Human immunoglobulin from transchromosomic bovines hyperimmunized with SARS-CoV-2 spike antigen efficiently neutralizes viral variants

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants with amino-acid substitutions and deletions in spike protein (S) can reduce the effectiveness of monoclonal antibodies (mAbs) and may compromise immunity induced by vaccines. We report a polyclonal, fully human, anti-SARS-CoV-2 immunoglobulin produced in transchromosomic bovines (Tc-hIgG-SARS-CoV-2) hyperimmunized with two doses of plasmid DNA encoding the SARS-CoV-2 Wuhan strain S gene, followed by repeated immunization with S protein purified from insect cells. The resulting Tc-hIgG-SARS-CoV-2, termed SAB-185, efficiently neutralizes SARS-CoV-2, and vesicular stomatitis virus (VSV) SARS-CoV-2 chimeras in vitro. Neutralization potency was retained for S variants including S477N, E484K, and N501Y, substitutions present in recent variants of concern. In contrast to the ease of selection of escape variants with mAbs and convalescent human plasma, we were unable to isolate VSV-SARS-CoV-2 mutants resistant to Tc-hIgG-SARS-CoV-2 neutralization. This fully human immunoglobulin that potently inhibits SARS-CoV-2 infection may provide an effective therapeutic to combat COVID-19.

KEYWORDS:

• SARS-cov-2
• variants
• polyclonal antibodies
• transchromosomic bovines

Acknowledgments

We thank Ma. Xenia G. Ilagan in automated microscope core facility, Spencer Stumpf for excellent technical assistance and Ali H. Ellebedy for generously providing 2H04.

Author contributions

Z.L designed and performed the VSV experiments. W.H and K.A.E produced the purified SARS-CoV-2 Spike pDNA and protein antigens. W.H immunized the Tc-bovines. C.L.B generated and purified SAB-185. T.C.G and M.D.D performed the neutralization assay at the Biosafety Level 3 facility. Z.L, H.W, T.C.L, W.B.K, E.J.S and S.P.J.W analyzed the data. Z.L, H.W, T.C.L, W.B.K, and S.P.J.W wrote the initial draft, with the other authors providing editing comments.

Disclosure of potential conflicts of interest

SAB Biotherapeutics, Inc., is receiving support from the Department of Defense (DoD) Joint Program Executive Office for Chemical, Biological, Radiological, and Nuclear Defense (JPEO-CBRND) Joint Project Lead for Enabling Biotechnologies (JPL-EB), and from the Biomedical Advanced Research Development Authority (BARDA), part of the Assistant Secretary for Preparedness and Response (ASPR) at the US. Department of Health and Human Services, to develop SAB-185, a countermeasure to SARS-CoV-2 (Effort sponsored by the US. Government under Other Transaction number W15QKN-16-9-1002 between the Medical CBRN Defense Consortium (MCDC), and the Government). The US Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the US. Government. E.J.S, C.L.B, HW, K.A.E, and T.C.L are employees of SAB Biotherapeutics, Inc. SAB Biotherapeutics, Inc. S.P.J.W and Z.L are employees of Washington University of Saint Louis and conducted this research under a contract with SAB Biotherapeutics, Inc. W.B.K, T.C.G and M.D.D are employees of the University of Pittsburgh and conducted this research under a contract with SAB Biotherapeutics, Inc.

Investigational new animal drug (INAD) and ethics statement

SAB Biotherapeutics has an Investigational New Animal Drug (INAD) file (#I-011204) with FDA Center for Veterinary Medicine (CVM) on the complete genetic engineering of the Transchromosomic (Tc) bovine and the production of fully human antibody in the animals. SAB uses Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC) for accreditation of its animal care and use programs. The animal protocols contained in the study were approved by SAB Biotherapeutic Institutional Animal Care and Use Committee (IACUC).

Quantification and statistical analysis

All statistical tests were performed as described in the indicated figure legends. Non-linear regression (curve fit) was performed for Figures 2 and Figure 3a using Prism version 9.0. The number of independent experiments used are indicated in the relevant Figure legends.