(Fighting against New Coronary Pneumonia) Speed, accuracy, and difficulty
China news agency, Beijing, May 17 - Title: speed, accuracy, difficulty Peking University scholar to talk about a new virus detection crown
China News Service reporter Zhang Su
Wuhan has carried out nucleic acid detection of new crown virus throughout the city. Beijing, Harbin and other places have gradually opened up nucleic acid detection services to the public. Looking at the world, the United States, Italy, the United Kingdom and other countries have launched large-scale antibody tests in succession. "Unity II" project carries out serum antibody test research ...
The detection of new coronavirus has once again become the focus. Huang Yanyi, a professor at the School of Chemistry and Molecular Engineering at Peking University and the deputy director of the Beijing Future Genetic Diagnosis and Innovation Center, was invited to explain different detection methods at the scientific lecture "Understanding the Future".
Speed: Development of small devices to shorten detection time
The detection of new coronavirus is mainly divided into nucleic acid detection and antibody detection. The former is a "progressive" test to see if the subject is infected with new coronavirus; the latter is a "past tense" test to see whether the subject's serum has specific antibodies IgM or IgG, and then infer whether the subject has been infected with the new crown virus.
In practice, the application of nucleic acid detection is more intense. Massachusetts Institute of Technology scholar Hadley Sykes and others believe that one of the reasons is that nucleic acid detection technology has long been widely used to detect other viruses, and the development of nucleic acid detection kits is faster and easier. Currently, China's daily nucleic acid detection capacity can reach 1.5 million copies.
The conventional nucleic acid detection process is that after rapid sampling, the sample is stored in the transport medium, and the sample is accumulated to a certain amount for centralized inactivation, so that the virus loses its ability to infect. Then, nucleic acid extraction and PCR (polymerase chain reaction) are performed. "It takes about half a day to complete the whole experiment." Huang Yanyi said.
In his view, improved nucleic acid detection is first reflected in speed. If you want to test a single sample, skip some steps and do the test directly, "you can get the test result in about 30 minutes at the fastest". In the case of many samples, in order to reduce technical errors in operation, he suggested the development of small instruments that can be used at the collection site. At the same time, in order to improve the detection throughput, it is best to hand over the task of nucleic acid extraction to "tired and easy-to-make machine operations."
Hadley Sykes said that antibody testing usually takes only a few minutes to complete and does not require instrument-assisted testing. However, the sensitivity of nucleic acid detection and antibody detection is not 100%, and more efforts are needed to improve the accuracy of detection.
Accuracy: select the detection method according to the time node
The most common sample for nucleic acid detection is a nasopharyngeal swab, which requires high sampling techniques. Since the outbreak, the Chinese and foreign scientific research teams have heard good news-the possibility of using saliva to detect new coronavirus in West China Hospital of Sichuan University Sex is even better than nasopharyngeal swabs ".
The biologics laboratory of Rutgers University in New Jersey announced in mid-April that the technology for detecting new coronavirus by collecting saliva has received emergency authorization approval from the US Food and Drug Administration. Another French pharmaceutical company said that it will use the smartphone's optical system to try to detect the new coronavirus from personal respiratory samples. It is expected that it will only take 30 minutes from the sample collection to the results.
Huang Yanyi said that saliva sampling testing is a very encouraging new method. But he repeatedly emphasized that when making a compromise between the speed and accuracy of the experiment, the accuracy must first be guaranteed.
He further pointed out that molecular detection is never perfect, and people need to understand the advantages and disadvantages of each detection method. In particular, the choice of detection method has an extremely important correlation with time nodes. Specifically, when the viral nucleic acid load in the sample is not large, "the throat swab or alveolar lavage fluid is easier to detect than the stool, but the stool may be present for a longer period of time"; the antibody comes out late in the disease, and the IgM antibody The decline is faster, and the IgG antibody declines more slowly.
Difficulty: The new sequencing library construction method is simple and easy
The virus is constantly mutating. Will the detection kit misjudge? Huang Yanyi replied: The currently designed site detection effect is relatively stable, and it is not a high-frequency region where mutation occurs. But it will take longer to verify this "theoretical possibility."
Will I cross-infection when I take a nucleic acid sample and take off my mask? Huang Yanyi believes that the current domestic prevention and control is effective, and the probability of cross-infection during sampling is "far below imagination", and the public need not worry.
Huang Yanyi is mainly engaged in the research of life analytical chemistry, and has been committed to developing new methodologies to improve the practical difficulties encountered in virus sequencing. In January this year, he and Wang Tsinghua University professor Wang Jianbin, Peking University professor Xie Xiaoliang and other scientists published papers, and proposed a simple RNA (ribonucleic acid) sequencing method "SHERRY". According to the release of Peking University on May 15, this joint team and collaborators from Beijing Ditan Hospital affiliated to Capital Medical University jointly developed a sensitive and simple new coronavirus sequencing method, named "MINERVA".
"This method doesn't pick samples very much, pharyngeal swabs, sputum, and feces are all acceptable." Huang Yanyi said that SHERRY is characterized by "three-step method for sequencing", which greatly reduces the difficulty of experimental operations and makes the experimental results more stable and reliable. MINERVA is based on SHERRY, through specific enrichment, to obtain high coverage and high depth of new coronavirus genome data.
He also said that he has studied the nucleic acid sequences of more than 80 samples and saw phenomena including mutations. "The deeper the understanding of the virus, the more conducive to the prevention and control of the epidemic and prepare for possible future threats." . (Finish)