• Guillermo Valenzuela Nieto, Ronald Jara, Daniel Watterson, Naphak Modhiran, Alberto A Amarilla, Johanna Himelreichs, Alexander A Khromykh, Constanza Salinas-Rebolledo, Teresa Pinto, Yorka Cheuquemilla, Yago Margolles, Natalia López González Del Rey, Zaray Miranda-Chacon, Alexei Cuevas, Anne Berking, Camila Deride, Sebastián González-Moraga, Héctor Mancilla, Daniel Maturana, Andreas Langer, Juan Pablo Toledo, Ananda Müller, Benjamín Uberti, Paola Krall, Pamela Ehrenfeld, Javier Blesa, Pedro Chana-Cuevas, German Rehren, David Schwefel, Luis Ángel Fernandez, and Alejandro Rojas-Fernandez.
• Institute of Medicine, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile.
• Sci Rep. 2021 Feb 8; 11 (1): 3318.

AbstractDespite unprecedented global efforts to rapidly develop SARS-CoV-2 treatments, in order to reduce the burden placed on health systems, the situation remains critical. Effective diagnosis, treatment, and prophylactic measures are urgently required to meet global demand: recombinant antibodies fulfill these requirements and have marked clinical potential. Here, we describe the fast-tracked development of an alpaca Nanobody specific for the receptor-binding-domain (RBD) of the SARS-CoV-2 Spike protein with potential therapeutic applicability. We present a rapid method for nanobody isolation that includes an optimized immunization regimen coupled with VHH library E. coli surface display, which allows single-step selection of Nanobodies using a simple density gradient centrifugation of the bacterial library. The selected single and monomeric Nanobody, W25, binds to the SARS-CoV-2 S RBD with sub-nanomolar affinity and efficiently competes with ACE-2 receptor binding. Furthermore, W25 potently neutralizes SARS-CoV-2 wild type and the D614G variant with IC50 values in the nanomolar range, demonstrating its potential as antiviral agent.

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