Evaluation of molecular strategies to develop a live dengue vaccine.
BACKGROUND
Millions of individuals are estimated to become infected with dengue virus each year, particularly in tropical and subtropical regions. Mortality is low but infection can lead to a severe form of dengue, characterised by haemorrhage and shock. A safe and effective vaccine against dengue is still not available.


OBJECTIVE
To use the successful construction of dengue type 4 virus (DEN4) cDNA, which yields infectious RNA transcripts, to provide a new approach to the development of safe and effective dengue vaccines.


METHODS
The 3' and 5' noncoding (NC) regions of the genome were targeted to construct DEN4 deletion mutants, because the sequences in these regions are thought to play an important role in the regulation of viral replication. DEN4 cDNA was also employed to construct a viable chimeric virus with dengue type 1, 2 or 3 antigenicity, by substitution of heterotypic structural protein genes.


RESULTS
Most viable mutants, recovered from the cDNA constructs, were partially restricted for growth in simian cells as analysed by plaque morphology assay and viral yield analysis. Several 3' NC deletion mutants which exhibited a range of growth restriction in cell culture were further evaluated for infectivity and immunogenicity in rhesus monkeys. Occurrence and duration of viraemia were reduced for these deletion mutants, compared to the wild type DEN4. Analysis of antibody response to infection in rhesus monkeys also indicated that some of these mutants were attenuated. These DEN4 deletion mutants represent promising live dengue vaccine candidates that merit further clinical evaluation. Chimera DEN1/DEN4 or DEN2/DEN4 which expresses DEN1 or DEN2 antigenicity were also used to infect monkeys. Most monkeys immunised with these chimeric viruses, singly or in combination, developed high titres of neutralising antibodies and were protected against homotypic wild type DEN1 or DEN2 challenge.


CONCLUSIONS
DEN4 and its derived chimeric viruses of other three dengue serotype specificity, that contain appropriate attenuating mutations, have a potential use in a tetravalent live vaccine against dengue.
Lai
C J
CJ
Molecular Viral Biology Section, Laboratory of Infectious Diseases, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. clai@atlas.niaid.nih.gov
Bray
M
M
Men
R
R
Cahour
A
A
Chen
W
W
Kawano
H
H
Tadano
M
M
Hiramatsu
K
K
Tokimatsu
I
I
Pletnev
A
A
Arakai
S
S
Shameem
G
G
Rinaudo
M
M
D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis; D003715:Dengue / Q000517:prevention & control*; D003716:Dengue Virus / Q000235:genetics* / Q000276:immunology* / Q000472:pathogenicity / Q000502:physiology; D017353:Gene Deletion; D006801:Humans; D007114:Immunization; D008253:Macaca mulatta; D009500:Neutralization Tests; D011993:Recombinant Fusion Proteins / Q000235:genetics; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology; D019444:Vaccines, DNA / Q000235:genetics* / Q000276:immunology*; D014765:Viral Vaccines / Q000235:genetics* / Q000276:immunology*; D014779:Virus Replication
D000914:Antibodies, Viral; D011993:Recombinant Fusion Proteins; D014613:Vaccines, Attenuated; D019444:Vaccines, DNA; D014765:Viral Vaccines