Asparaginase Display of Human Cholesteryl Ester Transfer Protein (CETP) B Cell Epitopes for Inducing High Titers of Anti-CETP Antibodies In Vivo

In Silico Design of a Chimeric Humanized L-asparaginase

Acute lymphoblastic leukemia (ALL) is the most common cancer among children worldwide, characterized by an overproduction of undifferentiated lymphoblasts in the bone marrow. The treatment of choice for this disease is the enzyme L-asparaginase (ASNase) from bacterial sources. ASNase hydrolyzes circulating L-asparagine in plasma, leading to starvation of leukemic cells. The ASNase formulations of E. coli and E. chrysanthemi present notorious adverse effects, especially the immunogenicity they generate, which undermine both their effectiveness as drugs and patient safety. In this study, we developed a humanized chimeric enzyme from E. coli L-asparaginase which would reduce the immunological problems associated with current L-asparaginase therapy. For these, the immunogenic epitopes of E. coli L-asparaginase (PDB: 3ECA) were determined and replaced with those of the less immunogenic Homo sapiens asparaginase (PDB:4O0H). The structures were modeled using the Pymol software and the chimeric enzyme was modeled using the SWISS-MODEL service. A humanized chimeric enzyme with four subunits similar to the template structure was obtained, and the presence of asparaginase enzymatic activity was predicted by protein-ligand docking.

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.

Anti-atherosclerosis effect of different doses of CETP vaccine in rabbit model of atherosclerosis

AIM

To evaluate atheroprotective effects of different doses of cholesteryl ester transfer protein (CETP) vaccine, three doses of Tetanus toxoid-CETP (TT-CETP) peptide including 10, 50 and 100/rabbit, termed FA10, FA50, FA100, respectively, were administered in rabbit model of atherosclerosis.

METHODS

Animals were vaccinated subcutaneously (S.C.) with 100μl of vaccine in presence of complete Freund's adjuvant (CFA) for the first administration. Rabbits were boosted 4 times at 3 weeks intervals with the same peptide dose formulated in incomplete Freund's adjuvant (IFA). Animals were fed with diet supplemented with 2% cholesterol from week 11 to week 19. Anti-TT-CETP specific antibody and CETP activity in sera were determined. Therapeutic response was examined by tracking plasma lipoprotein levels (HDL-C, LDL-C and total cholesterol), and pathologic observation of intima/media thickness at the site of aortic lesions.

RESULTS

All TT-CETP vaccine doses generated strong anti TT-CETP antibody response. CETP activity reduced in rabbits vaccinated with FA100 (P=0.031). FA100 showed significant increase in level of HDL-C rather than control group (P=0.006). However, no significant reduction were found in atherosclerotic lesion when compared to control.

CONCLUSION

Inhibition of CETP activity and increased HDL-C were found with FA100, but the vaccine failed to prevent aortic lesion development in immunized rabbits when compared to control. Our result supports the hypothesis stated that CETP may not be an attractive therapeutic target for the prevention of cardiovascular disease.

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.

A novel virus-like particle based on hepatitis B core antigen and substrate-binding domain of bacterial molecular chaperone DnaK

Hepatitis B virus core (HBc) protein has been proved to be an attractive carrier for foreign epitopes, and can display green fluorescent protein (GFP) on its surface. The structure of substrate-binding domain of DnaK [DnaK (394-504 aa), DnaK SBD] is similar to GFP, we therefore reasoned that DnaK SBD might also be tolerated. Electron microscopic observations suggested that the chimeric proteins containing the truncated HBc (HBcDelta) and DnaK SBD could self-assemble into virus-like particle (VLP). Then the accessibility of DnaK SBD and the adjuvanticity of VLP HBcDelta-SBD were demonstrated by two recombinant peptide vaccines against gonadotropin-releasing hormone (GnRH), GhM and GhMNR. The latter carries in addition the peptide motif NRLLLTG which is known to bind to DnaK and DnaK SBD. The combination of VLP HBcDelta-SBD and GhMNR elicited stronger humoral responses and caused further testicular atrophy than the combinations of VLP HBcDelta and GhMNR or VLP HBcDelta-SBD and GhM in Balb/c mice. These findings indicate VLP HBcDelta-SBD might serve as an excellent carrier for GhMNR and some other peptide vaccines.

L-Asparaginase: A Promising Chemotherapeutic Agent

This article comprises detailed information about L-asparaginase, encompassing topics such as microbial and plant sources of L-asparaginase, treatment with L-asparaginase, mechanism of action of L-asparaginase, production, purification, properties, expression and characteristics of l-asparaginase along with information about studies on the structure of L-asparaginase. Although L-asparaginase has been reviewed by Savitri and Azmi (2003), our effort has been to include recent and updated information about the enzyme covering new aspects such as structural modification and immobilization of L-asparaginase, recombinant L-asparaginase, resistance to L-asparaginase, methods of assay of L-asparagine and L-asparaginase activity using the biosensor approach, L-asparaginase activity in soil and the factors affecting it. Also, side-effects of L-asparaginase treatment in acute lymphoblastic leukemia (ALL) have been discussed in the current review. L-asparaginase has been and is still one of the most widely studied therapeutic enzymes by researchers and scientists worldwide.

Vaccines for cholesterol management

Over the last 50 years, several attempts have been made to harness the power and economy of vaccines in the fight against cardiovascular disease. Vaccines directed to lipoproteins, cholesterol itself, and molecules involved in cholesterol metabolism have all demonstrated success in modifying progression of disease in animal models of atherosclerosis. One vaccine that elicits antibodies to cholesteryl ester transfer protein has also progressed into the realm of human clinical testing. This review summarizes the published scientific work describing the various approaches that have been tried, their strengths and weaknesses, and where this field may go in the future.

Long-lasting specific antibodies against P277 induced by mucosal administration of P277 repeat sequences carried by Hsp65 in the absence of adjuvants

To improve the weak immunogenicity of peptide P277, the recombinant expression plasmid pET28-Hsp65-6 x P277 was constructed by inserting 5 x P277 which was amplified by PCR into the vector pET28-Hsp65-P277. It was transformed into Escherichia coli BL21 (DE3) and the fusion protein (Hsp65-6 x P277) was expressed effectively as soluble protein after inducing by lactose. The fusion protein was purified by means of cell disruption, ammonium sulfate precipitation, double-distilled H2O dialysis, DEAE52-cellulose column chromatography, and then used to immunize female NOD mice with three i.n. inoculations in the absence of adjuvants. Serum samples from the immunized mice were collected at 3 weeks interval. Antibodies against P277 and HSP65 were detected in immunized mice sera by enzyme-linked immunosorbent assay (ELISA) and Western blot. Specific antibodies were successfully induced and lasted for more than 20 weeks in animals immunized with the fusion protein via intranasal route even in the absence of adjuvants.