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Clinical and Diagnostic Laboratory Immunology, Jul 1997, 423-428, Vol 4, No. 4
Y Zhang, P McAtee, PO Yarbough, AW Tam and T Fuerst
The hepatitis E virus (HEV) open reading frame-2 (ORF-2) is predicted to
encode a 71-kDa putative capsid protein involved in virus particle
formation. When insect Spodoptera frugiperda (Sf9) cells were infected with
a recombinant baculovirus containing the entire ORF-2 sequence, two types
of recombinant proteins were produced; an insoluble protein of 73 kDa and a
soluble protein of 62 kDa. The 62-kDa species was shown to be a proteolytic
cleavage product of the 73-kDa protein. N-terminal sequence analysis of the
62-kDa protein indicated that it lacked the first 111 amino acids that are
present in the full-length 73-kDa protein. A soluble 62-kDa protein was
produced without the proteolytic processing by inserting the coding
sequence of amino acids 112 to 660 of ORF-2 in a baculovirus expression
vector and using the corresponding virus to infect Sf9 cells. The two
recombinant 62-kDa proteins made by different mechanisms displayed
immunoreactivities very compatible to each other. The 62-kDa proteins
obtained by both proteolytic processing and reengineering demonstrated much
higher sensitivities in detecting anti-HEV antibodies in human sera than
the antigens made from bacteria, as measured by enzyme-linked immunosorbent
assay. The data suggest that the soluble 62-kDa protein made from insect
cells contains additional epitopes not present in recombinant proteins made
from bacteria. Therefore, the 62-kDa protein may be useful for HEV
diagnostic improvement and vaccine development. The reengineered construct
allows for the consistent large-scale production of the soluble 62-kDa
protein without proteolytic processing.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Expression, characterization, and immunoreactivities of a soluble hepatitis E virus putative capsid protein species expressed in insect cells
Genelabs Technologies, Inc., Redwood City, California 94063, USA.
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