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J. Virol., Jan 1998, 349-357, Vol 72, No. 1
Y Zhang and GG Kaplan
To determine whether hepatitis A virus (HAV) could tolerate the insertion
of exogenous sequences, we constructed full-length HAV cDNAs containing
in-frame insertions at the N terminus of the polyprotein and transfected
the derived T7 RNA polymerase in vitro transcripts into FRhK-4 cells.
Replication of HAVvec1, a construct containing an insertion of 60
nucleotides coding for a polylinker, a 2B/2C cleavage site for HAV protease
3Cpro, and two initiation codons that restored the sequence of the N
terminus of the polyprotein, was detected 2 weeks after transfection by
indirect immunofluorescence analysis using anti- HAV monoclonal antibodies.
Western blot analysis of HAVvec1-infected cells using anti-VP2 and anti-VP4
antibodies failed to detect the expression of the inserted sequences.
Insertion of a 24-mer oligonucleotide coding for a FLAG epitope into
HAVvec1 resulted in its HAV-mediated expression which was retained upon
deletion of a Gln residue from the inserted 2B/2C cleavage site. Western
blot analysis using anti-FLAG and anti-VP2 antibodies showed that the FLAG
epitope accumulated in infected cells fused to VP0. Replacement of the FLAG
epitope with an epitope of the circumsporozoite protein (CSP) of Plasmodium
falciparum resulted in its stable HAV-mediated expression for at least six
serial passages in FRhK-4 cells. Sedimentation analysis in sucrose density
gradients showed that the CSP epitope accumulated in infected cells fused
to VP0, forming 80S empty capsids which also contained native VP0. Our data
suggest that the HAV internal ribosome entry site can efficiently direct
dual initiation of translation of the polyprotein from AUG codons separated
by 66 to 78 nucleotides and show that HAV can tolerate insertions at the N
terminus of the polyprotein.
Copyright © 1998, American Society for Microbiology
Characterization of replication-competent hepatitis A virus constructs containing insertions at the N terminus of the polyprotein
Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
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