Virus antigen

Like RNA, structural protein is also a specific marker of coronavirus, and it is also a viral antigen that stimulates patients to produce specific antibodies. As shown in Table 1, virus antigen detection not only has all the advantages of antibody detection (fast, simple, convenient, economical, does not require equipment, and does not require high levels of operators, damage environment, etc.), but also has all the advantages of nucleic acid detection (early Diagnosis, high reliability, etc.). It is worth noting that in coronavirus particles, the antigen content can reach thousands of times the nucleic acid content; according to literature reports, a coronavirus particle contains only 1 RNA, and the average content of its S1 protein and N protein is 222 Molecules and more than 3000 molecules. Based on this calculation, when the sensitivity (lowest detection limit) of S1 antigen detection reaches 6-30 pg/mL or the sensitivity (lowest detection limit) of N antigen detection reaches 40-200 pg/mL, its resistance to mature coronavirus The detection sensitivity can be equal to nucleic acid detection (200-1000 copies/mL, that is, 3-15pg/mL). In addition, because the virus releases a large amount of free antigen without nucleic acid in the early stage of virus replication, nucleic acid-negative samples in the very early and active stages of infection may also be antigen-positive. For example, in the early stage of SARS-CoV infection (days 1-10), as many as 70% of patients have high levels of N protein in their blood, and the nucleic acid content in the blood can hardly reach the detection level. Therefore, antigens are theoretically more ideal detection targets than nucleic acids.