Gamma-Immunoglobulin Response Characterization, in COVID-19 Convalescent Patients, Against the Spike Protein S2 Subunit with Eight Linear Peptides for Monoclonal Antibody Generation

By Airela Llamo, Daily Hernández, Cristina García, Marcos González, Williams Ferro, Hilda Garay, David Diago, Abel Fajardo, Luis Espinosa, Sigifredo Padilla, Leonardo Gómez, Glay Chinea, and Rodolfo Valdés
Volume 22, Open Access (March 2023)

The SARS-CoV-2 spike protein S2 subunit plays an essential role in the virus-host cell membrane fusion process. Therefore, the subject of this study was to characterize the gamma-immunoglobulin (IgG) response, in a group of COVID-19 convalescent patients, against the S2 subunit with eight¬†linear peptides to generate a monoclonal antibody (mAb) against the immunodominant linear peptide to be used for therapeutic and diagnostic purposes. Results of antibody percentages against assessed linear peptides were 100% for A21P73, A21P74, A21P75, A21P76, M20P51, M20P65, M20P83, and 66.7% for M20P85. Plasma samples were also used for purifying IgG to corroborate specificity against the same linear peptides, where results reproduced those applying plasmas directly to ELISA-plates. Within these peptides, A21P75 was chosen as immunodominant (100% of recognition with higher absorbance). The A21P75 linear peptide showed poor immunogenicity in mice (1:4000‚Äď8000 after four doses), allowing the generation of a CB.HS2A21P75 hybridoma for mAb production that recognized the A21P75 linear peptide with middle-to-high affinity constant (Kaff) (0.8√ó108 M-1).

This study concludes that the A21P75 linear peptide is the assessed immunodominant linear peptide for this COVID-19 convalescent patient group. This peptide is located in the HR1 region that plays an important role in SARS-CoV-2 host cell membrane fusion process and is highly conserved between SARS-CoV-2 and SARS-CoV. Thus, due to CB.S2A21P75 mAb specificity and Kaff, it might be the proper reagent to study inhibition of virus-host cell membrane fusion, and as a diagnostic reagent for coronavirus. Finally, the combination of A21P75 linear peptide with other peptides (e.g., receptor binding domain [RBD]) could be suitable reagents for the development of vaccines and therapeutic antibodies with virus infection-blocking capacity.

Llamo A, Hernández D, García C, González M, Ferro W, Garay H, Diago D, Fajardo A, Espinosa L, Padilla S, Gómez L, Chinea G, Valdés R. Gamma-immunoglobulin response characterization, in COVID-19 convalescent patients, against the spike protein S2 subunit with eight linear peptides for monoclonal antibody generation. BioProcess J, 2023; 22.

Posted online March 6, 2023.