Generation and characterization of a new mammalian cell line continuously expressing virus-like particles of Japanese encephalitis virus for a subunit vaccine candidate

Abstract

BackgroundJapanese encephalitis virus (JEV) is the most important cause of epidemic encephalitis in most Asian regions. There is no specific treatment available for Japanese encephalitis, and vaccination is the only effective way to prevent JEV infection in humans and domestic animals. The purpose of this study is to establish a new mammalian cell line stably and efficiently expressing virus-like particle of JEV for potential use of JEV subunit vaccine.ResultsWe generated a new cell clone (BJ-ME cells) that stably produces a secreted form of Japanese encephalitis virus (JEV) virus-like particle (VLP). The BJ-ME cells were engineered by transfecting BHK-21 cells with a code-optimized cDNA encoding JEV prM and E protein expression plasmid. Cell line BJ-ME can stably produces a secreted form of Japanese encephalitis virus virus-like particle (JEV-VLP) which contains the JEV envelope glycoprotein (E) and membrane protein (M). The amount of JEV-VLP antigen released into the culture fluid of BJ-ME cells was as high as 15–20 μg/ml. JEV-VLP production was stable after multiple cell passages and 100% cell expression was maintained without detectable cell fusion or apoptosis. Cell culture fluid containing the JEV-VLP antigen could be harvested five to seven times continuously at intervals of 4–6 days while maintaining the culture. Mice immunized with the JEV-VLP antigen with or without adjuvant developed high titers of neutralizing antibodies and 100% protection against lethal JEV challenge.ConclusionThese results suggest that the recombinant JEV-VLP antigen produced by the BJ-ME cell line is an effective, safe and affordable subunit Japanese encephalitis vaccine candidate, especially for domestic animals such as pig and horse.

Viral vaccines and their manufacturing cell substrates: New trends and designs in modern vaccinology

“…Cell line development for stable production of VLPs has been used when the viral proteins are not cytotoxic. Two very recent examples are HEK-G cells developed for the production of rabies VLPs [107] and BJ-BM cells for the production of Japanese encephalitis virus VLPs [108] (Table 2). When the proteins are cytotoxic, transient approaches are used instead.…”

“…Stable expression of the structural gene pIX from human adenovirus increased the titers of poxvirus, the main viral product manufactured in AGE1 ® cells ( Table 3). The authors suggested that the improvement in viral titers is mediated via induction of heat shock pathway [108].…”

Virus-Like Particle Systems for Vaccine Development against Viruses in the Flaviviridae Family

“…Similar immunogenicity/protection in mice and pigs was respectively observed when plasmids encoding JEV prME genes were stably expressed in rabbit kidney-derived RK13 and CHO cells [40,41]. Following the above discoveries, several other groups also expressed plasmid vectors encoding JEV prME genes to produce JEV VLPs in different mammalian cells, yielding similar immunogenicity/protection in mice [42,43]. On the other hand, many groups have also successfully used the insect cell expression system to generate JEV VLPs [44][45][46][47][48].…”

Recent Advances in Vaccine Technologies

“…Nevertheless, several systems are available for the expression of proteins in mammalian cells and have been successfully used to express candidate vaccine proteins for bovine viral diarrhea (BVD), 13 CSF, 14 and VLPs for Japanese encephalitis virus. 15…”