Vaccination of rhesus macaques against dengue-2 virus with a plasmid DNA vaccine encoding the viral pre-membrane and envelope genes.
A nucleic acid vaccine for dengue-2 virus was developed, consisting of a plasmid DNA vector with the pre-membrane (prM) and envelope (E) genes expressed from a cytomegalovirus promoter. The DNA was adsorbed onto gold microspheres for administration by a gene gun. Expression was demonstrated by transfection of mouse cells in culture where the prM and E antigens were detected intracellularly, and the E antigen was detected in the culture supernatant fluid, similar to a natural infection. The vaccine elicited neutralizing antibodies to dengue-2 virus and antigen-specific cytotoxic T lymphocyte responses in mice. Several vaccination regimens were evaluated in rhesus macaques for the ability to elicit neutralizing antibodies and protect against viremia after challenge with live dengue-2 virus. Neutralizing antibodies were measured in three of three animals that received four 2-microg doses of DNA and in two of six animals that received two 1-microg doses. No antibodies were detected in three animals that received a single 1-microg dose. When dengue virus challenge was performed one month after vaccination, the three animals that received four 2-microg doses exhibited 0, 0, and 1 day of viremia compared with unimmunized controls which exhibited 4, 4, and 6 days of viremia. Three animals that received two 1-microg doses also exhibited 0, 0, and 1 day of viremia, whereas three animals that received a single 1-microg dose exhibited 2, 3, and 5 days of viremia compared with unimmunized controls, which exhibited 4 days of viremia each. When challenge was performed 7 months after vaccination, three animals that received two 1-microg doses exhibited 0, 3, and 5 days of viremia compared with unimmunized controls, which exhibited 4, 5, and 9 days of viremia. These results suggest that a regimen consisting of two 1-microg doses of DNA can confer satisfactory protection at one month, but not at seven months, after vaccination. Long-term protection following DNA vaccination may require revaccination, higher doses of DNA, or a vaccine that contains additional epitopes or adjuvants.
Putnak
Robert
R
Department of Virus Diseases, Walter Reed Army Institute of Research, Silver Spring, Maryland 20910-7500, USA. Robert.putnak@na.amedd.army.mil
Fuller
James
J
VanderZanden
Lorna
L
Innis
Bruce L
BL
Vaughn
David W
DW
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D019470:Biolistics; D003715:Dengue / Q000517:prevention & control*; D003716:Dengue Virus / Q000235:genetics / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D015967:Gene Expression Regulation, Viral; D005822:Genetic Vectors; D008253:Macaca mulatta; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008863:Microspheres; D009500:Neutralization Tests; D010957:Plasmids; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D013997:Time Factors; D014611:Vaccination / Q000379:methods*; D019444:Vaccines, DNA / Q000008:administration & dosage; D014759:Viral Envelope Proteins / Q000235:genetics; D014763:Viral Matrix Proteins / Q000235:genetics; D014765:Viral Vaccines / Q000008:administration & dosage
D000914:Antibodies, Viral; D019444:Vaccines, DNA; D014759:Viral Envelope Proteins; D014763:Viral Matrix Proteins; D014765:Viral Vaccines