Abstract
Japanese encephalitis virus (JEV) non-structural protein 1 (NS1) contributes to virus replication and elicits protective immune responses during infection. JEV NS1-specific antibody responses could be a target in the differential diagnosis of different flavivirus infections. However, the epitopes on JEV NS1 are poorly characterized. The present study describes the full mapping of linear B-cell epitopes in JEV NS1. We generated eleven NS1-specific monoclonal antibodies from mice immunized with recombinant NS1. For epitope mapping of monoclonal antibodies, a set of 51 partially-overlapping peptides covering the entire NS1 protein were expressed with a GST-tag and then screened using monoclonal antibodies. Through enzyme-linked immunosorbent assay (ELISA), five linear epitope-containing peptides were identified. By sequentially removing amino acid residues from the carboxy and amino terminal of peptides, the minimal units of the five linear epitopes were identified and confirmed using monoclonal antibodies. Five linear epitopes are located in amino acids residues 5AIDITRK11, 72RDELNVL78, 251KSKHNRREGY260, 269DENGIVLD276, and 341DETTLVRS348. Furthermore, it was found that the epitopes are highly conserved among JEV strains through sequence alignment. Notably, none of the homologous regions on NS1 proteins from other flaviviruses reacted with the MAbs when they were tested for cross-reactivity, and all five epitope peptides were not recognized by sera against West Nile virus or Dengue virus. These novel virus-specific linear B-cell epitopes of JEV NS1 would benefit the development of new vaccines and diagnostic assays.
Highlights
Japanese encephalitis (JE) is caused by the Japanese encephalitis virus (JEV), and is one of the most important mosquito-borne diseases with a mortality rate as high as 20% to 50%, and is widely distributed in most of East and South-east Asia and parts of Oceania
Production of monoclonal antibodies (MAbs) Recombinant JEV non-structural protein 1 (NS1) was successfully expressed in E. coli
The results showed that neither sera against West Nile virus (WNV) nor Dengue virus (DENV) reacted with the five JEV NS1 epitopes (Fig. 5)
Summary
Japanese encephalitis (JE) is caused by the Japanese encephalitis virus (JEV), and is one of the most important mosquito-borne diseases with a mortality rate as high as 20% to 50%, and is widely distributed in most of East and South-east Asia and parts of Oceania. A wide range of animals including swine, equines and birds can be infected. JEV infection has accounted for significant economic losses in the pig industry due to fetal encephalitis and reproductive failure in pregnant sows and hypospermia in boars [4]. There is no specific treatment available for JE, and vaccination is the only effective way to prevent JEV infection in humans and domestic animals. Like other flaviviruses, NS1 is able to elicit protective immunity without the risk of antibody-dependent enhancement. These characteristics make NS1 an attractive alternative immunogen. NS1 is not present in the virion, NS1-induced antibodies can protect against infection in vivo by an undetermined mechanism, which presumably depends on the Fc portion of the antibody since they kill their target cells through a complement-dependent pathway [10,11]
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