Charles W. Rittershaus

Vaccine-Induced Antibodies Inhibit CETP Activity In Vivo and Reduce Aortic Lesions in a Rabbit Model of Atherosclerosis

Using a vaccine approach, we immunized New Zealand White rabbits with a peptide containing a region of cholesteryl ester transfer protein (CETP) known to be required for neutral lipid transfer function. These rabbits had significantly reduced plasma CETP activity and an altered lipoprotein profile. In a cholesterol-fed rabbit model of atherosclerosis, the fraction of plasma cholesterol in HDL was 42% higher and the fraction of plasma cholesterol in LDL was 24% lower in the CETP-vaccinated group than in the control-vaccinated group. Moreover, the percentage of the aorta surface exhibiting atherosclerotic lesion was 39.6% smaller in the CETP-vaccinated rabbits than in controls. The data reported here demonstrate that CETP activity can be reduced in vivo by vaccination with a peptide derived from CETP and support the concept that inhibition of CETP activity in vivo can be antiatherogenic. In addition, these studies suggest that vaccination against a self-antigen is a viable therapeutic strategy for disease management.

The safety and immunogenicity of a CETP vaccine in healthy adults

A cholesterol ester transfer protein (CETP) vaccine (CETi-1) that induces auto-antibodies that specifically bind and inhibit activity of endogenous CETP has been demonstrated in rabbits to significantly increase HDL-C and reduce the development of atherosclerosis. In a Phase I human trial with CETi-1, one patient at the highest dose (250 mg) out of a total of 36 patients who received a single injection developed anti-CETP antibodies. In an extension study of 23 patients, 53% (8/15) who received a second injection of the active vaccine developed anti-CETP antibodies compared with 0% (0/8) in the placebo group. The vaccine was well tolerated and no significant laboratory abnormalities occurred. CETi-1 is a feasible therapy in humans to induce CETP auto-antibodies. Future research will determine if repeat inoculations will induce a sufficient anti-CETP antibody response to inhibit CETP and increase HDL levels.

Co-administration of a CpG adjuvant (VaxImmuneTM, CPG 7909) with CETP vaccines increased immunogenicity in rabbits and mice

Cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that facilitates the transfer of neutral lipids and phospholipids between lipoproteins and contributes to the regulation of the plasma concentration of high density lipoprotein cholesterol (HDL-C). Vaccines have been developed that elicit antibodies that bind to and reduce the lipid transfer function of CETP as a way to increase the plasma concentration of HDL-C and prevent or treat atherosclerosis. This study assessed the immunogenicity of two vaccine peptides. The first, CETi-1, is a dimerized synthetic peptide, including residues 461-476 of human CETP and residues 830-843 of tetanus toxoid, TT(830-843). The second, PADRE-CETP, is a monomeric peptide, in which a PADRE T cell epitope (aK-Cha-VAAWTLKAa) replaces the TT(830-843) T cell epitope of CETi-1. Both peptides were formulated with aluminum-containing adjuvants (Alhydrogel®), and tested in mice and rabbits with or without the co-administration of the investigational TLR9 agonist VaxImmuneTM (CPG 7909). In both mice and rabbits, the vaccine peptide utilizing the PADRE T cell epitope elicited stronger anti-CETP antibody responses than the CETi-1 vaccine. Also, co-administration of VaxImmune enhanced the anti-CETP antibody responses to both vaccines. Isotype analysis of the murine anti-CETP antibody response to both vaccines demonstrated a switch from IgG1 to IgG2a upon co-administration of VaxImmune. We conclude that 1) the PADRE T cell epitope is more potent than the TT(830-843) epitope in providing help for the anti-CETP antibody response; and 2) co-administration of VaxImmune with either vaccine increased immunogenicity as measured by antibody response.

Characterization of monoclonal antibodies specific for the Vβ3 family of the human T cell receptor generated using soluble TCR β-chain

Abstract A soluble, recombinant form of the human T cell receptor (TCR) β-chain containing the Vβ3.1 sequence has been constructed, expressed in Chinese hamster ovary cells, amplified by dihydrofolate reductase selection, and purified in quantities appropriate for the generation of monoclonal antibodies (mAb). The Vβ3 sequence was chosen because of its reported elevated usage in the synovial T cells of rheumatoid arthritis patients but the approach described should be applicable to other known human Vβ gene sequences. By this method, two mAb were prepared which reacted with up to 10% of normal, live peripheral blood T cells but with reactivity varying greatly among individual donors. Both mAb specifically bound to a murine T cell line transfected with a human TCR Vβ3.1 and immunoprecipated a protein of the expected molecular weight for the TCR β-chain. Both antibodies were mitogenic for T cells and analysis of peripheral blood lymphocyte cultures stimulated with the mAb suggested that both were specific for the Vβ3.1 subfamily and not Dβ or Jβ. Clones expressing Vβ3, which were derived from mAb-stimulated peripheral blood lymphocytes of a single individual, preferentially (8/13), but not exclusively, utilized the Jβ2.7 gene segment. The Vβ3.1 usage showed no preference for the CD8+ or CD4+ subpopulations of normal peripheral blood T cells.