Overview

 

The Medical Need

The death rate from cardiovascular disease has declined by one third in the period of 1994–2004. This decline is the result of new pharmaceuticals, surgical practices, and medical devices being introduced.  In spite of these medical advances, cardiovascular disease still remains the number 1 killer, not only of Americans, but of people worldwide.  Coronary heart disease is the most prevalent form of atherosclerotic cardiovascular disease.  Other manifestations of atherosclerosis include carotid artery disease and peripheral artery occlusive disease. The American Heart Association estimates that more than 16 million Americans have some form of coronary heart disease and some 450,000 of these will die from their disease. Coronary heart disease is estimated to cost the US economy more than $200 billion in 2008.

 

 

The Product

CVX-210-H is a break-through treatment to ameliorate atherosclerosis through effecting changes in the bodies’ immune responses to the conditions which give rise to atherosclerosis, chiefly high blood levels of LDL cholesterol and its breakdown products.  CVX-210-H is comprised of peptide fragments of apoB-100 conjugated to recombinant human serum albumin and combined with aluminum hydroxide collide gel.

 

The current view on the role of autoimmunity in atherosclerosis suggests that immune responses against oxidized LDL and other plaque-associated antigens are on the whole protective.  However, when the immune system is challenged by prolonged, excessive cardiovascular risk factors, such as hypercholesterolemia, it mounts an aggressive pro-inflammatory response that promotes disease. 

 

Investigations into the mechanisms of action of the vaccine suggest that it affects a shift away from pro-inflammatory Th1 responses towards protective Th2 responses mediated by antibodies and regulatory T cells (see Figure 1).  Supporting evidence comes from experiments conducted in relevant animal models as well as from epidemiological observations.

 

 

Animal Experiments

1. Immunization with the vaccine inhibits the development of atherosclerosis
2. Immunization with the vaccine activates expression of peptide-specific and oxidized LDL-specific antibodies
3. Immunizations result in a change in IgG expression from IgG2a to IgG1 suggesting activation of a Th2 response.
4. Treatment of hypercholesterolemic mice with anti-apo B peptide antibodies inhibits the development of atherosclerosis

 

Epidemiological Observations

1. In patients, there is an inverse association between the level of antibodies and the severity of atherosclerosis as assessed by coronary angiography and carotid ultrasound
2. Patients who developed acute coronary events have lower levels of naturally occurring antibodies against p210 in plasma

The evidence supporting a role for activation of regulatory T cells in mediating the effect of the vaccine is based upon data from ongoing experiments conducted in relevant animal models.

 

 

Animal Experiments

1. Immunization with the vaccine increases the expression of CD4+/CD25+/Foxp3 regulatory cells in the spleen and in the circulation 
2. When vaccinated mice are given a blocking antibody against CD25 (a critical receptor on regulatory T cells) the mice become depleted of regulatory T cells and protection against atherosclerosis is neutralized
   
   

 

 

Recruitment and Activation of Immune Cells in Atherosclerotic Plaques

		Figure 1. (a) Low-density lipoprotein (LDL) diffuses from the blood into the innermost layer of the artery, where LDL particles can associate with proteoglycans of the extracellular matrix. The LDL of this extracellular pool is modified by enzymes and oxygen radicals to form molecules such as oxidized LDL (oxLDL). Biologically active lipids are released and induce endothelial cells to express leukocyte adhesion molecules, such as vascular cell-adhesion molecule 1 (VCAM1). Monocytes and T cells bind to VCAM1-expressing endothelial cells through very late antigen 4 (VLA4) and respond to locally produced chemokines by migrating into the arterial tissue.
		Figure 1. (b) Monocytes differentiate into macrophages in response to local macrophage colony-stimulating factor (M-CSF) and other stimuli. Expression of many pattern-recognition receptors increases, including scavenger receptors and Toll-like receptors (TLRs). Scavenger receptors mediate macrophage uptake of oxLDL particles, which leads to intracellular cholesterol accumulation and the formation of foam cells. TLRs bind lipopolysaccharide (LPS), heat-shock protein 60 (HSP60), oxLDL and other ligands, which instigates the production of many pro-inflammatory molecules by macrophages.
		Figure 1. (c) T cells undergo activation after interacting with antigen-presenting cells (APCs), such as macrophages or dendritic cells, both of which process and present local antigens including oxLDL. A T helper 1 (TH1)-cell-dominated response ensues, possibly owing to the local production of interleukin-12 (IL-12), IL-18 and other cytokines. Antigen presentation and TH1-cell differentiation might also occur in regional lymph nodes.
		Figure 1. (d) TH1 cells produce inflammatory cytokines including interferon-γ (IFNγ) and tumor-necrosis factor (TNF) and express CD40 ligand (CD40L). These messengers prompt macrophage activation, production of proteases and other pro-inflammatory mediators, activate endothelial cells, increase adhesion-molecule expression and the propensity for thrombus formation, and inhibit smooth-muscle-cell proliferation and collagen production.
		Figure 1. (e) Plaque inflammation might be attenuated in response to the anti-inflammatory cytokines IL-10 and transforming growth factor-β (TGFβ), which are produced by several cell types including regulatory T cells, macrophages, and for TGFβ, also vascular cells and platelets. TCR, T-cell receptor. (Hansson & Libby 2006)

Drs. Shah and Nilsson have proposed that antigen specific atheroprotective immunity can be achieved by administering a vaccine comprised of a peptide fragment of apo B-100 conjugated to a carrier molecule and formulated with an adjuvant.  They postulate that the vaccine reduces plaque inflammation and alters plaque composition, in part, by attenuating the pro-inflammatory actions of Th1 cells.  As a result of the presence of a specific immunogenic epitope T cells interacting with antigen presenting cells (depicted below) give rise to Th2 cells and regulatory T cells.

While all details of the mechanisms of action have yet to be elucidated, the groups of Drs. Shah and Nilsson have demonstrated that immunization with the vaccine does induce a shift from a Th1 to a Th2 specific antibody expression in apo E -/- mice.33  Similar results have been demonstrated in the Swiss Webster and C57/Black6 mouse strains (unpublished, data on file).

 

In animal models of human atherosclerosis, CVX-210-H has been shown to:

 

1. Change the composition of atherosclerotic lesions
2. Slow / stop the progression of atherosclerosis
3. Promote the regression of atherosclerosis.