Cross-reactive antibodies targeting surface-exposed non-structural protein 1 of dengue virus-infected cells recognize epitopes on the spaghetti loop of the [beta]-ladder domain

• Published in: PloS one Vol. 17; no. 5; p. e0266136
• Main Authors: Kraivong, Romchat, Traewachiwiphak, Somchoke, Nilchan, Napon, Tangthawornchaikul, Nattaya, Pornmun, Nuntaya, Poraha, Ranyikar, Sriruksa, Kanokwan, Limpitikul, Wannee, Avirutnan, Panisadee, Malasit, Prida, Puttikhunt, Chunya
• Format: Journal Article
• Language: English
• Published: Public Library of Science 26.05.2022
• Subjects: Analysis; Antibodies; Dengue viruses; Genetic aspects; Health aspects; Immune response; Proteins; Viral antibodies; Thailand
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0266136

Non-structural protein 1 (NS1) is a glycoprotein component of dengue virus (DENV) that is essential for viral replication, infection and immune evasion. Immunization with NS1 has been shown to elicit antibody-mediated immune responses which protect mice against DENV infections. Here, we obtained peripheral blood mononuclear cells from human subjects with secondary dengue infections, which were used to construct a dengue immune phage library displaying single-chain variable fragments. Phage selective for DENV NS1 were obtained by biopanning. Twenty-one monoclonal antibodies (mAbs) against DENV NS1 were generated from the selected phage and characterized in detail. We found most anti-NS1 mAbs used IGHV1 heavy chain antibody genes. The mAbs were classified into strongly and weakly-reactive groups based on their binding to NS1 expressed in dengue virus 2 (DENV2)-infected cells. Antibody binding experiments with recombinant NS1 proteins revealed that the mAbs recognize conformational epitopes on the [beta]-ladder domain (amino acid residues 178-273) of DENV NS1. Epitope mapping studies on alanine-substituted NS1 proteins identified distinct but overlapping epitopes. Protruding amino acids distributed around the spaghetti loop are required for the binding of the strongly-reactive mAbs, whereas the recognition residues of the weakly-reactive mAbs are likely to be located in inaccessible sites facing toward the cell membrane. This information could guide the design of an NS1 epitope-based vaccine that targets cross-reactive conserved epitopes on cell surface-associated DENV NS1.