Virus Shedding And Antibody Response Of COVID-19 Patients

The coronavirus disease 2019(COVID-19)pandemic,caused by the 2019 novel coronavirus(2019-n CoV,also known as severe acute respiratory syndrome coronavirus 2(SARS-CoV-2))are continuing on the earth,which poses a serious threat to public health.However,the viral shedding pattern and the antibody response in COVID-19 patients have not been fully clarified,which hinder the prevention and control of the COVID-19.Herein,we aim to clarify the virus shedding patterns and the regular of antibody response in the COVID-19 patients.First we developed a molecular detection kit(triple targets)targeting S,ORF1 ab and S genes,which showed well sensitivity and specificity.A total of 302 clinical samples from 23COVID-19 patients,including nasopharyngeal swabs,feces,sera/plasma,urine and hand swabs,were collected and detected by the triple-targets kit.The results showed that viral RNA was mainly detected in the upper respiratory tract(nasopharyngeal swabs)and fecal samples,while all the sera/plasma samples were negative,and 2urine and 1 hand swabs were also positive during the detection.Notably,although the first positive time-point of virus shedding in fecal samples was slower than the nasopharyngeal swabs,the peak viral titers(～5623 RNA copies/m L)of fecal samples were higher than that of nasopharyngeal swabs(～2535 RNA copies/m L),and virus shedding period is longer for the fecal samples(～22 days)compared to nasopharyngeal swabs(～10 days).In order to study the antibody response of COVID-19 patients,a total of 338 sequential plasma/serum samples were collected in 49 non-severe and 43 severe patients within 4 months after symptom onset.IgM and IgG antibody levels of nucleocapsid protein(NP)and spike protein receptor binding domain(S-RBD)were detected by ELISA kits.The results displayed that the NP-IgG antibody response level of COVID-19 patients was higher than that of S-RBD-IgG,but the NP-IgM antibody response level was lower than that of S-RBD-IgM.In addition,NP-IgG antibodies remain positive for 100 days after symptom onset(dao),while about 69%of patients become seronegative for the S-RBD-IgG titers at 100 dao.Further analysis showed that the antibody level of the severe patients is significantly higher than that of non-severe patients.S-RBD-IgG titer still has an average of 1:160 at 100 dao,while non-severe patients turn negative within 100 dao.Compared with younger patients(≤ 65-year-old group,that is,18-65 years old group)with severe illness,the older patients(> 65-year-old group)present higher average antibody titers.The peak titers of NP-IgM and NP-IgG in the high-age group were significantly higher than those in the low-age group(NP-IgM: high-age group: 1:80,low-age group 1:20;NP-IgG: high-age group: 1: 2560,low-age group 1:640).In addition,there was no significant difference in the peak antibody titers between male and female patients.Comparison of virus shedding and antibody titers showed that there is no significant correlation between the time of virus shedding and antibody titers in all patients.These results of this study provide theoretical bases for the screening,diagnosis,isolation,and discharge testing standards of COVID-19 patients;clarifying the relationship of disease progress and antibody responses of COVID-19 patients.This may shed new light on the vaccine development and passive antibody therapy with the transfusion of convalescent plasma/sera into critically ill patients against SARS-CoV-2 infection.