Objective To construct a library of human-derived anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) single-chain variable fragments (scFv) and screen for broad-spectrum neutralizing antibodies to identify candidate molecules for the development of diagnostic and therapeutic agents. Methods Peripheral blood mononuclear cells (PBMCs) were isolated from the peripheral blood of patients who had recovered from novel coronavirus infection. Total RNA was extracted from these PBMCs and reverse transcribed into cDNA, which was used as a template for constructing a human anti-SARS-CoV-2 scFv library. Phage display technology was used to screen for scFv antibodies specific to the SARS-CoV-2 S protein. Full-length IgG antibodies were synthesized through sequence analysis and human IgG expression, and their binding capacity and neutralizing activity against SARS-CoV-2 were evaluated. Results A human-derived scFv antibody library against SARS-CoV-2 with a capacity of 1.56×10⁷ CFU was successfully constructed. Two specific scFv antibodies were screened from this library and expressed as full-length IgG antibodies (IgG-A10 and IgG-G6). IgG-A10 exhibited strong neutralizing activity against both the original SARS-CoV-2 strain (WT) and the XBB subvariant of the Omicron variant. However, the neutralizing activity of this antibody against the JN.1 sub lineage of the Omicron BA.2.86 variant was moderate. Conclusion This study has successfully constructed a human anti-SARS-CoV-2 scFv antibody library from the peripheral blood of recovered patients, and screened and expressed anti-SARS-CoV-2 IgG antibodies with neutralizing activity, laying a foundation for the prevention, diagnosis, and treatment of SARS-CoV-2 infection.
Humans ; Single-Chain Antibodies/genetics* ; SARS-CoV-2/immunology* ; COVID-19/immunology* ; Immunoglobulin G/genetics* ; Antibodies, Viral/genetics* ; Peptide Library ; Spike Glycoprotein, Coronavirus/immunology* ; Antibodies, Neutralizing/immunology* ; Leukocytes, Mononuclear/immunology* ; Broadly Neutralizing Antibodies/immunology*

Hundreds of broadly neutralizing antibodies(bNAbs) were successfully isolated from long-term nonprogression(LTNP) of human immunodeficiency virus type 1(HIV-1) infected individuals. Some bNAbs were illustrated could reduce the viral load and the risk of HIV-1 infection. Today, HIV-1 bNAbs are at the center of vaccine development and passive immunization treatment. Usually, the activity of neutralizing antibodies depends on the epitope. The affinity of neutralizing antibodies also plays a vital role in its inhibitory effect. Multiple affinity maturation in vivo actually provides the broad and potent neutralizing activity of HIV-1 bNAbs. When high affinity HIV-1 bNAbs applied in clinic, it can help immune system to remove virus with lower dosage and fewer side effect. While affinity maturation, HIV-1 bNAbs shows unique characteristics, such as extensive of somatic hypermutation(SHM), in-frame insertion and deletion and long CDR 3 region of heavy chain. The key points in the progress that HIV-1 bNAbs affinity maturation will help us understand the relationship between antibodies neutralizing capability and its characteristics.It also potentially provide a reference to design effective HIV-1 immunogen.
Antibodies, Neutralizing ; Broadly Neutralizing Antibodies ; HIV Antibodies ; HIV Infections ; HIV-1 ; Humans