Ahmed, Mohamed Ibraheem MohamedMohamed Ibraheem MohamedAhmedPlank, MichaelMichaelPlankCastelletti, NoemiNoemiCastellettiDiepers, PaulinaPaulinaDiepersEser, Tabea M.Tabea M.EserRubio-Acero, RaquelRaquelRubio-AceroNoreña, Iván EnriqueIván EnriqueNoreñaReinkemeyer, ChristinaChristinaReinkemeyerZapf, DorinjaDorinjaZapfHoelscher- von Lovenberg, MichaelMichaelHoelscher- von LovenbergJanke, ChristianChristianJankeWieser, AndreasAndreasWieserGeldmacher, Jan ChristofJan ChristofGeldmacher2023-08-142023-08-142023https://publica.fraunhofer.de/handle/publica/44810310.3390/diagnostics130610242-s2.0-85152390847The currently prevailing variants of SARS-CoV-2 are subvariants of the Omicron variant. The aim of this study was to analyze the effect of mutations in the Spike protein of Omicron on the results Quan-T-Cell SARS-CoV-2 assays and Roche Elecsys anti-SARS-CoV-2 anti-S1. Omicron infected subjects ((n = 37), vaccinated (n = 20) and unvaccinated (n = 17)) were recruited approximately 3 weeks after a positive PCR test. The Quan-T-Cell SARS-CoV-2 assays (EUROIMMUN) using Wuhan and the Omicron adapted antigen assay and a serological test (Roche Elecsys anti-SARS-CoV-2 anti-S1) were performed. Using the original Wuhan SARS-CoV-2 IGRA TUBE, in 19 of 21 tested Omicron infected subjects, a positive IFNy response was detected, while 2 non-vaccinated but infected subjects did not respond. The Omicron adapted antigen tube resulted in comparable results. In contrast, the serological assay detected a factor 100-fold lower median Spike-specific RBD antibody concentration in non-vaccinated Omicron infected patients (n = 12) compared to patients from the pre Omicron era (n = 12) at matched time points, and eight individuals remained below the detection threshold for positivity. For vaccinated subjects, the Roche assay detected antibodies in all subjects and showed a 400 times higher median specific antibody concentration compared to non-vaccinated infected subjects in the pre-Omicron era. Our results suggest that Omicron antigen adapted IGRA stimulator tubes did not improve detection of SARS-CoV-2-specific T-cell responses in the Quant-T-Cell-SARS-CoV-2 assay. In non-vaccinated Omicron infected individuals, the Wuhan based Elecsys anti-SARS-CoV-2 anti-S1 serological assay results in many negative results at 3 weeks after diagnosis.enbreakthrough infectionsomicronSARS-CoV-2spike-specific immune responsejournal article