An Exclusive Interview with Virologist, Associate Professor, Dr. Kitazato Kaio from Nagasaki University

Virologist Associate Professor, Dr. Kitazato Kaio from Nagasaki University(Picture Provided by  Dr. Kitazato Kaio)

(Beijing,Friday, April 24)The COVID-19 has swept more than 200 countries and regions, which causes an increasing number of infected cases day by day.

Dr. Kitazato Kaio, Associate Professor from Nagasaki University in Japan, is quite concerned about this pandemic. In an interview with the Science and Technology Daily reporter, he made a detailed analysis in terms of virus transmission characteristics, the scientific and long-term nature of virus traceability, the achievements made by Chinese scientists, and called for a global joint-operation.

The transmission characteristics of novel coronavirus and main causes of global pandemic

Dr.Kitazato Kaio concluded that, based on many research reports from all over the world, this new coronavirus has several new salient features compared with the previously discovered SARS-CoV and MERS-CoV.

First, the spike protein (S protein) of the novel coronavirus is the surface envelope protein responsible for the virus particles entry into their infected cells, which is the human angiotensin converting enzyme 2 (ACE2) binding protein. The S protein of the novel coronavirus binds to its cell receptor ACE2 with an affinity that is 10 to 20 times higher than that of the SARS-CoV S protein. The high affinity of the S protein to the receptor shows that the virus particles have a strong attachment to the cells and it is easy to infect the cells.

Like the infectious enveloped virus, such as influenza virus, the novel coronavirus has the characteristics of protease dependence in the infection process of invading infected cells. The S protein itself is a precursor protein and has no cell fusion activity. It is only cleaved into two protein fragments S1 and S2 by the protease of the host cell. After the exposure of fusion peptide (FP) responsible for cell membrane fusion in S2 fragment, the S protein is activated and the virus particles can fuse with the infected cell membrane, invades the cell, and completes its infection process.

The second characteristic of the novel coronavirus is that its S protein has a furin protease cleavage site between S1 and S2 which do not exist in SARS-CoV or MERS-CoV. The furin protease is a ubiquitous protease in human cells. When the novel coronavirus particles are assembled and released from infected human cells, the S protein of the virus has been cleaved into the activated state of S1 and S2 by the furin protease in the cells. And its virus particles have already had a strong cell infection and fusion membrane activity, which makes the infection efficiency of the new coronavirus nearly 1,000 times higher than SARS-CoV.

Finally, the structural characteristics of the novel coronavirus S protein determine its ability to infect cells and replicate rapidly. Therefore, the person who is infected can release a large number of highly infectious virus particles in the early stage of infection before the systemic symptoms appear. Stronger infectivity than influenza virus is the main reason why the novel coronavirus can be pandemic in the world.

Virus searching is a very serious scientific issue, which needs to be supported by clear scientific evidence

Dr. Kitazato Kaio said that coronavirus can be classified into four genera: α, β, γ, and δ. γ and δ mainly infect birds, while α and β mainly infect mammals. The novel coronavirus is classified as β group. The natural host is likely to orginate from bats. It has also been reported that similar viruses have been found in pangolins, snakes and other wild animals.

Currently, the route of infection remains a question to the public. The novel coronavirus infects people through the intermediate hosts or just directly infect people from the natural reservoir, which are both under rigorous research. So, virus searching, seeking for intermediate hosts, and research on the transmission of viruses to people are the important steps to completely cut off the spread of the virus.

This is a very serious scientific issue, which needs to be supported by solid scientific evidence. The solution to this crisis requires the joint efforts of scientists from all over the world.

Screening of serum antibodies in patients with suspected influenza cases may provide clues to search the virus origin

Dr. Kitazato Kaio believes that the continuous plague records in human history indicate that new viruses could invade people from other organisms. With the emergence of the new virus, it is impossible to effectively prevent the infection through the immune system due to the reason that the human body does not have specific immunity. The virus will continue to spread and replicate its “off-springs" in the crowd. Only until the majority of people are immune to it can we successfully contain the development of the pandemic.

The most effective way for humans to deal with the infection of emerging viruses is to research and develop vaccines. Before achieving the goal of herd immunity, everyone is susceptible to the virus and no one can stay out of the possible infection.

The immune system has a memory function for the infection of pathogens that invade the body. With the current technology, as long as the antibodies in the blood are detected, it is possible to screen out the past infected experience of various pathogens.

If the serum antibodies of clinically suspected influenza cases and other patients are widely screened in the future, it will help to provide clues for finding the source of novel coronavirus infections.

Chinese scientists guard well against new challenges

In the early stage of the epidemic, Chinese doctors and scientists efficiently isolated the virus in the shortest time and analysed the whole genome sequence of the virus. In addition, China has been timely releasing information on COVID-19 to the rest of the world since the onset of the epidemic, making the international community informed about the emergence of the COVID-19.

This fully demonstrates the professional performance and the sense of responsibility of Chinese scientists to the public health, and lays a solid foundation for the public to face new challenges together.

In addition, in order to quickly contain the spread of the epidemic, the Chinese government took strict and comprehensive prevention and control measures including city lockdowns to contain the virus and protect its citizens. These efforts and sacrifices of China have won precious time for the world to jointly fight the epidemic, and are highly appreciated by the World Health Organization (WHO) and relevant experts from various countries.

“Joint Global Operation” is essential to successfully contain the COVID-19

When COVID-19 occurs at the early stage, countries around the world should have been vigilant with all kinds of preparedness. However, some politicians failed to take positive measures to prevent the spread of the pandemic in their own countries, which led to spread across the world. They made dangerous attempts to politicize COVID-19, casting a shadow on our joint fight against our common enemy.

The novel coronavirus pandemic, regarded as a once-in-a-century global challenge, is extracting a huge cost in terms of human lives and health, and posing challenges to political, economic and national management system.

COVID-19 poses a huge threat to human life and health. The pandemic does not distinguish the country, race, gender, age and social status. All countries should join hands to fight against COVID-19 with our global wisdom and scientific strength when confronted with our common enemy. Only with solidarity and by cooperation can the international community prevail over the pandemic and safeguard the common homeland of humanity.

Dr. Kitazato Kaio reminds that the COVID-19 may break out again at any time before widespread vaccination. Human community should actively make back-up plans to deal with such possible outbreaks without affecting the normal development of society.