ALL STEM CELLS

The novel coronavirus (SARS-CoV-2) and the common cold virus are of the same coronavirus family.

The name 'Corona' got its name because the shape of the virus particles protruding from the surface of the spikes resembles a crown.

The coronaviruses that have been confirmed to cause infectious diseases in humans so far include the new corona, SARS (Severe Acute Respiratory Syndrome, SARS-CoV), MERS (Middle East Respiratory Syndrome, MERS-CoV), and four types of seasonal human coronavirus (HCoVs). There are 7 types in all.
Among them, 'seasonal human corona' is the common cold virus.

Humans have been exposed to the same corona virus, that is, a cold virus, long before the new corona appeared.
This is the reason why many scientists paid attention to the possibility of 'cross-immunity' between the new coronavirus and the cold corona as the COVID-19 (novel coronavirus infection) pandemic broke out.
Of course, not everyone who has a cold develops immunity to COVID-19.

So, who can greatly benefit from this cross-immunity?

A study has found that people with a specific type of white blood cell antigen (HLA) have a strong immune response to COVID-19 after they catch a cold.
(Dr. Shinichiro Fuji's team at the Institute of Physics and Chemistry (RIKEN) Integrative Medicine Center in Japan)
When this type of antigen carrier contracted COVID-19, killer T cells that destroy infected cells showed a strong response. These killer T cells had immune memories that responded to specific spike protein sites in the cold corona.
It means that the immune memory that was infected with the cold virus stimulated the killer T cells to respond to COVID-19.

This research paper will be published in the open access journal Communications Biology, published by Nature Research.

According to the outline of the paper previously published on the American Association for the Advancement of Science (AAAS) site (www.eurekalert.org) on ​​the 28th, the research team focused on A24 HLA carriers, which are common in some Asian countries, including Japan.
The purpose of this study was to find out why people in Asian countries are relatively resistant to new corona infection.

HLA, whose type is determined by genes, is one of human histocompatibility antigens.

In order to avoid rejection during organ transplantation, the HLA antigen must match first. Through computer simulation, the research team found six epitopes, which are likely to bind well with A24-type HLA, in the spike protein of the novel coronavirus.

An antigenic determinant refers to an amino acid sequence to which immune cells respond.
Next, the peripheral immune cell responses of A24 HLA carriers who have never been infected with the new coronavirus were observed.

Immune cells of A24-type HLA carriers responded strongly to a single peptide called 'QYI epitope' even without a history of infection.
Surprisingly, the killer T cells of A24-type carriers that remember this peptide also showed cross-reactivity to the epitope of other corona viruses.

These epitopes were well conserved in human coronaviruses, including the seasonal cold virus.
This cross-reactivity has also been observed in patients with hematologic cancer.
If a patient with blood cancer with a severely compromised immune system gets COVID-19, the risk of progression to severe disease is very high.

However, a hotspot that induces a strong immune response in blood cancer patients was present in the spike protein of the novel coronavirus.
Amino acid 27 located near the QYI epitope was that site.
The results showed that 100% of uninfected blood donors and 65% of blood cancer patients responded to this hotspot.
This suggests that it is possible to develop a vaccine that amplifies the immune response in immunocompromised infected people, such as blood cancer patients.

The spike protein was found to change shape several times after binding to the host cell's ACE2 receptor.

The main goal of this study is to find ways to reduce the number of COVID-19 deaths.
Researchers emphasized, "We hope to develop a vaccine that strongly stimulates a targeted T-cell response in the body of a person infected with the novel coronavirus. At least for A24-type HLA carriers, we have confirmed that this is possible."