Written by NEC biology tutor Josie Briggs, learn about how studying biology can help during this time.
Most people know by now what the virus that causes COVID-19 looks like, with pictures of it every time we watch the news on TV. This tiny pathogen is essentially a sphere with spikes on it.
The spikes are proteins which attach to receptors on a cell surface, after which the viral contents can enter the cell to do their worst. Corona viruses have RNA genomes which, once inside the host cell, act as mRNA to make the viral proteins, using the normal cell mechanism for translation. These new proteins, with other viral components, are then compiled into a large number of new viruses which are released from the dying cell to attack other cells.
Research into potential antiviral drugs and vaccines focuses mainly on disabling the viral spike proteins so the virus cannot attach to receptors on cell membranes. There are several possible approaches including blocking the spikes so they cannot fit into the receptors, and boosting the immune system to be more effective at making antibodies to the spike proteins and killing the virus. Other approaches involve trying to reduce the inflammation caused by overreaction of the immune system in some patients.
The body’s response to infection is complex and involves several types of cells and other components of the immune system. When a pathogen enters your body, the immune system springs into action, with phagocytes engulfing some of the pathogens and other cells producing antibodies specific to the pathogen. If the pathogen is new to the body, especially if the viral loading is high, the immune system may struggle to cope and the disease takes hold.
Memory cells are produced as part of the response, so that subsequent infections can be dealt with quickly and before symptoms develop. Length of resistance time to coronaviruses varies from months to years, according to the variety of virus, and it is not yet known how long a person will remain resistant to the COVID-19 virus after first infection.
Many groups throughout the world are researching potential vaccines to this virus and at least one is already undergoing clinical trials. Others are being tested in animal studies.
Researchers at Oxford University’s Jenner Institute, collaborating with Oxford Vaccine Group clinical teams, have begun to vaccinate several hundred volunteers, some with the trial vaccine and others with a control injection. Both groups will be monitored for safety and to see if the vaccine leads to an immune response.
Unlike the flu vaccination, which contains viral antigens to stimulate production of antibodies and memory cells, this experimental vaccine uses a harmless adenovirus as a vector to carry genetic material from the coronavirus. Genes for the coronaviruses spike proteins are inserted into the vector virus. On entering the body, these genes enter cells and produce viral spike proteins, some of which are presented on cell surfaces or released outside the cell. These should be recognised as alien antigens by the immune system.
The safety and effectiveness of the trial vaccine are being tested in the Oxford clinical trial. If successful, the next stage clinical trials on a larger scale will begin.
Section 1 Topic 2 describes the basic structure of viruses and how they can only reproduce by invading cells and taking over the cells’ mechanisms to make new viruses.
Section 2 Topic 3 explains the structure and functions of proteins. The COVID-19 spikes consist of complex proteins that can attach to certain molecules in cell membranes.
Section 8 Topic 1 shows the structure of DNA. Many viruses contain genes made of DNA; others, for example coronaviruses and viruses that cause colds and flu, have genes made of RNA. RNA is similar in structure to DNA, and human cells make and use RNA when producing proteins using the information in our genes.
Section 10 Topic 5 tells how viruses can be used as vectors to carry genes from one organism into cells of a different organism. This technique is used to produce genetically modified organisms. Some research groups making and testing potential vaccines for COVID-19 are using a similar technique, placing some of this virus’s genes inside a harmless virus which can then deliver the genes into patients’ own cells.
Section 2 Topic 4 goes into detail about the structures and roles of DNA and RNA, the genetic code, and transcription and translation of genes to produce polypeptide chains which will be processed into proteins. The RNA genome of the COVID-19 virus means that its genes can function as messenger RNA, hence by-passing the transcription stage of protein synthesis.
Section 6 Topics 1 to 5 describe the body’s immune response to infection, using HIV (another RNA genome virus) as an example. Topic 4 explains how different types of vaccine (active and passive) work. Many trial vaccines for COVID-19 are active, in that they are expected to activate the body’s immune system against viral antigens.
One of the questions in Assignment 6 contains information and a flow chart showing how DNA vaccines work. Many trial vaccines are using viral RNA genes (or DNA retro-transcribed from these) to induce patients’ cells to produce viral antigens.
Josie Briggs is one of our amazing biology tutors, supporting students at both GCSE and A level. She also wrote ‘Why I love Biology’ which you can read here.
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