Building a better monoclonal antibody

Expression of immunoglobulin genes tandem in eukaryotic cells under the control of T7 bacteriophage RNA polymerase

A tandem of recombinant mouse/human immunoglobulin (Ig) genes was constructed and inserted into the plasmid pGEM1 under the control of T7 phage RNA polymerase promoter. Sp2/0 lymphoid cell line and Chinese Hamster Ovary (CHO) cells were used as the targets for gene transfection. Both cell lines contained in their genomes a T7 RNA polymerase gene modified with a nuclear-located signal derived from SV40 large T-antigen. Cell lines transfected with the gene tandem effectively synthesized mRNA (up to 9 x 10(3) bp) that hybridized with epsilon- and kappa-gene probes. Separate transcripts corresponding to mRNAs of individual heavy and light chains were not detected in either transfected cell line. It follows from these data that transcription in the transfected cells is controlled mainly by the T7 phage polymerase promoter. Both lymphoid and nonlymphoid cell lines transfected with the gene tandem synthesized the epsilon-heavy (70 kDa) and kappa-light (25 kDa) Ig polypeptide chains. Production of chimeric antibodies by the myeloma Sp2/0 cells was higher than that by the CHO cells. Individual clones synthesized up to 150 ng/mL chimeric IgE. However, only lymphoid Sp2/0 cells were capable of efficient secretion of the recombinant antibodies. The mechanism of translation of mRNA synthesized in eukaryotic cells by T7 phage RNA polymerase is discussed.

Production of recombinant antibodies in lymphoid and non-lymphoid cells

A recombinant tandem of 'chimeric' mouse/human immunoglobulin (Ig) genes was constructed and inserted into plasmid pGEM1 under the control of the T7 bacteriophage RNA polymerase promoter. Lymphoid (Sp2/0) and non-lymphoid (CHO) cell lines used for transfection contained in their genomes a semisynthetic gene of T7 RNA polymerase and steadily expressed this enzyme. It was shown for the first time that a stable polycystronic transcription of the Ig gene tandem occurs under the control of a single T7 phage promoter, both in lymphoid and non-lymphoid cells. Synthesis of kappa-light and epsilon-heavy Ig chains and functionally active antibodies was observed in the above-mentioned transfected cell lines.

Immunotherapy with monoclonal antibodies in metastatic melanoma

Therapy for metastatic melanoma has been disappointing to date. Treatment with chemotherapy only uncommonly results in complete responses and rarely results in long-term survivors. The identification of human melanoma cell surface antigens has led to the development of an array of mouse monoclonal antibodies (MAb) for use in the diagnosis and therapy of patients with metastatic melanoma. Strategies utilizing MAbs based on immunologic approaches have been developed. Naked MAbs directed against glycoprotein surface antigens or conjugated to toxins or radionuclides have shown little biologic or clinical activity. However, phase I studies of MAb directed against glycolipid antigens have yielded objective tumor shrinkage with occasional complete responses. Severe toxicity has been seen infrequently. Possible anti-tumor mechanisms include complement activation and antibody-dependent cellular cytotoxicity utilizing natural killer cells or monocytes as effector cells. Strategies to enhance the anti-tumor effects of MAb, including combinations with cytotoxic agents and cytokines, have been introduced with limited success thus far. The development of a human IgG anti-mouse antibody has been seen in nearly all treated patients. A new generation of MAb engineered to overcome the immunogenicity of mouse MAb and to enhance immune effector function will soon enter clinical trials.

Use of deuterium labelling in NMR studies of antibody combining site structure

Antibody molecules secreted by B-lymphocytes play a central role in the immune defense systems of higher organisms. The major function of the antibody molecule is to bind specifically to foreign molecules (antigens) and to effect their inactivation and/or removal. Antibody molecules exist in millions of different forms, each with a unique amino acid sequence and combining site structure. Collectively called immunoglobulins (abbreviated as Ig), they form one of the major classes of proteins present in the blood, constituting 20% of the total plasma protein by weight.