The SARS-CoV-2 receptor-binding domain elicits a potent neutralizing response without antibody-dependent enhancement

Brian D Quinlan; Huihui Mou; Lizhou Zhang; Yan Gao; Wenhui He; Amrita Ojha; Mark S Parcells; Guangxiang Luo; Wenhui Li; Guocai Zhong; Hyeryun Choe; Michael Farzan

To evaluate this possibility, we produced and purified the SARS-CoV-2 RBD (sequence shown in Figure 1D ), fused to the Fc domain as an expedient for rapid purification. This RBD fusion protein was conjugated to a Keyhole limpet hemocyanin (KLH) carrier protein and mixed with the AS01 adjuvant formulation now used in at least two human vaccines. This antigen/adjuvant combination was injected intramuscularly into four female Sprague-Dawley rats with a schedule of seven increasing (2.5-fold) doses, one each day, ultimately administering a total of 500 µg of the SARS-CoV RBD-Fc. Thirty days after the first administration, RBD fused to a 4-amino acid C-tag was . CC-BY-NC-ND 4.0 International license author/funder. It is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.04.10.036418 doi: bioRxiv preprint purified with a C-tag affinity column, again conjugated to KLH, and the immunization regimen was repeated. Again a total of 500 µg of RBD was administered.