Researchers across the globe are working on the cure for COVID-19. By the time they come out with a cure, we the common man need to understand the cure.
I being a Graduate in Biotechnology trying to make an attempt to make general masses understand as how a cure is developed for such a pandemic.
What are Monoclonal Antibodies?
The Monoclonal Antibodies (mAB or moAb) are our fighting force against the virus. These are antibodies specific for one type of Antigen (Here- Corona Virus 2019-nCoV).
Antigen is an extracellular (Foreign Cell) species which activates our immune system (i.e. Stimulates Antibody Production) in our body . It may be a bacteria, virus, protozoa or fungi etc.
How will the mAB fight Corona Virus 2019-nCoV?
In case of COVID-19 the Corona Virus 2019-nCoV is the antigen. An antigen after entering a host body (Human is our case) stimulates B-Lymphocytes (Immunity Cells) which is then converted into a Plasma cell. These plasma cells are the fighters which starts secreting Antibodies for the antigens sensed by B-Lymphocytes. These antibodies kill the Antigen by blocking its active sites.
How can we produce Monoclonal Antibodies for Corona Virus?
There is a set procedure of producing mAB for any antigen. Let me explain it in simple steps.
- Inject the antigen in a living body.
- Isolate Spleen Cells from the living body.
- Fuse these spleen cells with a Cancerous (Myeloma) Cell for form Hybridomas.
- Culture these Hybridomas in selective (HAT) Media.
- Isolate best quality Monoclonal Antibodies from the viable cells.
Let us now understand the process in detail and in simple terms.
Why Inject Virus in living body?
We need to produce Antibodies for a deadly antigen like corona virus 2019-nCoV. Researchers will first inject corona virus 2019-nCoV to a mice or a guinea pig.
The injection will be done intravenously or in simple words virus will be directly injected into the blood stream of that mice.
This will activate the immune response in the mice and later antibodies will be generated and that is what we want.
Why Spleen Cells?
As the injection has been done directly into the blood stream, the antigens will be trapped into the spleen, which is the secondary lymphoid organ.
The virus 2019-nCoV, will stimulate the B-Cell (immune response) inside the Spleen cells converting it into plasma cells generating Antibodies to kill Corona Virus 2019-nCoV.
Why fuse the Spleen cells with Cancerous cells?
After taking out the mice spleen one can ask why it is required to fuse the spleen cells with myeloma cells? Why can’t we simply extract the antibodies from plasma cells using a culture medium?
The reason why plasma cells can not be used to extract Antibodies directly is due to their shorter life spans. The plasma cells have a very short life span which is not enough for the process of cell culture and antibody extraction.
Myeloma cells are cancerous cells which are immortal cells and have very fast rate of multiplication. Hence fusing a plasma cell with Myeloma cell will result in immortalisation of Plasma cells by formation of a Hybridoma (Hybrid cell of Plasma and Myeloma).
So now we have a cell which has an endless life and potential to generate Antibodies.
Why we need to Culture Hybridomas in selective Media?
During the fusion of Myeloma and Plasma cells five types of cells can possibly form.
Out of which Only Fused Plasma (Plasma+Plasma), Hybridoma (Plasma+Myeloma) and Unfused Plasma (Single Plasma) cells are of our use as they only have property of generating 2019-nCoV specific antibodies.
HAT medium- How it selects the desirable cells?
HAT stands for Hypoxanthine, Aminopterin and Thymidine. These are the three ingredients of the selective medium chosen to culture the Hybridomas so that it can generate desirable antibodies.
All mother cells divides into daughter cells by replication of DNA, for this syntheses of Nucleic acid is required. This synthesis of Nucleic Acid can be done by two pathways.
De-Novo pathway– Where Nucleic Acid is synthesised from basic molecules.
Salvage Pathway– Where Nucleic acid is synthesised from degraded nucleotides.
Now in HAT Media, due the presence of Aminopterin cells can not replicate thorugh De Novo Pathway, as Aminopterin blocks a key enzyme Dihydrofolatereductase.
Now the cells in HAT media has only way to replicate is through Salvage Process. But, here is the catch. Cells need HGPRT(Hypoxanthine Guanine Phospho Ribosil Transferase) enzyme to relplicate through Salvage process.
Myeloma cells- NO HGPRT
Plasma Cells(Fused and Unfused) and Hybridoma cells- Has HGPRT enzyme, Hence replicates in HAT Medium.
Plasma cells and fused plasma cells having very small life span will automatically perish in HAT media and Hybridoma cells will only survive.
These Hybridomas will yield the Monoclonal Antibodies, which will be our weapon against the Corona Virus- 2019-nCoV.
Many researchers are working on the same lines for generating a cure for this deadly virus. Till the time they succeed, let’s keep the fingers crossed.
PC: Google Images & Sajid Shaikh