Mutation is a Latin word mutationem meaning "a changing."
Mutation can be defined as an alteration in the genetic material (the genome) of a cell of a living organism or of a virus that is more or less permanent and that can be transmitted to the cell’s or the virus’s descendants. The genomes of organisms are all composed of DNA, whereas viral genomes can be either of DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining cause an error during other forms of repair or cause an error during replication. Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements.
Mutation in Covid19 virus:
A study published in a medical journal has revealed that SARS-CoV-2, which causes Covid-19, has undergone multiple mutations in its “spike proteins”. This is the protein that gives the virus the ability to infiltrate the human cells. Once this occurs, the virus starts replicating, which leads to infection.
The paper published in Journal of Laboratory Physicians was based on an analysis of 1,604 spike proteins extracted from 1,325 complete genomes and 279 partial spike coding sequences of SARS-CoV-2 available at National Center for Biotechnology Information (NCBI) in the US till May 1.
The maximum genetic mutations were observed in spike proteins extracted from genomes of SARS-CoV-2 from the US, the experts said. “Viruses are known to mutate or change their genetic structure upon exposure to different environments. But in this case, the change is happening quite fast. We are not sure how it will affect the disease spread,” Singh said.
The others participants of the study included experts from Infectious Diseases and Immunity in Global Health Programme Research Institute of McGill University Health Center, and McGill International TB Center, Canada. The study said spike protein was the major target for vaccine development, but several mutations were predicted in the antigenic epitopes across all genomes available globally.
“The emergence of various mutations within a short period might result in conformational changes in the protein structure, which suggests that developing a universal vaccine could be a challenging task,” the study added.
Mutation was also found in the antigens responsible for producing antibodies, indicating that the patients infected with the mutants would have very low or nil antibodies.
Recently, Hong Kong reported a case of re-infection due to Covid-19. Similar cases have also been documented in the US and India. “Even if a person gets Covid-19 again due to a mutated strain of the virus, the likelihood of severe symptoms would be less as seen in the patient in Hong Kong. This is because the antibodies against one strain of Covid-19 can offer protection against the mutated virus too. However, further scientific study and analysis is needed to ascertain this. The disease is new and we are still learning about it,” said a virologist from Maulana Azad Medical College.
The genome of SARS-CoV-2 contains four structural proteins are named as
(i) Spike protein or S
(ii) Membrane protein or M
(iii) Envelope protein or E
(iv) Nucleocapsid protein or N
(i) Spike protein or S: The S protein is a highly glycosylated and large type I transmembrane fusion protein that is made up of 1,160 to 1,400 amino acids, depending upon the type of virus. It mediate membrane fusion and finally facilitates virus entry. The S protein is a major target of vaccine development.
(ii) Membrane protein or M: M protein determines the shape of the virus envelope
(iii) Envelope protein or E: E protein is the smallest protein in the SARS-CoV-2 structure which plays the role in production and maturation of virus.
(iv) Nucleocapsid protein or N: N protein involves in processes related to viral replication cycle and the cellular response of host cells to viral infections.