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. 2024 Jul;54(7):e2451035.
doi: 10.1002/eji.202451035. Epub 2024 Apr 16.

Combining SARS-CoV-2 interferon-gamma release assay with humoral response assessment to define immune memory profiles

William Mouton  1   2 , Guy Oriol  2 , Christelle Compagnon  2 , Carla Saade  1   2 , Kahina Saker  2 , Priscille Franc  2 , Bouchra Mokdad  2 , Aurore Fleurie  2 , Xavier Lacoux  3 , Soizic Daniel  3 , Franck Berthier  4 , Cécile Barnel  2 , Bruno Pozzetto  1   5 , Jean-Baptiste Fassier  6   7 , Valérie Dubois  8 , Sophia Djebali  1 , Maxence Dubois  1 , Thierry Walzer  1 , Jacqueline Marvel  1 , Karen Brengel-Pesce  2 , Sophie Trouillet-Assant  1   2 ; Covid ser study group
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Free article

Combining SARS-CoV-2 interferon-gamma release assay with humoral response assessment to define immune memory profiles

William Mouton et al. Eur J Immunol. 2024 Jul.
Free article

Abstract

Objectives: In the post-SARS-CoV-2 pandemic era, "breakthrough infections" are still documented, due to variants of concerns (VoCs) emergence and waning humoral immunity. Despite widespread utilization, the definition of the anti-Spike (S) immunoglobulin-G (IgG) threshold to define protection has unveiled several limitations. Here, we explore the advantages of incorporating T-cell response assessment to enhance the definition of immune memory profile.

Methods: SARS-CoV-2 interferon-gamma release assay test (IGRA) was performed on samples collected longitudinally from immunocompetent healthcare workers throughout their immunization by infection and/or vaccination, anti-receptor-binding domain IgG levels were assessed in parallel. The risk of symptomatic infection according to cellular/humoral immune capacities during Omicron BA.1 wave was then estimated.

Results: Close to 40% of our samples were exclusively IGRA-positive, largely due to time elapsed since their last immunization. This suggests that individuals have sustained long-lasting cellular immunity, while they would have been classified as lacking protective immunity based solely on IgG threshold. Moreover, the Cox regression model highlighted that Omicron BA.1 circulation raises the risk of symptomatic infection while increased anti-receptor-binding domain IgG and IGRA levels tended to reduce it.

Conclusion: The discrepancy between humoral and cellular responses highlights the significance of assessing the overall adaptive immune response. This integrated approach allows the identification of vulnerable subjects and can be of interest to guide antiviral prophylaxis at an individual level.

Keywords: Cell‐mediated immunity; Immune memory profile; Interferon‐gamma release assay.

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