SARS-CoV-2-COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for the coronavirus disease of 2019 (COVID-19). First identified in Wuhan (Hubei, China) in December of 2019, it has since been declared a pandemic by the World Health Organization in March of 2020.

The molecular structure of the SARS-CoV-2 Envelope protein has been identified by researchers using nuclear magnetic resonance.

The molecular structure of a protein found on the surface of the SARS-CoV-2 virus has been determined by researchers and the protein, called the Envelope (E) protein, forms a cation-selective channel and plays a key role in the virus’s ability to replicate itself and stimulate the host cell’s inflammation response. The study was conducted at the Massachusetts Institute of Technology (MIT), US. 

How does the coronavirus spread?

As of now, researchers know that the coronavirus is spread through droplets and virus particles released into the air when an infected person breathes, talks, laughs, sings, coughs or sneezes. Larger droplets may fall to the ground in a few seconds, but tiny infectious particles can linger in the air and accumulate in indoor places, especially where many people are gathered and there is poor ventilation. This is why mask-wearing, hand hygiene and physical distancing are essential to preventing COVID-19.

Symptoms

Patients who test positive for SARS-CoV-2 and are symptomatic are diagnosed with COVID-19. Symptoms can vary drastically; they include fever , chills, dry cough, sputum production , fatigue, lethargy, arthralgias, myalgias , headache, dyspnea , nausea, vomiting, anorexia , and diarrhea . Some carriers may be asymptomatic, whereas others can experience acute respiratory distress syndrome (ARDS) and death. Severity seems to also vary with age, disproportionately affecting those of advanced age and those with pre-existing chronic medical conditions.

Diagnosis

Diagnosis is ultimately confirmed by real-time reverse transcription polymerase chain reaction (rRT-PCR) on respiratory or blood samples. Note that rRT-PCR positive-to-negative conversion has been reported at 6.9 ± 2.3 days . Some reports detail imaging findings suggestive of COVID-19, although these findings can be nonspecific and reliability has not yet been established . Computed tomography (CT) findings include bilateral multilobar ground-glass opacities, with peripheral posterior distribution, mainly in the lower lung lobes. Less commonly, septal thickening, bronchiectasis, pleural thickening, and subpleural involvement have been reported. As disease progression occurs, repeat CT scan may show multifocal consolidations with a paving pattern.

Immune Response

Immune responses to CoVs. (A) When the SARS-CoV-2 virus invades the host, it is first recognized by the angiotensin converting enzyme (ACE) 2 receptor present on respiratory epithelial cells allowing viral entry. Following viral replication within the cells, the virus is released where it is met by the host’s innate immune system. T lymphocytes and dendritic cells are activated through pattern recognition receptors (PRRs) including C-type lectin-like receptors, Toll-like receptor (TLR), NOD-like receptor (NLR), and RIG-I-like receptor (RLR). The virus induces the expression of numerous inflammatory factors, maturation of dendritic cells, and the synthesis of type I interferons (IFNs) which limits the viral spread and accelerates macrophage phagocytosis of viral antigens resulting in clinical recovery. However, the N protein of SARS-CoV can help the virus escape from the immune responses and overreaction of the immune system generates high levels of inflammatory mediators and free radicals. These induce severe local damage to the lungs and other organs, and, in the worst scenario, multi-organ failure and even death. (B) The adaptive immune response joins the fight against the virus. T lymphocytes including CD4 + and CD8 + T cells play an important role in this defense. CD4 + T cells stimulate B cells to produce virus-specific antibodies whilst CD8 + T cells are able to directly kill virus-infected cells. T helper cells produce pro-inflammatory cytokines to help the defending cells. However, SARS-CoV-2 can inhibit T cells by inducing programmed cell death (apoptosis). (C) Humoral immunity including complement factors such as C3a and C5a and specific B cell-derived antibodies are also essential in combating SARS-CoV-2 infection.

Vaccine

Killed Type- Covaxin

India's indigenous COVID-19 vaccine by Bharat Biotech is developed in collaboration with the Indian Council of Medical Research (ICMR) - National Institute of Virology (NIV).

The India's indigenous, inactivated vaccine is developed and manufactured in Bharat Biotech's BSL-3 (Bio-Safety Level 3) high containment facility.

The vaccine is developed using Whole-Virion Inactivated Vero Cell derived platform technology. Inactivated vaccines do not replicate and are therefore unlikely to revert and cause pathological effects. They contain dead virus, incapable of infecting people but still able to instruct the immune system to mount a defensive reaction against an infection.

Why develop Inactivated Vaccine? Conventionally, inactivated vaccines have been around for decades. Numerous vaccines for diseases such as Seasonal Influenza, Polio, Pertussis, Rabies, and Japanese Encephalitis use the same technology to develop inactivated vaccines with a safe track record of >300 million doses of supplies to date. It is the well-established, and time-tested platform in the world of vaccine technology.

Adenovector Type-Sputnik V and Covishield

Sputnik V is a viral-vector vaccine. That means that it uses a modified version of a different virus as a tool to transport genetic material to a cell. Sputnik V was developed using adenoviruses, which normally causes respiratory infections, but other viruses (including influenza or measles virus) have also been used in other viral-vector therapies,” a report in the Radio Free Europe/Radio Liberty (RFERL). 

The virus, which is used as a vector, is altered so it poses no threat of causing an illness. For Covid-19 vaccines, this gene contains instructions on how to make a spike protein, which is found on the surface of the coronavirus.

Once a person gets the vaccine, the vector enters a cell and uses it to make spike proteins. As soon as the immune system recognizes the spike proteins, it starts producing antibodies and activates other immune processes in the body.

Covishield, the Oxford-AstraZeneca vaccine being manufactured by the Serum Institute of India, follows the same philosophy. It is made from a weakened version of a common cold virus (known as an adenovirus) from chimpanzees. It has been modified to look more like coronavirus – although it can’t cause illness.

Mutants

Single, Double, Triple

Immune Escape

Vaccine Escape

Fast Transmission, Low Virulence

References

https://www.frontiersin.org/articles/10.3389/fimmu.2020.02037/full

https://www.mdpi.com/1999-4915/9/12/369

https://www.bharatbiotech.com/

https://www.drugtargetreview.com/news/76167/researchers-reveal-structure-of-sars-cov-2-envelope-protein/