Vaccines for the prevention of cardiovascular disease

Development of an effective liposomal cholesterol ester transfer protein (CETP) vaccine for protecting against atherosclerosis in rabbit model

Clinical trials of cholesterol ester transfer protein (CETP) peptide vaccine were stopped after disappointing results in humans due to the inadequacy of adjuvant aluminum hydroxide in stimulating the immune response against the self-antigen of CETP. To increase the efficacy of the CETP vaccine, we developed a novel liposomal form of tetanus toxoid-CETP (TT-CETP) peptide (Lip CETP) with well-characterized properties and high encapsulation efficiency. The vaccine efficacy against atherosclerosis was evaluated in rabbits challenged with a high cholesterol diet. Rabbits were immunized with Lip-CETP or liposome containing CETP with CpG ODN (Lip CETP/CpG). Control groups received empty liposomes or buffer. Anti-TT-CETP specific antibodies in serum were determined and gene expression of cytokine IFN-γ and IL-4 were measured in blood peripheral mononuclear cells. Therapeutic response was evaluated by titration of plasma lipoproteins during the study and pathologic analysis of aorta atherosclerotic lesions at the end. Lip-CETP/CpG elicited strong anti-TT-CETP antibodies and a higher IFN-γ level than the buffer. IL-4 was lower than the buffer in all vaccinated groups. Plasma lipoproteins showed no significant difference in the studied groups. Atherosclerosis thickness grade of the aorta was lower than the buffer group (p < 0.001) in rabbits vaccinated with Lip-CETP but not with Lip-CETP/CpG. In conclusion, Lip-CETP showed a strong atheroprotective effect.

Recent Advances in the Development of Vaccines for Diabetes, Hypertension, and Atherosclerosis

Vaccines are commonly used in the prevention of infectious diseases. The basic principle of vaccination is to use specific antigens, endogenous or exogenous to stimulate immunity against the specific antigens or cells producing them. Autoantigen or oligo vaccination has been used for disease animal models. More recently humanized monoclonal antibodies have been successfully used for the treatment of neoplastic disorders or familial hypercholesterolemia. Humanized monoclonal antibody therapy needs repeated injection, and the therapy is expensive. Therapeutic vaccination can lead to persistent immunized or immune tolerant against the therapeutic molecule(s) or site. However, immunization against those endogenous substances may also elicit persistent autoimmune reaction or destruction that do harm to health. Therefore, rigorous studies are needed before any clinical application. In this review, we briefly reviewed vaccines used in protection against common metabolic diseases including atherosclerosis, hypertension, and diabetes mellitus.

A novel atheroprotective role of MF59-like adjuvant when co-administered with CETP vaccine in rabbit model of atherosclerosis

OBJECTIVES

In this study, for the first time, MF59 adjuvant was used to develop a cholesteryl ester transfer protein (CETP) vaccine. The efficacy of the vaccine was compared with the efficacy of CETP vaccine formulated with Alum/CpG, the formulation that its immunogenicity has been already demonstrated in rabbit and mice.

MATERIALS AND METHODS

Tetanus toxoid- CETP peptide (TT-CETP) was mixed with Alum/CpG or MF59-like and administered subcutaneously for total five times in rabbit model of atherosclerosis. Anti-TT-CETP specific antibody, CETP activity in sera and mRNA level of cytokine IL-4 and IFN-γ in peripheral mononuclear cells were determined. Therapeutic response was also examined by tracking serum lipoprotein levels and pathologic observation of atherosclerotic lesions at aortic site.

RESULTS

More anti-TT-CETP antibody was found in Alum/CpG vaccinated rabbits compared to buffer (P<0.001). Antibody induced by MF59-like formulation was not significantly higher than buffer. CETP activity and lipoprotein levels were not significantly different between vaccinated and control rabbits. The mRNA level of IL-4 was significantly lower than buffer while, IFN-γ gene expression was significantly higher in both vaccinated groups. Atherosclerosis thickness grade of aorta was dramatically lower than buffer (P<0.01) in both vaccinated groups.

CONCLUSION

It is concluded that MF59-adjuvanted CETP vaccine showed anti-atherosclerosis properties, but the protective effect could not be directly attributed to the immune response induced by anti TT-CETP antibody and CETP inhibition. Further studies are needed to explain the anti-atherosclerosis properties of MF59 in the presence of TT-CETP peptide.

Coagulation factor XI vaccination: an alternative strategy to prevent thrombosis

Essentials Coagulation Factor (F) XI is a safe target for the development of antithrombotics. We designed an antigen comprising the human FXI catalytic domain and diphtheria toxin T domain. Antigen immunization reduced plasma FXI activity by 54% and prevented thrombosis in mice. FXI vaccination can serve as an effective strategy for thrombosis prevention.

SUMMARY

Background Coagulation factor XI serves as a signal amplifier in the intrinsic coagulation pathway. Blockade of FXI by mAbs or small-molecule inhibitors inhibits thrombosis without causing severe bleeding, which is an inherent risk of currently available antithrombotic agents. Objectives To design an FXI vaccine and assess its efficacy in inhibiting FXI activity and preventing thrombosis. Methods An FXI antigen was generated by fusing the catalytic domain of human FXI to the C-terminus of the transmembrane domain of diphtheria toxin. The anti-FXI antibody response, plasma FXI activity and antithrombotic efficacy in mice immunized with the FXI antigen were examined. Results The antigen elicited a significant antibody response against mouse FXI, and reduced the plasma FXI activity by 54.0% in mice. FXI vaccination markedly reduced the levels of coagulation and inflammation in a mouse model of inferior vena cava stenosis. Significant protective effects were also observed in mouse models of venous thrombosis and pulmonary embolism. Conclusions Our data demonstrate that FXI vaccination can serve as an effective strategy for thrombosis prevention.

Peptide-based anti-PCSK9 vaccines - an approach for long-term LDLc management

BACKGROUND

Low Density Lipoprotein (LDL) hypercholesterolemia, and its associated cardiovascular diseases, are some of the leading causes of death worldwide. The ability of proprotein convertase subtilisin/kexin 9 (PCSK9) to modulate circulating LDL cholesterol (LDLc) concentrations made it a very attractive target for LDLc management. To date, the most advanced approaches for PCSK9 inhibition are monoclonal antibody (mAb) therapies. Although shown to lower LDLc significantly, mAbs face functional limitations because of their relatively short in vivo half-lives necessitating frequent administration. Here, we evaluated the long-term efficacy and safety of PCSK9-specific active vaccines in different preclinical models.

METHODS AND FINDING

PCSK9 peptide-based vaccines were successfully selected by our proprietary technology. To test their efficacy, wild-type (wt) mice, Ldlr+/- mice, and rats were immunized with highly immunogenic vaccine candidates. Vaccines induced generation of high-affine PCSK9-specific antibodies in all species. Group mean total cholesterol (TC) concentration was reduced by up to 30%, and LDLc up to 50% in treated animals. Moreover, the PCSK9 vaccine-induced humoral immune response persisted for up to one year in mice, and reduced cholesterol levels significantly throughout the study. Finally, the vaccines were well tolerated in all species tested.

CONCLUSIONS

Peptide-based anti-PCSK9 vaccines induce the generation of antibodies that are persistent, high-affine, and functional for up to one year. They are powerful and safe tools for long-term LDLc management, and thus may represent a novel therapeutic approach for the prevention and/or treatment of LDL hypercholesterolemia-related cardiovascular diseases in humans.

Vaccination for atherosclerosis

Atherosclerosis is an inflammatory disease, and several antigens have been shown to activate the immune response and affect the development of atherogenesis. This suggests that modulation of the immune system could represent a useful approach to prevent and/or treat this disorder. A vaccination approach might be a useful, effective tool in the modern arsenal of cardiovascular therapy and could possibly be used on a large scale at a low cost. Several modalities of vaccines have been tested against lipoproteins, cholesterol, molecules involved in cholesterol metabolism, atherosclerosis-associated microorganisms, and other molecules (heat shock protein, CD99, vascular endothelial growth factor-receptor, interleukin-2), with promising results. Nevertheless, a deeper understanding of the role of immunization in atherosclerosis will be essential to the use of vaccines in clinical medicine.

Vaccination, atherosclerosis and systemic lupus erythematosus

Atherosclerosis is an inflammatory disease, leading to the formation of pro-inflammatory and pro-oxidative lipids that generate an immune response. Several antigens have been shown to activate the immune response and affect the development of atherogenesis. Systemic lupus erythematosus is an autoimmune and inflammatory disease strongly associated with premature development of atherosclerotic plaques. Modulation of the immune system could represent a useful approach to prevent and/or treat atherosclerosis. A vaccination-based approach might be a useful, effective tool in the modern arsenal of cardiovascular therapies and could be used on a large scale at a low cost. In non-systemic lupus erythematosus populations, vaccines against oxidized low-density lipoprotein, beta-2-glycoprotein I, heat shock proteins, lipoproteins, cholesterol, molecules involved in cholesterol metabolism, and other molecules (CD99, vascular endothelial growth factor-receptor, and interleukin-2) have been tested, with promising results. However, there are no studies of vaccination against atherosclerosis in systemic lupus erythematosus.