Monoclonal antibodies are special types of proteins made in the laboratory and can specifically bind antigens (Proteins on the surface of cells). Antigens are proteins that you have on the surface of all your normal and abnormal cells throughout the body.
In modern medicine, monoclonal antibodies are widely used for both diagnostic and therapeutic purposes. They have particularly found use in cancer and other terminal disease management.
In this article, we want to discuss monoclonal antibodies. We shall discuss how they are produced, their different types, and their application in Medicine.
How are Monoclonal Antibodies Produced?
For you to produce monoclonal antibodies (mAbs), you need to, first of all, make mAb-producing cells called hybridomas. Hybridomas as produced by fusing myeloma cells and splenocytes together. Does it sound a bit technical? Let’s simplify it this way:
Splenocytes: These a spleen cells capable of producing antibodies (B cells). To get splenocytes, inject mice with an antigen of interest against which you want to produce monoclonal antibodies.
After some time, the blood of mice is screened for antibodies against the antigen for which they were immunized. This confirmation of the presence of antibodies of interest will lead you to isolate mice splenocytes awaiting fusion with myeloma cells.
Myeloma Cells: These are immortalized cells that are now prepared for invitro (In the laboratory) fusion with splenocytes to produce hybridomas.
Hybridomas production: Myeloma cells and splenocytes are fused to form hybridomas. This process is facilitated by polyethylene glycol(PEG) to ensure that the plasma membranes of the two cell types are completely fused. The hybridomas are now ready for mAb-production though in a mixture of other things to be sorted in clonal selection.
Clones Selection and Characterization: The clones of hybridomas are screened and selected based on two factors. That is antigen specificity and the immunoglobulin class (e.g. IgG, IgM…). The right high-antibody-producing clones are confirmed and validated using a serological method, mostly ELISA.
Scaling Up: At this point, the mAbs-producing hybridomas are now ready for scale-up for high yields of monoclonal antibodies for use in medical applications.
FDA-Approved Monoclonal Antibodies
Monoclonal antibodies (mAbs) are used as immunotherapy in the treatment of some conditions in the modern practice of medicine. Immunotherapy has become the alternative for many forms of treatments today.
In some cases, immunotherapy complements other treatments for better disease outcomes. Immunotherapy is the use of immune components to manipulate the immune system to fight an antigen in a better way.
Immunologists have come up with different types of monoclonal antibodies for immunotherapy. The conditions that are treated using mAbs include cancers, autoimmune diseases, and post-transplantation reactions. More recently there have been monoclonal antibodies-based treatments tried against COVID-19.
The types of monoclonal antibodies used as treatment regimens are discussed below in the order of discovery:
Mouse Monoclonal Antibodies
These were the first monoclonal antibodies to be discovered. They were murine antibodies in which a human protein is injected into a mouse to produce antibodies against it.
An FDA-approved example is murine IgG2a anti-CD3 and OKT3 (known as muromonab) for acute transplant rejection. The challenge is that the drug was rejected by the human immune system because it was treated as a foreign antibody.
Chimeric Monoclonal Antibodies
An improvement of the murine mAbs where the variable region of the mouse was fused with constant regions of the human mAbs. It was a great improvement but did not completely eliminate the rejection problem.
An example of this is Rituximab (Rituxan) was approved by FDA in 1997 for the treatment of B cell lymphomas (non-Hodgkin’s Lymphoma). It was also indicated for the treatment of chronic lymphocytic leukemia (CLL).
Rheumatoid arthritis (RA) was also targeted by Rituximab. In the treatment of non-Hodgkin’s lymphoma, the mAbs that have been used successfully in this category are the Anti-CD20. CD20 is an important marker in the pathogenesis of this type of cancer where its expression is greatly overexpressed.
Humanised Monoclonal Antibodies
The complementarity determining regions of mice were transplanted into the corresponding areas in a human mAbs so that the mAbs were 90% human.
An example is Trastuzumab (Herceptin) used as a blocking antibody for human epidermal growth factor receptor 2 which is an important antigen in the pathogenesis of breast cancer.
Fully humanized Monoclonal Antibodies
Finally, to overcome the immune-rejection problem completely, fully humanized monoclonal antibodies were produced. Two approaches were employed. One approach was the use of recombinant technology to produce human antibodies.
The other approach was where mice were genetically engineered to make them able to produce human-like antibodies.
An example of FDA-approved mAbs of this type is Adalimumab which was approved for the treatment of some autoimmune diseases including Rheumatoid arthritis, Crohn’s disease, juvenile idiopathic arthritis, and psoriasis.
This humanized monoclonal antibody blocks the activity of TNF to reduce inflammation. Inflammation is a major cause of pathogenesis and painful experience in patients.
Another example is Panitumumab (Vectibix) which is FDA-approved for the treatment of colorectal cancer. This antibody blocks the epidermal growth factor receptor and slows the growth of the cancer cells. Therefore, it reduces the metastases (spread) of cancer cells and hence the prognosis.
Other Immunotherapeutic Products
Magic bullets and CARs
This involves CAR T cells where T lymphocytes are harvested from the patient’s blood through leukapheresis. The T cells are manipulated ex vivo using CAR-encoding viral vectors.
Their number is amplified multifold and then they are re-infused back into the patient’s blood circulation. This immunotherapy does not have rejection challenges because the treatment is autologous.
It is, however, tedious to do it for every patient. A single infusion is enough to treat the patient and completely cause remission of cancer. A few products have been approved by FDA as CAR-T therapy in hemato-oncology, particularly lymphomas and leukemias.
Immune checkpoints Immunotherapy
This is another type of immunotherapy mostly given to cancer patients. The treatment regimen could be mAbs raised against specific proteins involved in immune regulatory mechanisms.
Since they block the proteins that limit the strength of the immune system, they boost the ability of the immune system to fight cancer cells.
Conclusion
The discovery of monoclonal antibodies was a great milestone in immunology research. It has now contributed immensely to immunotherapy, perhaps more than any other immunotherapeutic agent. This is particularly true in the treatment of cancer and other incurable conditions. The gains are more than anyone would have anticipated.
