key: cord-0785068-32hign6a
authors: Benning, Louise; Morath, Christian; Bartenschlager, Marie; Reineke, Marvin; Töllner, Maximilian; Nusshag, Christian; Kälble, Florian; Reichel, Paula; Schaier, Matthias; Klein, Katrin; Schnitzler, Paul; Zeier, Martin; Süsal, Caner; Bartenschlager, Ralf; Speer, Claudius
title: Neutralizing antibody activity against the B.1.617.2 (delta) variant 8 months after two-dose vaccination with BNT162b2 in health care workers
date: 2022-02-03
journal: Clin Microbiol Infect
DOI: 10.1016/j.cmi.2022.01.011
sha: 99ad240e24c359debcb866f0fc922b2de06c8c75
doc_id: 785068
cord_uid: 32hign6a

OBJECTIVES: Humoral immunity wanes over time after two-dose BNT162b2 vaccination. Emerging variants of concern, such as the B.1.617.2 (delta) variant, are increasingly responsible for breakthrough infections due to their higher transmissibility and partial immune escape. Longitudinal data on neutralization against the B.1.617.2 (delta) variant are urgently needed to guide vaccination strategies. METHODS: In this prospective longitudinal observational study, anti-S1 IgG and neutralizing surrogate antibodies were measured in 234 collected samples from 60 health care workers after two-dose vaccination with BNT162b2 at five different time points over an 8-month period. In addition, antibodies against various SARS-CoV-2 epitopes, neutralization against wild-type, and cross-neutralization against the B.1.617.2 (delta) variant using a live virus assay were measured 6 weeks (second time point) and 8 months (last time point) after first vaccine dose. RESULTS: Median (IQR) anti-S1 IgG, surrogate neutralizing, and receptor-binding domain antibodies decreased significantly from a maximum level of 147 (102–298), 97 (96–98), and 20,159 (19,023–21,628) to 8 (4–13), 92 (80–96), and 15,324 (13,055–17,288) at the 8-month follow-up, respectively (P<0.001 for all). Neutralization against the B.1.617.2 (delta) variant was detectable in 36/36 (100%) participants 6 weeks and in 50/53 (94%) participants 8 months after first vaccine dose. Median (IQR) ID(50) as determined by a live virus assay decreased from 160 (80–320) to 40 (20–40) (P<0.001). CONCLUSIONS: Although humoral immunity wanes over time after two-dose BNT162b2 vaccination in healthy individuals, most individuals still had detectable neutralizing activity against the B.1.617.2 (delta) variant after 8 months.

Since a cluster of pneumonia cases was first reported in Wuhan, Hubei Province in December 28 2019, coronavirus disease 2019 (COVID- 19) has become a global burden, resulting in more 29 than 240 million cases and over 4.9 million deaths worldwide by October 2021 [1] . COVID- 30 19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which enters 31 host cells via the glycosylated spike protein [2] . The receptor-binding domain (RBD) of the 32 SARS-CoV-2 spike protein is a major target of neutralizing antibodies that block viral 33 attachment to the host cell via angiotensin converting enzyme type-II (ACE2) receptor binding 34 [3] . trial reported a gradual decline in vaccine efficacy from 96% between 7 days and 2 months after 39 the second dose to 84% between 4 and 6 months after the second dose [4] . The decline in 40 vaccine efficacy is caused by a combination of waning humoral immunity and the emergence 41 of variants of concern with partial immune escape [5] [6] [7] [8] The study is part of an ongoing single-center study to determine immunogenicity of Written informed consent was obtained from all study participants.

We used the SARS-CoV-2 Total Assay (Siemens, Eschborn, German) to measure the IgG 75 response against the S1 protein with a semi-quantitative index ≥1 defining positivity. This cut-76 off for detection gives a specificity of 100% with a sensitivity of 89%. IgG against the 77 nucleocapsid protein was measured by the semi-quantitative Elecsys anti-SARS-CoV-2 assay 78 (Roche, Mannheim, Germany). Assays were performed according to the manufacturers' 79 instructions. 81 We used a surrogate virus neutralization test (Medac, Wedel, Germany) to detect surrogate 82 neutralizing antibodies in a sample, as described previously by us and others [10] [11] [12] [13] [14] . The test 83 mimics the interaction between the virus and the host cell by direct protein-protein interaction 84 using purified RBD protein from the viral spike protein and the host cell receptor angiotensin 85 converting enzyme 2 (ACE2) [14] . With a cut-off of ≥30% inhibition of RBD:ACE-2 binding, 86 the test achieves 99.9% specificity with 95-100% sensitivity to detect surrogate neutralizing 87 antibodies.

IgG antibodies against different SARS-CoV-2 target epitopes 89 To identify IgG antibodies against different SARS-CoV-2 target epitopes, a multiplex bead-90 based assay for the Luminex platform (LabScreen COVID Plus, One Lambda Inc., West Hill, 91 CA, USA) was performed [15] . The assay detects antibodies against the SARS-CoV-2 92 nucleocapsid protein and against 4 distinct fragments of the SARS-CoV-2 spike protein, namely 93 the full spike protein, the spike S1, the spike S2, and the receptor-binding domain of the spike Figure 2B ). During the first 8 weeks after first vaccination, anti-S1 IgG and surrogate neutralizing antibody levels did not decrease significantly, whereas anti-S1 IgG levels and surrogate neutralizing antibodies were 150 significantly lower 4 months (t4) and 8 months (t5) after first vaccination when compared to 151 maximum levels 3 weeks (t2) after second vaccination (P<0.001 for all; Figure 2A and 2B). Legend to Figure 1 In total, 60 participants were included in this study. Anti-S1 IgG and surrogate neutralizing antibodies were determined at five different time points (t1-t5). A bead-based analysis of antibodies against different SARS-CoV-2 target epitopes and a live virus neutralization assay to determine neutralization against wild-type and the B.1.617.2 (delta) variant of concern were performed in a representative subgroup analysis 3 weeks (t2) and 7 months (t5) after second vaccination. IQR, interquartile range; N, number.

Anti-S1 IgG, surrogate neutralizing, full spike, spike S1, spike receptor-binding domain, and spike S2 antibodies in health care workers at different time points after BNT162b2 vaccination. Live virus neutralization against wild-type and the B.1.617.2 (delta) variant of concern 6 weeks and 8 months after first vaccination in a representative subgroup of health care workers. Figure 3 (A) Neutralization against wild-type and the B.1.617.2 (delta) variant was determined in a SARS-CoV-2 infection assay using VeroE6 target cells and serial 2-fold dilutions of sera from 36 and 53 health care workers at 6 weeks (t2) and 8 months (t5) after first vaccination. The ID50 is defined as the serum dilution that inhibits 50% of the infectivity. The dashed black line indicates the cut-off for detection. (B) Spearman's rank coefficient of correlation between anti-

Geneva: World Health Organization

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