Question

The Pfizer Covid-19 vaccine and Johnson&Johnson vaccine are two of the vaccines currently being rolled out for mass vaccination in South Africa to protect the population against SARS-CoV-2 Infection and COVID-19. 1. Name the active compound for each of these two vaccines. [2] 2. How does administration of elther of these vaccines results in protection against COVID-19? [2] 3. Assume a person receives the Johnson&Johnson vaccine. Briefly list the cellular processes or molecular mechanisms that will take place within the human cells that will result in the expression of the coronavirus antigen. [2] 4. With the Pfizer vaccine, genetic material is packaged in lipid nanoparticles from where this is released into the cytoplasm of the cell. What fundamental cellular process is conducted ex vivo in the manufacture of the Pfizer vaccine, that is not a necessary step in the manufacture of the Johnson&Johnson vaccine? (1) 5. Step 1 of how Prizer makes its vaccines illustrates that the starting material for production of these vaccines is a copy of a coronavirus gene cloned into a DNA plasmid. The SARS-CoV-2 viral genetic material is single-stranded RNA. Based on your knowledge of molecular genetics and recombinant DNA technology from GTS 251, outline the basic steps that will be required to obtain the recombinant DNA plasmid in step 1. [2] 6. One of the arguments often put forward in social media with respect to the risks associated with the Pfizer vaccine is that it can change your DNA. Is this statement potentially valld? Base you answer on the material provided for this project, plus your knowledge on cellular molecular

Answer 1

1. The active compound in the Pfizer-BioNTech COVID-19 vaccine is BNT162b2, a lipid nanoparticle-formulated, nucleoside-modified RNA vaccine. The active compound in the Johnson & Johnson COVID-19 vaccine is Ad26.COV2.S, a recombinant, replication-incompetent adenovirus type 26 vector expressing the SARS-CoV-2 spike protein.

2. The administration of these vaccines results in protection against COVID-19 through an immune response. In the Pfizer vaccine, the mRNA instructs the cells to make a harmless piece of the spike protein found on the surface of the SARS-CoV-2 virus. The immune system recognizes this protein as foreign and mounts an immune response. If the person is later exposed to the virus, their immune system can recognize the spike protein and respond more effectively. The Johnson & Johnson vaccine works similarly, but instead of mRNA, it uses a harmless adenovirus to deliver the spike protein gene into cells.

3. In the case of the Johnson & Johnson vaccine, the following processes occur:

- The adenovirus enters the cell.

- The cell's machinery reads the genetic instructions to produce the spike protein.

- The spike protein is displayed on the cell surface.

- The immune system recognizes the spike protein as foreign and mounts an immune response.

- Memory cells are created. If the person is exposed to the SARS-CoV-2 virus in the future, these memory cells will recognize the spike protein and prompt a quick immune response.

4. The Pfizer vaccine uses mRNA, which requires a transcription process from a DNA template in its manufacturing process. This transcription process is conducted ex vivo (outside the organism). The Johnson & Johnson vaccine, on the other hand, uses a DNA vector (adenovirus), which does not require this transcription step in its manufacturing process. Instead, the DNA is directly inserted into the adenovirus vector.

5. To obtain the recombinant DNA plasmid:

- The SARS-CoV-2 RNA is converted to complementary DNA (cDNA) using reverse transcriptase.

- The cDNA corresponding to the spike protein gene is amplified and isolated.

- This cDNA is inserted into a DNA plasmid using restriction enzymes and DNA ligase. This forms the recombinant DNA plasmid.

- The plasmid is introduced into bacteria (usually E. coli) for amplification.

6. The statement that the Pfizer vaccine can change your DNA is not valid. The mRNA in the Pfizer vaccine never enters the cell's nucleus, where the DNA is located. The mRNA is transcribed in the cytoplasm and quickly breaks down after it is used. It does not have the ability to integrate into the genome and therefore cannot change a person's DNA.