Abstract
The COVID-19 pandemic has highlighted the importance of understanding the immune response to seasonal human coronavirus (HCoV) infections such as HCoV-NL63, how existing neutralising antibodies to HCoV may modulate responses to SARS-CoV-2 infection, and the utility of seasonal HCoV as human challenge models. Therefore, in this study we quantified HCoV-NL63 neutralising antibody titres in a healthy adult population using plasma from 100 blood donors in Australia. A microneutralisation assay was performed with plasma diluted from 1:10 to 1:160 and tested with the HCoV-NL63 Amsterdam-1 strain. Neutralising antibodies were detected in 71% of the plasma samples, with a median geometric mean titre of 14. This titre was similar to those reported in convalescent sera taken from individuals 3–7 months following asymptomatic SARS-CoV-2 infection, and 2–3 years post-infection from symptomatic SARS-CoV-1 patients. HCoV-NL63 neutralising antibody titres decreased with increasing age (R2 = 0.042, p = 0.038), but did not differ by sex. Overall, this study demonstrates that neutralising antibody to HCoV-NL63 is detectable in approximately 71% of the healthy adult population of Australia. Similar titres did not impede the use of another seasonal human coronavirus (HCoV-229E) in a human challenge model, thus, HCoV-NL63 may be useful as a human challenge model for more pathogenic coronaviruses.
Highlights
Within the Coronaviridae family, human coronavirus (HCoV)-NL63 is classified as an alphacoronavirus and, like SARS-CoV-2, it binds to angiotensin-converting enzyme 2 (ACE2) on the cell surface to mediate cellular entry [2]
Neutralising antibodies against HCoV-NL63 were detected within the sensitivity range of our assay in 71 (71%) of the plasma samples
The incidence of HCoV-NL63 infection decreases with age [16], and so we investigated if there was any correlation between age and neutralising antibody titre
Summary
The current pandemic is caused by a betacoronavirus called SARS-CoV-2. This virus is believed to have spread to humans through zoonotic transmission, its wide dissemination has sparked renewed interest in the four globally endemic seasonal circulating human coronaviruses (HCoVs): HCoV-NL63, HCoVOC43, HCoV-229E, and HCoV-HKU1. These viruses most commonly cause respiratory tract infections in children, with manifestations ranging from asymptomatic infection to croup, bronchiolitis, and pneumonia. They usually present as mild upper respiratory tract symptoms [1]. Within the Coronaviridae family, HCoV-NL63 is classified as an alphacoronavirus and, like SARS-CoV-2, it binds to angiotensin-converting enzyme 2
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