loading page

Serological and cellular non-responders in a long-term cross-sectional cohort of SARS-CoV-2-specific PCR-positive individuals
  • +5
  • Giovanni Almanzar,
  • Charlotte Winzig,
  • Hanna Jury,
  • Eric Psota,
  • Timotheos Christoforou,
  • Johanna Block,
  • Sissy Sonnleitner,
  • Martina Prelog
Giovanni Almanzar
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik

Corresponding Author:almanzar_g@ukw.de

Author Profile
Charlotte Winzig
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik
Author Profile
Hanna Jury
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik
Author Profile
Eric Psota
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik
Author Profile
Timotheos Christoforou
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik
Author Profile
Johanna Block
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik
Author Profile
Sissy Sonnleitner
Department of Virology Medical Laboratory Dr Gernot Walder GmbH Ausservillgraten Austria
Author Profile
Martina Prelog
Universitatsklinikum Wurzburg Kinderklinik und Poliklinik
Author Profile

Abstract

During the first pandemic wave, the dark figure of SARS-CoV-2 exposure was estimated to be high, however, an accelerated loss of antibodies was reported after about 6 months post infection. This study was performed to unveil the group of serological non-responders (NR) in PCR+ individuals 6-9 months after the first pandemic SARS-CoV-2 wave in spring 2020 and to evaluate their specific cellular immune response towards spike-molecule compared to PCR- and not PCR-tested (NT) household contact persons. SARS-CoV-2-specific antibodies were quantified using a commercial ELISA kit. The synergistic binding strength was assessed as relative avidity index (RAI) using ammonium-thiocyanate as chaotropic agent. The specific IFNγ-production in response to spike-protein was determined in spot-forming-units (SFU) by ELISPOT-assay. In PCR- 50.0%, in PCR+ 35.3% and in NT 20.7% had undetectable IgG-anti-SARS-CoV-2 and were considered non-responders (NR). All seropositive responders from the PCR-, 45.5% of PCR+ and 43.0% of NT developed high avidity (RAI>60%). In serological responders, cellular responses were detected in 75.0% PCR-, 75.8% PCR+ and 66.7% NT. In serological NR, positive SFU were found in 75.0% PCR-, 22.2% PCR+ and 17.4% NT. Significantly higher stimulation-indices were seen in PCR+ responders compared to PCR+ serological NR. Our findings showed that also PCR- and household contact persons who were not tested (NT) developed SARS-CoV-2-specific humoral and cellular immune responses. The relatively large proportion of serological non-responders but also the proportion of cellular non-responders within the group of IgG-positive individuals after PCR+ infection underlines the need for COVID-19 vaccinations in the reconvalescent group.