Differences in the post-translational modifications of human papillomavirus type 6b major capsid protein expressed from a baculovirus system comparedwith a vaccinia virus system
Nx. Fang et al., Differences in the post-translational modifications of human papillomavirus type 6b major capsid protein expressed from a baculovirus system comparedwith a vaccinia virus system, BIOT APP B, 32, 2000, pp. 27-33
Virus-like particles (VLPs) are being currently investigated in vaccines ag
ainst viral infections in humans. There are different recombinant-protein-e
xpression systems available for obtaining the necessary VLP preparation for
vaccination. However, the differences in post-translational modifications
of the recombinant proteins obtained and their differences in efficacy in e
liciting an anti-viral response in vaccines are not well established. In th
is study we have compared the posttranslational modifications of human papi
llomavirus type-6b major capsid protein L1 (HPV 6bL1) expressed using recom
binant baculovirus (rBV) in Sf9 (Spodoptera frugiperda) insect cells, with
the protein expressed using recombinant vaccinia virus (rVV) in CV-1 kidney
epithelial cells, Two-dimensional gel electrophoresis of biosynthetically
labelled rBV-expressed HPV 6bL1 showed several post-translationally modifie
d variants of the protein, whereas rVV-expressed HPV 6bL1 showed only a few
variants. Phosphorylations were detected at threonine and serine residues
for the L1 expressed from rBV compared with phosphorylation at serine resid
ues only for the L1 expressed from rVV. HPV 6bL1 expressed using rBV incorp
orated [H-3]mannose and [H-3]galactose, whereas HPV 6bL1 expressed using rV
V incorporated only [H-3]galactose. We conclude that post-translational mod
ification of recombinant HPV 6bL1 can differ according to the system used f
or its expression. Since recombinant L1 protein is a potential human-vaccin
e candidate, the implication of the observed differences in post-translatio
nal modifications on immunogenicity of L1 VLPs warrants investigation.