Previous Article | Next Article 
Journal of Virology, March 2000, p. 2920-2925, Vol. 74, No. 6
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Enhancement of Immunoglobulin G2a and Cytotoxic T-Lymphocyte
Responses by a Booster Immunization with Recombinant Hepatitis C
Virus E2 Protein in E2 DNA-Primed Mice
Man Ki
Song,1
Seung Woo
Lee,1
You Suk
Suh,1
Ki Jeong
Lee,1 and
Young Chul
Sung1,2,*
Department of Life
Science1 and School of Environmental
Engineering,2 Pohang University of Science
and Technology, Pohang, Republic of Korea
Received 29 July 1999/Accepted 13 December 1999
 |
ABSTRACT |
The induction of strong cytotoxic T-lymphocyte (CTL) and humoral
responses appear to be essential for the elimination of persistently infecting viruses, such as hepatitis C virus (HCV). Here, we tested several vaccine regimens and demonstrate that a combined vaccine regimen, consisting of HCV E2 DNA priming and boosting with recombinant E2 protein, induces the strongest immune responses to HCV E2 protein. This combined vaccine regimen augments E2-specific immunoglobulin G2a
(IgG2a) and CD8+ CTL responses to a greater extent than
immunizations with recombinant E2 protein and E2 DNA alone,
respectively. In addition, the data showed that a protein boost
following one DNA priming was also effective, but much less so than
those following two DNA primings. These data indicate that sufficient
DNA priming is essential for the enhancement of DNA encoded
antigen-specific immunity by a booster immunization with recombinant E2
protein. Furthermore, the enhanced CD8+ CTL and IgG2a
responses induced by our combined vaccine regimens are closely
associated with the protection of BALB/c mice from challenge with
modified CT26 tumor cells expressing HCV E2 protein. Together, our
results provide important implications for vaccine development for many
pathogens, including HCV, which require strong antibody and CTL responses.
| |
TEXT |
Hepatitis C virus (HCV) is a major
causative agent of non-A, non-B hepatitis (7, 18). Previous
studies indicate that the development of chronic liver disease and
hepatocellular carcinoma is closely associated with persistent
infection of HCV (30). Currently, the lack of efficient
antiviral treatment against HCV makes the development of a vaccine
highly desirable. It is unclear which type of immunity is essential for
HCV resolution. Recombinant protein vaccination facilitates strong
antibody responses and stimulates primarily Th2 cells, which are
defined by their secretion of the cytokines interleukin-4 (IL-4), IL-5,
and IL-10. Protein vaccination with HCV envelope glycoproteins E1 and
E2 induced protective immunity against homologous virus challenge in
chimpanzees (8). In this model, the protection appeared to
be correlated to the titers of anti-E2 antibodies, suggesting that
antibody responses are important for protection against HCV infection. Furthermore, there are growing evidences that Th1 and cytotoxic T-lymphocyte (CTL) responses to HCV proteins may play a key role in
virus resolution during natural infection (9, 11, 24, 28).
It has been reported that the prevalent cytokine pattern of circulating
HCV-specific CD4+ T cells is Th1-like in patients who
recovered from acute hepatitis, as exhibited by the secretion of IL-2
and gamma interferon (11). In addition, chimpanzees which
generated high levels of CTL responses to HCV proteins eliminated HCV
infection (9). Thus, an effective HCV vaccine must elicit
both strong humoral and cell-mediated immune responses, especially Th1
and CTL responses.
Since it has been documented that DNA immunization preferentially
induces Th1 immunity and CTL responses to many viral antigens (5,
26, 36), DNA vaccine approaches have been applied to generate
protective immunity to a variety of pathogens (10, 12, 33).
However, DNA immunization was also demonstrated to generate weaker
antibody and CTL responses than did protein and live attenuated
vaccinations, respectively (22, 32). In general, immunity
generated by DNA vaccination alone appeared to be sufficient to protect
against pathogens in only a few animal models (2, 23). To
circumvent these limits of DNA vaccination, many groups have employed
combinatorial vaccination regimens (3, 22, 29, 32). Antibody
avidity and neutralizing antibody (nAb) titers to human
immunodeficiency virus (HIV) gp160 were greatly enhanced in rabbits by
DNA priming followed by protein boosting as compared to either DNA or
protein immunization only (29). Furthermore, recombinant
protein booster immunization of DNA-primed macaques had an enhancement
of antibody responses of approximately 100-fold and protection from
nonpathogenic simian/human immunodeficiency virus infection
(22). Although antibody responses were greatly modulated
quantitatively as well as qualitatively by protein boosting in
DNA-primed animals, the effects of protein boosting on the induction of
T-cell-based immunity, especially CD8+ CTL responses, have
not been investigated. Here, we performed DNA priming-protein boosting
vaccination regimens against HCV E2 to assess the effects of protein
booster immunization on both antibody and CTL responses in mice. Both
CTL and bulk antibody responses, especially immunoglobulin G2a (IgG2a)
responses, were strongly increased by an E2 protein boosting in mice
primed twice with E2 DNA. Moreover, the group of mice given the DNA
priming-protein boosting vaccine regimen had the highest protection
rate against challenge by tumor cells expressing HCV E2 protein. Even
though other factors, such as antigen dosage, route of immunization, and kind of adjuvant, could affect the immune responses, our DNA priming-protein boosting may provide a general vaccination regimen for
the induction of strong antibody and CTL responses.
Preparation of DNA vaccine constructs and recombinant
proteins.
The DNA vaccine vector pTV2sE2t was constructed to
encode HCV E2 sequences (amino acid [aa] residues 384 to 719) of type
1b (Korean isolate) (19) fused to the herpes simplex virus
type 1 glycoprotein D (gD) signal sequence (aa residues 1 to 34)
(20). To obtain recombinant herpes simplex virus type 1 gD
and HCV E2 proteins, stable Chinese hamster ovary (CHO) cell lines
expressing gD and gDE2t were constructed. Briefly, the cDNA fragment
encoding the C-terminal truncated gD protein (aa 1 to 316) was
amplified by PCR from the KOS-1 strain by using primers 5'-ATC CTG
CAG GTC TCT TTT GT-3' and 5'-CGC GAA TTC CTG GAT CGA CGG
GAT-3' and was inserted into pMT3 to produce pMT3-gD
(19). To construct pMT3-gDE2t, the E2 region spanning aa
residues 386 to 693 was obtained by PCR using E2N (5'-CCA TAT GCG
CGT GAC AGG AGG AAC G-3') and 2420A (5'-TGT TCT AGA GGA GGT
GGA TTA ACC CA-3') primers and fused in-frame to aa residue 326 of gD in pMT3-gD. The resulting constructs were used to establish
recombinant CHO cell lines expressing either gD or gDE2t protein as
previously described (19). The recombinant CHO cell lines
were initially screened by immunoblotting and enzyme-linked immunosorbent assay (ELISA) using anti-gD (Fitzgerald Inc., Concord, Mass.) and anti-E2 monoclonal antibodies (mAbs) (19) and
were subjected to five subsequent rounds of methotrexate (Sigma, St. Louis, Mo.) selection. To purify gD and gDE2t, the gD mAb affinity column was prepared by coupling the gD mAb to the CNBr-activated Sepharose-4B (Pharmacia Biotech Inc.). The secreted gD and gDE2t proteins were purified to 90% purity by repeating immunoaffinity chromatography twice (19).
Antibody responses induced by different combinatorial
vaccinations.
To investigate the effect of protein boosting in
DNA-primed mice, we compared antibody responses induced by several
vaccination regimens, as shown in Table
1. Briefly, 6-week-old female BALB/c mice
were injected either intramuscularly (i.m.) in the anterior tibialis
muscles with 100 µg of DNA following pretreatment with bupivacaine-HCl (ASTRA) and/or subcutaneously (s.c.) with 5 µg of
protein, with alum hydroxide serving as adjuvant. The booster immunizations were performed either once or twice with the same amount
of DNA or protein at 1-month intervals. Sera were collected by eye
bleeding at selected time points and assayed for the presence of
E2-specific antibodies by ELISA using E2 and human growth hormone (hgh)
fusion protein, which was purified from a recombinant CHO cell line
(19). The end-point titrations were performed by ELISA with
serial dilutions of pooled sera to determine the E2-specific antibody
responses semiquantitatively. Mice given an injection with pTV2sE2t DNA
(designated E2 DNA) induced a weak antibody response to E2 protein,
which was enhanced approximately 4- to 12-fold by consecutive booster
immunization with the same DNA (Table 1, group V). The gDE2t
recombinant protein immunizations (group VII) elicited antibody
responses that were five times higher than those induced by E2 DNA
injections. Interestingly, when a booster immunization with gDE2t
protein was performed after two rounds of E2 DNA injections, the
antibody titer was dramatically increased (approximately 29-fold),
which was even higher than that of gDE2t protein immunizations alone
(Table 1, groups IV and VII). The protein priming-DNA boosting regimen
induces a lower level (approximately four- to fivefold) of antibodies
than those induced by DNA priming-protein boosting (Table 1, groups IV
and VI), which supports a previous report that the specific order of immunization is important for the induction of optimal immune responses in prime-boost immunization strategies with different vaccine
preparations (32). In addition, when a gDE2t booster immunization was performed in mice given a single E2 DNA injection, the
antibody titer was increased to three times higher than that induced by
E2 DNA boosting, but it was still lower than that induced by two rounds
of recombinant gDE2t protein immunizations alone (Table 1, group VIII).
These experiments demonstrate that booster-immunization-amplified antibody responses correlated with the type of priming regimen (DNA or
protein) or upon the number of rounds of DNA priming that were
administered. As expected, the effect of a gDE2t protein boosting was
not observed in mice primed two times with control pTV2 DNA (Table 1,
group II). Taken together, our data suggest that the enhancement of
total IgG by a protein booster immunization is specific to antigen
which is primed by DNA and not due to the nonspecific bystander
activation of B cells by immunostimulatory effects of bacterial DNA
(15).
It is likely that DNA immunization predominantly induces IgG2a
antibodies, which is generally accepted as an indicator of
Th1 immunity
(
26). The presence of E2-specific IgG isotypes
were assayed
by ELISA using horseradish peroxidase-conjugated
sheep anti-mouse IgG1
or IgG2a secondary antibodies (Southern
Biotechnology Associates). As
expected, the dominant IgG subclasses
induced by gDE2t protein and E2
DNA immunizations were IgG1 and
IgG2a, respectively (Fig.
1). Interestingly, a booster immunization
with gDE2t protein in E2 DNA-primed mice dramatically increased
E2-specific IgG1 and IgG2a isotype titers (Fig.
1). Although this
enhanced IgG1 titer was comparable to that raised in mice that
received
three rounds of gDE2t protein immunizations alone, the
level of IgG2a
titer was approximately 15 and 150 times higher
than that of mice given
three rounds of E2 DNA and gDE2t protein
immunizations, respectively.
However, a reverse-ordered immunization
regimen which performed booster
immunizations with E2 DNA after
priming twice with gDE2t protein
slightly enhanced both IgG1 and
IgG2a titers, which were approximately
2 and 40 times lower than
those induced by the DNA priming-protein
boosting regimen, respectively
(Fig.
1). Our data strongly suggest that
the predetermined dominance
of the IgG2a isotype was not significantly
changed by booster
immunization with antigens which induce the IgG1
isotype or vice
versa. Our data, together with a previous report that
-galactosidase
(
-Gal) protein booster immunization in
-Gal
DNA-primed mice
significantly enhanced the IgG2a titer and caused
secretions of
smaller amounts of IL-4 and IL-5 than those from mice
given protein
immunization only (
26), suggest that the
Th1-dominated immune
responses raised after DNA priming was preserved
by protein booster
immunization. This DNA priming-protein boosting
regimen has great
potential for inducing Th1-like immunity, which is
likely to be
essential for the clearance of intracellular pathogens. It
has
been previously reported that antibodies directed to hypervariable
region 1 (HVR1) of the E2 protein have neutralizing activity
(
31)
and that a booster immunization with HIV gp120 protein
in gp120
DNA-primed mice strongly enhanced the nAb titers
(
29). To determine
whether antibodies specific to HVR1
peptide are enhanced by a
gDE2t protein booster immunization in E2
DNA-primed mice, we analyzed
HVR1-specific antibodies following this
regimen. Although we previously
reported that immunization with E2 DNA
induces both homologous
and heterologous HVR1-specific antibodies in
Buffalo rats (
20,
21), mice did not generate HVR1-specific
antibodies in our present
experiments (data not shown). These
conflicting results may stem
from differences in the genetic
backgrounds of mice and rats.
View larger version (27K):
[in this window]
[in a new window]
|
FIG. 1.
Determination of anti-E2 isotype antibodies in the
immunized mice. IgG1 (A) and IgG2a (B) isotypes of anti-E2 antibodies
in sera from immunized mice were determined by ELISA using purified
hghE2t protein and isotype-specific secondary antibodies. The mean
titers of anti-E2 antibodies of eight mice per group (plus standard
error of the mean) obtained at week 3 after the first ( ), second
( ), and final ( ) injections are shown. The different vaccination
regimens are at the bottom; the number of injections are indicated.
|
|
Enhancement of CTL responses by a protein booster
immunization.
To investigate the effects of protein boosting on
the level of CD8+ T-cell responses generated by DNA
priming, we compared the level of CTL responses induced by various
vaccination regimens. Briefly, eight mice from each group were tested
by a conventional 51Cr-release assay (34) for
the ability to generate CTLs at 3 weeks after the final immunization.
CT26-hghE2t cell lines expressing HCV E2t which were fused to hgh
(19) were generated under continuous selective pressure with
350 µg of G418 (GIBCO BRL) per ml and were used to raise CTLs by in
vitro stimulation of spleen cells from the immunized mice for 7 days in
the presence of 10 U of murine IL-2 (Pharmingen) per ml. As target
cells, we used CT26, CT26-hghE2t, and P815, which was infected with
recombinant vaccinia virus expressing -Gal or HCV structural
proteins (aa residues 1 to 740). As expected, mice immunized with E2
DNA, but not with recombinant gDE2t protein, elicited E2-specific CTL
responses (Fig. 2). In order to determine
whether different booster immunization regimens affect the generation
of CTL responses in mice primed by DNA or protein injection, we
analyzed CTL activities in mice primed twice with E2 DNA or gDE2t
protein followed by a booster immunization with the same DNA or
protein. A booster immunization with gDE2t protein, but not with
control gD protein, in mice primed twice with E2 DNA significantly
enhanced CTL activity (Fig. 2A and B, P value of <0.05 by
Fisher's exact test between group III and IV). This activity was
somewhat higher than that induced by three rounds of E2 DNA
immunizations alone. In contrast, no group of mice showed specific CTL
activities against two control targets, CT26 and P815, which were
infected with recombinant vaccinia virus expressing -Gal (data not
shown). Interestingly, a booster immunization with gDE2t protein after
priming once with E2 DNA did not significantly enhance CTL responses,
which were much lower than those induced by two rounds of E2 DNA
immunization alone (Fig. 2C and D). Together, these observations
demonstrated that E2-specific CTL responses were significantly enhanced
by gDE2t protein booster immunization in two rounds of E2 DNA-primed
mice, suggesting that sufficient priming with E2 DNA immunization is
necessary to enhance CTL activity by protein boosting, as was seen in
antibody responses. An E2 DNA booster injection appeared to generate
CTL activity in mice given by two rounds of gDE2t protein
administration, which was comparable to what was induced by a single E2
DNA immunization. Therefore, it is likely that a DNA priming-protein
boosting regimen would optimize the elicitation of high levels of HCV
E2-specific CTL responses. In order to determine which population of
effector CTLs was increased by a booster immunization with gDE2t
protein after E2 DNA priming, we performed a CTL assay with either
enriched CD4+ or CD8+ T cells sorted by the
MACS system (Milteny Biotec), which yielded enriched T-cell populations
of approximately 95%, as confirmed by fluorescence-activated cell
sorter analysis (CellQuest software; Becton Dickinson). Enriched T-cell
populations were stimulated by the addition of CT26-hghE2t cells and
IL-2 (50 U/ml) in the presence of mitomycin C (Sigma)-treated naive
splenocytes. These experiments indicated that only CD8+
effector cells, but not CD4+ cells, were demonstrated to
generate E2-specific cytotoxicity (data not shown), suggesting that
gDE2t protein booster immunization further increased the
CD8+ CTL population primed by E2 DNA injection.
View larger version (32K):
[in this window]
[in a new window]
|
FIG. 2.
E2-specific CTL responses in the immunized BALB/c mice.
Spleen cells obtained at week 3 after third (A and B) or second (C and
D) immunizations were maintained in RPMI 1640 medium supplemented with
10 mM HEPES buffer, 5 × 10 5 M 2-mercaptoethanol,
and 10% fetal bovine serum (GIBCO BRL). Responder cells (2.0 × 107) were restimulated in vitro with mitomycin C-treated
(25 µg/ml) CT26-hghE2t cells (1.0 × 106) at 37°C.
After a 1-week in vitro culture, effector cells were tested in a
conventional cytotoxicity assay against two different target cells,
such as CT26-hghE2t (A and C) or P815 infected with recombinant
vaccinia virus expressing HCV core and E1 and E2 proteins (B and D).
Data are represented as percentage of specific lysis (plus standard
error of the mean) versus effector-to-target ratios, where n = 8.
|
|
Although the mechanism by which a protein booster immunization further
enhanced CD8
+ CTL responses in DNA-primed mice is unclear,
there are several
possible explanations. First, since DNA vaccination
appeared to
predominantly induce both Th1 and CD8
+ CTL
immunity, protein boosting in DNA-primed mice may further
stimulate
preformed memory Th1 cells which produce IL-2 and gamma
interferon in
secondary lymphoid organs. Next, these cytokines
would make memory
CD8
+ CTL to further proliferate. Second, since the
cross-priming ability
of dendritic cells could be increased by Th1
cytokines and/or
CD40L on activated Th cells (
4,
6,
13,
17,
18), it
is possible that these dendritic cells may cross-present
the exogenous
gDE2t protein to memory CD8
+ T cells.
Alternatively, the antigen-IgG immune complexes were
demonstrated to
enhance the ability of dendritic cells' cross-presentation
via
Fc
R-mediated endocytosis (
27). Since mouse IgG2a binds
more strongly to Fc
R than IgG1 (
37), it is likely that
the
complexes of gDE2t with IgG2a induced by E2 DNA priming may be
cross-presented.
Tumor protection studies.
To confirm the antibody and CTL
immunity induced by various vaccination regimens in vivo as previously
reported (35), 2 × 106 CT26-hghE2t tumor
cells were s.c. injected into the groups of the immunized mice at 4 weeks after the last immunization. As shown in Fig.
3, the groups of mice immunized three
times with either control DNA or with gDE2t protein displayed tumor
formation and began succumbing at approximately 4 to 5 weeks, and all
displayed tumor formation and had succumbed by 9 weeks postinjection.
However, the group of mice that received three rounds of E2 DNA
injection were delayed in tumor formation and lethargy, resulting in a
final survival rate of 44%, which is not statistically significant
when compared to those of groups I and II (P = 0.082).
The group of mice that were booster immunized with gDE2t protein,
following E2 DNA priming two times, showed the highest survival rate:
approximately 78% at week 20, which was significantly different from
groups I and II (P < 0.03). Thus, these data suggest
that HCV E2-specific antibody and CTL responses induced by a DNA
priming and protein boosting regimen confers in vivo protection against
modified tumor challenge. Although it is not easy to evaluate relative
effects of antibody and CTL responses on tumor protection in vivo, it is likely that both contribute to the elimination of tumor cells. E2-specific CD8+ CTLs could directly kill the CT26-hghE2t
cells, as shown in the in vitro CTL assay, and antibodies, especially
IgG2a, which strongly binds to FcR on macrophages and natural killer
cells, could mediate antibody-dependent cell-mediated cytotoxicity
(1, 14, 25).
View larger version (17K):
[in this window]
[in a new window]
|
FIG. 3.
Protection of immunized mice from modified CT26 tumor
cells expressing hghE2t. BALB/c (nine per group) mice immunized with
control vector, pTV2sE2t, and/or gDE2t protein were injected s.c. with
2.0 × 106 CT26-hghE2t tumor cells. The vitality of
individual mice was monitored for 20 weeks after tumor cell
injection.
|
|
In conclusion, we have shown that consecutive immunizations involving
priming twice with HCV E2 DNA and boosting with a recombinant
gDE2t
protein elicits enhanced antibody and CTL responses which
protected
mice from a lethal tumor challenge. Our DNA priming
and protein
boosting vaccine strategy thus offers promise for
vaccine development
against many
pathogens.
| |
ACKNOWLEDGMENTS |
This work was supported by grants from the Ministry of Health and
Welfare of Korea (grant 97-B-1-0004) and the Korean Green Cross Corp.
We express great thanks to Sang Chun Lee for elaborate animal care and
support of animal experiments.
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Dept. of Life
Science, Pohang University of Science and Technology, San 31, Hyoja
Dong, Pohang 790-784, Korea. Phone: 82-562-279-2294. Fax:
82-562-279-5544. E-mail:
ycsung{at}vision.postech.ac.kr.
| |
REFERENCES |
| 1.
|
Adams, D. O.,
T. Hall,
Z. Steplewski, and H. Koprowski.
1984.
Tumors undergoing rejection induced by monoclonal antibodies of the IgG2a isotype contain increased numbers of macrophages activated for a distinctive form of antibody-dependent cytolysis.
Proc. Natl. Acad. Sci. USA
81:3506-3510[Abstract/Free Full Text].
|
| 2.
|
Allsopp, C. E.,
M. Plebanski,
S. Gilbert,
R. E. Sinden,
S. Harris,
G. Frankel,
G. Dougan,
C. Hioe,
D. Nixon,
E. Paoletti,
G. Layton, and A. V. Hill.
1996.
Comparison of numerous delivery systems for the induction of cytotoxic T lymphocytes by immunization.
Eur. J. Immunol.
26:1951-1959[Medline].
|
| 3.
|
Barnett, S. W.,
S. Rajasekar,
H. Legg,
B. Doe,
D. H. Fuller,
J. R. Haynes,
C. M. Walker, and K. S. Steimer.
1997.
Vaccination with HIV-1 gp120 DNA induces immune responses that are boosted by a recombinant gp120 protein subunit.
Vaccine
15:869-873[CrossRef][Medline].
|
| 4.
|
Bevan, M. J.
1987.
Antigen recognition. Class discrimination in the world of immunology.
Nature
325:192-194[Medline].
|
| 5.
|
Boyer, J. D.,
B. Wang,
K. E. Ugen,
M. Agadjanyan,
A. Javadian,
P. Frost,
K. Dang,
R. A. Carrano,
R. Ciccarelli,
L. Coney,
W. V. Williams, and D. B. Weiner.
1996.
In vivo protective anti-HIV immune responses in non-human primates through DNA immunization.
J. Med. Primatol.
25:25242-25250.
|
| 6.
|
Brossart, P., and M. J. Bevan.
1997.
Presentation of exogenous protein antigens on major histocompatibility complex class I molecules by dendritic cells: pathway of presentation and regulation by cytokines.
Blood
90:1594-1599[Abstract/Free Full Text].
|
| 7.
|
Choo, Q.-L.,
G. Kuo,
A. Weiner,
L. R. Overby,
D. W. Bradley, and M. Houghton.
1989.
Isolation of a cDNA clone derived from blood-borne non-A, non-B viral hepatitis genome.
Science
244:359-362[Abstract/Free Full Text].
|
| 8.
|
Choo, Q.-L.,
G. Kuo,
R. Ralston,
A. Weiner,
D. Chien,
G. Van Nest,
J. Han,
K. Berger,
K. Thudium,
C. Kao,
J. Kansopon,
J. McFarland,
A. Tabuzi,
K. Ching,
B. Moss,
L. B. Cummins,
M. Houghton, and E. Muchmore.
1994.
Vaccination of chimpanzees against infection by the hepatitis C virus.
Proc. Natl. Acad. Sci. USA
91:1294-1298[Abstract/Free Full Text].
|
| 9.
|
Cooper, S.,
A. L. Erickson,
E. J. Adams,
J. Kansopon,
A. J. Weiner,
D. Y. Chien,
M. Houghton,
P. Parham, and C. M. Walker.
1999.
Analysis of a successful immune response against hepatitis C virus.
Immunity
10:439-449[CrossRef][Medline].
|
| 10.
|
Donnelly, J. J.,
A. Friedman,
D. Martinez,
D. L. Montgomery,
J. W. Shiver,
S. L. Motzel,
J. B. Ulmer, and M. A. Liu.
1993.
Preclinical efficacy of a prototype DNA vaccine: enhanced protection against antigenic drift in influenza virus.
Nat. Med.
6:583-587.
|
| 11.
|
Ferrari, C.,
A. Penna,
A. Bertoletti,
A. Cavalli,
G. Missale,
V. Lamonaca,
C. Boni,
A. Valli,
R. Bertoni,
S. Urbani,
P. Scognamiglio, and F. Fiaccadori.
1998.
Antiviral cell-mediated immune responses during hepatitis B and hepatitis C virus infections.
Recent Results Cancer Res.
154:330-336[Medline].
|
| 12.
|
Fynan, E. F.,
R. G. Webster,
D. H. Fuller,
J. R. Haynes,
J. C. Santoro, and H. L. Robinson.
1993.
DNA vaccines: protective immunizations by parenteral, mucosal, and gene-gun inoculations.
Proc. Natl. Acad. Sci. USA
90:11478-11482[Abstract/Free Full Text].
|
| 13.
|
Jondal, M.,
R. Schirmbeck, and J. Reimann.
1996.
MHC class I-restricted CTL responses to exogenous antigens.
Immunity
5:295-302[CrossRef][Medline].
|
| 14.
|
Kipps, T. J.,
P. Parham,
J. Punt, and L. A. Herzenberg.
1985.
Importance of immunoglobulin isotype in human antibody-dependent, cell-mediated cytotoxicity directed by murine monoclonal antibodies.
J. Exp. Med.
161:1-17[Abstract/Free Full Text].
|
| 15.
|
Krieg, A. M.,
A. K. Yi,
S. Matson,
T. J. Waldschmidt,
G. A. Bishop,
R. Teasdale,
G. A. Koretzky, and D. M. Klinman.
1995.
CpG motifs in bacterial DNA trigger direct B-cell activation.
Nature
374:546-549[CrossRef][Medline].
|
| 16.
|
Kuo, G.,
Q. L. Choo,
H. J. Alter,
G. L. Gitnick,
A. G. Redeker,
R. H. Purcell,
T. Miyamura,
J. L. Dienstag,
M. J. Alter,
C. E. Stevens, et al.
1989.
An assay for circulating antibodies to a major etiologic virus of human non-A, non-B hepatitis.
Science
244:362-364[Abstract/Free Full Text].
|
| 17.
|
Kurts, C.,
H. Kosaka,
F. R. Carbone,
J. F. Miller, and W. R. Heath.
1997.
Class I-restricted cross-presentation of exogenous self-antigens leads to deletion of autoreactive CD8(+) T cells.
J. Exp. Med.
186:239-245[Abstract/Free Full Text].
|
| 18.
|
Labeur, M. S.,
B. Roters,
B. Pers,
A. Mehling,
T. A. Luger,
T. Schwarz, and S. Grabbe.
1999.
Generation of tumor immunity by bone marrow-derived dendritic cells correlates with dendritic cell maturation stage.
J. Immunol.
162:168-175[Abstract/Free Full Text].
|
| 19.
|
Lee, K. J.,
Y. A. Suh,
Y. G. Cho,
Y. S. Cho,
G. W. Ha,
K. H. Chung,
J. H. Hwang,
Y. D. Yun,
D. S. Lee,
C. M. Kim, and Y. C. Sung.
1997.
Hepatitis C virus E2 protein purified from mammalian cells is frequently recognized by E2-specific antibodies in patient sera.
J. Biol. Chem.
272:30040-30046[Abstract/Free Full Text].
|
| 20.
|
Lee, S. W.,
J. H. Cho, and Y. C. Sung.
1998.
Optimal induction of hepatitis C virus envelope-specific immunity by bicistronic plasmid DNA inoculation with the granulocyte-macrophage colony-stimulating factor gene.
J. Virol.
72:8430-8436[Abstract/Free Full Text].
|
| 21.
|
Lee, S. W.,
J. H. Cho,
K. J. Lee, and Y. C. Sung.
1998.
Hepatitis C virus envelope DNA-based immunization elicits humoral and cellular immune responses.
Mol. Cell
8:444-451.
|
| 22.
|
Letvin, N. L.,
D. C. Montefiori,
Y. Yasutomi,
H. C. Perry,
M. E. Davies,
C. Lekutis,
M. Alroy,
D. C. Freed,
C. I. Lord,
L. K. Handt,
M. A. Liu, and J. W. Shiver.
1997.
Potent, protective anti-HIV immune responses generated by bimodal HIV envelope DNA plus protein vaccination.
Proc. Natl. Acad. Sci. USA
94:9378-9383[Abstract/Free Full Text].
|
| 23.
|
Lu, S.,
J. Arthos,
D. C. Montefiori,
Y. Yasutomi,
K. Manson,
F. Mustafa,
E. Johnson,
J. C. Santoro,
J. Wissink,
J. I. Mullins,
J. R. Haynes,
N. L. Letvin,
M. Wyand, and H. L. Robinson.
1996.
Simian immunodeficiency virus DNA vaccine trial in macaques.
J. Virol.
70:3978-3991[Abstract].
|
| 24.
|
Nelson, D. R.,
C. G. Marousis,
G. L. Davis,
C. M. Rice,
J. Wong,
M. Houghton, and J. Y. Lau.
1997.
The role of hepatitis C virus-specific cytotoxic T lymphocytes in chronic hepatitis C.
J. Immunol.
1583:1473-1481.
|
| 25.
|
Parham, P.,
T. J. Kipps,
F. E. Ward, and L. A. Herzenberg.
1983.
Isolation of heavy chain class switch variants of a monoclonal anti-DC1 hybridoma cell line: effective conversion of noncytotoxic IgG1 antibodies to cytotoxic IgG2 antibodies.
Hum. Immunol.
8:141-151[CrossRef][Medline].
|
| 26.
|
Raz, E.,
H. Tighe,
Y. Sato,
M. Corr,
J. A. Dudler,
M. Roman,
S. L. Swain,
H. L. Spiegelberg, and D. A. Carson.
1996.
Preferential induction of a Th1 immune response and inhibition of specific IgE antibody formation by plasmid DNA immunization.
Proc. Natl. Acad. Sci. USA
93:5141-5145[Abstract/Free Full Text].
|
| 27.
|
Regnault, A.,
D. Lankar,
V. Lacabanne,
A. Rodriguez,
C. Thery,
M. Rescigno,
T. Saito,
S. Verbeek,
C. Bonnerot,
P. Ricciardi-Castagnoli, and S. Amigorena.
1999.
Fcgamma receptor-mediated induction of dendritic cell maturation and major histocompatibility complex class I-restricted antigen presentation after immune complex internalization.
J. Exp. Med.
189:371-380[Abstract/Free Full Text].
|
| 28.
|
Rehermann, B.,
K. M. Chang,
J. McHutchinson,
R. Kokka,
M. Houghton,
C. M. Rice, and F. V. Chisari.
1996.
Differential cytotoxic T-lymphocyte responsiveness to the hepatitis B and C viruses in chronically infected patients.
J. Virol.
70:7092-7102[Abstract/Free Full Text].
|
| 29.
|
Richmond, J. F.,
S. Lu,
J. C. Santoro,
J. Weng,
S. L. Hu,
D. C. Montefiori, and H. L. Robinson.
1998.
Studies of the neutralizing activity and avidity of anti-human immunodeficiency virus type 1 Env antibody elicited by DNA priming and protein boosting.
J. Virol.
72:9092-9100[Abstract/Free Full Text].
|
| 30.
|
Saito, I.,
T. Miyamura,
A. Ohbayashi,
H. Harada,
T. Katayama,
S. Kikuchi,
Y. Watanabe,
S. Koi,
M. Onji,
Y. Ohta, et al.
1990.
Hepatitis C virus infection is associated with the development of hepatocellular carcinoma.
Proc. Natl. Acad. Sci. USA
87:6547-6549[Abstract/Free Full Text].
|
| 31.
|
Scarselli, E.,
A. Cerino,
G. Esposito,
E. Silini,
M. Mondelli, and C. Traboni.
1995.
Occurrence of antibodies reactive with more than one variant of the putative envelope glycoprotein (gp70) hypervariable region 1 in viremic hepatitis C virus-infected patients.
J. Virol.
69:4407-4412[Abstract].
|
| 32.
|
Schneider, J.,
S. C. Gilbert,
T. J. Blanchard,
T. Hanke,
K. J. Robson,
C. M. Hannan,
M. Becker,
R. Sinden,
G. L. Smith, and A. V. Hill.
1998.
Enhanced immunogenicity for CD8+ T cell induction and complete protective efficacy of malaria DNA vaccination by boosting with modified vaccinia virus Ankara.
Nat. Med.
4:4397-4402.
|
| 33.
|
Tedeschi, V.,
T. Akatsuka,
J. W.-K. Shih,
M. Batlegay, and S. M. Feinstone.
1997.
A specific antibody response to HCV E2 elicited in mice by intramuscular inoculation of plasmid DNA containing coding sequences for E2.
Hepatology
25:459-462[CrossRef][Medline].
|
| 34.
|
Toes, R. E.,
R. Offringa,
R. J. Blom,
R. M. Brandt,
A. J. van der Eb,
C. J. Melief, and W. M. Kast.
1995.
An adenovirus type 5 early region 1B-encoded CTL epitope-mediating tumor eradication by CTL clones is down-modulated by an activated ras oncogene.
J. Immunol.
154:3396-3405[Abstract].
|
| 35.
|
Tokushige, K.,
T. Wakita,
C. Pachuk,
D. Moradpour,
D. B. Weiner,
V. R. Zurawski, Jr., and J. R. Wands.
1996.
Expression and immune response to hepatitis C virus core DNA-based vaccine constructs.
Hepatology
24:14-20[CrossRef][Medline].
|
| 36.
|
Ulmer, J. B.,
J. J. Donnelly,
S. E. Parker,
G. H. Rhodes,
P. L. Felgner,
V. J. Dwarki,
S. H. Gromkowski,
R. R. Deck,
C. M. DeWitt,
A. Friedman, et al.
1993.
Heterologous protection against influenza by injection of DNA encoding a viral protein.
Science
259:1745-1749[Abstract/Free Full Text].
|
| 37.
|
Unkeless, J. C.
1979.
Characterization of a monoclonal antibody directed against mouse macrophage and lymphocyte Fc receptors.
J. Exp. Med.
150:580-596[Abstract/Free Full Text].
|
Journal of Virology, March 2000, p. 2920-2925, Vol. 74, No. 6
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
-
Youn, J.-W., Hu, Y.-W., Tricoche, N., Pfahler, W., Shata, M. T., Dreux, M., Cosset, F.-L., Folgori, A., Lee, D.-H., Brotman, B., Prince, A. M.
(2008). Evidence for Protection against Chronic Hepatitis C Virus Infection in Chimpanzees by Immunization with Replicating Recombinant Vaccinia Virus. J. Virol.
82: 10896-10905
[Abstract]
[Full Text]
-
Chaitra, M. G., Shaila, M. S., Nayak, R.
(2007). Evaluation of T-cell responses to peptides with MHC class I-binding motifs derived from PE_PGRS 33 protein of Mycobacterium tuberculosis. J Med Microbiol
56: 466-474
[Abstract]
[Full Text]
-
Liang, R., van den Hurk, J. V., Babiuk, L. A., van Drunen Littel-van den Hurk, S.
(2006). Priming with DNA encoding E2 and boosting with E2 protein formulated with CpG oligodeoxynucleotides induces strong immune responses and protection from Bovine viral diarrhea virus in cattle.. J. Gen. Virol.
87: 2971-2982
[Abstract]
[Full Text]
-
Majid, A. M., Ezelle, H., Shah, S., Barber, G. N.
(2006). Evaluating Replication-Defective Vesicular Stomatitis Virus as a Vaccine Vehicle. J. Virol.
80: 6993-7008
[Abstract]
[Full Text]
-
Araujo, A. F. S., de Alencar, B. C. G., Vasconcelos, J. R. C., Hiyane, M. I., Marinho, C. R. F., Penido, M. L. O., Boscardin, S. B., Hoft, D. F., Gazzinelli, R. T., Rodrigues, M. M.
(2005). CD8+-T-Cell-Dependent Control of Trypanosoma cruzi Infection in a Highly Susceptible Mouse Strain after Immunization with Recombinant Proteins Based on Amastigote Surface Protein 2. Infect. Immun.
73: 6017-6025
[Abstract]
[Full Text]
-
Yu, H., Babiuk, L. A., van Drunen Littel-van den Hurk, S.
(2004). Priming with CpG-enriched plasmid and boosting with protein formulated with CpG oligodeoxynucleotides and Quil A induces strong cellular and humoral immune responses to hepatitis C virus NS3. J. Gen. Virol.
85: 1533-1543
[Abstract]
[Full Text]
-
Hechard, C., Grepinet, O., Rodolakis, A.
(2003). Evaluation of protection against Chlamydophila abortus challenge after DNA immunization with the major outer-membrane protein-encoding gene in pregnant and non-pregnant mice. J Med Microbiol
52: 35-40
[Abstract]
[Full Text]
-
Tanghe, A., D'Souza, S., Rosseels, V., Denis, O., Ottenhoff, T. H. M., Dalemans, W., Wheeler, C., Huygen, K.
(2001). Improved Immunogenicity and Protective Efficacy of a Tuberculosis DNA Vaccine Encoding Ag85 by Protein Boosting. Infect. Immun.
69: 3041-3047
[Abstract]
[Full Text]
-
Lee, S. W., Song, M. K., Baek, K. H., Park, Y., Kim, J. K., Lee, C. H., Cheong, H.-K., Cheong, C., Sung, Y. C.
(2000). Effects of a Hexameric Deoxyriboguanosine Run Conjugation into CpG Oligodeoxynucleotides on Their Immunostimulatory Potentials. J. Immunol.
165: 3631-3639
[Abstract]
[Full Text]
Top
Abstract
Text
