Only last week, the world woke up to the news of a new variant of coronavirus detected in the UK -- that is 70% more transmissible than the older variant -- being transmitted across the globe. It is nonetheless unfounded to postulate the worsening of the Covid-19 situation, losing precious sleep over what humanity may suffer because of the mutation. All stakeholders need to worry less about mutant variation and emphasize more on masking, distancing, and vaccination, adhering to the very essence of preventing transmission.
However, I may as well explain, for the awareness of my readers of Surgeon’s Note, the importance of viral sequencing to detect new variants. We are likely to pick up new mutations, depending on the intensity of viral sequence analysis. The UK is at the forefront of viral sequencing, whereas in the US, the picture is quite spotty. Of the over 19 million people infected with coronavirus in the country, the US has done sequencing in less than 0.7% of cases, compared to the UK, which analyzes more than 10,000 per week, and even more now with the detection of this variant. More sequencing means faster detection of a new variant, and faster containment if a variant is regarded as problematic.
But I do also understand our readers’ concern about the consequence of SARS-CoV-2 mutation detected by viral sequence analysis on the effectiveness of vaccines which have just started to circulate, and only a precious few have had the opportunity to be inoculated. The question arises: Does the detection of a new variant mean that the Covid-vaccines would become ineffective?
How our immune mechanism protects us
When our body is exposed to invasion by a harmful virus, our immune mechanism protects us against an external attack response via three main mechanisms: 1. Response mediated through the Cytotoxic cells, 2. Response via proteins known as Interferon, and 3. Antibody mediated response.
A virus, in order to continue its life, has to be able to enter a host cell and replicate. Once the virus enters the human cell, increases in numbers by replication and in the case of coronavirus, in abundance, kills the host cells and huge numbers are released to be able to invade multiples of human cells, destroying tissues and organs, and ultimately leading to death.
Before I explain the mechanism of destruction of a virus such as the coronavirus, it is important for the readers to have a clear conception of the structure of this life-restricting and life-destroying virus. The virion, that is the entire virus particle, in this case of the coronavirus consists of an outer envelope and an inner core of an RNA. The genetic material of novel coronavirus consists of the virus and four structural proteins; a surface spike protein (S), an envelope protein (E), a membrane protein (M), a protein (N) closest to the virus, itself an RNA moiety.
S protein is the major inducer of protective immune responses, and variation in the S protein may help one strain of virus to avoid immunity induced in the host by another strain of the same species.
The S protein mediates the attachment of the virus to the host cells, and is capable of determining which host cell would be susceptible to the virus, and triggers fusion of the virus envelope with the host cell wall. Once within the susceptible cell, the coronavirus genomic component is released from the virion into the host cells, immediately recognized, and rapid multiplication of the virus is initiated, converting the host cells into factories of production line for the virus.
Let’s now see our body’s immune responses to the invading virus.
1. Response mediated Cytotoxic T-cells: Once viruses enter the human cell, other cells of the body, including the immunological cells, are incapable of visualizing the viruses. However, the invaded cell itself has an in-built mechanism which shows part of the virus on its surface for other human cells to visualize. This then immediately attracts the attention of Cytotoxic T-cells that kills the infected cell and with it the virus.
2. Response via proteins known as Interferon: Interferon is a naturally occurring protein produced in human body, and is predestined to inform and initiate the body’s initial antiviral responses. Once the coronavirus gains access to our organ systems, mainly the respiratory system through our nostril, mouth and eyes, the endogenous INF-beta’s response, preordained to warn body’s immune mechanism of the impending viral attack, culminates in an organized all-out immune offensive against the entering virus, ending in the destruction of the virus.
3. Antibody mediated response: Antibodies are the major component of human defense mechanism. They destroy viruses not through a single but through multiple pathways. A. Initially antibodies are able to recognize viruses as foreign bodies and promptly neutralize them rendering them useless in infecting host cells. B. Many antibodies work in unison and ensure enforcement of the viruses sticking together -- a method called “agglutination.” C. The third mechanism used by the antibodies is the activation of body’s defense cells, called “phagocytes.” Antibodies bind to the virus, and then the virus-bound antibody attaches on the surface of the phagocyte and triggers “phagocytosis.” D. Antibodies wake up the other immune mechanism called “complement system,” that not only promotes and enhances phagocytosis, but can also cause destruction of the envelope of the virus.
It is not against a singular component of the virus that the vaccines's generated immune response is effective, but the response is in fact directed against the multifocal component of the virus. It is also imperative for us to understand prior to despair that the vaccine triggers a number of immune mechanisms, and though the coronavirus is undoubtedly readily transmissible, virulent and deadly, the virus’s ability to elude the vaccine’s efficacy remains.
Dr Raqibul Mohammad Anwar is Specialist Surgeon, Global Health Policy and Planning Expert, and Retired Colonel, Royal Army Medical Corps, UK Armed Forces.
