By John Kiragu, MPH(Ongoing)
SARSCoV2 virus and Covid19 Vaccines
The SARSCoV2 virus causes the Covid-19 disease and is the cause of over 2 million deaths globally and over 1700 deaths in Kenya since it was discovered in Wuhan China 12 months ago(1). In this article, we explain the structure of the SARS-CoV2 virus and how the vaccines work against it to prevent the Covid-19 disease.
The Spike (S) protein on the surface of the SARSCoV2 virus enhances its entry into the human body cells by binding on the Angiotensin-Converting Enzyme (ACE) receptor on the surface body cells.
Once the S protein is bound by the ACE receptor on the human body cells, it enters the body cells where it initiates replicative processes which end up with the release of more viral particles and damaging of the human host cell (2)
Where are the ACE receptors located in the body? The ACE2 receptors are found on the surface of the oral mucosa (mouth cavity), nasal cavity, small intestines, brain, alveolar epithelial cells in the lung and the walls of the blood vessels. The distribution of the ACE2 receptors determine the routes by which the virus enters the body. For example, most infections have been attributed to occur by the way of inhalation of the viral droplets through the nose and the mouth cavity(3).
To prevent the SARS-CoV-2 from entering the human host cells, SARS-CoV 2 spike protein S is the main target by the current vaccines developed for Covid-19 disease(4). The Covid19 vaccines are developed in form of a weakened SARSCoV2 whole virus or part of it that is non-dangerous but sufficient enough to trigger our bodies to produce specific SARSCoV2 virus disease-fighting proteins called antibodies. When the real dangerous SARSCoV2 virus infects the body, the antibodies that were released in response to the Covid19 vaccine bind to the virus and stop it from binding ACE receptors thus it is prevented from entering the Human body cells. This process is called neutralization of the virus by the antibodies(4).
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Buchholz UJ, Bukreyev A, Yang L, Lamirande EW, Murphy BR, Subbarao K, et al. Contributions of the structural proteins of severe respiratory syndrome coronavirus to protective immunity. Proc Natl Acad Sci U S A. 2004;101(26):9804–9.
Hamming I, Timens W, Bulthuis MLC, Lely AT, Navis GJ, van Goor H. Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis. J Pathol. 2004;203(2):631–7.
WHO. COVID-19 Weekly Epidemiological Update. World Heal Organ [Internet]. 2020;(November):1;4. Available from: https://www.who.int/docs/default-source/coronaviruse/situation-reports/20201012-weekly-epi-update-9.pdf