key: cord-0026100-xjybygd3
authors: Krüttgen, Alexander; Kleines, Michael
title: Reply to the letter from Dr. Nikolayevskyy et al. referring to our publication published in the Journal of Virological Methods 298 (2021)11:4295 “Evaluation of the QuantiFERON SARS-CoV-2 Interferon-ɣ release assay in mRNA-1273 vaccinated health care workers”
date: 2022-01-21
journal: J Virol Methods
DOI: 10.1016/j.jviromet.2022.114473
sha: 0b081f950b1264ac67ff5d5dd2e4e1ad0a7d6837
doc_id: 26100
cord_uid: xjybygd3

nan

In our study, we evaluated a novel assay from Qiagen measuring Tcell responses to two SARS-CoV-2 peptide antigen pools (antigen pool 1 and antigen pool 2) in healthy probands vaccinated twice with the Moderna vaccine mRNA-1723 against SARS-CoV-2.We reported that only 8/18 vaccinees tested positive in our cohort when assaying Interferon-ɣ release from lymphocytes.

In their letter, Nikolayevskyy et al. wonder if the low positivity rate might be caused by our data analysis, as using OD values instead of IU/ mL might yield different results. They expect a significantly higher positivity rate based on IU/mL. We wish to thank these authors for their useful suggestion. We want to use this opportunity to present our results side-by-side as either "IU/mL" (Fig. 1a) or "OD values" (Fig. 1b) . When comparing Fig. 1a and b, both graphs look pretty similar. Moreover, the previously reported positivity rate of 8/18, for positivity in at least one of the two antigen pools, remains almost unchanged with 8/18 regarding antigen pool 1 (Ag1) and 9/18 regarding antigen pool 2 (Ag2) when using a cutoff of 0,15 IU/mL (Fig. 1a) . In other words the positivity rate based on at least one pool being positive per specimen changed from 44 % to 50 % positivity. We wish to apologize for this error based on wrongly picking OD values instead of IU/mL data during the process of writing the manuscript after an initial IU/mL-based analysis. However, this obviously does not change the key message of the paper, the rather low rate of Interferon-ɣ release in half of the probands when using this novel IGRA assay in a cohort of healthy health care workers vaccinated twice with Moderna mRNA-1273

Controversies about the clinical interpretation of Quantiferon assay results for other pathogens have been published; for example Valle-Arroyo et al. (Valle-Arroyo and Aguado, 2020) reported a lack of QuantiFERON-CMV response in CMV-seropositive healthy individuals which is reminiscent of our finding for SARS-CoV-2 vaccinees presenting with positive serology and negative IGRA results. We propose that in order to improve the positivity rate of the novel kit, perhaps the peptide-pool of the kit might need to be improved. Supporting this hypothesis, Qiagen already offers an "extended" SARS-CoV-2 peptide pool ("antigen pool 3", Cat No 626215) for their SARS-CoV-2 QuantiFERON assay (this extended peptide pool -which might lead to higher positivity rates-was not available for our study). An additional way to obtain higher positivity rates might be to measure TNF-α release instead of INF-ɣ release because after mRNA-1273 vaccination INF-ɣ responses were rather low whereas TNF-α responses were high as reported by Moderna (Anderson and Rouphael, 2020) .

More studies of independent academic labs using different and larger cohorts are needed to evaluate this promising and convenient new kit aimed at determining cellular immunity against SARS-CoV-2.

The authors declare no conflict of interest. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for profit sector. Fig. 1. a) Comparison of Interferon-gamma release in vaccinees (IU/mL). Y-axis in IU/mL. The arrow indicates a cutoff of 0,15 IU/mL. We found large differences between our 18 vaccinees. Considering antigen pool 1 (Ag1) and a cutoff of 0,15 IU/mL (indicated by arrow) 8 of 18 samples would be regarded as positive (vaccinees 2, 3, 4, 10, 13, 14, 16 and 18) . When regarding antigen pool 2 (Ag2) and a cutoff of 0,15 IU/mL (indicated by arrow), 9 of 18 of our vaccinees would be regarded as positive (vaccinees 2, 3, 4, 7, 10, 13, 14, 16, 18) . Thus, many vaccinees showed rather low responses. b) Comparison of Interferon-gamma release in vaccinees (OD). Y-axis in OD. Also in this analysis we found large differences between our 18 vaccinees. Considering antigen pool 1 (Ag1) or antigen pool 2 (Ag2) and a cutoff of 0,15 (indicated by arrow) 8 of 18 samples would be regarded as positive (vaccinees 2, 3, 4, 10, 13, 14, 16 and 18) . Thus, many vaccinees showed rather low responses.

Safety and immunogenicity of SARS-CoV-2 mRNA-1273 vaccine in older adults

Lack of cytomegalovirus (CMV)-specific cellmediated immune response using QuantiFERON-CMV assay in CMV-seropositive healthy volunteers: fact not artifact