Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019

Abstract

BackgroundThe novel coronavirus SARS-CoV-2 is a newly emerging virus. The antibody response in infected patient remains largely unknown, and the clinical values of antibody testing have not been fully demonstrated. MethodsA total of 173 patients with confirmed SARS-CoV-2 infection were enrolled. Their serial plasma samples (n = 535) collected during the hospitalization period were tested for total antibodies (Ab), IgM and IgG against SARS-CoV-2 using immunoassays. The dynamics of antibodies with the progress and severity of disease was analyzed. ResultsAmong 173 patients, the seroconversion rate for Ab, IgM and IgG was 93.1% (161/173), 82.7% (143/173) and 64.7% (112/173), respectively. Twelve patients who had not seroconverted were those only blood samples at the early stage of illness were collected.The seroconversion sequentially appeared for Ab, IgM and then IgG, with a median time of 11, 12 and 14 days, respectively. The presence of antibodies was < 40% among patients in the first 7 days of illness, and then rapidly increased to 100.0%, 94.3% and 79.8% for Ab, IgM and IgG respectively since day 15 after onset. In contrast, the positive rate of RNA decreased from 66.7% (58/87) in samples collected before day 7 to 45.5% (25/55) during days 15 to 39. Combining RNA and antibody detections significantly improved the sensitivity of pathogenic diagnosis for COVID-19 patients (p < 0.001), even in early phase of 1-week since onset (p = 0.007). Moreover, a higher titer of Ab was independently associated with a worse clinical classification (p = 0.006). ConclusionsThe antibody detection offers vital clinical information during the course of SARS-CoV-2 infection. The findings provide strong empirical support for the routine application of serological testing in the diagnosis and management of COVID-19 patients.

Neutralizing Antibodies Responses to SARS-CoV-2 in COVID-19 Inpatients and Convalescent Patients

“…The results of our study indicated that convalescent patients had a higher antibody level than inpatients, which highlight the positive correlation between recovery and days since onset (Spearman correlation coefficient=0.5426, P<0.0001). Besides, we also found that antibody levels in asymptomatic or mild patients were slightly lower than moderate or severe patients, which was in line with other previous studies [16][17] . Zhang [17] came to a similar conclusion that severe cases were more frequently found in COVID-19 patients with high IgG levels, compared to those who with low IgG levels.…”

“…The effect of gender was also not statistically significant in both univariate (P=0.9426) and multivariate (P=0.8543) GEE analysis. A significant neutralizing antibody response was observed in older patients with a geometric mean titer of 1:220.1 (95% CI, 71.8 to 674.8) compared to patients at age of [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] (1:71.0, 95% CI, 27.7 to 181.8) and at age of 31-60 (1:200.6, 95% CI, 150.4 to 267.6) (P=0.0140).…”

Serology characteristics of SARS-CoV-2 infection since the exposure and post symptoms onset

“…Zhao et al [19] reported that the overall RNA positive rate was lower than 70% in patients on the first week post symptoms onset and fall to 50% on the next week.…”

Contribution of anosmia and dysgeusia for diagnostic of COVID-19 in outpatients

“…In our series, 23/112 patients in G2 had crackling sounds heard on pulmonary auscultation, and it is probable that some of them may have presented CT scan findings enabling us to validate a diagnosis of COVID-19. In recent studies, combination of RT-PCR (on respiratory samples) and serological tests also seems to enhance the sensitivity for COVID biological diagnosis [13].…”