Jk. He et al., DNA INOCULATION WITH A PLASMID VECTOR CARRYING THE HEPATITIS-E VIRUS STRUCTURAL PROTEIN GENE INDUCES IMMUNE-RESPONSE IN MICE, Vaccine, 15(4), 1997, pp. 357-362
The plasmid construct, pJHEV, containing the full-length open reading
frame 2 (ORF-2) of hepatitis E virus (HEV) gene, expresses the HEV str
uctural protein ORF-2 in Cos-7 cells under the control of a hCMV promo
ter. No ORF-2 protein could be detected in Cos-7 cells transfected wit
h either vector alone or with a vector containing the ORF-2 of HEV in
the incorrect orientation. The successful construct was further tested
in BALB/c (H-2d) mice for the induction of an ORF-2 specific immune r
esponse. Intramuscular (i.m.) immunization of mice pretreated 24 h ear
lier with bupivacaine with the naked DNA construct elicited a humoral
immune response in 80% and 100% of two separate groups of mice, respec
tively. No anti-ORF-2 responses were observed in mice immunized with t
he vector only. Sera from mice injected with pJHEV specifically recogn
ized HEV ORF-2 structural protein expressed in recombinant baculovirus
in an enzyme-linked-immunosorbent assay (ELISA) and Western blot, Ant
i-ORF-2 serum titers peaked at ca 1:5000 in the ELISA and 1:1000 in th
e Western blot. These titers have remained constant for over 12 months
after the last boost of pJHEV. To our knowledge, this is the first re
port of the use of DNA-based immunization for the generation of an imm
une response to a HEV structural protein.