Serological assays for differentiating natural COVID-19 infection from vaccine induced immunity

Samuel M S Cheng; Jonathan J Lau; Leo C H Tsang; Kathy Leung; Cheuk Kwong Lee; Asmaa Hachim; Niloufar Kavian; Sara Chaothai; Ricky W K Wong; Jennifer K M Yu; Zacary Y H Chai; Masashi Mori; Chao Wu; Karen Yiu; David S C Hui; Gaya K Amarasinghe; Leo L M Poon; Joseph T Wu; Sophie A Valkenburg; Malik Peiris

doi:10.1016/j.jcv.2023.105621

Serological assays for differentiating natural COVID-19 infection from vaccine induced immunity

J Clin Virol. 2024 Feb:170:105621. doi: 10.1016/j.jcv.2023.105621. Epub 2023 Dec 1.

Authors

Samuel M S Cheng¹, Jonathan J Lau², Leo C H Tsang¹, Kathy Leung², Cheuk Kwong Lee³, Asmaa Hachim⁴, Niloufar Kavian⁵, Sara Chaothai¹, Ricky W K Wong¹, Jennifer K M Yu¹, Zacary Y H Chai¹, Masashi Mori⁶, Chao Wu⁷, Karen Yiu⁸, David S C Hui⁸, Gaya K Amarasinghe⁹, Leo L M Poon¹⁰, Joseph T Wu², Sophie A Valkenburg¹¹, Malik Peiris¹²

Affiliations

¹ School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
² School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; Laboratory of Data Discovery for Health (D24H), Hong Kong Science Park, Hong Kong SAR, China.
³ Hong Kong Red Cross Blood Transfusion Service, Hospital Authority, Hong Kong SAR, China.
⁴ HKU-Pasteur Research Pole, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
⁵ HKU-Pasteur Research Pole, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, & Assistance Publique-Hôpitaux de Paris, Hôpital Universitaire Paris Centre, Centre Hospitalier Universitaire Cochin, Service d'Immunologie Biologique, Paris, France.
⁶ Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi, Japan.
⁷ Shenzhen Bay Laboratory, Guangdong, China.
⁸ Department of Medicine and Therapeutics and SH Ho Research Center for Infectious Diseases, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong SAR, China.
⁹ Department of Pathology and Immunology, Washington University School of Medicine at St. Louis, St. Louis, Missouri, United States.
¹⁰ School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; HKU-Pasteur Research Pole, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Australia.
¹¹ HKU-Pasteur Research Pole, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, Australia.
¹² School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China; Centre for Immunology and Infection(C2i), Hong Kong Science Park, Hong Kong SAR, China. Electronic address: malik@hkucc.hku.hk.

PMID: 38056114
DOI: 10.1016/j.jcv.2023.105621

Abstract

Background: Natural SARS-CoV-2 infection may elicit antibodies to a range of viral proteins including non-structural protein ORF8. RNA, adenovirus vectored and sub-unit vaccines expressing SARS-CoV-2 spike would be only expected to elicit S-antibodies and antibodies to distinct domains of nucleocapsid (N) protein may reliably differentiate infection from vaccine-elicited antibody. However, inactivated whole virus vaccines may potentially elicit antibody to wider range of viral proteins, including N protein. We hypothesized that antibody to ORF8 protein will discriminate natural infection from vaccination irrespective of vaccine type.

Methods: We optimized and validated the anti-ORF8 and anti-N C-terminal domain (NCTD) ELISA assays using sera from pre-pandemic, RT-PCR confirmed natural infection sera and BNT162b2 (BNT) or CoronaVac vaccinees. We then applied these optimized assays to a cohort of blood donor sera collected in April-July 2022 with known vaccination and self-reported infection status.

Results: We optimized cut-off values for the anti-ORF8 and anti-N-CTD IgG ELISA assays using receiver-operating-characteristic (ROC) curves. The sensitivity of the anti-ORF8 and anti-N-CTD ELISA for detecting past infection was 83.2% and 99.3%, respectively. Specificity of anti-ORF8 ELISA was 96.8 % vs. the pre-pandemic cohort or 93% considering the pre-pandemic and vaccine cohorts together. The anti-N-CTD ELISA specificity of 98.9% in the pre-pandemic cohort, 93% in BNT vaccinated and only 4 % in CoronaVac vaccinated cohorts. Anti-N-CTD antibody was longer-lived than anti-ORF8 antibody after natural infection.

Conclusions: Anti-N-CTD antibody assays provide good discrimination between natural infection and vaccination in BNT162b2 vaccinated individuals. Anti-ORF8 antibody can help discriminate infection from vaccination in either type of vaccine and help estimate infection attack rates (IAR) in communities.

Keywords: COVID-19; N-CTD; Natural infection; ORF8; SARS-CoV-2; Vaccine induced immunity; antibody.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Antibodies, Viral
BNT162 Vaccine
COVID-19* / diagnosis
COVID-19* / prevention & control
Humans
SARS-CoV-2
Vaccination
Viral Vaccines*

Substances

BNT162 Vaccine
Viral Vaccines
Antibodies, Viral