Poster Presentation 8th Australasian Vaccines & Immunotherapeutics Development Meeting 2020

Linear B-cell epitopes in the spike and nucleocapsid proteins as markers of SARS-CoV-2 exposure and disease severity (#319)

Siti Naqiah Amrun 1 2 , Cheryl Lee 1 2 , Bernett Lee 2 , Siew Wai Fong 1 2 3 , Barnaby Edward Young 4 5 6 , Rhonda Chee 1 2 , Nicholas Yeo 1 2 , Anthony Torres-Ruesta 1 2 7 , Guillaume Carissimo 1 2 , Chek Meng Poh 1 2 , Zi Wei Chang 1 2 , Matthew Tay 1 2 , Yi-Hao Chan 1 2 , Mark I-Cheng Chen 4 8 , Jenny Guek-Hong Low 9 10 , Paul A. Tambyah 4 11 , Shirin Kalimuddin 9 10 , Surinder Pada 12 , Seow-Yen Tan 13 , Louisa Jin Sun 14 , Yee-Sin Leo 4 5 6 15 , David C. Lye 4 5 6 15 , Laurent Renia 1 2 , Lisa Ng 1 2 7 16 17
  1. Infectious Diseases Horizontal Technology Centre, Singapore, SINGAPORE
  2. Singapore Immunology Network, Singapore, SINGAPORE
  3. Department of Biological Sciences, National University of Singapore, Singapore, SINGAPORE
  4. National Centre for Infectious Diseases, Singapore, SINGAPORE
  5. Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore, SINGAPORE
  6. Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, SINGAPORE
  7. Department of Biochemistry, National University of Singapore, Singapore, SINGAPORE
  8. Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore, SINGAPORE
  9. Department of Infectious Diseases, Singapore General Hospital, Singapore, SINGAPORE
  10. Emerging Infectious Disease Program, Duke-NUS Medical School, Singapore, SINGAPORE
  11. Department of Medicine, National University Hospital, Singapore, SINGAPORE
  12. Division of Infectious Diseases, Ng Teng Fong Hospital, Singapore, SINGAPORE
  13. Department of Infectious Diseases, Changi General Hospital, Singapore, SINGAPORE
  14. Alexandra Hospital, Singapore, SINGAPORE
  15. Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, SINGAPORE
  16. Health Protection Research Unit in Emerging and Zoonotic Infections, University of Liverpool, Liverpool, United Kingdom
  17. Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, United Kingdom

Background

Given the unceasing worldwide surge in COVID-19 cases, there is an imperative need to develop highly specific and sensitive serology assays to define exposure to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).

Methods

Pooled plasma samples from PCR positive COVID-19 patients were used to identify linear B-cell epitopes from a SARS-CoV-2 peptide library of spike (S), envelope (E), membrane (M), and nucleocapsid (N) structural proteins by peptide-based ELISA. Hit epitopes were further validated with 79 COVID-19 patients with different disease severity status, 13 seasonal human CoV, 20 recovered SARS patients and 22 healthy donors.

Findings

Four immunodominant epitopes, S14P5, S20P2, S21P2 and N4P5, were identified on the S and N viral proteins. IgG responses to all identified epitopes displayed a strong detection profile, with N4P5 achieving the highest level of specificity (100%) and sensitivity (>96%) against SARS-CoV-2. Furthermore, the magnitude of IgG responses to S14P5, S21P2 and N4P5 were strongly associated with disease severity.

Interpretation

IgG responses to the peptide epitopes can serve as useful indicators for the degree of immunopathology in COVID-19 patients, and function as higly specific and sensitive sero-immunosurveillance tools for recent or past SARS-CoV-2 infections. The flexibility of these epitopes to be used alone or in combination will allow for the development of improved point-of-care-tests (POCTs).