Recombinant Chimeric Yellow Fever-Dengue Type 2 Virus Is Immunogenic and Protective in Nonhuman Primates

Abstract

A chimeric yellow fever (YF)-dengue type 2 (dengue-2) virus (ChimeriVax-D2) was constructed using a recombinant cDNA infectious clone of a YF vaccine strain (YF 17D) as a backbone into which we inserted the premembrane (prM) and envelope (E) genes of dengue-2 virus (strain PUO-218 from a case of dengue fever in Bangkok, Thailand). The chimeric virus was recovered from the supernatant of Vero cells transfected with RNA transcripts and amplified once in these cells to yield a titer of 6.3 log 10 PFU/ml. The ChimeriVax-D2 was not neurovirulent for 4-week-old outbred mice inoculated intracerebrally. This virus was evaluated in rhesus monkeys for its safety (induction of viremia) and protective efficacy (induction of anti-dengue-2 neutralizing antibodies and protection against challenge). In one experiment, groups of non-YF-immune monkeys received graded doses of ChimeriVax-D2; a control group received only the vaccine diluents. All monkeys (except the control group) developed a brief viremia and showed no signs of illness. Sixty-two days postimmunization, animals were challenged with 5.0 log 10 focus forming units (FFU) of a wild-type dengue-2 virus. No viremia (<1.7 log 10 FFU/ml) was detected in any vaccinated group, whereas all animals in the placebo control group developed viremia. All vaccinated monkeys developed neutralizing antibodies in a dose-dependent response. In another experiment, viremia and production of neutralizing antibodies were determined in YF-immune monkeys that received either ChimeriVax-D2 or a wild-type dengue-2 virus. Low viremia was detected in ChimeriVax-D2-inoculated monkeys, whereas all dengue-2-immunized animals became viremic. All of these animals were protected against challenge with a wild-type dengue-2 virus, whereas all YF-immune monkeys and nonimmune controls became viremic upon challenge. Genetic stability of ChimeriVax-D2 was assessed by continuous in vitro passage in VeroPM cells. The titer of ChimeriVax-D2, the attenuated phenotype for 4-week-old mice, and the sequence of the inserted prME genes were unchanged after 18 passages in Vero cells. The high replication efficiency, attenuation phenotype in mice and monkeys, immunogenicity and protective efficacy, and genomic stability of ChimeriVax-D2 justify it as a novel vaccine candidate to be evaluated in humans.

In vitro and in vivo characterization of chimeric duck Tembusu virus based on Japanese encephalitis live vaccine strain SA14-14-2

“…1b). These findings are consistent with the previous observations that chimeric flaviviruses could express the prM and E genes of heterologous flaviviruses, and exhibited growth-similar characteristics (Arroyo et al, 2001;Bhatt et al, 2000;Chambers et al, 1999;Guirakhoo et al, 2000;Pletnev et al, 2001Pletnev et al, , 2003.…”

“…Especially, using live attenuated strains as the genetic backbone, multiple versions of chimeric flaviviruses have been successfully designed and well-explored in the development of vaccines against DENV, WNV, JEV and TBEV (Brandler et al, 2005;Chambers et al, 1999;Guirakhoo et al, 2000;Guy & Jackson, 2016;Pletnev et al, 2002;Wright et al, 2008). The JEV live attenuated vaccine virus SA14-14-2 has been widely used in most JEV-endemic countries (Yu, 2010) with an excellent safety and efficacy profile (Bista et al, 2001;Kumar et al, 2009;Tandan et al, 2007).…”

Evaluation of St. Louis encephalitis virus/dengue virus type 4 antigenic chimeric viruses in mice and rhesus monkeys

“…Since the first reports of the generation of intratypic (DEN2/DEN4) and intertypic (TBE/ DEN4) antigenic chimeric flaviviruses using reverse genetics [15,22], numerous chimeric viruses have been created using genes from tick-borne and mosquito-borne flaviviruses, and many of these viruses are currently being evaluated as vaccines [10,16,19,20,[23][24][25][26]. Recent clinical studies have indicated that antigenic chimeric flaviviruses are attenuated and immunogenic in human volunteers and may serve as live attenuated virus vaccines for protection against disease caused by DEN, JE, WN, and TBE viruses [27][28][29][30][31].…”

Single-dose vaccine against tick-borne encephalitis

“…3A). In this experiment, the effect of WN preimmunity was less pronounced compared with the effect of YF preimmunity on ChimeriVax-DEN2 vaccine in a NHP study described previously (26).…”