subtilisin/kexin type 9 (PCSK-9) inhibitors are a group of drugs whose main mechanism of action is binding to the PCSK-9 molecule, which reduces the degradation of the low-density lipoprotein receptor (LDL-R) and, hence, increases the uptake of low-density lipoprotein cholesterol (LDLc) from the bloodstream as well as reducing its concentration. The effectiveness of three monoclonal antibodies, namely, alirocumab (human IgG1/κ monoclonal antibody, genetically engineered in Chinese hamster ovary cells), evolocumab (the first fully human monoclonal antibody), and bococizumab (humanized mouse antibody), in inhibiting the action of PCSK-9 and reducing LDLc levels has been confirmed. The first two, after clinical trials, were approved by the Food and Drug Administration (FDA) and are used primarily in the treatment of autosomal familial hypercholesterolemia and in cases of statin intolerance. They are currently used both as monotherapy and in combination with statins and ezetimibe to intensify therapy and achieve therapeutic goals following the American Heart Association (AHA) and European Society of Cardiology (ESC) guidelines. However, the lipid-lowering effect is not the only effect of action described by researchers that PCSK-9 inhibitors have. This paper is a review of the literature describing the pleiotropic effects of PCSK-9 inhibitors, which belong to a group of drugs that are being increasingly used, especially when standard lipid-lowering therapy fails. The article focuses on activities other than lipid-lowering, such as the anti-atherosclerotic effect and stabilization of atherosclerotic plaque, the anti-aggregation effect, the anticoagulant effect, the antineoplastic effect, and the ability to influence the course of bacterial infections. In this publication, we try to systematically review the current scientific data, both from our own scientific work and knowledge from international publications.

Impact of PCSK9 Immunization on Glycemic Indices in Diabetic Rats

METHODS

To prepare the anti-PCSK9 vaccine, a peptide construct called Immunogenic Fused PCSK9-Tetanus (IFPT) was linked to the surface of nanoliposome carriers. Healthy rats received four subcutaneous injections of the vaccine at biweekly intervals. Two weeks after the last vaccination, anti-PCSK9 antibody titers, PCSK9 targeting, and inhibition of PCSK9-low-density lipoprotein receptor (LDLR) interaction were evaluated. After verification of antibody generation, the immunized rats were intraperitoneally treated with a single dose (45 mg/kg) of streptozotocin (STZ) to induce diabetes mellitus. The levels of fasting blood glucose (FBG) were measured, and the oral glucose tolerance test (OGTT) as well as the insulin tolerance test (ITT) were carried out to assess glycemic status. At the end of the study, the total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglyceride, and high-density lipoprotein cholesterol concentrations were assayed. Histopathology examination of the liver and pancreas was also performed using the hematoxylin-eosin staining method.

RESULTS

The prepared nanoliposomal vaccine could strongly induce anti-PCSK9 antibodies in the vaccinated rats. Within one week following the STZ injection, the FBG level was lower in the vaccinated group vs. diabetic control group (49% (-171.7 ± 35 mg/dL, p < 0.001)). In the OGTT, the injected rats showed improved glucose tolerance as reflected by the reduction of blood glucose levels over 180 min, compared with the diabetic controls. Moreover, the ITT demonstrated that, after the insulin injection, blood glucose concentration declined by 49.3% in the vaccinated group vs. diabetic control group. Expectedly, the vaccinated rats exhibited lower (-26.65%, p = 0.03) plasma LDL-C levels compared with the diabetic controls. Histopathology examination of pancreas tissue demonstrated that the pancreatic islets of the vaccinated rats had a slight decline in the population of β-cells and few α-cells. Normal liver histology was also observed in the vaccinated rats.

CONCLUSION

PCSK9 inhibition through the liposomal IFPT vaccine can improve the glucose and insulin tolerance impairments as well as the lipid profile in diabetes.

PCSK9 immunization using nanoliposomes: preventive efficacy against hypercholesterolemia and atherosclerosis

INTRODUCTION

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.

RESULTS

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.

CONCLUSIONS

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.

Future Directions of Therapeutic Vaccines for Chronic Diseases

Vaccines are well-known therapies for infectious disease and cancer; however, recently, we and others have developed vaccines for other chronic diseases, such as hypertension, diabetes and dyslipidemia. Although we have many treatment options for hypertension, including angiotensin II type 1 receptor blockers, calcium-channel blockers, and diuretics, a substantial portion of the hypertensive population has uncontrolled blood pressure due to poor medication adherence. When these vaccines are established in the future as therapeutic options for chronic diseases, their administration regimen, such as several times per year, will replace daily medication use. Thus, therapeutic vaccines might be a novel option to control the progression of cardiovascular diseases. Importantly, regarding the development of vaccines against self-antigens (i.e., angiotensin II), the vaccine should efficiently induce a blocking antibody response against the self-antigen without provoking cytotoxic T cells. Therefore, to address the safety and efficiency of therapeutic vaccines, we have developed an original B-cell vaccine to induce antibody production and used carrier proteins, which include exogenous T-cell epitopes through the major histocompatibility complex. In this review, we will introduce the challenges in developing therapeutic vaccines for chronic diseases and describe the therapeutic potential for cardiovascular diseases.

Proprotein convertase subtilisin/kexin type 9 inhibition in cardiovascular disease: current status and future perspectives

Proprotein convertase subtilisin/kexin type 9 (PCSK9) targets the degradation of low-density lipoprotein (LDL) receptors; it has been proved that its inhibition improves cardiovascular outcomes in patients with established atherosclerotic cardiovascular disease (ASCVD). Herein, we review the current status of PCSK9 inhibitors in clinical practice and the future scope of PCSK9 inhibition. The results of two recent large clinical trials reveal that two PCSK9 monoclonal antibodies evolocumab and alirocumab reduce the risk of a cardiovascular event on top of background statin therapy in patients with stable ASCVD and those with recent acute coronary syndrome, respectively. However, there are several ongoing concerns regarding the efficacy in reducing mortality, cost-effectiveness, and long-term safety of extremely low LDL cholesterol levels with PCSK9 inhibition. The results of ongoing cardiovascular outcomes trials with PCSK9 monoclonal antibodies for primary prevention and with small interfering RNA to PCSK9 for secondary prevention may help to shape the use of this new therapeutic class.

PCSK9Qβ-003 Vaccine Attenuates Atherosclerosis in Apolipoprotein E-Deficient Mice

PURPOSE

Our group has developed a therapeutic vaccine targeting proprotein convertase subtilisin/kexin type 9 (PCSK9), named PCSK9Qβ-003. In this study, we investigated the potential effectiveness of the PCSK9Qβ-003 vaccine on atherosclerosis.

METHODS

Male ApoE^-/- mice were randomly assigned to three groups: a phosphate-buffered saline (PBS) group, Qβ virus-like particles (VLP) group, and PCSK9Qβ-003 vaccine group. Mice in the PCSK9Qβ-003 group were injected with the PCSK9Qβ-003 vaccine four times (100 μg/time) over a period of 18 weeks. The effects of the vaccine on atherosclerotic plaque, cholesterol transport, inflammation and apoptosis were investigated.

RESULTS

The PCSK9Qβ-003 vaccine obviously decreased total cholesterol and low-density lipoprotein cholesterol in ApoE^-/- mice. Compared with the other groups, the PCSK9Qβ-003 vaccine significantly reduced the lesion area and promoted the stability of atherosclerotic plaque. The vaccine regulated cholesterol transport in the aorta of ApoE^-/- mice by up-regulating the expression level of liver X receptor α and ATP binding cassette transporter A1. Additionally, macrophage infiltration and expression of monocyte chemoattractant protein-1 and tumor necrosis factor-α were significantly decreased in the mice administered the PCSK9Qβ-003 vaccine. The vaccine also markedly reduced apoptosis in the lesion area of the aorta in ApoE^-/- mice.

CONCLUSIONS

The results demonstrated that the PCSK9Qβ-003 vaccine attenuated the progression of atherosclerosis by modulating reverse cholesterol transport and inhibiting inflammation infiltration and apoptosis, which may provide a novel therapeutic approach for atherosclerosis and greatly improve treatment compliance among patients.

New Pharmacological Approaches to Target PCSK9

PURPOSE OF REVIEW

Proprotein convertase subtilisin kexin 9 (PCSK9) plays a crucial role in regulating circulating levels of LDL-C as a consequence of its ability to inhibit LDL receptor recycling in the liver. Loss of function variants in the PCSK9 gene result in low LDL-C levels and associate with reduced cardiovascular risk, whereas gain of-function variants associate with hypercholesterolemia and increased risk of early cardiovascular events. Thus, PCSK9 inhibition has been established as an additional approach for the treatment of hypercholesterolemia. The aim of this review is to provide a brief overview of current strategies targeting PCSK9 and discuss clinical results of the emerging approaches.

RECENT FINDINGS

Two monoclonal antibodies targeting circulating PCSK9 (evolocumab and alirocumab) have been approved for the treatment of hypercholesterolemia and cardiovascular disease. Later, a gene silencing approach (inclisiran), which inhibits hepatic PCSK9 synthesis, was shown to be as effective as monoclonal antibodies but with a twice a year injection and is currently under evaluation for approval. Due to the elevated costs of such therapies, several other approaches have been explored, including peptide-based anti PCSK9 vaccination, and small oral PCSK9 inhibitors, which are still in preclinical phase. In the coming years, we will assist to a progressive introduction of novel anti-PCSK9 approaches in the clinical practice for the treatment of patients with hypercholesterolemia as well as patients at high cardiovascular risk.

Immunotherapy of Endothelin-1 Receptor Type A for Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a chronic fatal disease. The treatment of PAH is less than ideal and the control is far from satisfactory worldwide. Vaccination provides a promising approach for treatment of PAH.

OBJECTIVES

This study sought to find a vaccine against endothelin-1 (ET-1) receptor type A (ETAR) for treating PAH.

METHODS

The ETRQβ-002 vaccine was screened and the specific antibodies against epitope ETR-002 belonging to the second extracellular loop of ETAR (including the polyclonal and monoclonal antibody) were produced. The effect of the antibodies on Ca²⁺-dependent signal transduction events was investigated. In vivo, ETRQβ-002 vaccine was used to vaccinate monocrotaline (MCT)- and Sugen/hypoxia-induced pulmonary hypertension animals. The monoclonal antibody (mAb) against ETR-002 was also injected into the PAH animals. The effect of ETRQβ-002 vaccine on pulmonary hypertension and remodeling of pulmonary arterioles and right ventricle (RV) was carefully evaluated. Further, the possible immune-mediated damage was detected in normal vaccinated animals.

RESULTS

ETR-002 peptide has perfect immunogenicity and ETRQβ-002 vaccine could induce strong antibody production. In vitro, the anti-ETR-002 antibody bound to ETAR and inhibited Ca²⁺-dependent signal transduction events, including extracellular signal-regulated kinase phosphorylation and elevation of intracellular Ca²⁺ concentration induced by ET-1. In vivo, both ETRQβ-002 vaccine and the mAb significantly decreased the RV systolic pressure up to 20 mm Hg and 10 mm Hg in MCT-exposed rats and Sugen/hypoxia-exposed mice, respectively. Also, ETRQβ-002 vaccine/mAb obviously ameliorated pathological remodeling of pulmonary arterioles and hypertrophy of the RV in PAH animals. Additionally, no significant immune-mediated damage was detected in vaccinated animals.

CONCLUSIONS

ETRQβ-002 vaccine/mAb attenuated remodeling of pulmonary arterioles and RV in MCT- and Sugen/hypoxia-induced PAH animals and decreased RV systolic pressure effectively through diminishing the pressure response and inhibiting signal transduction initiated by ET-1. ETRQβ-002 vaccine/mAb may provide a novel and promising method for PAH treatment.

Novel strategies to target proprotein convertase subtilisin kexin 9: beyond monoclonal antibodies

Since the discovery of the role of proprotein convertase subtilisin kexin 9 (PCSK9) in the regulation of low-density lipoprotein cholesterol (LDL-C) in 2003, a paradigm shift in the treatment of hypercholesterolaemia has occurred. The PCSK9 secreted into the circulation is a major downregulator of the low-density lipoprotein receptor (LDLR) protein, as it chaperones it to endosomes/lysosomes for degradation. Humans with loss-of-function of PCSK9 exhibit exceedingly low levels of LDL-C and are protected from atherosclerosis. As a consequence, innovative strategies to modulate the levels of PCSK9 have been developed. Since 2015 inhibitory monoclonal antibodies (evolocumab and alirocumab) are commercially available. When subcutaneously injected every 2-4 weeks, they trigger a ∼60% LDL-C lowering and a 15% reduction in the risk of cardiovascular events. Another promising approach consists of a liver-targetable specific PCSK9 siRNA which results in ∼50-60% LDL-C lowering that lasts up to 6 months (Phases II-III clinical trials). Other strategies under consideration include: (i) antibodies targeting the C-terminal domain of PCSK9, thereby inhibiting the trafficking of PCSK9-LDLR to lysosomes; (ii) small molecules that either prevent PCSK9 binding to the LDLR, its trafficking to lysosomes or its secretion from cells; (iii) complete silencing of PCSK9 by CRISPR-Cas9 strategies; (iv) PCSK9 vaccines that inhibit the activity of circulating PCSK9. Time will tell whether other strategies can be as potent and safe as monoclonal antibodies to lower LDL-C levels.

PCSK9 inhibitors: clinical evidence and implementation

The gene encoding PCSK9 was first identified and linked to the phenotype of familial hypercholesterolaemia approximately 15 years ago. Soon after, studies uncovered the role of PCSK9 in the regulation of LDL-receptor recycling and identified loss-of-function variants of PCSK9 that were associated with low circulating levels of LDL cholesterol (LDL-C) and a reduced risk of coronary artery disease. With amazing rapidity, monoclonal antibodies against PCSK9 were developed and studied in large clinical programmes. These PCSK9 inhibitors lowered plasma LDL-C levels by approximately 60%, even in patients already receiving maximum-dose statin therapy. In the past year, three cardiovascular outcome trials were completed and showed that PCSK9 inhibitors significantly reduce the risk of major vascular events. Reassuringly, this benefit comes with no major offsetting adverse events, such as an excess of myalgias, elevation of hepatic aminotransferases levels in the plasma, incident diabetes mellitus or neurocognitive adverse events. The clinical benefit of PCSK9 inhibitors seen in these trials occurred in the setting of reducing LDL-C levels to unprecedentedly low levels, suggesting that more aggressive LDL-C targets should be adopted. New technologies to inhibit PCSK9 are now being harnessed and might further revolutionize our treatment of dyslipidaemia.

Vaccine Against PCSK9 Improved Renal Fibrosis by Regulating Fatty Acid β-Oxidation

Background

Defects in the renal fatty acid β‐oxidation pathway have been implicated in the development of renal fibrosis. Our group has developed a therapeutic vaccine targeting PCSK9 (proprotein convertase subtilisin/kexin type 9), named PCSK9Qβ‐003. In this study, we investigated the potential effectiveness of the PCSK9Qβ‐003 vaccine on hypercholesterolemia with renal fibrosis.

Methods and Results

The low‐density lipoprotein receptor^+/− male mice fed with a high‐cholesterol (1%) Western diet were randomly assigned into 4 groups: the sham group (or the control group), the phosphate‐buffered saline group, the Qβ virus‐like particles group and the PCSK9Qβ‐003 vaccine group. Mice of the PCSK9Qβ‐003 group were injected with the PCSK9Qβ‐003 vaccine (100 μg/time) every 2 or 4 weeks. The mice were administered with either unilateral ureteral obstruction for 2 weeks or N‐nitro‐l‐arginine methyl ester (50 mg/kg per day) for 6 weeks to establish a renal fibrosis model. Compared with the other 3 groups, the PCSK9Qβ‐003 vaccine obviously decreased total cholesterol and low‐density lipoprotein cholesterol in low‐density lipoprotein receptor^+/− mice with hypercholesterolemia. Compared with the phosphate‐buffered saline and Qβ virus‐like particles groups, the PCSK9Qβ‐003 vaccine improved hepatic steatosis and renal function. Histology analysis showed that the PCSK9Qβ‐003 vaccine significantly ameliorated renal lipid accumulation and renal fibrosis. Moreover, the PCSK9Qβ‐003 vaccine obviously upregulated the expression of low‐density lipoprotein receptor, very‐low‐density lipoprotein receptor, sterol‐regulatory element binding protein 2, and fatty acid β‐oxidation–related factors, and ameliorated renal fibrosis‐related molecules both in the unilateral ureteral obstruction and N‐nitro‐l‐arginine methyl ester models.

Conclusions

This study suggested that the PCSK9Qβ‐003 vaccine improved renal lipid accumulation and renal fibrosis by regulating fatty acid β‐oxidation, which may provide a promising method for treating hypercholesterolemia with renal fibrosis.

Therapeutic effect of nanoliposomal PCSK9 vaccine in a mouse model of atherosclerosis

BACKGROUND

Proprotein convertase subtilisin/kexin 9 (PCSK9) is an important regulator of low-density lipoprotein receptor (LDLR) and plasma levels of LDL cholesterol (LDL-C). PCSK9 inhibition is an efficient therapeutic approach for the treatment of dyslipidemia. We tested the therapeutic effect of a PCSK9 vaccine on dyslipidemia and atherosclerosis.

METHODS

Lipid film hydration method was used to prepare negatively charged nanoliposomes as a vaccine delivery system. An immunogenic peptide called immunogenic fused PCSK9-tetanus (IFPT) was incorporated on the surface of nanoliposomes using DSPE-PEG-maleimide lipid (L-IFPT) and adsorbed to Alhydrogel® (L-IFPTA⁺). The prepared vaccine formulation (L-IFPTA⁺) and empty liposomes (negative control) were inoculated four times with bi-weekly intervals in C57BL/6 mice on the background of a severe atherogenic diet and poloxamer 407 (thrice weekly) injection. Antibody titers were evaluated 2 weeks after each vaccination and at the end of the study in vaccinated mice. Effects of anti-PCSK9 vaccination on plasma concentrations of PCSK9 and its interaction with LDLR were determined using ELISA. To evaluate the inflammatory response, interferon-gamma (IFN-γ)- and interleukin (IL)-10-producing splenic cells were assayed using ELISpot analysis.

RESULTS

L-IFPTA⁺ vaccine induced a high IgG antibody response against PCSK9 peptide in the vaccinated hypercholesterolemic mice. L-IFPTA⁺-induced antibodies specifically targeted PCSK9 and decreased its plasma consecration by up to 58.5% (- 164.7 ± 9.6 ng/mL, p = 0.0001) compared with the control. PCSK9-LDLR binding assay showed that generated antibodies could inhibit PCSK9-LDLR interaction. The L-IFPTA⁺ vaccine reduced total cholesterol, LDL-C, and VLDL-C by up to 44.7%, 51.7%, and 19.2%, respectively, after the fourth vaccination booster, compared with the control group at week 8. Long-term studies of vaccinated hypercholesterolemic mice revealed that the L-IFPTA⁺ vaccine was able to induce a long-lasting humoral immune response against PCSK9 peptide, which was paralleled by a significant decrease of LDL-C by up to 42% over 16 weeks post-prime immunization compared to control. Splenocytes isolated from the vaccinated group showed increased IL-10-producing cells and decreased IFN-γ-producing cells when compared with control and naive mice, suggesting the immune safety of the vaccine.

CONCLUSIONS

L-IFPTA⁺ vaccine could generate long-lasting, functional, and safe PCSK9-specific antibodies in C57BL/6 mice with severe atherosclerosis, which was accompanied by long-term therapeutic effect against hypercholesterolemia and atherosclerosis.

Vaccine Targeted Alpha 1D-Adrenergic Receptor for Hypertension

The α1-AR (α1 adrenergic receptor) blockers currently on the market cannot meet clinical needs because of low-selectivity for subtypes of α1-ARs, short half-life, and uncertain role in cardiovascular end point events. The study sought to find a vaccine specifically against α1D-AR (α1D-adrenergic receptor) for treating hypertension. A short peptide ADR-004 (cgiteeagy) belonging to α1D-AR was screened, and the ADRQβ-004 vaccine was produced and injected into spontaneously hypertensive rats model (including a short-term study, 10 weeks, and a long-term observation study, 39 weeks) and NG-nitro-l-arginine methyl ester + spontaneously hypertensive rats model (15 weeks). The antihypertensive effect and target organ protection of the ADRQβ-004 vaccine were carefully evaluated. The possible immune-mediated damage was detected in normal vaccinated Sprague Dawley rats. The ADR-004 peptide has perfect immunogenicity, and the ADRQβ-004 vaccine could induce strong antibody production. In the short-term study, the ADRQβ-004 vaccine averagely decreased the systolic blood pressure of spontaneously hypertensive rats up to 15 mm Hg and that of NG-nitro-l-arginine methyl ester+spontaneously hypertensive rats up to 29 mm Hg. In the long-term observation model, the antihypertensive effect of the ADRQβ-004 vaccine was quite stable, and the average decline of systolic blood pressure was 22 mm Hg. The ADRQβ-004 vaccine effectively prevented vascular structural remodeling, cardiac hypertrophy and fibrosis, and renal injury of hypertensive animals, superior to prazosin at renal level. Moreover, the ADRQβ-004 vaccine obviously downregulated the expression of α1D-AR, but not α1A-AR. Additionally, no significant immune-mediated damage was detected in immunized animals. The present results demonstrate that the ADRQβ-004 vaccine may provide a novel and promising method for the treatment of hypertension.

Future role of proprotein convertase subtilisin/kexin type 9 inhibitors in preventive cardiology

PURPOSE OF REVIEW

The use of therapeutic monoclonal antibodies to target proprotein convertase subtilisin/kexin type 9 (PCSK9) represents a novel approach to the management of hypercholesteremia and prevention of atherosclerotic cardiovascular disease. We review the most recent literature relevant to PCSK9 inhibition with emphasis on how recent results and ongoing trials have and will continue to shape the use of this new therapeutic class in preventive cardiology.

RECENT FINDINGS

PCSK9 inhibitors reduce plasma lipoprotein(a) concentrations but a mechanistic understanding remains elusive. Evaluation of evolocumab for use in patients without prior myocardial infarction or stroke is underway (NCT03872401). Concerns regarding the cost-effectiveness of PCSK9 inhibitors have continued to thwart access to these drugs, though innovative models of care delivery and price reductions have improved this situation. Inclisiran, a small interfering ribonucleic acid (siRNA), reduces translation of PCSK9 and demonstrates more durable reductions in low-density lipoprotein-cholesterol (LDL-C). It is currently evaluated in the context of a phase III cardiovascular outcome trial in patients with established vascular disease (NCT03705234).

SUMMARY

The current scope of PCSK9 inhibitor therapy in preventive cardiology is limited to patients with familial hypercholesterolemia and/or established atherosclerotic cardiovascular disease. Future cardiovascular outcome trial results with PCSK9 blocking antibodies in primary prevention and with siRNA to PCSK9 in secondary prevention, improved understanding of the drivers of lipoprotein(a) reduction with PCSK9 inhibition, and cost-effectiveness will determine the future role of this therapeutic class.

Keep recycling going: New approaches to reduce LDL-C

Hypercholesterolemia represents a leading cause in the development of atherosclerotic plaques, increasing the risk for ACVS. It actually counts as a major cause of cardiovascular disease etiopathogenesis. The causes of hypercholesterolemia are multifactorial, spanning from genetic constitution, age, sex, to sedentary lifestyle and diets rich in sugars and lipids. Although dietary restriction in saturated fats, increased exercise, and other modification in lifestyle represent a first-line approach to treat very initial stages in hypercholesterolemia, most patients will require the addition of pharmacological agents. Pharmacological approaches include inhibition of cholesterol synthesis, decreased fat absorption from the GI tract, and increased degradation of FA. These strategies present a series of side effects, low therapeutic efficiency in some patients, and reduced tolerability. One of the major goals in treatment for hypercholesterolemia is to decrease the levels of low density lipoproteins (LDL), while maintaining those of high density lipoproteins (HDL). LDL particles contain about 80% of lipids, most of it cholesterol and cholesteryl esters, and 20% of the ApoB-100 protein. LDL carries cholesterol to the tissues, to be incorporated to biological membranes, or to be transformed to steroids. Excess of LDL translates into increased levels of circulating cholesterol particles and accumulation in certain tissues, especially vascular tissue, initiating a fatty streak, which may evolve to an atheroma, causing a series of cardiovascular problems, including impaired circulation, high blood pressure, increased cardiac workload, and coronary artery disease. It is essential to prevent LDL accumulation into the bloodstream to avoid the formation of these fatty streaks and the initiation of a cascade that will lead to the development of atherosclerosis. In healthy individuals. Under physiological conditions, LDL is effectively removed from circulation through receptor-mediated endocytosis. LDL clearance involves binding to its receptor, LDLR, which enables the internalization of the LDL particle and drives its degradation in lysosomes. Once the LDL particle is degraded, the free receptor recycles to the plasma membrane, and captures new LDL particles. Adequate levels of LDLR are essential to remove the excess of cholesterol-laden LDL. Proprotein convertase, subtilysin kexin type 9 (PCSK-9), expressed in liver and intestine, binds to LDLR, and internalized. Once inside the cell, PCSK-9 catalyzes the proteolysis of LDLR, preventing its recycling to the cell surface, and effectively decreasing the number of LDLR, notoriously decreasing the ability to clear LDL from circulation. Levels of PCSK-9 varies with age, gender, and levels of insulin, glucose, and triglycerides. Loss-of-function mutations in PCSK-9 gene invariably translates into lower levels of LDL, and decreased risk of developing coronary artery disease. Conversely, increased activity or expression of this enzyme leads to hypercholesterolemia. Inhibition of PCSK9 has proven to be successful in decreasing LDL levels and risk of the development of hypercholesterolemia with its associated higher risk for ASCVD. Patient with gain-of-function mutations in the PCSK9 undoubtedly benefit from therapies based on PCSK-9 inhibitors. However, millions of patients show statin intolerance, or cannot be efficiently controlled by statins alone- the most prevalent therapy for hypeprcholesterolemia. This commentary will evaluate the possibilities, caveats and future directions in the treatment of hypercholesterolemia, and therapies with combination of drugs.