Recombinant Vaccines A recombinant vaccine is a vaccine produced through recombinant DNA technology. This involves inserting the DNA encoding an antigen (such as a bacterial surface protein) that stimulates an immune response into bacterial or mammalian cells.

Types of Recombinant Vaccine 1) Subunit recombinant vaccines: These are components of the pathogenic organisms. Subunit vaccines include proteins, peptides and DNA. 2) Attenuated recombinant vaccines: These are genetically modified pathogenic organisms (bacteria, viruses) that are made non-pathogenic and used as vaccines. 3) Vector recombinant vaccines: These are the genetically modified viral vectors that can be used as vaccines against pathogens.

Recombinant Vaccines Few diseases against which recombinant vaccines have been produced are: Viral diseases: Chicken pox, Genital ulcers, hemorrhagic fever, acute infantile gastroenteritis etc., Bacterial diseases: Cholera, pneumonia, tetanus, tuberculosis, typhoid, meningitis etc., Parasitic diseases: Malaria, Filariasis, sleeping sickness etc.,

Monoclonal Antibodies Monoclonal antibodies (MAb) is a single type of antibody that are made by identical immune cells which are directed against a specific epitope (the part of the antigen that is recognized by the antibody) Hybridoma Technology: The production of monoclonal antibodies by the hybrid cells (antibody-producing B-lymphocytes and myeloma cells in vitro) is referred to as Hydridoma Technology.

Hybridoma Technology The establishment of hybridoma and production of monoclonal antibodies involves the following steps: Immunization Cell fusion Selection of hybridomas Screening the products Cloning and propagation Characterization and storage

Hybridoma Technology Georges Kohler It is technique of producing hybrid cell lines called “hybridomas” by the fusion of a specific antibody-producing lymphocyte B cell with a myeloma cell that has an ability to grow in tissue culture Hydridoma produce antibodies that have single specificity and are called monoclonal antibodies. This technique was discovered Georges Kohler of West Germany, Cesal Milstein of Argentina and Niels Jerne of Denmark in 1975. They were awarded Nobel Prize for Physiology and Medicine the 1984 Cesal Milstein Niels Jerne

Antibody producing lymphocyte B cell are isolated from the spleen cell of mouse immunized with red blood cells from sheep Single myeloma cell is a bone marrow tumour cell capable of multiplying indefinitely. Fused hybrid cells or hybridoma have the antibody producing capability inherited from lymphocytes and have the ability to grow continuously or immortal like malignant cancer cells.

Steps in monoclonal antibody production by hybridoma technology Immunize a rabbit through repeated injection of a specific antigen for the production of specific antibody, facilitated due to proliferation of the desired B cells. Produce tumors in a mouse or a rabbit. Culture separately the spleen cells that produce specific antibodies and the myeloma cells that produce tumors Myeloma cells cannot synthesize antibodies as they lack HGPRT gene required for the synthesize the enzyme, hypoxanthine guanine phosphoribosyl transferase

Fusion Fusion of spleen cells to myeloma cells is induced using polyethylene glycol (PEG), to produce hybridoma Hybridomas are grown in selective hypoxanthine aminopterin thymidine (HAT) medium. HAT medium contains a drug, aminopterin that blocks one pathway for nucleotide synthesis, making the cells dependent on another pathway that needs HGPRT enzyme, which is absent in myeloma cells. Myeloma cells that do not fuse with B cells will die. B cells that do not fuse will also die because they lack tumorigenic property of immortal growth.

Selection and Storage Select desired hybridoma for cloning and antibody production Prepare single cell colonies that can grow and use them to screen of antibody producing hybridomas Only one in several hundred cell hybrids will produce antibodies of the desired specificity Culture selected hybridoma cells for the production of monoclonal antibodies in large quantities Hybridoma cells can be frozen for future use or can be injected in the body of an animal, so that antibodies will be produced in the body and recovered later from the body fluid.

Applications Serological: Identification of ABO blood groups. Diagnosis: Detection of pregnancy Detection of pathogens Diagnosis of Cancers, hormonal disorders, infectious diseases. Therapeutic Applications: To destroy pathogens In the treatment of Cancer In the treatment of AIDS In the treatment of Autoimmune diseases