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Journal of Clinical Microbiology, April 2001, p. 1487-1493, Vol. 39, No. 4
Food Animal Health Research Program,
Department of Veterinary Preventive Medicine, Ohio Agricultural
Research and Development Center, The Ohio State University, Wooster,
Ohio 44691
Received 25 September 2000/Returned for modification 29 November
2000/Accepted 31 December 2000
Porcine enteric calicivirus (PEC) causes diarrhea and intestinal
lesions in pigs. PEC strain Cowden grows to low to moderate titers in
cell culture but only with the addition of intestinal contents from
uninfected gnotobiotic pigs (W. T. Flynn and L. J. Saif,
J. Clin. Microbiol. 26:206-212, 1988; A. V. Parwani, W. T. Flynn, K. L. Gadfield, and L. J. Saif, Arch. Virol.
120:115-122, 1991). Cloning and sequence analysis of the PEC Cowden
full-length genome revealed that it is most closely related genetically
to the human Sapporo-like viruses. In this study, the complete PEC capsid gene was subcloned into the plasmid pBlueBac4.5 and the recombinant baculoviruses were identified by plaque assay and PCR. The
PEC capsid protein was expressed in insect (Sf9) cells inoculated with
the recombinant baculoviruses, and the recombinant capsid proteins
self- assembled into virus-like particles (VLPs) that were released
into the cell supernatant and purified by CsCl gradient centrifugation.
The PEC VLPs had the same molecular mass (58 kDa) as the native virus
capsid and reacted with pig hyperimmune and convalescent-phase sera to
PEC Cowden in enzyme-linked immunosorbent assay (ELISA) and Western
blotting. The PEC capsid VLPs were morphologically and antigenically
similar to the native virus by immune electron microscopy. High titers
(1:102,400 to 204,800) of PEC-specific antibodies were induced in
guinea pigs inoculated with PEC VLPs, suggesting that the VLPs could be
useful for future candidate PEC vaccines. A fixed-cell ELISA and VLP
ELISA were developed to detect PEC serum antibodies in pigs. For the
fixed-cell ELISA, Sf9 cells were infected with recombinant
baculoviruses expressing PEC capsids, followed by cell fixation with
formalin. For the VLP ELISA, the VLPs were used for the coating
antigen. Our data indicate that both tests were rapid, specific, and
reproducible and might be used for large-scale serological
investigations of PEC antibodies in swine.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.4.1487-1493.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Expression and Self-Assembly in Baculovirus of
Porcine Enteric Calicivirus Capsids into Virus-Like Particles and Their
Use in an Enzyme-Linked Immunosorbent Assay for Antibody
Detection in Swine
*
Corresponding author. Mailing address: Food Animal
Health Research Program, Department of Veterinary Preventive Medicine, Ohio Agricultural Research and Development Center, The Ohio State University, 1680 Madison Ave., Wooster, OH 44691. Phone: (330) 263-3744. Fax: (330) 263-3677. E-mail: saif.2{at}osu.edu.
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