Nadeem Dar
The covid-19 virus is humanity’s newest foe, with the potential to prematurely end millions of lives. To control this new coronavirus, we need to understand it. Labs around the world are now working around the clock in a bid to know their enemy. Conaviruses are a group of viruses belonging to the family of Coronaviridae, which infect both animals and humans. Human coronaviruses can cause mild disease similar to a common cold, while others cause more severe disease (such as MERS – Middle East Respiratory Syndrome and SARS – Severe Acute Respiratory Syndrome). A new coronavirus named SARS-CoV-2 by International Committee on Taxonomy of Viruses (ICTV) that previously has not been identified in humans emerged in Wuhan, China in December 2019. The coronavirus disease of 2019 was named COVID-19 by the World Health Organization (WHO) in a press release on February 11, 2020. The name was based on letters from the words- “co” for corona, “vi” for virus and “d” for disease and because the outbreak began in 2019.
Between chemistry and biology
“It is switching between alive and not alive”, said Gary Whittakar, a Cornell University professor of virology. He described a virus as being somewhere “between chemistry and biology”. Outside a host, viruses are dormant. They have none of the traditional trappings of life: metabolism, motion, the ability to reproduce. And they can last this way for quite a long time. When viruses encountered a host, they use proteins on their surfaces to unlock and invade its unsuspecting cells. Then they control of those cells” molecular machinery to produce and assemble the materials needed for more viruses.
Virus entry mechanism
The new coronavirus has four kinds of structural proteins: The spike (S) protein, the nucleocapsid (N) protein, the membrane (M) protein, and the envelope (E) protein. The S protein helps the virus’s membrane and the cells to fuse together. This offers promise, as therapies to treat Covid-19 could actually use ACE2 antibodies to block the novel coronavirus entry. Such studies are currently being conducted in many parts of the world. It makes the journey through our airways to attach itself to the ACE2 receptors via the S protein on its fuzzy crown-like surface. ACE stands for Angiotensin converting enzyme, and ACE2 is an enzyme that is attached to the cell membranes in our lungs, kidneys, heart, intestines, and arteries. Smoking makes these receptors more vulnerable. Once it binds itself comfortably on these receptors, it releases a small RNA material into the cell in the cytoplasm. This is a tiny genome with about 30000 bases as compared to the human one which is 3.2 billion base pairs. Now inside the cell, the virus hijacks the cell’s machinery like the ER, Golgi apparatus and makes many copies of itself.
Scientists are working around the clock to understand the biology of the covid- 19 virus and how it infects human cells, which will help us design treatments to stop it
How does covid-19 affect the body?
It is thought that covid-19 shares many similarities with SARS, which has three phases of attack-viral replication, hyper-reactivity of immune system and pulmonary destruction. Early on an infection, coronavirus invades two types of cells in lungs- mucus producing (Goblet) cells and ciliated cells. Mucus keeps lungs from drying out and protects them from pathogens. Cilia beat the mucus towards the exterior of the body clearing the breathe including viruses out of the lungs. When these cells die, they slough off into the airways, filling them with debris and fluid. Symptoms include fever, cough and breathing difficulties. Many of those infected get pneumonia in both lungs. Immune cells recognize the virus in flood into the lungs, the lung tissue becomes inflamed. During normal immune function, the inflammatory process is highly regulated and is confined to infected areas. Sometimes the immune system overreacts, and this results in damage to healthy tissue. More cells die and slough off into the lungs. Further clogging them and worsening the pneumonia. As damage to the lungs increases, resulting in respiratory failure. Proteins called cytokines are the immune system’s alarm system, recruiting immune cells to the infection site. Over production of cytokines can result in a cytokine storm, results in large scale inflammation in lungs, blood vessels become more permeable which causes fluid to leak into the lungs and finally it becomes difficult for oxygen to rest of the body and can result in multi-organ failure. This is happened in most of the severe cases of covid-19.
(The author is a Senior Research Fellow (SRF) at SKUAST-K, Shalimar Srinagar. Views are his own, [email protected])
