Virology/Immunology In Relation to Covid-19

It has been several months since COVID-19 has been declared a global pandemic resulting in millions of cases and thousands of deaths worldwide. Labelled as one of the greatest challenges to mankind, it is much more than a mere health crisis as it continues to negatively impact our daily lives and handicap world economies (UNDP). But what is the virology and immunology behind this strain of virus? Is it possible for us to develop a lasting immunity? Answers to these critical questions are crucial in developing a vaccine or a cure for SARS-CoV-2. Realising the significant threat the pandemic poses, approximately 140 vaccines are being developed globally with around a dozen undergoing clinical trials (BBC News). People are now panicking over reinfection, as there have been cases of those recovering only to be reinfected. Immunologists studying the virus have found that immune responses for antibodies against COVID are looking really good, despite not knowing the longevity of their effects.

Figure 1 shows the spherical structure of SARS-CoV-2 sith protein spikes protruding from its surface.

The novel coronavirus, which belongs to the family Coronaviridae, has a spherical structure with protein spikes protruding from its surface (figure 1). These spikes bind to a special receptor present in the respiratory system known as the Angiotensin Converting Enzyme (ACE-2), helping the virus attach itself to human cells and thus causing infection. Researchers believe the spike protein, which plays a pivotal role in infecting human cells, could be a key target for vaccines and therapeutics (Wrap et al).

Information on how a virus is transmitted can be crucial to understanding its virology. Since scientists have suspected that the virus emerged from an animal, such as a bat or pangolin, which was then transmitted to humans, the virus would be referred to as a zoonosis. Many past pandemic outbreaks have also been caused by bats, as they are a common breeding ground for deadly diseases. Scientists were prompted to study the reasons why, and they discovered that DNA in bat cytoplasm can trigger rapid production of interferons, which are signaling proteins designed to launch an immune response against infections. A mutation has allowed for the interferon pathway to switch on and off just enough to stop the bat’s immune system from going into overdrive. In other words, bats are able to carry many deadly viruses without experiencing their negative side effects, which also means high transmission rates.

Several teams of researchers have isolated neutralizing antibodies but he severity of infection has to be taken into account. Those with the most severe infections experience the highest level of antibody responses. When a virus attacks, it causes a large number of lymphocytes to be generated in order to recognize pieces of the virus. However, after the infection is gone, levels of T-cells and B-cell (lymphocytes) drop which could explain why reinfections occur. But this does not happen so suddenly. There are some special lymphocytes called memory B-cells that linger in the bone marrow until the virus returns and are capable of mounting an even stronger immune response. Although the data on these memory B-cells are incomplete which makes it more difficult for them to be located, preliminary research has shown that they are still capable of producing antibodies. Studies so far also suggest that T-cells could recognize the SARS-CoV-2 virus at high rates, and most people have good T-cell responses.

Figure 2 shows the two types of lymphocytes, B and T cells, which proliferate in response to infections and help kill pathogens. While T cells are capable of killing viruses directly, B cells produce antibodies against viral antigens which prevent viruses from infecting new cells.

Sterilizing immunity will be the most ideal way to approach this virus as it reduces the risk of people with infections spreading the virus but at this point, a vaccine that could reduce mortality rate will be more beneficial. When developing vaccines, researchers have looked at similar coronaviruses and compared it to SARS-CoV-2, which suggests that there may be cross immunity between the two. There are many trials underway for treatments that would allow for reduction of symptoms and provide better immunity in the future but the process is long. Scientists are suspecting a vaccine could come soon, while others are hoping the virus will go away on its own. Regardless, it is important that everyone help keep themselves as well as others around them safe and healthy. Remember to do your part and wash your hands, socially distance and wear a mask!

References

Dr. Biology. (2011, February 16). B-cells. ASU - Ask A Biologist. Retrieved September 8, 2020 from https://askabiologist.asu.edu/b-cell

Gallagher, J. (2020, July 21). Coronavirus vaccine: When will we have one? Retrieved September 04, 2020, from https://www.bbc.com/news/health-51665497

Ledford, H. (2020). What the immune response to the coronavirus says about the prospects for a vaccine.Nature. https://www.nature.com/articles/d41586-020-02400-7

Lodish, H. (1970). Viruses: Structure, Function, and Uses. NCBI. https://www.ncbi.nlm.nih.gov/books/NBK21523/

Sandoiu, A. (2020). Why are infections from animals so dangerous to humans? Medical news today. https://www.medicalnewstoday.com/articles/zoonotic-diseases-why-are-infections-from-animals-so-dangerous-to-humans

UNDP. (2020, July 07). Coronavirus disease COVID-19 pandemic. Retrieved September 04, 2020, from https://www.undp.org/content/undp/en/home/coronavirus.html

Wrapp, D., Wang, N., Corbett, K. S., Goldsmith, J. A., Hsieh, C. L., Abiona, O., Graham, B. S., & McLellan, J. S. (2020). Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science (New York, N.Y.), 367(6483), 1260–1263. https://doi.org/10.1126/science.abb2507

Zimmer, K. (2018). Why Bats Make Such Good Viral Hosts. The Scientist. https://www.the-scientist.com/notebook/why-bats-make-such-good-viral-hosts-64251