Single-round infectious particles enhance immunogenicity of a DNA vaccine against West Nile virus

Abstract

DNA vaccines encoding replication-defective viruses are safer than inactivated or live attenuated viruses but may fail to stimulate an immune response sufficient for effective vaccination. We augment the protective capacity of a capsid-deleted flavivirus DNA vaccine by co-expressing the capsid protein from a separate promoter. In transfected cells, the capsid-deleted RNA transcript is replicated and translated to produce secreted virus-like particles lacking the nucleocapsid. This RNA is also packaged with the help of co-expressed capsid protein to form secreted single-round infectious particles (SRIPs) that deliver the RNA into neighboring cells. In SRIP-infected cells, the RNA is replicated again and produces additional virus-like particles, but in the absence of capsid RNA no SRIPs are formed and no further spread occurs. Compared with an otherwise identical construct that does not encode capsid, our vaccine offers better protection to mice after lethal West Nile virus infection. It also elicits virus-neutralizing antibodies in horses. This approach may enable vaccination against pathogenic flaviviruses other than West Nile virus.

West Nile Virus Genome with Glycosylated Envelope Protein and Deletion of Alpha Helices 1, 2, and 4 in the Capsid Protein Is Noninfectious and Efficiently Secretes Subviral Particles

“…In order to assess the impact of E glycosylation on SVP secretion from C-deleted WNV cDNAs, we chose to investigate this parameter in the context of large internal deletions similar or analogous to those used in the construction of published vaccine candidates. The dC18-100 deletion has been utilized previously by our group in a KUNV-based single-round infectious particle (SRIP)-producing DNA vaccine (23), and the dC33-100 C deletion is similar to that utilized by the Mason group in their WNV RepliVAX series of vaccines (dC30-101) (24,25). Plasmids encoding KUNV genomic cDNA under the control of cytomegalovirus promoter and containing these large internal deletions in C ( Fig.…”

“…Plasmids encoding KUNV genomic cDNA under the control of cytomegalovirus promoter and containing these large internal deletions in C ( Fig. 1) were constructed from pKUN1 (23,26). In parallel, analogous plasmids containing the glycosylation motif found within the E protein of other circulating WNV and KUNV strains (19-21) (NYS, generated by the F156S mutation; designated gE) were also constructed.…”

“…1B). These resulting plasmid DNAs were transfected into cells alongside fully infectious cDNA clones pKUN1 (23,26) and pKUN1/gE (derivative of pKUN1 with an F156S mutation in E, introducing the NYS glycosylation motif). Culture fluids and cell lysates were harvested at 2 days posttransfection (dpt) and assayed for the presence of any infectious virions (culture fluid) and for the relative abundance of viral C and E proteins (culture fluid and cell lysates) (Fig.…”

Production of single-round infectious chimeric flaviviruses with DNA-based Japanese encephalitis virus replicon

“…In addition, our replicon plasmids have the potential for application to DNA-based vaccines, as described previously (Cao et al, 2011;Chang et al, 2008;Huang et al, 2012).…”

A Hydrogen Peroxide-Inactivated Virus Vaccine Elicits Humoral and Cellular Immunity and Protects against Lethal West Nile Virus Infection in Aged Mice

“…A vaccine based on a virulent WNV-NY strain necessitates the generation of high-titer virus stocks for inactivation in biosafety level 3 (BSL3) facilities, which adds to production costs, and an absolute requirement for inactivation to prevent transmission of viable virulent virus into vulnerable vaccine recipients. An alternative to using virulent WNV-NY is to develop a vaccine based on a naturally attenuated strain, such as WNV-KUNV (30)(31)(32).…”