Abstract
BackgroundThe West Nile virus (WNV) nonstructural protein 1 (NS1) is an important antigenic protein that elicits protective antibody responses in animals and can be used for the serological diagnosis of WNV infection. Although previous work has demonstrated the vital role of WNV NS1-specific antibody responses, the specific epitopes in the NS1 have not been identified.ResultsThe present study describes the identification of two linear B-cell epitopes in WNV NS1 through screening a phage-displayed random 12-mer peptide library with two monoclonal antibodies (mAbs) 3C7 and 4D1 that directed against the NS1. The mAbs 3C7 and 4D1 recognized phages displaying peptides with the consensus motifs LTATTEK and VVDGPETKEC, respectively. Exact sequences of both motifs were found in the NS1 (895LTATTEK901 and 925VVDGPETKEC934). Further identification of the displayed B cell epitopes were conducted using a set of truncated peptides expressed as MBP fusion proteins. The data indicated that 896TATTEK901 and925VVDGPETKEC934 are minimal determinants of the linear B cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. Antibodies present in the serum of WNV-positive horses recognized the minimal linear epitopes in Western blot analysis, indicating that the two peptides are antigenic in horses during infection. Furthermore, we found that the epitope recognized by 3C7 is conserved only among WNV strains, whereas the epitope recognized by 4D1 is a common motif shared among WNV and other members of Japanese encephalitis virus (JEV) serocomplex.ConclusionsWe identified TATTEK and VVDGPETKEC as NS1-specific linear B-cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. The knowledge and reagents generated in this study may have potential applications in differential diagnosis and the development of epitope-based marker vaccines against WNV and other viruses of JEV serocomplex.
Highlights
The West Nile virus (WNV) nonstructural protein 1 (NS1) is an important antigenic protein that elicits protective antibody responses in animals and can be used for the serological diagnosis of WNV infection
Production of recombinant NS1 Recombinant WNV NS1 was successfully expressed in E. coli TB1 cells, predominantly as soluble protein, after induction with isopropyl b-D-1-thiogalactopyranoside (IPTG)
Among them two cell lines were selected for their strongest reactivity against recombinant NS1 using indirect enzyme-linked immunosorbent assay (ELISA), Western blot (WB) (Figure 2a), and against native NS1 in immunofluorescence assay (IFA) using WNV antigen slides (Figure 2b)
Summary
The West Nile virus (WNV) nonstructural protein 1 (NS1) is an important antigenic protein that elicits protective antibody responses in animals and can be used for the serological diagnosis of WNV infection. The 10.7-kilobase genome of WNV encodes a single polyprotein, which is cleaved into three structural proteins (C, prM/M, and E) and seven nonstructural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5) by both virusand host-encoded proteases. The seven nonstructural proteins (glycoprotein NS1 and NS2A, protease cofactor NS2B, protease and helicase NS3, NS4A, NS4B and the polymerase NS5) associate with viral RNA to form the replication complex [5]. NS1 is believed to function as a cofactor in viral RNA replication, and specific amino acids substitutions in NS1 can attenuate viral RNA accumulation [8].In vivo, highly circulating levels of the Dengue virus (DENV) NS1 early in Dengue illness correlated with the development of Dengue hemorrhagic fever and other severely associated diseases [9]
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