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Journal of Virology, August 2000, p. 6885-6892, Vol. 74, No. 15
IRIS Research Center, Chiron, 53100 Siena,
Italy,1 and Chiron Corporation,
Emeryville, California 946082
Received 31 January 2000/Accepted 4 May 2000
Hepatitis C virus (HCV) is the leading causative agent of
blood-borne chronic hepatitis and is the target of intensive vaccine research. The virus genome encodes a number of structural and nonstructural antigens which could be used in a subunit vaccine. The
HCV envelope glycoprotein E2 has recently been shown to bind CD81 on
human cells and therefore is a prime candidate for inclusion in any
such vaccine. The experiments presented here assessed the optimal form
of HCV E2 antigen from the perspective of antibody generation. The
quality of recombinant E2 protein was evaluated by both the capacity to
bind its putative receptor CD81 on human cells and the ability to
elicit antibodies that inhibited this binding (NOB antibodies). We show
that truncated E2 proteins expressed in mammalian cells bind with high
efficiency to human cells and elicit NOB antibodies in guinea pigs only
when purified from the core-glycosylated intracellular fraction,
whereas the complex-glycosylated secreted fraction does not bind and
elicits no NOB antibodies. We also show that carbohydrate moieties are
not necessary for E2 binding to human cells and that only the monomeric
nonaggregated fraction can bind to CD81. Moreover, comparing
recombinant intracellular E2 protein to several E2-encoding DNA
vaccines in mice, we found that protein immunization is superior to DNA
in both the quantity and quality of the antibody response elicited.
Together, our data suggest that to elicit antibodies aimed at blocking
HCV binding to CD81 on human cells, the antigen of choice is a
mammalian cell-expressed, monomeric E2 protein purified from the
intracellular fraction.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Evaluation of Hepatitis C Virus Glycoprotein E2 for Vaccine
Design: an Endoplasmic Reticulum-Retained Recombinant Protein Is
Superior to Secreted Recombinant Protein and DNA-Based
Vaccine Candidates
*
Corresponding author. Mailing address: IRIS Research
Center, Chiron, Via Fiorentina 1, Siena 53100, Italy. Phone: (39) 0577 243 032. Fax: (39) 0577 243 564. E-mail:
sergio_abrignani{at}biocine.it.
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