Hemocyanins from gastropod mollusks are highly potent T-cell dependent immunostimulatory proteins and adjuvants. The hemocyanin from Megaturacrenulata (KLH) has an extensive history of safe and effective use in humans for vaccine development and immunological research. However, the sovereignty of KLH was challenged eight years ago by the emergence in the world market of a novel hemocyanin obtained from the Chilean mollusk Concholepas concholepas (CCH), which in addition to the remarkable immunogenic properties of KLH is more stable and efficient as a carrier protein for the production of antibodies to haptens and peptides; in the last years more than 10 kilograms of CCH were sold by Biosonda in the world market, under the trade mark of BlueCarrier®. Moreover, it has excellent properties as an immunostimulant and adjuvant for the formulation of vaccines for the treatment of cancer and infectious diseases
CCH is the high molecular mass respiratory glycoprotein obtained from the hemolymph of the marine mollusk Concholepas concholepas. The large size of the CCH protein, which has a native didecamer mass of ~ 8,000 kD contributes to its efficient endocytosis by antigen presenting cells (APCs) wherein it is processed into peptides, bound to MHC class II molecules, and presented to the immune system on the APC surface membrane. APC presentation of antigenic peptides in the context of MHC class II initiates the binding, priming and proliferation of CD4+ T helper cells, driving T cell lymphokine secretion and a cascade of cellular and humoral responses. However, research performed at Biosonda, unraveled the unique structure of CCH; in contrast to KLH the CCH decamer in made by two different polypeptides CCA-A and CCH-B, thus conferring to the molecule more stability and makes possible the generation of a broader variety of immunogenic peptides after processing by APCs than KLH.
Advantages of using thehemocyanin from Concholepas concholepas (CCH)
|Although, CCH and KLH both are hemocyanins, the integrity of CCH does not depends on the presence of Ca+2 and Mg+2, thus the stability of CCH prevents the lost of immunogenicity during storage of the vaccine.
|KLH is a mixture of two isoforms that are controlled by independent genes, and therefore the composition of KLH varies from batch to batch. CCH expression is also controlled by two genes, but the protein has equimolecular amounts of CCH-A and CCH-B subunits, so the composition of CCH remains constant from batch to batch.
|The presence of two subunits CCH-A and CCH-B, generates a broader repertoire of immunogenic peptides than KLH that are available to bind different haplotypes of MHC. Therefore, more T cells should be stimulated than using KLH. Research performed at Biosonda and other companies, indicated that less amount of CCH is required as a carrier for the production of antibodies to haptens and peptides.
|CCH has been successfully used as immunostimulant in preclinical mice models for treatment of bladder cancer and melanomas. Recently, CCH has been used in phase III human clinical trials of dendritic cell vaccines to treat melanomas.
|In the field of veterinary vaccines, the incorporation of CCH increases protection to bacterial infections in about 40%.
|The physicochemical properties the hemocyanin from Concholepas concholepas and the purification procedures developed by Biosonda, allow to reach protein concentrations as high as 300 mg / ml, this makes possible the incorporation of CCH minimizing the dilution of other vaccine active components. KLH isavailable in the market at maximum concentration of 50 mg / ml.
|Chemical activation: Due to its high stability and solubility, CCH gives higher yields after activation and reconstitution of the activated protein in coupling buffers than KLH