Vaccination of Mice Using the West Nile Virus E-Protein in a DNA Prime-Protein Boost Strategy Stimulates Cell-Mediated Immunity and Protects Mice against a Lethal Challenge

Marina De Filette,Niek N Sanders,Michael S Diamond,Alessandro Sinigaglia,Stefan Roels,Sebastian Ulbert,Julianna Lisziewicz,Orsolya Lorincz,Luisa Barzon,Justin Richner,Silke Soehle

doi:10.1371/journal.pone.0087837

Abstract

West Nile virus (WNV) is a mosquito-borne flavivirus that is endemic in Africa, the Middle East, Europe and the United States. There is currently no antiviral treatment or human vaccine available to treat or prevent WNV infection. DNA plasmid-based vaccines represent a new approach for controlling infectious diseases. In rodents, DNA vaccines have been shown to induce B cell and cytotoxic T cell responses and protect against a wide range of infections. In this study, we formulated a plasmid DNA vector expressing the ectodomain of the E-protein of WNV into nanoparticles by using linear polyethyleneimine (lPEI) covalently bound to mannose and examined the potential of this vaccine to protect against lethal WNV infection in mice. Mice were immunized twice (prime – boost regime) with the WNV DNA vaccine formulated with lPEI-mannose using different administration routes (intramuscular, intradermal and topical). In parallel a heterologous boost with purified recombinant WNV envelope (E) protein was evaluated. While no significant E-protein specific humoral response was generated after DNA immunization, protein boosting of DNA-primed mice resulted in a marked increase in total neutralizing antibody titer. In addition, E-specific IL-4 T-cell immune responses were detected by ELISPOT after protein boost and CD8+ specific IFN-γ expression was observed by flow cytometry. Challenge experiments using the heterologous immunization regime revealed protective immunity to homologous and virulent WNV infection.

Highlights

West Nile virus (WNV) is a single-stranded positive polarity enveloped RNA virus and member of the Flavivirus genus of the Flaviviridae family
WNV-DermaVir nanoparticles were administered by three different routes (ID, IM or topical) to mice, and the humoral and cellular immune response was evaluated
Using a heterologous DNA prime/protein boost immunization strategy, we showed that antibody titers against the E-protein can be induced using these WNV-DermaVir nanoparticles

Summary

Introduction

West Nile virus (WNV) is a single-stranded positive polarity enveloped RNA virus and member of the Flavivirus genus of the Flaviviridae family. WNV infections usually remains asymptomatic or causes a mild undifferentiated febrile illness called West Nile fever [2]. WNV has circulated in the United States since 1999 [4] and subsequently spread across continental North America, the Caribbean and South America [5]. It was soon recognized as one of the most widely distributed flaviviruses, with its geographic range including Africa [6], the Middle East [6] western Asia [6], Europe [6] and Australia [7]. Since there is no treatment for WNV infection available, there is an urgent need for effective vaccines to prevent WNV infection in humans

Methods

Results

Conclusion