# Selection and characterization of human scFvs targeting the SARS-CoV-2 nucleocapsid protein isolated from antibody libraries of COVID-19 patients

## TL;DR

This paper describes the creation and testing of antibody fragments targeting the SARS-CoV-2 nucleocapsid protein from patients, offering new tools for research and diagnostics.

## Contribution

The study introduces a novel panel of scFvs targeting the SARS-CoV-2 nucleocapsid protein, providing a new platform for research and potential diagnostic use.

## Key findings

- A panel of scFvs was successfully constructed and characterized against the SARS-CoV-2 nucleocapsid protein.
- Selected scFvs showed high binding activity as intrabodies and nanomolar affinity as recombinant proteins.
- The scFv panel represents a valuable resource for studying SARS-CoV-2 and developing diagnostics.

## Abstract

In 2019, the novel SARS-CoV-2 coronavirus emerged in China, causing the pneumonia named COVID-19. At the beginning, all research efforts were focused on the spike (S) glycoprotein. However, it became evident that the nucleocapsid (N) protein is pivotal in viral replication, genome packaging and evasion of the immune system, is highly immunogenic, which makes it another compelling target for antibody development alongside the spike protein. This study focused on the construction of single chain fragments variable (scFvs) libraries from SARS-CoV-2-infected patients to establish a valuable, immortalized and extensive antibodies source. We used the Intracellular Antibody Capture Technology to select a panel of scFvs against the SARS-CoV-2 N protein. The whole panel of scFv was expressed and characterized both as intrabodies and recombinant proteins. ScFvs were then divided into 2 subgroups: those that exhibited high binding activity to N protein when expressed in yeast or in mammalian cells as intrabodies, and those purified as recombinant proteins, displaying affinity for recombinant N protein in the nanomolar range. This panel of scFvs against the N protein represents a novel platform for research and potential diagnostic applications.