key: cord-0702841-tb538rkv
authors: Kamar, Nassim; Abravanel, Florence; Marion, Olivier; Romieu-Mourez, Raphaelle; Couat, Chloé; Del Bello, Arnaud; Izopet, Jacques
title: Assessment of 4 Doses of SARS-CoV-2 Messenger RNA–Based Vaccine in Recipients of a Solid Organ Transplant
date: 2021-11-24
journal: JAMA Netw Open
DOI: 10.1001/jamanetworkopen.2021.36030
sha: 1db29717b6c2eac785b5de5f135826182e96ed51
doc_id: 702841
cord_uid: tb538rkv

This case series study assesses whether a fourth dose of a SARS-CoV-2 messenger RNA (mRNA)–based vaccine is associated with improved anti–SARS-CoV-2 antibody response in solid organ transplant recipients in France.

Anti-SARS-CoV-2 spike protein total antibodies were assessed before each jab using the Wantai semiquantitative microplate ELISA (Wantai SARS-CoV-2 Ab ELISA, Beijing Wantai Biological Pharmacy Enterprise CO., Ltd, Beijing, China). A positive result was defined by a signal-to-cut off (S/CO) ratio greater or equal 1.1. A linear relationship was obtained between the S/CO ratio and SARS-CoV-2 antibody concentration using the first WHO international standard (NIBSC code: 20/136, National Institute for Biological Standards, and Control, Potter Bar, Hertfordshire, EN6QG, UK). Dilutions using PBS plus 7.5% bovine serum albumin as a diluent was set up to analyse samples giving a saturated signal. Results are expressed in binding antibody units (BAU)/mL. Using this assay, we have previously reported a 100% specificity and 100% sensitivity in immunocompetent patients tested at 2 to 14 days post symptom-onset and at 15 to 45 days post symptom-onset, suggesting it as the ability to detect low level of antibodies 1 .

Neutralizing antibody titers were assessed using a live virus neutralization assay and a clinical 

To analyze T-cell responses, enzyme-linked immunospot assay (EliSpot) measuring interferonγ produced by specific SARS-CoV-2 T-cells were performed, the day of each dose and 1 month after the third dose. PBMCs were thawed and left to recover overnight at 37 °C (2 × 10 6 cells/mL) in culture medium (RPMI supplemented with glutamine, pyruvate, penicillin, streptomycin and 5% fetal calf serum). ELISpot assays were performed using plates, capture antibodies and detection reagents from the Diaclone kit for detecting IFN-γ. 

Clinical performance of a rapid test compared to a microplate test to detect total anti SARS-CoV-2 antibodies directed to the spike protein