ChimeriVax-West Nile Virus Live-Attenuated Vaccine: Preclinical Evaluation of Safety, Immunogenicity, and Efficacy

Abstract

(14), Jamaica, and the Dominican Republic (13, 17). The rapid geographic expansion of the virus is attributed to movement by viremic birds during local and migratory flight behavior. To date, there is no effective drug treatment against WN virus infection and surveillance and mosquito control measures have not significantly influenced the number of human infections (27). A vaccine against WN virus represents an important approach to the prevention and control of this emerging disease.The ChimeriVax technology has been successfully used to develop a live vaccine against Japanese encephalitis (JE) virus that is now in phase II trials (23). JE virus is a close genetic relative of WN virus (31), a fact that expedited use of this technology to develop multiple WN virus vaccine candidates. The ChimeriVax technology employs the yellow fever (YF) 17D vaccine capsid and nonstructural genes to deliver the envelope genes (prM and E) of other flaviviruses. In the work presented here, the envelope genes of YF 17D were replaced with the corresponding genes of the wild-type WN virus NY99 strain previously described by Lanciotti et al. (19). The resulting YF/WN chimera lacked the mouse neuroinvasive property of WN virus and is less neurovirulent than YF 17D vaccine in both mouse and monkey models. Because WN virus, like other flaviviruses in the genus, is neurotropic for mammals (21, 29), attenuating point mutations were later introduced in the envelope of the YF/WN chimera to further reduce its virulence. Mutation sites were targeted only to regions of the envelope (E) protein gene and were based on previous observations by others (1,3,28,32) pertaining to attenuation phenotypes in related flaviviruses: specifically JE and tick-borne encephalitis viruses. Site-directed mutations in the WN virus E gene of the chimeric prototype vaccine, ChimeriVax-West Nile 01 , (ChimeriVax-WN 01 ) resulted in a significant reduction in virus neurovirulence. Here we discuss a vaccine in a YF vaccine backbone; the WN virus envelope (E) protein mutagenesis rationale; and the assessment of the safety, immunogenicity, efficacy, and genetic stability of these ChimeriVax-WN vaccine candidates in the mouse and macaque models. MATERIALS AND METHODSYF/WN chimeric clones and molecular procedures for virus assembly. Chimeric flaviviruses were constructed with the ChimeriVax two-plasmid technology previously described (9). Briefly, the two-plasmid system provides plasmid stability in Escherichia coli by dividing the cloned YF backbone into two plasmids. This provides smaller plasmids that are more stable to manipulate the YF sequences facilitating replacement of the prM and E genes of the flavivirus target vaccine. The WN virus prM and E genes used were cloned from the WN flamingo isolate 383-99 sequence (GenBank accession no. AF196835; kindly provided by John Roehrig, Centers for Disease Control and Prevention, Fort Collins, Colo.). Virus prME sequence cDNA was obtained by reverse transcription-PCR (RT-PCR) (XL-PCR kit; Applied Biosystems, Foster City, C...

Immunization of Flavivirus West Nile Recombinant Envelope Domain III Protein Induced Specific Immune Response and Protection against West Nile Virus Infection

“…With no specific treatment against WNV infection, precedence is given to developing an effective vaccine against it. A number of WNV vaccine candidates had been evaluated in animal models and approved for usage on horses (17)(18)(19)(20)(21)(22). These include an inactivated WNV horse vaccine and a recombinant vaccine using the canarypox virus to express WNV Ags (18,19).…”

“…These include an inactivated WNV horse vaccine and a recombinant vaccine using the canarypox virus to express WNV Ags (18,19). Another study used a chimeric live virus incorporating the NY99 WNV prM (precursor membrane protein), and the E gene inserted into the infectious clone backbone of the yellow fever or dengue virus serotype 4 have been constructed and serotype 4 and is now pending evaluation in clinical trials (21)(22). However, the risk of immune enhancement of heterologous flavivirus infection with inactivated virus and the legitimate safety concerns with the chimeric flaviviruses are highly debatable.…”

Development and Characterization of New Peptidomimetic Inhibitors of the West Nile Virus NS2B–NS3 Protease

“…24 Therefore, the prM and E proteins of the YFV vaccine strain were replaced with the WNV prM and E proteins in chimeric viruses, which have shown promise for vaccine development. 58 The different stages of the WNV replication cycle could be used to develop new antiviral therapies. One strategy is the blocking of the virus entry utilizing antibodies directed against the E protein, subsequently inhibiting receptor binding and thus preventing the internalization of the virion into the host cell.…”

Recent advances in human flavivirus vaccines

“…To reduce neurovirulence and further attenuate the virus, 3 additional mutations were added on the E protein [31]. ChimeriVax-WN02induced strong neutralising antibody and T cell responses as well as protected hamsters, mice and rhesus macaques against WNV challenges [31,32]. A phase I study in volunteers revealed that ChimeriVax-WN02 was well tolerated and highly immunogenic [33].…”

“…Genes encoding the WNV prM and E protein were inserted into the backbone of the yellow fever virus (YFV) 17D vaccine strain. To reduce neurovirulence and further attenuate the virus, 3 additional mutations were added on the E protein [31]. ChimeriVax-WN02induced strong neutralising antibody and T cell responses as well as protected hamsters, mice and rhesus macaques against WNV challenges [31,32].…”