Madhavi Bhatia, NIPER Guwahati
SARS-CoV-19, well known as a severe acute respiratory syndrome that affects mainly the respiratory system of humans has become a global pandemic. Various vaccines have been approved worldwide to curb the disease. In Australia, the Pfizer and Moderna vaccine is approved. Both these vaccines are a type of encapsulated mRNA vaccine, these contain tiny fragments of the genetic material i.e mRNA.
How do these vaccines work?
The Pfizer and Moderna vaccine contains mRNA which encodes for the coronavirus spike protein is protected in a lipid nanoparticle (like a soap bubble). The mRNA present in the vaccine is taken up by the cells in the human body and reach the cytoplasm of each cell. Human cells naturally make thousands of their own mRNA which code for the desired protein. The same is the case with the mRNA vaccine it encodes for SARS-CoV-2 spike protein in the cytoplasm and the human immune system recognizes that the protein is different, starts to produce antibodies. The mRNA present in the vaccine is short-lived and undergoes rapid breakdown in the cytoplasm after it induces an immune response. Thus, these vaccines give temporary instructions to human cells to make coronavirus spike protein. This protein is found on the surface of SARS-CoV-2, it is the virus that causes COVID-19. The vaccine teaches the human immune system to protect against the virus if ever encounter in future.
Why mRNA can’t insert into human genetic code?
The human genetic code is made up of deoxyribonucleic acid (DNA) which is closely related to the vaccine mRNA. The vaccine mRNA cannot insert into the human DNA due to 2 reasons-
- Human DNA and mRNA have different chemistry, they differ in sugar and nucleotide base.
- The vaccine mRNA enters the cytoplasm of the cell while the human DNA is present in the nucleus of the cell. There are no transporter molecules known till now that can carry mRNA into the nucleus.
But there are some rare exceptions-
- Retrotransposons hijack the cellular mRNA, convert it into DNA and then insert that DNA back into the human genetic material. This has occurred occasionally throughout the evolution, producing ancient copies of mRNA which are scattered throughout the human genome to form pseudogenes.
- Some retroviruses, for eg HIV, can also insert their RNA into human DNA by using a similar technique used in retrotransposons.
However, there is a negligibly small chance of a naturally occurring retro-transposon to become active in a cell that has just received an mRNA vaccine and also a very little chance of being infected with HIV at precisely the same time while receiving the mRNA vaccine. Even if a retro-transposon is active or virus-like HIV is present, the chances of finding the COVID vaccine mRNA among the ten thousand naturally occurring mRNAs is next to impossible because vaccine mRNA is degraded within few hours of entering the body. In case the vaccine mRNA becomes a pseudogene, it would not produce the SARS-COV-2 virus but will produce one of the viral products- the harmless spike protein.
However, there is no reported evidence of integration of coronavirus RNA into the human genome.
Also read: Epigenetic Changes can cause permanent changes to offsprings
References:
- Zhang, L., Richards, A., Barrasa, M. I., Hughes, S. H., Young, R. A., & Jaenisch, R. (2021). Reverse-transcribed SARS-CoV-2 RNA can integrate into the genome of cultured human cells and can be expressed in patient-derived tissues. Proceedings of the National Academy of Sciences, 118(21), e2105968118. https://doi.org/10.1073/pnas.2105968118
- Fox, Archa, et al. “Can the Pfizer or Moderna MRNA COVID Vaccines Affect Your Genetic Code?” SciTechDaily, 11 July 2021, https://scitechdaily.com/can-the-pfizer-or-moderna-mrna-covid-vaccines-affect-your-genetic-code/
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About the author- Madhavi Bhatia is currently pursuing a Master of Science in Pharmaceutical Biotechnology from NIPER, Guwahati. Her area of interest lies in understanding the role of gene mutation in the development of various diseases and developing treatments for such diseases.
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