The coronary virus SARS-CoV-2, which caused the pandemic, left China for a world tour last winter, just a few months ago.
However, a huge number of variations are already circulating on Earth, which are slightly different.
When viruses infect a person, multiply in the body, and then come out with droplets thrown out of the airways, a cloud exactly like the one that went in no longer pops out.
Attached video: The researchers modeled how the coronavirus could spread in a restaurant.
In the viral population has occurred. Viable, pro-competitive changes move forward in the chain of infection, and viruses that have lost a competitive advantage are destroyed. In this way, more changes gradually accumulate.
Vaccines are generally designed to make the antibodies produced by them bind only to sites on the virus that are unable to change.
Some researchers interpret the changes as saying that several different virus strains of SARS-CoV-2 are already circulating, while others speak of only one identified strain.
According to the latter school, a new strain can only be talked about when the biological properties of the virus have changed, but so far there is no strong evidence of this.
Coronavirus transformation is being studied extensively around the world. Image from the Israeli HMO Maccabi Laboratory.
Photo: Gil Cohen-Magen / AFP / Journal
It is good to remember that changes are a completely natural part of virus development. They are mapped by examining the genome of viruses, the genome.
Professor of Virology Olli Vapalahti describes genomes as fingerprints of viruses.
- From them, it can be deduced how the infection chains go and where viruses accumulate, Vapalahti tells IS.
Now follows the Bible parable. The Holy Book was once copied by hand.
- The monks made mistakes, and the mistake was always copied. You can follow the route of the book from them, but its message does not change, Vapalahti says.
IS compiled the following answers to questions related to virus transformation.
1. How do mutations arise?
The coronavirus is mainly transformed in small point mutations.
The genome, or genome, is in a single-stranded rna molecule located within the envelope of a virus that has about 30,000 bases. Their order determines what kind of proteins the virus programs the cell to produce.
The bases are denoted by the letters a, c, g, and u, and they always appear as strings of three letters, codons. One codon is the smallest unit in the genome, a control tag that makes up one amino acid when a virus begins to program cell function.
The coronavirus has evolved in evolution with a proofreading feature that corrects errors when the virus is copied. Still, there are small changes to rna from time to time - the letter order of the base chain changes. Letters are dropped or replaced. Codons change.
Often, a mutation is dumb: it changes a gene but does not affect the protein that the gene controls. However, certain letter changes also change the structure of a protein by changing the amino acids that make up the protein. Because proteins can have hundreds or thousands of amino acids, the change may not matter.
Viruses can also exchange genes if several different viruses invade the same cell and their genome merges.
Electron micrograph of SARS-CoV-2 coronaviruses marked in orange from a patient sample.
Photo: National Institute of Allergy and Infectious Diseases / NIH
2. How is the genome of the virus examined?
In the laboratory, viral rna is isolated by disrupting the structures of the cells in a patient sample and releasing their nucleic acids: the rna and dna chains. A cocktail containing rna and dna from all viruses, bacteria, and human cells in the sample is obtained. Rna is converted by enzymes into dna, from which the genome of the coronavirus is then amplified in a targeted manner by pcr technique.
The final step in the study is sequencing by new generation methods. Thus, the order of the letter pairs of the DNA bases amplified from the virus becomes clear. The new generation methods enable accurate and cost-effective analysis even for large sample volumes.
In Finland, this work is carried out by, among others, the Department of Virology of the University of Helsinki, the Finnish Institute of Molecular Medicine FIMM and the Institute of Biotechnology in their joint project.
3. Why is it important to find out the different positions?
The key reason is the traceability of the virus in identifying the chains of infection.
- When there are several possible exposures, information on different strains may help to find out where the infection actually took place, if there have been different strains in these separate exposure situations, says Pekka Ellonen, Head of the FIMM Sequencing Laboratory, IS.
- Patient A has strain 1, patient B has strain 2. When patient C in the same exposure situations becomes ill and strain 2 is found, it can be deduced where C's strain most likely came from, even if he had been in contact with both.
Sequencing also determines the geographical distribution of the virus and helps to acquire capabilities for possible subsequent waves of the epidemic. For example, it can be used to distinguish the local spread of the virus from new infections imported.
Coronavirus samples will be analyzed in a laboratory in Helsinki in May. Hundreds of virus genomes have already been sequenced in Finland from viruses found in patient samples.
Photo: Markku Ulander / Lehtikuva
4. What different variants have been found in Finland?
About 300 confirmed coronavirus genomes have been sequenced from Finnish samples, which contain at least 95% of the entire genome of the virus, says Teemu Smura, a researcher leading the sequencing work of the University of Helsinki's zoonotic virology research group.
According to Smura, the changes are generally insignificant, especially those that do not affect the amino acids encoded by the gene.
However, there are some exceptions here as well. Significant mutations, on the other hand, cause an amino acid change. Its practical effect depends on where in the structure of the virus it hurts.
- If there is a mutation that becomes common and goes to a functional area and that could potentially affect the function of the protein, it is worth taking a closer look and starting to find out in cell and animal models, Smura says.
No more detailed analysis of significant changes in Finnish sequences has yet been made.
- At the moment, I would say that there is nothing terribly special about them, Smura says.
- And of these Finnish samples, it hasn't really been studied yet. It takes a lot of time, which would require cell-level experiments and possibly also animal experiments before such information could be found out.
The sequences show that the viruses found in Finland at the beginning of the epidemic did not come directly from China - they were similar to the viruses that spread from Italy to the rest of Europe. During the spring, the coronavirus has also entered Finland from Germany, Belgium, China and the United States.
A 3D printed model of a new coronavirus peak protein. Changes in this protein can affect the ability of the virus to invade the cell.
Photo: National Institute of Allergy and Infectious Diseases / NIH
5. Do mutations make the virus even more dangerous?
There is no conclusive research evidence on this. Mutations may not be relevant to a patient infected with the virus. The majority of the changes are neutral: they do not affect the functional properties of the virus, such as virulence.
- The birth of a mutation is a trade of chance. Whether a virus can be viable is no longer a coincidence, it comes with a natural choice in the game. Most amino acid mutations are harmful to the virus, Smura says.
However, the picture of Covid-19 disease varies in different patients. There are many reasons behind this, including age and underlying diseases.
Virus sequencing may contribute to finding explanations for this phenomenon. The more difficult disease may be explained by the fact that the virus has achieved some new functionality through mutations.
In addition to the viral genome, researchers are also exploring patients ’own genomes. It is possible that the virus will cause a more serious illness for certain types of people who have certain types of their own genes.
6. What mutations are of most concern to researchers?
Changes in the viral envelope peak protein can be significant. The spike protein attaches to a receptor on the cell surface like a door handle and opens the way for the virus to enter the body.
Modifications to the peak protein are being vigorously investigated as they may complicate the development of vaccines and antiviral drugs. Again, vaccine developers have their own means; researchers know that antibodies bind to a specific part of the peak protein.
"Vaccines are usually designed to make the antibodies they produce only bind to areas of the virus that cannot change," says Smura.
The birth of a mutation is a trade of chance. Whether a virus can be viable is no longer a coincidence, it comes with a natural choice in the game.
An unreported study report from the U.S. National Laboratory in Los Alamos described a mutation in the peak protein called D614G that is suspected of making the virus more contagious. The mutation has become more common: it has been found in two-thirds of the coronavirus sequences studied worldwide.
- It alone is not enough to prove that it is in some way more contagious. There has been a lot of debate about this. The research requires confirmation, Smura says.
- That type of prevalence may be due to epidemiology alone.
The prevalence of a mutation can be explained, for example, by a so-called founding effect: the mutation has spread from a very small population, as if through a genetic bottleneck, to a larger population, narrowing its variability.
Sources: Biomedicum.fi; Medical News Today; Elsevier; Science News; Gisaid.org; The New York Times; Cornell Alliance for Science