myelin-basic-protein and Multiple-Myeloma

Multiple myeloma is currently an incurable cancer of plasma B cells often characterized by overproduction of abnormally high quantities of a patient-specific, clonotypic immunoglobulin "M-protein." The M-protein is expressed on the cell membrane and secreted into the blood. We previously showed that ligand-toxin conjugates (LTC) incorporating the ribosome-inactivating Ricin-A toxin were very effective in specific cytolysis of the anti-ligand antibody-bearing target cells used as models for multiple myeloma. Here, we report on the incorporation of the membrane-disruptive Cyt1Aa toxin from Bacillus thuringiensis subsp. israelensis into LTCs targeted to murine myeloma cells. Proteolytically activated Cyt1Aa was conjugated chemically or genetically through either its amino or carboxyl termini to the major peptidic epitope VHFFKNIVTPRTP (p87-99) of the myelin basic protein. The recombinant fusion-encoding genes were cloned and expressed in acrystalliferous B. thuringiensis subsp. israelensis through the shuttle vector pHT315. Both chemically conjugated and genetically fused LTCs were toxic to anti-myelin basic protein-expressing murine hybridoma cells, but the recombinant conjugates were more active. LTCs comprising the Cyt1Aa toxin might be useful anticancer agents. As a membrane-acting toxin, Cyt1Aa is not likely to induce development of resistant cell lines.

Topics: Animals; Antibodies, Monoclonal; Antineoplastic Agents; Bacillus thuringiensis; Bacillus thuringiensis Toxins; Bacterial Proteins; Bacterial Toxins; Cell Line, Tumor; Drug Resistance, Neoplasm; Endotoxins; Gene Expression; Hemolysin Proteins; Hybridomas; Immunotoxins; Ligands; Mice; Models, Biological; Multiple Myeloma; Myelin Basic Protein; Myeloma Proteins; Peptides; Recombinant Fusion Proteins; Ricin

Increasingly it is being discovered that short segments of proteins can provoke an immune response. Sequential determinants are as important as conformational determinants. It is the thesis of this paper that a string of three amino acid residues (a tripeptide) is antigenic when it is located on a large carrier, that is, when it is part of a protein. Conceptually this has great explanatory power in understanding (a) autoimmune phenomena (b) the intriguing finding that monoclonal antibodies which are supposed to be exquisitely specific cross-react with disparate, non-homologous proteins. Clinical syndromes such as the neuropathies of myeloma, hepatitis and multiple sclerosis are discussed in the light of this concept by computer analysis of the putative antigenic sites of myelin basic protein, hepatitis B and A proteins and measles peptides.

Topics: Amino Acid Sequence; Antibodies, Monoclonal; Antigens, Viral; Autoimmune Diseases; Computer Simulation; Cross Reactions; Epitopes; Hepatitis A Antigens; Hepatitis B Surface Antigens; Humans; Multiple Myeloma; Myelin Basic Protein; Peptides; Software

Topics: Epitopes; Humans; Multiple Myeloma; Myelin Basic Protein; Nervous System Diseases