Complement-mediated enhancement of SARS-CoV-2 antibody neutralisation potency in vaccinated individuals

Abstract

With the continued emergence of SARS-CoV-2 variants and concerns of waning immunity, there is a need for better defined correlates of protection to aid future vaccine and therapeutic developments. Whilst neutralising antibody titres are associated with protection, these are typically determined in the absence of the complement system, which has the potential to enhance neutralisation titres and strengthen correlates with protection in vivo. Here we show that replenishment of the complement system in neutralisation assays can significantly enhance neutralisation titres, with up to an ~83-fold increase in neutralisation of the BA.1.1.529 strain using cross-reactive sera from vaccination against the ancestral strain. The magnitude of enhancement significantly varies between individuals, viral strains (wild-type/VIC01 and Omicron/BA.1), and cell lines (Vero E6 and Calu-3), and is abrogated following heat-inactivation of the complement source. Utilising ACE2 competition assays, we show that the mechanism of action is partially mediated by reducing ACE2-spike interactions. Through the addition of compstatin (a C3 inhibitor) to live virus neutralisation assays, the complement protein C3 is shown to be required for maximum efficiency. These findings further our understanding of SARS-CoV-2 immunity and neutralisation, with implications for protection against emerging variants and assessing future vaccine and therapeutic developments.

Metadata

Item Type:	Article
Authors/Creators:	Mellors, J. https://orcid.org/0000-0001-7761-8341 Dhaliwal, R. Longet, S. Tipton, T. McInnes, I. Siebert, S. Kearns, P. Rea, D. Cook, G. Willicombe, M. Thomas, D. de Silva, T. https://orcid.org/0000-0002-6498-9212 Wedderburn, L. Brugha, R. Bate, J. Goodyear, C. Richter, A. Snowden, J. https://orcid.org/0000-0001-6819-3476 Satsangi, J. Lim, S.H. Kirkham, A. Bowden, S. Magwaro, S. Hughes, A. Pope, A. Insch, E. Churchill, V. Beesley, R. MacDonald, E. Bibi, S. Conlon, C.P. Deeks, A.S. Dold, C. Dunachie, S. Frater, J. Jeffery, K. Kronsteiner, B. Lambe, T. Longet, S. Mentzer, A.J. Skelly, D. Stafford, L. Barnes, E. Dunachie, S.J. Klenerman, P. Hiscox, J. Carroll, M. https://orcid.org/0000-0002-7026-7187
Copyright, Publisher and Additional Information:	© The Author(s) 2025. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Keywords:	SARS-CoV-2; Humans; Antibodies, Neutralizing; COVID-19; Animals; COVID-19 Vaccines; Antibodies, Viral; Chlorocebus aethiops; Vero Cells; Spike Glycoprotein, Coronavirus; Angiotensin-Converting Enzyme 2; Complement System Proteins; Vaccination; Neutralization Tests; Cross Reactions; Female; Peptides, Cyclic
Dates:	Submitted: 5 July 2024 Accepted: 5 March 2025 Published (online): 18 March 2025 Published: 18 March 2025
Institution:	The University of Sheffield
Academic Units:	The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > School of Medicine and Population Health
Funding Information:	Funder Grant number MEDICAL RESEARCH COUNCIL MR/W02067X/1 Medical Research Council MR/X009297/1
Depositing User:	Symplectic Sheffield
Date Deposited:	07 Apr 2025 13:36
Last Modified:	07 Apr 2025 13:36
Status:	Published
Publisher:	Springer Science and Business Media LLC
Refereed:	Yes
Identification Number:	10.1038/s41467-025-57947-8
Related URLs:	PubMed URL Dataset Dataset
Open Archives Initiative ID (OAI ID):	oai:eprints.whiterose.ac.uk:225254