Expression of GPI-anchored SARS-CoV-2 receptor binding domain in mammalian cells for serological use

M. L. Kernich, P. J. Adamson, J. J. Wang, L. P. Kris, B. L. Armour, D. Beroukas, G. Best, J. M. Carr, T. P. Gordon, D. L. Gordon

Research output: Contribution to journalMeeting Abstractpeer-review


Introduction: The gold standard for diagnosing SARS-CoV-2 infection remains RT-PCR; however serological testing has an important role in epidemiology and assessment of vaccine responses. We expressed the receptor binding domain (RBD) of the spike (S) protein as a glycosylphosphatidylinositol (GPI)-anchored protein on CHO cells transfected with a generated construct and determined binding of RBD specific antibodies by immunofluorescence (IF) and flow cytometry (FACS) assays.

Methods and results: IF and FACS demonstrated cell surface RBD expression using anti-S RBD mAb and macaque immune sera. GPI anchored expression was confirmed through loss of positive cells on FACS post GPI anchor cleavage with phosphoinositide phospholipase C (PI-PLC). Binding of antibodies from COVID-19 convalescent sera to RBD- and mock-transfectants was performed by FACS. Positive results on serial dilutions of patient sera down to 1:3200 were observed and compared to in-house RBD ELISA which lost positivity at a 1:800 dilution. Soluble recombinant ACE2 bound to RBD-CHOs and binding was inhibited by COVID-19 convalescent sera indicating the RBD was expressed in a functional conformation and that neutralising antibodies were detected.

Conclusion: Mammalian cells expressing GPI-anchored RBD can successfully be used to detect previous SARS-CoV-2 infection and likely indicate the presence of neutralising antibodies in COVID-19 survivors.
Original languageEnglish
Pages (from-to)S50-S51
Number of pages2
Issue numberSuppl. 1
Publication statusPublished - Jul 2021
EventAustralasian Society for Infectious Diseases Annual Meeting -
Duration: 24 Mar 202126 Mar 2021


  • COVID-19 testing
  • RT-PCR
  • GPI-anchored RBD


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