key: cord-0953779-97mz0hks
authors: Leach, Susannah; Harandi, Ali M.; Bergström, Tomas; Andersson, Lars‐Magnus; Nilsson, Staffan; van der Hoek, Lia; Gisslén, Magnus
title: Comparable endemic coronavirus nucleoprotein‐specific antibodies in mild and severe Covid‐19 patients
date: 2021-05-03
journal: J Med Virol
DOI: 10.1002/jmv.27038
sha: 03e698ab38d5373ccc4912dea14e11e6879ceeba
doc_id: 953779
cord_uid: 97mz0hks

The severity of disease of Covid‐19 is highly variable, ranging from asymptomatic to critical respiratory disease and death. Potential cross‐reactive immune responses between SARS‐CoV‐2 and endemic coronavirus (eCoV) may hypothetically contribute to this variability. We herein studied if eCoV nucleoprotein (N)‐specific antibodies in the sera of patients with mild or severe Covid‐19 are associated with Covid‐19 severity. There were comparable levels of eCoV N‐specific antibodies early and during the first month of infection in Covid‐19 patients with mild and severe symptoms, and healthy SARS‐CoV‐2‐negative subjects. These results warrant further studies to investigate the potential role of eCoV‐specific antibodies in immunity to SARS‐CoV‐2 infection.

type 1 and 2 10 ), were collected from the subjects' medical records.

Information on the smoking status of the study participants was incomplete and therefore not included. Serum samples retrieved from healthy volunteers who tested negative for SARS-CoV-2 with PCR (n = 27; 56% female; age range, 20-79 years) between January 29 and September 23, 2020, were included as controls. In the study that compared antibody levels between the mild and severe Covid-19 patient groups, acute serum samples collected within 10 days after debut of symptoms (mean four days post symptom onset for patients with mild disease and eight days for patients with severe disease) were used. For the analysis of longitudinal antibody development, subjects were included for which two or more samples from the first 30 days after symptom debut were available (n = 23).

Antibodies specific for HCoV-NL63, HCoV-229E, HCoV-HKU1, and

HCoV-OC43 were analyzed using the C-terminal part of the Nprotein as antigen in enzyme-linked immunosorbent antibodies (ELISAs) as described elsewhere. 1 SARS-CoV-2-specific total antibody was analyzed using the SARS-CoV-2 N-protein double recognition ELISA INgezim test as previously described. 11 This assay is based on the use of the same protein (in this case, the N protein) as the target antigen and detection molecule, using the principle that antibodies possess multiple antigen-binding regions (2 for IgG, 4 for IgA, and 10 for IgM), allowing their simultaneous binding to both the target and detection antigen. Double recognition tests have the advantage that they detect all antigen-specific antibodies, regardless of their class (IgA, IgG, or IgM).

Differences between the groups were analyzed using analysis of variance with Tukey's multiple comparisons test for eCoV antibodies, and Fisher's exact test for SARS-CoV-2 antibodies for which there is a cut-off for positivity. Correlations were analyzed using Pearson.

p < 0.05 was considered statistically significant.

Due to the ubiquitous nature of the eCoV, all adults are considered to be exposed to eCoVs, though eCoV-specific antibody levels have been shown to rapidly wane and reinfections are common. 1 developed, using N-specific antibody ELISAs. No statistically significant differences in the levels of N-specific antibodies against any of the four eCoVs were observed in Covid-19 patients with mild disease, severe disease, or healthy controls ( Figure 1A) . Although SARS-CoV-2 N-specific antibodies were higher in patients with severe compared to mild symptoms, this difference is likely partly due to the longer duration of disease in the patients with severe symptoms. At least one pre-existing comorbidity known to increase the risk of severe Covid-19 was present in a higher proportion of patients with severe disease (27%) compared with mild disease (14%), which could bias these results. However, when all subjects with comorbidities (n = 9)

were excluded, conclusions based on statistical significance levels remain unchanged.

There were no statistically significant correlations between the magnitudes of SARS-CoV-2 N-specific antibodies and any of the eCoV N-specific antibodies (data not shown). This confirms that SARS-CoV-2 N-specific antibodies have no substantial crossreactivity with eCoV epitopes in the C-terminal part of the N-protein used as antigen in the present study. Our finding on the lack of inverse correlation between eCoV N-specific antibodies and disease severity is in line with, and extends, a previous report on the lack of cross-reactive neutralizing activity against SARS-CoV-2 in the prepandemic sera of individuals with prior PCR-confirmed eCoV infection. 12 As the samples in patients with mild disease were collected mean 4 days earlier than in patients with severe disease, the antibody levels in patients with mild disease could be misleadingly low.

To examine this, longitudinal samples retrieved from the same patients during the first month of infection were analyzed. As expected, SARS-CoV-2 antibody levels increased significantly over time (r = 0.4; p = 0.003; Figure 1B ). In contrast, N-specific antibody levels to F I G U R E 1 (A) Magnitudes (mean ± SD where relevant) of N-specific antibodies against SARS-CoV-2 and the endemic coronaviruses. Samples collected within 10 days of symptom onset in Covid-19 patients with mild symptoms (n = 21, blue) or severe/critical symptoms (n = 22, red), and SARS-CoV-2-negative controls (n = 27, green). (B) Serial samples collected during the first 30 days since symptom onset in Covid-19 patients with mild symptoms (n = 5, blue) or severe/critical symptoms (n = 18, red). Dotted line in (A) indicates assay cut-off for positivity for SARS-CoV-2 antibodies. ****p < 0.0001, *p < 0.05, ns: not significant

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