Preliminary Communication

INHIBITION OF CHOLESTEROL ATHEROSCLEROSIS BY IMMUNISATION WITH BETA-LIPOPROTEIN

Atherosclerosis is a multifactorial disease influenced by genetics, lifestyle and environmental factors. Despite therapeutic advances that reduce the risk of cardiovascular events, atherosclerosis-related diseases remain the leading cause of mortality worldwide. Precise targeting of genes involved in lipoprotein metabolism is an emerging approach for atherosclerosis prevention and treatment. This article focuses on the latest developments, clinical potential and current challenges of monoclonal antibodies, vaccines and genome/transcriptome modification strategies, including antisense oligonucleotides, genome/base editing and gene therapy. Multiple lipid lowering biological therapies have already been approved by the FDA with impressive results to date, while many more promising targets are being pursued in clinical trials or pre-clinical animal models.

El reconocimiento de la aterogénesis como un proceso dinámico en vez de un depósito pasivo de colesterol ha subrayado la existencia de mecanismos inflamatorios claves. Así, la respuesta inmune, tanto innata como adaptativa, desempeña un papel importante en el inicio y la progresión de la aterosclerosis. Más recientemente, algunos estudios clínicos han sido diseñados para abordar el impacto de las estrategias de intervención antiinflamatoria en la reducción del riesgo de enfermedad cardiovascular más allá del control de los factores clásicos de riesgo. Por todo ello, revisamos en primer lugar la contribución fisiopatológica de la inflamación en la aterosclerosis y el efecto del tratamiento farmacológico hipolipidemiante en los marcadores de inflamación. A continuación, abordamos el efecto de los fármacos antiinflamatorios clásicos, de los tratamientos farmacológicos dirigidos a mediadores inflamatorios específicos y de las vacunas en la prevención cardiovascular.

The recognition of atherogenesis as an active process rather than a passive cholesterol storage disease has underlined key inflammatory mechanisms. Hence, innate and adaptive immune responses play an important role in the onset and progression of atherosclerosis. More recently, some clinical studies were designed to address the impact of anti-inflammatory intervention strategies in reducing risk of cardiovascular disease beyond the management of classic risk factors. Therefore, we review first the pathophysiological contribution of inflammation to atherosclerosis and the effect of lipid-lowering drugs on inflammatory biomarkers. Next, we address the effect of classic anti-inflammatory drugs, pharmacological therapies targeting specific inflammatory mediators and vaccines in cardiovascular prevention.

Modulation of the inflammatory response through vaccination has shown promise in animal models of atherogenesis and obesity—main risk factors for cardiovascular diseases. Tableted preparation, V-6, containing pooled antigens derived from pig adipose tissue was administered per os daily to 13 volunteers for 3 months. Total cholesterol and LDL levels have not changed from the baseline value; 193.4 vs 191.8 (p = 0.75) and 113.8 vs 117.2 (p = 0.18), respectively. Triglyceride levels declined by 26.1% from 163 to 120.5 mg/dL (p = 0.29). HDL increased by 25.9% from 38.6 to 48.5 mg/dL (p = 0.000002) in 12 out 13 patients. Despite negligible effect of V6 on weight and body mass index, i.e., 67.87 vs 66.58 kg (−1.9%; p = 0.46) and 26.25 vs 25.75 kg/m² (−1.9%; p = 0.35), statistically significant reduction in waist (−7.6%; p = 0.002), mid-arm (−3.3%; p = 0.049), and thigh (−7.6%; p = 0.0003) circumferences were observed. Blood pressure systolic and diastolic values were not affected, i.e., 115.6 vs 121 (p = 0.2) and 77.1 vs 83 (p = 0.55). No changes were observed in liver ALT and AST enzymes. Creatinine decreased; 0.877 vs 0.842 mg/dL (p = 0.02), while BUN has shown slight increase; 14.8 vs 16.1 mg/dL (p = 0.03) but within normal range. Fasting blood sugar levels were also within normal range, i.e., 94.8 vs 98.8 (p = 0.04). Complete blood cell analysis has not revealed any change except slight decrease in hemoglobin 13.25–13.19 g/dL (p = 0.0004), but its amount per red blood cell (MCH) increased from 25.62 up to 26.42 picograms/cell (p = 0.000003). The average red blood cell size (MCV) increased from 78.5 to 80.0 fl (p = 0.00009) but hemoglobin concentration relative to size of the cell (MCHC) has not changed (p = 0.2). Hematocrit and red blood cells count decreased slightly, but within normal range 40.7–40.2% (p = 0.02) and 5.22–5.05 × 10⁶ cells/mm³ (p = 0.002). The number of platelets moved upward, 2.471 vs 2.921 × 10⁵ per mm³ (p = 0.009). The white blood cells count and percent of leukocytes and neutrophils were not affected. Pro-inflammatory eosinophils declined from 4.0% down to 2.4% (p = 0.29). These results show that V6 is safe and holds a promise as an anti-atherogenic and overweight/obesity immune intervention.

The articles in this issue present a spectrum of information regarding the vaccine technologies and recent, new, and up and coming immunizations for protection against a variety of infectious diseases. The methodologies used for the production of these vaccines can and have been applied to much more unconventional targets. This article details immunizations being developed to prevent pregnancy, peptic ulcer, gastric carcinoma, cocaine abuse, and atherosclerosis.

Immunization of rabbits with a protein-free formulation consisting of liposomes containing 71% cholesterol and lipid A as an adjuvant induced anticholesterol antibodies that caused complement-dependent lysis of liposomes lacking lipid A. The antibodies, immunoglobulin G (IgG) and immunoglobulin M (IgM), also recognized nonoxidized crystalline cholesterol as an antigen by enzyme-linked immunosorbent assay (ELISA). The effects of immunization against cholesterol on elevations in serum cholesterol and development of atherosclerosis were examined in rabbits fed a diet containing 0.5% to 1.0% cholesterol. Although the mean serum cholesterol level, mainly in the form of very-low-density lipoprotein cholesterol, rose as much as 60-fold in the nonimmunized rabbits, the elevation was significantly less—as much as 35% lower—in the immunized rabbits. Elevation of serum cholesterol was accompanied by an apparent drop in the level of antibodies on initiating the diet, followed by a rebound on stopping the diet, thus suggesting that the antibodies were adsorbed to cholesterol that was present in circulating lipoproteins. When lipoprotein fractions—composed of either very-low-density and intermediate-density lipoproteins derived from cholesterol-fed nonimmunized rabbits or human low-density lipoproteins—were tested as capture antigens by solid-phase ELISA, reactivity was observed with IgG and IgM antibodies present in the serum of immunized rabbits. Immunization also resulted in a marked decrease in the risk of developing atherosclerosis. Analysis of aortic atherosclerosis by quantitative histologic examination and fatty streaks by automated morphometric probability-of-occurrence mapping showed diminished atherosclerosis in most areas of the aorta in vaccine recipients. It is proposed that immunization with liposomes containing 71% cholesterol and lipid A can reduce diet-induced hypercholesterolemia and atherosclerosis.