We have already seen that with the advent of the fall-winter season, the trajectory of the COVID-19 pandemic has suddenly worsened. We saw it a year ago. The same thing is happening now. The rapidly increasing number of infections is not necessarily caused by more adaptive variants of the virus, or even frequent meetings in closed and unventilated rooms, caused by the weather. Instead, COVID-19 has certain characteristics that make it a seasonal virus.
New analysis done by Prof.’s team. Gustavo Caetano-Anollés demonstrated that the molecular structure on its surface is responsible for the seasonal nature of SARS-CoV-2. This discovery could help predict future mutations and potentially pave the way for new treatments or vaccines.
We were the first to identify a type of viral sensor that responds to external environmental conditions. We believe this structure should become a key component in the processes of anticipating, mitigating and making informed decisions about public health, explains Prof. Caetano Anolis.
The structure in question is embedded in the N-terminal domain of the virus. It belongs to a large group of proteins known as lectins. All organisms produce lectins, although plant production is suspected only initially. Lectins are involved in various interactions between cells, including carbohydrate recognition and commitment and the formation of adaptive and innate immune responses. It is also known to help viruses and other microbes attach to host cells. However, scientists recently discovered that some lectins also play a role in detecting changes in environment temperature.
It happened in 2019. Researchers in China then noticed that one type of lectin, galectin, was involved in the cross-recognition processes of coral polyps and tiny algae called dinoflagellates. However, they note that when the water temperature is outside the narrow thermal range (25-30 °C), the recognition mechanism does not work as efficiently as before. This was the first indication that the galectins were felt by the external heat. This explains the mystery of coral bleaching and the disappearance of coral reefs in warm waters.
Hear this discovery, Professor. Caetano Anolis and colleagues analyzed tens of thousands of SARS-CoV-2 genomes and found a galectin-like structure on the virus’ barbed protein. Scientists believe this structure senses external conditions and, when it’s not too hot or humid, causes a change in the composition of the spiky protein, allowing the viral RNA to enter the host cells.
– Imagine that the spike is a small jar with a lid on top. When the temperature is high, they remain closed and their infectious contents cannot spill out. But when the cap hits the host cell under favorable conditions, which are somewhat cool and dry, the jar opens and releases a fusion peptide that helps connect the viral and host membranes. This allows the virus to enter the cell and begin to multiply, says the lead author of the publication.
As he adds, viruses are constantly changing. And when a particular part of the genome begins to change (mutate) faster than before, this is a sign that the virus is exploring new and better ways to survive and spread within its host. – In other words, such rapid mutations mean that the virus thoughtlessly throws sticky arrows at the target to see what is attached – the researcher clearly explains.
These rapid, accumulated mutations often appear in the regions responsible for transmission, infection, and immune escape, as these traits are most useful in spreading the virus. As the environmental response has proven to be very important for SARS-CoV-2, it is understood that the galectin-like structure is also one of the regions most intensely mutated.
“We found that the galectin-like structure is a common target for mutation because it helps the virus evade or modulate the physiological responses of the host to increase proliferation and survival,” says Caetano Anolis.
By tracking mutations in the galectin-like protein region, the scientists were able to determine the seasonal pattern of SARS-CoV-2 that is common worldwide. They found cumulative outbreaks of mutations throughout 2020, which often led to worrisome new variants. These events occurred in parts of the world where it was winter, or in higher regions where temperatures are low all year round. In the summer and in the lower equatorial regions, such severe spikes did not occur.
The scientists also confirmed that most of the seasonal outbreaks of mutations occurred in the N-terminal region of the spike protein, where the galectin-like structure is located. Tracking the occurrence of mutations in this structure allowed us to determine the seasonal pattern in the context of the pandemic. Depends on the hemisphere and is driven by the outbreak of mutations. Caetano-Anolis explains that these eruptions are responsible for the delta variable and other variables of concern.
The laboratory, led by the professor, is currently analyzing millions of viral sequences from around the world to determine how the genetic makeup of the virus changes the behavior of the virus. Scientists hope to find more molecular evidence of the seasonality of SARS-CoV-2.
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