By Capt. Dr. Kushilab Bose – Director, Medical Operations, Healthspring
There are four families, of coronaviruses. All seven coronaviruses are known to infect humans belong to either the alpha or beta families. The two in the alpha family, 229E and NL63, cause common colds. The beta family is more problematic for humans: It includes all three viruses that have caused deadly outbreaks in humans: SARS-CoV-1, SARS-CoV-2 and MERS.
All viruses constantly change through mutation and this includes SARS-CoV-2. This can lead to the emergence of new variants that may have different characteristics. A variant has one or more mutations that differentiate it from other variants in circulation.
Genomic sequencing analyzes the viral genes and learn more about the virus. Genomic sequencing studies monitor how the virus changes over time into new variants, understand how these changes affect the characteristics of the virus, and use this information to better understand how it might impact health.
Variant viruses are of particular concern because they spread more easily, cause more severe disease, or may escape the body’s immune response.
Variants of viruses are classified into three groups -Variants of Interest (VOI), Variants of Concern (VOC) & Variants of High Consequence (VOHC). Currently, there are no SARS-CoV-2 variants that are in the level of High Consequence.
B.1.617 variant – The B.1.617 version of the coronavirus carries the nickname “double mutant,” because it has more than two sequence changes from older SARS-CoV-2 variants. It is currently classified as a Variant of Concern (VOC)
B.1.617.2 (Also known as DELTA variant): This variant was first detected in India in December 2020 andis currently classified as a Variant of Concern (VOC). It is said to be behind the severe second wave of Covid in India, which has affected more children than in the first wave. This variant also has three sub-lineages — b.1.617.2, b.1.617.3 and b.1.617.1. Preliminary modelling by WHO suggests that B.1.617 has a higher growth rate than other circulating variants in India, suggesting potential increased transmissibility. About 60% of covid-19 cases in Maharashtra by mid-February are said to have been the b.1.617 variants.
There is also a new variant from the b.1.617.2 subgroup, known as “Delta plus”, AY.1, or B.1.617.2.1, which has an extra mutation in the spike protein of the virus.
WHO estimates that Delta & Delta Plus will become the predominant global variant in the future.
According to the BMJ, these mutations appear to help the virus partially evade immunity conferred by prior infection or vaccines.
These variants seem to spread more easily and quickly than other variants, which may lead to more cases of COVID-19. An increase in the number of cases will put more strain on healthcare resources, lead to more hospitalizations, and potentially more deaths.
It can negatively affect the detection of the virus by reverse transcription (RT) PCR. Mutations in the loci recognized by DNA primers may reduce the amplification of viral sequences and, as a result, potentially miss the detection of the virus in samples from COVID-19–positive individuals. It is recommended that diagnostic tests include more than one target to ensure proper SARS-CoV-2 detection. While a number of products already include multiple genetic targets, some COVID-19 RT-PCR assays have only one target and are not to be used for testing.
Another cause of concern is that there will be a potential reduction in neutralization by some monoclonal antibody treatments, as well as reduced immune response post-vaccination.
These issues are also well known with the Influenza Virus – the first virus to cause a global pandemic, starting in 1918 pandemic which is estimated to have been responsible for the deaths of 50–100 million people. Influenza epidemics and pandemics have recurred five times since then, however, no effective medication or long-lasting vaccination has been developed. The genetic diversity of influenza viruses gives them the ability to rapidly mutate and evade the body’s defenses.
The good news is that although coronaviruses also mutate—as is clear from the continuous threat from new variants of SARS-CoV-2—they do so at a much slower rate than influenza viruses do.
Coronavirus vaccinesare expected to work against the emerging variants because there are two ways that vaccines provide the immune response against the viruses (and variants) – either stimulating the production of antibodies, proteins that recognize foreign invaders and attack them before they infect a cell, OR recruiting T cells, a type of immune cell that shows up later to destroy cells after they’ve become infected.
T cell responses are great because unlike antibodies, which have to some extent a more limited repertoire, T cells will actually recognize parts of the virus that get broken down inside the cell. Antibodies are very specific to one type of variant, but for all variants, T cell response is going to provide broader protection.
Corporate Comm India (CCI Newswire)
