Sv. Littel-van Den Hurk et al., Immune responses and protection induced by DNA vaccines encoding bovine parainfluenza virus type 3 glycoproteins, VIROLOGY, 260(1), 1999, pp. 35-46
This study was designed to assess the parameters influencing the magnitude
and type of immune responses generated to plasmids encoding the hemagglutin
in/neuraminidase (HN) and fusion (F) proteins of bovine parainfluenzavirus
type 3 (BPIV3). Mice immunized with plasmids expressing HN or F under contr
ol of the Rous sarcoma virus long terminal repeat promoter were primed, but
they did not develop measurable immune responses. In contrast, strong humo
ral and cellular immune responses were induced with constructs containing t
he human cytomegalovirus immediate-early promoter and intron A. After immun
ization with both HN- and F-encoding plasmids, enhanced responses were obse
rved. Analysis of in vitro protein synthesis confirmed that the presence of
the intron is crucial for the expression of the BPIV3 HN gene. Plasmid enc
oding HN induced significantly higher serum antibody liters by intradermal
injection than by intramuscular delivery, whereas antigen-specific T cell p
roliferation was stronger in intramusculary injected mice. Both the isotype
ratios and the cytokine profiles indicated a Th1-type response after intra
muscular immunization and a mixed to Th2-type response in intradermally imm
unized mice. A plasmid encoding a truncated, secreted form of HN induced a
Th2-type immune response, regardless of the route of delivery. In cotton ra
ts, HN- and F-encoding plasmids conferred protection from BPIV3 challenge.
(C) 1999 Academic Press.