• Vaccine Ontology ID: VO_0004275
• Type: Subunit vaccine
• Status: Research
• Antigen: Peptide-2, a peptide taken from the sequence of human apo B-100, with an amino acid sequence of ATRFKHLRKYTYNYEAESSS (Chyu et al., 2005).
• Adjuvant:
  • VO ID: VO_0000884
  • Description: Alum
• Preparation: Peptide antigen was prepared using Imject SuperCarrier EDC kit (Pierce, Rockford, IL) according to manufacturer’s instruction with minor modification. One milligram peptide in 500 μl conjugation buffer was mixed with 2 mg carrier in 200 μl deionized water. This mixture was then incubated with 1 mg conjugation reagent (EDC, 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide HCl) at room temperature for 2 h followed by dialysis against 0.083 M sodium phosphate, 0.9 M sodium chloride, pH 7.2, solution overnight at 4 °C. The dialyzed conjugate was diluted with Imject dry blend purification buffer to a final volume of 1.5 ml. Alum was used as immunoadjuvant and mixed with peptide conjugate with 1:1 dilution in volume. The amount of peptide in each immunization was 33 μg/100 μl per injection (Chyu et al., 2005).
• Immunization Route: subcutaneous injection

Mouse Response

• Host Strain: male apo E (−/−) mice
• Vaccination Protocol: Peptide immunization For early immunization study, male apo E (−/−) mice, maintained on normal chow diet, received subcutaneous primary immunization with peptide-1 (n = 10), peptide-2 (n = 10) or alum alone (n = 9) at 6–7 weeks of age, followed by an intra-peritoneal booster 3 weeks later. Two weeks after booster, diet was switched to high cholesterol chow (0.15% cholesterol, 21% fat, TD 88137, Harlan-Teklad) and continued until sacrifice at the age of 25 weeks. Blood samples were collected by retro-orbital bleeding 2 weeks after booster and at the time of sacrifice. For late immunization study, male apo E (−/−) mice were kept on high cholesterol diet since 6–7 weeks of age. Since peptide-1 immunization did not reduce atherosclerosis (see Result below), peptide-1 was omitted in this part of the study. At 16 weeks of age, mice received subcutaneous primary immunization with peptide-2 or alum alone, followed by an intra-peritoneal booster 3 weeks later. Mice were sacrificed at age of 30 weeks. A separate group of mice were kept on high cholesterol diet and sacrificed at 16 weeks of age to serve as baseline control (Chyu et al., 2005).
• Efficacy: Peptide-2 immunization reduced aortic atherosclerosis by 40% and plaque inflammation by 80% compared to controls without a reduction in circulating cholesterol levels whereas Peptide-1 immunization had no effect. Peptide-2 immunization also reduced the progression of aortic lesions when mice were immunized at 16 weeks of age, suggesting the possibility of immuno-modulation in treating established atherosclerosis (Chyu et al., 2005).