1 research outputs found
Characterization of porcine circovirus type 2 (PCV2) capsid particle assembly and its application to virus-like particle vaccine development
Porcine circovirus type 2 (PCV2) is the primary
causative agent of porcine circovirus-associated diseases in
pigs. The sole structural capsid protein of PCV2, Cap, consists
of major antigenic domains, but little is known about the
assembly of capsid particles. The purpose of this study is to
produce a large amount of Cap protein using Escherichia coli
expression system for further studying the essential sequences
contributing to formation of particles. By using codon optimization
of rare arginine codons near the 5′-end of the cap
gene for E. coli, a full-length Cap without any fusion tag
recombinant protein (Cap1-233) was expressed and proceeded
to form virus-like particles (VLPs) in normal Cap
appearance that resembled the authentic PCV2 capsid. The
N-terminal deletion mutant (Cap51-233) deleted the nuclear
localization signal (NLS) domain, while the internal deletion
mutant (CapΔ51-103) deleted a likely dimerization domain
that failed to form VLPs. The unique Cys108 substitution
mutant (CapC/S) exhibited most irregular aggregates, and
only few VLPs were formed. These results suggest that the
N-terminal region within the residues 1 to 103 possessing the
NLS and dimerization domains are essential for self-assembly
of stable Cap VLPs, and the unique Cys108 plays an important
role in the integrity of VLPs. The immunogenicity of
PCV2 VLPs was further evaluated by immunization of pigs
followed by challenge infection. The Cap1-233-immunized
pigs demonstrated specific antibody immune responses and are
prevented from PCV2 challenge, thus implying its potential use
for a VLP-based PCV2 vaccine