The Anamnestic Neutralizing Antibody Response Is Critical for Protection of Mice from Challenge following Vaccination with a Plasmid Encoding the Japanese Encephalitis Virus Premembrane and Envelope Genes

Abstract

For Japanese encephalitis (JE), we previously reported that recombinant vaccine-induced protection from disease does not prevent challenge virus replication in mice. Moreover, DNA vaccines for JE can provide protection from high challenge doses in the absence of detectable prechallenge neutralizing antibodies. In the present study, we evaluated the role of postchallenge immune responses in determining the outcome of JE virus infection, using mice immunized with a plasmid, pcDNA3JEME, encoding the JE virus premembrane (prM) and envelope (E) coding regions. In the first experiment, 10 mice were vaccinated once (five animals) or twice (remainder) with 100 μg of pcDNA3JEME. All of these mice showed low (6 of 10) or undetectable (4 of 10) levels of neutralizing antibodies. Interestingly, eight of these animals showed a rapid rise in neutralizing antibody following challenge with 10,000 50% lethal doses of JE virus and survived for 21 days, whereas only one of the two remaining animals survived. No unimmunized animals exhibited a rise of neutralizing antibody or survived challenge. Levels of JE virus-specific immunoglobulin M class antibodies were elevated following challenge in half of the unimmunized mice and in the single pcDNA3JEME-immunized mouse that died. In the second experiment, JE virus-specific primary cytotoxic T-lymphocyte (CTL) activity was detected in BALB/c mice immunized once with 100 μg of pcDNA3JEME 4 days after challenge, indicating a strong postchallenge recall of CTLs. In the third experiment, evaluation of induction of CTLs and antibody activity by plasmids containing portions of the prM/E cassette demonstrated that induction of CTL responses alone were not sufficient to prevent death. Finally, we showed that antibody obtained from pcDNA3JEME-immunized mice 4 days following challenge could partially protect recipient mice from lethal challenge. Taken together, these results indicate that neutralizing antibody produced following challenge provides the critical protective component in pcDNA3JEME-vaccinated mice.

Formalin Inactivation of Japanese Encephalitis Virus Vaccine Alters the Antigenicity and Immunogenicity of a Neutralization Epitope in Envelope Protein Domain III

“…The protective efficacy of vaccines against JEV infection is positively associated with the presence of neutralizing antibodies in mice [60]. Based on this we evaluated the correlation between Formalin Inactivation Alters the Immunogenicity of JEV the production of neutralizing antibodies binding to EDIII 329/331/389 across various vaccines.…”

Rapid Detection and Quantification of Japanese Encephalitis Virus by Real‐Time Reverse Transcription Loop‐Mediated Isothermal Amplification

“…The viral E protein, which is modified by glycosylation and dimerization during virion assembly, serves as the cellreceptor binding protein and the fusion protein for viral attachment and entry into the host. The E protein is directly associated with neutralization (11,22). Routine laboratory diagnosis of JEV infection is based on four basic types of assays: serologic, viral isolation, immunocytochemical, and molecular.…”

Yellow Fever Virus Encephalitis: Properties of the Brain-Associated T-Cell Response during Virus Clearance in Normal and Gamma Interferon-Deficient Mice and Requirement for CD4+Lymphocytes

“…T cells with virus-specific cytotoxic activity were isolated from the brains of mice with West Nile virus encephalitis (43), and studies with Japanese encephalitis (JE) virus suggest that both CD8 ϩ cytotoxic T cells and CD4 ϩ T cells are required for protection (49). Activation of virus-specific CD4 ϩ and CD8 ϩ T cells has been demonstrated in humans and laboratory animals after exposure to JE virus antigens (1,35,36,48), and T cells expressing these surface markers have been detected in perivascular infiltrates during encephalitis (32). Collectively, these studies also implicate virus-specific T cells in protection, although the critical effector functions involved in clearance of virus from the CNS are not known.…”