Plasmid DNA initiates replication of yellow fever vaccine in vitro and elicits virus-specific immune response in mice

Abstract

Yellow fever (YF) causes an acute hemorrhagic fever disease in tropical Africa and Latin America. To develop a novel experimental YF vaccine, we applied iDNA infectious clone technology. The iDNA represents plasmid that encodes the full-length RNA genome of 17D vaccine downstream from a cytomegalovirus (CMV) promoter. The vaccine was designed to transcribe the full-length viral RNA and to launch 17D vaccine virus in vitro and in vivo. Transfection with 10ng of iDNA plasmid was sufficient to start replication of vaccine virus in vitro. Safety of the parental 17D and iDNA-derived 17D viruses was confirmed in AG129 mice deficient in receptors for IFN-α/β/γ. Finally, direct vaccination of BALB/c mice with a single 20µg dose of iDNA plasmid resulted in seroconversion and elicitation of virus-specific neutralizing antibodies in animals. We conclude that iDNA immunization approach combines characteristics of DNA and attenuated vaccines and represents a promising vaccination strategy for YF.

Plasmid DNA launches live-attenuated Japanese encephalitis virus and elicits virus-neutralizing antibodies in BALB/c mice

“…Transfection was carried out essentially as described previously for plasmid encoding the full-length RNA viruses (Tretyakova et al, 2013; Tretyakova et al, 2014b). Replication of JEV and expression of JEV antigens in the transfected Vero cells were determined by the infectious center assay (ICA), indirect immunofluorescence assay (IFA) and western blot.…”

“…At 48 h posttransfection, cells were rinsed with PBS, dried and fixed with cold acetone, then IFA was carried out using JEV (Nakayama strain) specific mouse antiserum VR-1259AF (ATCC), followed by the secondary fluorescein-labeled antibody to mouse IgG (H+L) (KPL, Gaithersburg, MD) as described previously (Pushko et al, 2001; Tretyakova et al, 2014b). Mounting medium containing propidium iodide counterstain (Vector Labs, Burlingame, CA) was used to visualize nuclei of the cells.…”

“…This platform is based on the infectious clone technology and represents plasmid DNA that encodes the full-length virus RNA and can initiate replication of viral RNA and launch live-attenuated virus in vitro or in vivo (Jiang et al, 2015; Pushko et al, 2014; Tretyakova et al, 2014a; Tretyakova et al, 2014b). DNA-launched live-attenuated vaccines were sometimes called iDNA® vaccines in order to distinguish them from the standard DNA vaccines (Pushko et al, 2016; Tretyakova et al, 2013; Tretyakova et al, 2014b). In the previous studies, the full-length JEV infectious clone has been reported and used to launch JEV from a plasmid in vitro .…”

“…One potential reason for that was the difficulty of generating stable full-length JEV clone in E. coli . Hypothetically, JEV cDNA can contain cryptic bacterial promoters that drive synthesis of toxic proteins affecting genetic stability and DNA yields in E. coli (Rice et al, 1989; Tretyakova et al, 2014b; Yamshchikov et al, 2001). To improve stability of the plasmid in E. coli , the low-copy vector backbone has been used and two introns have been inserted into the full-length JEV cDNA clone.…”

Development of a human live attenuated West Nile infectious DNA vaccine

“…Despite the formal resemblance of iDNA to DNA vaccines, the principal difference between them is the ability of iDNA to establish a productive infection (hence the term) upon transfection or after inoculation. Earlier it has been shown that vaccination with DNA encoding replicative-competent flavivirus genomes or genome segments (replicons) (Hall et al, 2003;Seregin et al, 2006;Tretyakova et al, 2014) even at submicrogram doses induces much stronger immune responses in mice as compared to "standard" DNA vaccines encoding non-replicating gene cassettes. An increased immunogenicity of iDNA vaccines in primates is yet to be demonstrated.…”