# Construction and Evaluation of a Chimeric Japanese Encephalitis Virus Vaccine Candidate Strain with Chaoyang Virus as the Backbone

## TL;DR

Researchers developed a new Japanese encephalitis virus vaccine using a modified insect-specific virus backbone, showing it is safe and effective in mice.

## Contribution

A novel chimeric Japanese encephalitis virus vaccine candidate was constructed using Chaoyang virus as a safe backbone.

## Key findings

- CYV-JEV replicated efficiently in mosquito cells but not in mammalian cells.
- The vaccine provided complete protection against lethal challenge in mice.
- It activated T- and B-cells and showed no pathogenicity in tested mouse models.

## Abstract

Background: Pathogenic flaviviruses pose a serious threat to human health, and vaccines are an effective means of prevention and control. Although related vaccines have achieved significant progress, safety and efficacy limitations still exist, urgently requiring the development of novel vaccine platforms. The insect-specific flavivirus Chaoyang virus (CYV), with a structure similar to pathogenic flaviviruses and limited to insect cell replication, has potential as a safe vaccine vector. Methods: To systematically evaluate CYV’s potential as a universal flavivirus vaccine backbone and provide a vaccine candidate for type I Japanese encephalitis virus (JEV) prevention, this study constructed a chimeric JEV genotype I (GI) prME protein vaccine candidate CYV-JEV using CPER technology, systematically assessing its safety and immunoprotective effects. Results: Using the CPER method, CYV-JEV was successfully rescued, showing efficient replication in mosquito cells but defective replication in mammalian cells. As a vaccine backbone, CYV did not induce inflammatory responses or immune cell subset imbalances in IFNAR−/− mice. CYV-JEV exhibited no pathogenicity in adult and suckling IFNAR−/− mice. Immunisation of IFNAR−/− mice with 106 FFU twice provided complete protection against lethal challenge (100%) and effectively reduced paralysis rates (62.5%). Single-cell sequencing further revealed extensive T- and B-cell activation in the immune spleen. Conclusions: The results demonstrate that the CYV-based CYV-JEV candidate vaccine demonstrates both safety and efficacy, representing a promising alternative to attenuated JEV vaccines, with CYV showing potential as a safe and effective universal flavivirus vaccine backbone.