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It is commonly known that halogenation tends to decrease the lu- minescence quantum yield of an organ- ic dye, owing to the high electronega- tivity and heavy-atom effect of the hal- ogen atom. However, based on an in- vestigation of the effects of halogena- tion on the luminescence of the oligo(phenylene vinylene) (OPV) framework, we demonstrate that halo- genation can have positive impact on the solid-state fluorescence and elec- trochemiluminescence (ECL) proper- ties of OPV derivatives. The chlorinat- ed OPV exhibits a very high solid-state fluorescence quantum yield (91 %), whilst the brominated analogue gives the highest ECL emission intensity. Time-dependent density functional theory calculations, natural bond orbi- tal analysis, and natural transition orbi- tal analysis were performed to assist the understanding of the origin of these positive halogenation effects, which provide insight into the rational design of highly luminescent halogenat- ed organic materials for solid-state de- vices and ECL applications.

West Nile virus (WNV) non-structural protein 1 (NS1) elicits protective immune responses during infection of animals. WNV NS1-specific antibody responses can provide the basis for serological diagnostic reagents, so the antigenic sites in NS1 that are targeted by host immune responses need to be identified and the conservation of these sites among the Japanese encephalitis virus (JEV) serocomplex members also needs to be defined. The present study describes the mapping of linear B-cell epitopes in WNV NS1. We screened eight NS1-specific mAbs and antisera (polyclonal antibodies; pAbs) from mice immunized with recombinant NS1 for reactivity against 35 partially overlapping peptides covering the entire WNV NS1. The screen using mAbs identified four WNV-specific (including Kunjin virus) epitopes, located at aa 21–36, 101–116, 191–206 and 261–276 in WNV NS1. However, using pAbs, only three WNV-specific epitopes were identified, located at positions 101–116, 191–206 and 231–246. Two of these epitopes (aa 21–36 and 261–276) had different reactivity with mAbs and pAbs. The knowledge and reagents generated in this study have potential applications in differential diagnostics and epitope-based marker vaccine development for WNV and viruses of the JEV serocomplex.

Background 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. Although previous work has demonstrated the vital role of WNV NS1-specific antibody responses, the specific epitopes in the NS1 have not been identified. Results The 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. Conclusions We 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.

Background The West Nile virus (WNV) capsid (C) protein is one of the three viral structural proteins, encapsidates the viral RNA to form the nucleocapsid, and is necessary for nuclear and nucleolar localization. The antigenic sites on C protein that are targeted by humoral immune responses have not been studied thoroughly, and well-defined B-cell epitopes on the WNV C protein have not been reported. Results In this study, we generated a WNV C protein-specific monoclonal antibody (mAb) and defined the linear epitope recognized by the mAb by screening a 12-mer peptide library using phage-display technology. The mAb, designated as 6D3, recognized the phages displaying a consensus motif consisting of the amino acid sequence KKPGGPG, which is identical to an amino acid sequence present in WNV C protein. Further fine mapping was conducted using truncated peptides expressed as MBP-fusion proteins. We found that the KKPGGPG motif is the minimal determinant of the linear epitope recognized by the mAb 6D3. Western blot (WB) analysis demonstrated that the KKPGGPG epitope could be recognized by antibodies contained in WNV- and Japanese encephalitis virus (JEV)-positive equine serum, but was not recognized by Dengue virus 1-4 (DENV1-4)-positive mice serum. Furthermore, we found that the epitope recognized by 6D3 is highly conserved among the JEV serocomplex of the Family Flaviviridae. Conclusion The KKPGGPG epitope is a JEV serocomplex-specific linear B-cell epitope recognized by the 6D3 mAb generated in this study. The 6D3 mAb may serve as a novel reagent in development of diagnostic tests for JEV serocomplex infection. Further, the identification of the B-cell epitope that is highly conserved among the JEV serocomplex may support the rationale design of vaccines against viruses of the JEV serocomplex.