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Journal of Virology, June 2008, p. 5643-5649, Vol. 82, No. 11
0022-538X/08/$08.00+0 doi:10.1128/JVI.02564-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Recruitment of Antigen-Presenting Cells to the Site of Inoculation and Augmentation of Human Immunodeficiency Virus Type 1 DNA Vaccine Immunogenicity by In Vivo Electroporation
Jinyan Liu,1
Rune Kjeken,2
Iacob Mathiesen,2 and
Dan H. Barouch1*
Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215,1
Inovio Biomedical, San Diego, California 921212
Received 1 December 2007/
Accepted 11 March 2008

ABSTRACT
In vivo electroporation (EP) has been shown to augment the immunogenicity
of plasmid DNA vaccines, but its mechanism of action has not
been fully characterized. In this study, we show that in vivo
EP augmented cellular and humoral immune responses to a human
immunodeficiency virus type 1 Env DNA vaccine in mice and allowed
a 10-fold reduction in vaccine dose. This enhancement was durable
for over 6 months, and re-exposure to antigen resulted in anamnestic
effector and central memory CD8
+ T-lymphocyte responses. Interestingly,
in vivo EP also recruited large mixed cellular inflammatory
infiltrates to the site of inoculation. These infiltrates contained
45-fold-increased numbers of macrophages and 77-fold-increased
numbers of dendritic cells as well as 2- to 6-fold-increased
numbers of B and T lymphocytes compared to infiltrates following
DNA vaccination alone. These data suggest that recruiting inflammatory
cells, including antigen-presenting cells (APCs), to the site
of antigen production substantially improves the immunogenicity
of DNA vaccines. Combining in vivo EP with plasmid chemokine
adjuvants that similarly recruited APCs to the injection site,
however, did not result in synergy.

TEXT
Plasmid DNA vaccines have proven considerably less immunogenic
in clinical studies than in preclinical studies (
3,
9,
13,
24,
33), demonstrating the need to improve their potency. Various
strategies are currently being pursued, including the use of
plasmid cytokine and chemokine adjuvants (
5,
6,
11,
19,
26,
30), polymer adjuvants (
29), novel transcriptional regulatory
elements (
7), and improved delivery techniques such as in vivo
electroporation (EP) (
2,
23,
25). In vivo EP involves the administration
of electrical pulses to muscle tissue following intramuscular
(i.m.) injection of DNA vaccines and has been shown to enhance
the immunogenicity of DNA vaccines in a wide variety of small
and large animal models (
1,
8,
10,
12,
17,
18,
20,
22,
27,
32).
It has been suggested that in vivo EP functions in part by increasing
myocyte permeability and thereby facilitating plasmid uptake
and antigen expression by host cells (
2,
14-
16,
25,
28,
34).
We have previously reported that there are very few professional antigen-presenting cells (APCs) in muscles after DNA vaccination (6), and we therefore hypothesized that DNA vaccines may be limited by insufficient APCs at the site of antigen production. Consistent with this hypothesis, we observed that plasmid chemokines and growth factors such as plasmid MIP-1
and Flt3L were able to recruit dendritic cells (DCs) and macrophages to the site of inoculation and to enhance DNA vaccine-elicited immune responses (26, 30). Whether APCs are similarly recruited by in vivo EP, however, has not previously been investigated. In addition, the phenotype of cellular immune responses elicited by DNA vaccination with in vivo EP has not been assessed in detail. In the present study, we investigated the magnitude, phenotype, and durability of cellular immune responses elicited in mice by human immunodeficiency virus type 1 (HIV-1) Env DNA vaccination with or without in vivo EP and assessed the extent and nature of cellular inflammatory infiltrates at the site of inoculation.
In vivo EP augments DNA vaccine-elicited immune responses.
We initiated studies by assessing the immunogenicity of 50, 5, or 0.5 µg of a previously described HIV-1 Env IIIB gp120 DNA vaccine (6, 30) either alone or with two different methods of in vivo EP. BALB/c mice (four animals/group) were anesthetized and immunized i.m. in the quadriceps muscles, and in vivo EP was performed according to the manufacturer's protocols (Inovio Biomedical, San Diego, CA). Caliper EP involved application of electric pulses across intact muscle using surface electrodes with conductive gel after DNA vaccination (6 x 100-µs pulses at 600 V/cm). Needle EP involved delivery of electric pulses from electrodes inserted i.m. flanking the injection site after DNA vaccination (2 x 60-ms pulses at 200 V/cm).
CD8+ T-lymphocyte responses to the dominant Env P18 epitope (RGPGRAFVTI) (31) were assessed by Dd/P18 tetramer binding assays at multiple time points after immunization as previously described (6, 30). Cellular immune responses to a pool of overlapping Env peptides and the P18 epitope peptide were also assessed by gamma interferon (IFN-
) enzyme-linked immunospot (ELISPOT) assays at week 4 after immunization. As shown in Fig. 1A and B, the DNA vaccine alone elicited potent cellular immune responses at the dose of 50 µg and detectable responses at the dose of 5 µg, but no responses were observed at the dose of 0.5 µg. Caliper EP utilizing these experimental conditions had little adjuvant effect. In contrast, needle EP resulted in a significant threefold enhancement of the magnitude of CD8+ T-lymphocyte responses at the dose of 50 µg (P = 0.001 comparing tetramer binding responses on day 14 after immunization using two-tailed t tests). Cellular immune responses were also detected at the lowest dose of 0.5 µg, indicating that needle EP allowed a 10-fold reduction in the DNA vaccine dose. Needle EP also resulted in a significant fourfold augmentation of both IFN-
+ and IFN-
+/IL-2+ CD8+ T-lymphocyte responses by intracellular cytokine staining assays (P = 0.0002; Fig. 1C) (21) and a sixfold increase in Env-specific antibody titers by enzyme-linked immunosorbent assay (ELISA) (P = 0.01; Fig. 1D) (6, 30) at week 4 after immunization in mice that received the 50-µg dose. Needle EP was therefore utilized in subsequent studies, although we do not exclude the possibility that caliper EP could be further optimized.
In vivo EP does not augment rAd5 vaccine-elicited immune responses.
We next evaluated the capacity of in vivo needle EP to enhance
the immunogenicity of a recombinant adenovirus serotype 5 (rAd5)
vector-based vaccine. As shown in Fig.
2, in vivo EP did not
significantly augment responses elicited by 10
9, 10
7, or 10
5 viral particles (vp) rAd5 expressing Env IIIB gp120 (
4). These
data suggest that in vivo EP may prove more useful at improving
DNA vaccines rather than certain live vectors, perhaps as a
result of the innate inflammatory responses induced by these
viral vectors, together with the fact that in vivo EP would
not likely increase the infectivity of viral vectors that enter
host cells efficiently via specific cellular receptors.
Comparison of in vivo EP with plasmid chemokine adjuvants.
Previous studies have suggested that in vivo EP may function
in part by increasing the permeability of myocytes and enhancing
plasmid uptake and antigen expression (
2,
25,
28,
34). We have
previously reported that coadministration of plasmid chemokines
and growth factors, particularly the combination of plasmid
MIP-1

and Flt3L, recruited APCs to the site of inoculation and
enhanced DNA vaccine-elicited immune responses (
30). We therefore
hypothesized that combining plasmid chemokine adjuvants with
in vivo EP might result in synergistic effects by simultaneously
recruiting APCs to the injection site and improving transfection
of these cells. To explore this hypothesis, groups of mice (four
animals/group) were immunized with 50 µg (Fig.
3A) or
5 µg (Fig.
3B) of the gp120 DNA vaccine alone or with
plasmid MIP-1

/Flt3L, in vivo EP, or both. The plasmid chemokines
and in vivo EP resulted in similar threefold enhancements of
peak responses on days 10 to 14 after immunization, although
the effects of in vivo EP proved more durable. The combination
of plasmid chemokines and in vivo EP led to a transient additive
effect on day 10, but these responses contracted quickly, and
no long-term synergy was observed by combining these two adjuvant
strategies.
We next evaluated the memory phenotypes and recall responses
after priming with 50 µg of the gp120 DNA vaccine alone,
the DNA vaccine with in vivo EP, or the DNA vaccine with both
plasmid MIP-1

/Flt3L and in vivo EP. Env P18-specific responses
in total, effector memory/effector (EM/E; CD62L
–), central
memory (CM; CD44
+ CD62L
+), and naive (N; CD44
– CD62L
+)
CD8
+ T-lymphocyte subpopulations were evaluated by multiparameter
tetramer binding assays. As shown in Fig.
3C to F, in vivo EP
resulted in a durable 2.9-, 3.7-, and 2.0-fold augmentation
of total, EM/E, and CM CD8
+ T-lymphocyte responses for 168 days
after the priming immunization (
P = 0.007, 0.007, and 0.01,
respectively). In vivo EP did not skew the relative proportions
of memory phenotypes compared to DNA vaccination alone at this
time point.
At 6 months after the priming immunization, all groups of mice, including the sham-primed mice, were boosted with 50 µg of the gp120 DNA vaccine without any adjuvants (Fig. 3C to F, arrows). After the boost immunization, a robust 10-fold expansion of EM/E responses and a 3-fold increase in CM responses were detected in all groups. Mice that were primed with in vivo EP 168 days previously exhibited significantly threefold-higher anamnestic EM/E responses and twofold-higher CM responses after the boost immunization compared to mice that received the DNA vaccine alone (P = 0.01), demonstrating the durability of the effects of in vivo EP administered during the priming immunization. The addition of plasmid MIP1
/Flt3L to in vivo EP led to transiently greater peak responses but did not result in long-term synergistic effects.
In vivo EP recruits large cellular infiltrates to the site of inoculation.
We next evaluated the extent and nature of cellular infiltrates at the site of inoculation after DNA vaccination alone or with plasmid MIP-1
/Flt3L, in vivo EP, or both. As shown in Fig. 4A and B, only mild inflammation was observed in sections of injected muscles on day 7 after DNA vaccination alone, a finding consistent with our prior studies (6, 26, 30). In contrast, as depicted in Fig. 4C and D, large cellular infiltrates were detected after DNA vaccination with in vivo EP. These infiltrates consisted of large clusters of mixed inflammatory cells both in perivascular spaces and throughout muscle tissue and consisted of both polymorphonuclear and mononuclear cells. The extent of these infiltrates was greater than that observed with plasmid MIP-1
/Flt3L (30).
To evaluate the nature and composition of these infiltrates,
we extracted cells from injected muscles on day 7 after immunization
and evaluated them by multiparameter flow cytometry (
30). Compared
to DNA vaccination alone, DNA vaccination with in vivo EP led
to a substantial increase in total extracted cells (
P = 0.02;
Fig.
4E), as well as two- to sixfold increases in CD19
+ B lymphocytes,
CD3
+ CD4
+ T lymphocytes, and CD3
+ CD8
+ T lymphocytes (
P = 0.02,
0.002, and 0.004, respectively; Fig.
4F). Interestingly, in
vivo EP also led to dramatic 45-fold increases in CD3
– CD19
– CD11b
+ CD11c
– macrophages and 77-fold increases
in CD3
– CD19
– CD11c
+ DCs compared to DNA vaccination
alone (
P = 0.006 and 0.007, respectively; Fig.
4G and H), although
the absolute number of recruited professional APCs was lower
than the number of recruited lymphocytes and acute inflammatory
cells. In vivo EP also led to larger DC infiltrates compared
to plasmid MIP-1

/Flt3L, although a smaller percentage of DCs
recruited by in vivo EP expressed the activation marker CD83
(Fig.
4H). The infiltrates observed with the combination of
plasmid MIP-1

/Flt3L and EP, however, were only marginally greater
than those induced by EP alone. These data are consistent with
the lack of substantial immunologic synergy observed with these
two adjuvant modalities (Fig.
3). No differences in cell populations
were observed in blood, draining lymph nodes, and spleen in
mice after DNA vaccination with or without in vivo EP (data
not shown), suggesting that the mechanism of in vivo EP likely
involves local rather than systemic factors. The cellular inflammatory
infiltrates in all groups proved transient and were largely
resolved by day 14 after immunization (data not shown).
After DNA vaccination in the absence of adjuvants, antigen is primarily expressed in muscle tissue (35). The typical paucity of professional APCs at the site of inoculation and antigen production may therefore represent a critical limitation of DNA vaccines. Our data demonstrate that in vivo EP recruited large mixed cellular infiltrates that contained a proportionally concentrated number of APCs to the site of inoculation. It is likely that the increased numbers of APCs at the site of antigen production contributed substantially to the enhanced immunogenicity of the DNA vaccine. Consistent with this model, the lack of synergy between plasmid chemokines and in vivo EP may reflect their similar mechanisms of action. It is also possible that local cellular inflammation after in vivo EP may have provided an improved cytokine milieu that favored antigen presentation and immune priming.
In vivo EP significantly enhanced the magnitude and durability of DNA vaccine-elicited cellular and humoral immune responses. Qualitative aspects of CD8+ T-lymphocyte responses elicited by DNA vaccination with or without in vivo EP, however, appeared similar in terms of cytokine secretion profiles (Fig. 1C) and memory phenotypes (Fig. 3C to F). Our data extend previous studies by evaluating the durability and phenotype of CD8+ T-lymphocyte responses, as well as the extent and nature of cellular inflammatory infiltrates after DNA vaccination with in vivo EP. We propose that in vivo EP may function by a combination of mechanisms, including not only recruitment of APCs but also improved transfection of cells and increased antigen expression as previously reported (2, 14-16, 25, 28, 34). The potency of in vivo EP thus may reflect its capacity to facilitate multiple steps of the immune priming process.

ACKNOWLEDGMENTS
We thank Bonnie Ewald, Diana Lynch, Matt Denholtz, Faye Stephens,
Norman Letvin, Kathy Furr, and Michelle Lifton for generous
advice, assistance, and reagents. The HIV-1 Env overlapping
peptides were obtained from the UK Centralized Facility for
AIDS Reagents.
We acknowledge support from NIH grants AI058727 (D.H.B.) and P30 AI060354.

FOOTNOTES
* Corresponding author. Mailing address: Research East Room 213, Division of Viral Pathogenesis, Beth Israel Deaconess Medical Center, 330 Brookline Ave., Boston, MA 02215. Phone: (617) 667-4434. Fax: (617) 667-8210. E-mail:
dbarouch{at}bidmc.harvard.edu 
Published ahead of print on 19 March 2008. 

REFERENCES
1 - Ahlen, G., J. Soderholm, T. Tjelle, R. Kjeken, L. Frelin, U. Hoglund, P. Blomberg, M. Fons, I. Mathiesen, and M. Sallberg. 2007. In vivo electroporation enhances the immunogenicity of hepatitis C virus nonstructural 3/4A DNA by increased local DNA uptake, protein expression, inflammation, and infiltration of CD3+ T cells. J. Immunol. 179:4741-4753.[Abstract/Free Full Text]
2 - Aihara, H., and J. Miyazaki. 1998. Gene transfer into muscle by electroporation in vivo. Nat. Biotechnol. 16:867-870.[CrossRef][Medline]
3 - Barouch, D. H. 2006. Rational design of gene-based vaccines. J. Pathol. 208:283-289.[CrossRef][Medline]
4 - Barouch, D. H., P. F. McKay, S. M. Sumida, S. Santra, S. S. Jackson, D. A. Gorgone, M. A. Lifton, B. K. Chakrabarti, L. Xu, G. J. Nabel, and N. L. Letvin. 2003. Plasmid chemokines and colony-stimulating factors enhance the immunogenicity of DNA priming-viral vector boosting human immunodeficiency virus type 1 vaccines. J. Virol. 77:8729-8735.[Abstract/Free Full Text]
5 - Barouch, D. H., S. Santra, J. E. Schmitz, M. J. Kuroda, T. M. Fu, W. Wagner, M. Bilska, A. Craiu, X. X. Zheng, G. R. Krivulka, K. Beaudry, M. A. Lifton, C. E. Nickerson, W. L. Trigona, K. Punt, D. C. Freed, L. Guan, S. Dubey, D. Casimiro, A. Simon, M. E. Davies, M. Chastain, T. B. Strom, R. S. Gelman, D. C. Montefiori, M. G. Lewis, E. A. Emini, J. W. Shiver, and N. L. Letvin. 2000. Control of viremia and prevention of clinical AIDS in rhesus monkeys by cytokine-augmented DNA vaccination. Science 290:486-492.[Abstract/Free Full Text]
6 - Barouch, D. H., S. Santra, K. Tenner-Racz, P. Racz, M. J. Kuroda, J. E. Schmitz, S. S. Jackson, M. A. Lifton, D. C. Freed, H. C. Perry, M. E. Davies, J. W. Shiver, and N. L. Letvin. 2002. Potent CD4+ T-cell responses elicited by a bicistronic HIV-1 DNA vaccine expressing gp120 and GM-CSF. J. Immunol. 168:562-568.[Abstract/Free Full Text]
7 - Barouch, D. H., Z. Y. Yang, W. P. Kong, B. Korioth-Schmitz, S. M. Sumida, D. M. Truitt, M. G. Kishko, J. C. Arthur, A. Miura, J. R. Mascola, N. L. Letvin, and G. J. Nabel. 2005. A human T-cell leukemia virus type 1 regulatory element enhances the immunogenicity of human immunodeficiency virus type 1 DNA vaccines in mice and nonhuman primates. J. Virol. 79:8828-8834.[Abstract/Free Full Text]
8 - Buchan, S., E. Gronevik, I. Mathiesen, C. A. King, F. K. Stevenson, and J. Rice. 2005. Electroporation as a "prime/boost" strategy for naked DNA vaccination against a tumor antigen. J. Immunol. 174:6292-6298.[Abstract/Free Full Text]
9 - Calarota, S., G. Bratt, S. Nordlund, J. Hinkula, A. C. Leandersson, E. Sandstrom, and B. Wahren. 1998. Cellular cytotoxic response induced by DNA vaccination in HIV-1-infected patients. Lancet 351:1320-1325.[CrossRef][Medline]
10 - Dobano, C., G. Widera, D. Rabussay, and D. L. Doolan. 2007. Enhancement of antibody and cellular immune responses to malaria DNA vaccines by in vivo electroporation. Vaccine 25:6635-6645.[CrossRef][Medline]
11 - Egan, M. A., S. Y. Chong, S. Megati, D. C. Montefiori, N. F. Rose, J. D. Boyer, M. K. Sidhu, J. Quiroz, M. Rosati, E. B. Schadeck, G. N. Pavlakis, D. B. Weiner, J. K. Rose, Z. R. Israel, S. A. Udem, and J. H. Eldridge. 2005. Priming with plasmid DNAs expressing interleukin-12 and simian immunodeficiency virus gag enhances the immunogenicity and efficacy of an experimental AIDS vaccine based on recombinant vesicular stomatitis virus. AIDS Res. Hum. Retrovir. 21:629-643.[CrossRef][Medline]
12 - Folgori, A., S. Capone, L. Ruggeri, A. Meola, E. Sporeno, B. B. Ercole, M. Pezzanera, R. Tafi, M. Arcuri, E. Fattori, A. Lahm, A. Luzzago, A. Vitelli, S. Colloca, R. Cortese, and A. Nicosia. 2006. A T-cell HCV vaccine eliciting effective immunity against heterologous virus challenge in chimpanzees. Nat. Med. 12:190-197.[CrossRef][Medline]
13 - Graham, B. S., R. A. Koup, M. Roederer, R. T. Bailer, M. E. Enama, Z. Moodie, J. E. Martin, M. M. McCluskey, B. K. Chakrabarti, L. Lamoreaux, C. A. Andrews, P. L. Gomez, J. R. Mascola, and G. J. Nabel. 2006. Phase 1 safety and immunogenicity evaluation of a multiclade HIV-1 DNA candidate vaccine. J. Infect. Dis. 194:1650-1660.[CrossRef][Medline]
14 - Gronevik, E., I. Mathiesen, and T. Lomo. 2005. Early events of electroporation-mediated intramuscular DNA vaccination potentiate Th1-directed immune responses. J. Gene Med. 7:1246-1254.[CrossRef][Medline]
15 - Gronevik, E., S. Tollefsen, L. I. Sikkeland, T. Haug, T. E. Tjelle, and I. Mathiesen. 2003. DNA transfection of mononuclear cells in muscle tissue. J. Gene Med. 5:909-917.[CrossRef][Medline]
16 - Gronevik, E., F. V. von Steyern, J. M. Kalhovde, T. E. Tjelle, and I. Mathiesen. 2005. Gene expression and immune response kinetics using electroporation-mediated DNA delivery to muscle. J. Gene Med. 7:218-227.[CrossRef][Medline]
17 - Hirao, L. A., L. Wu, A. S. Khan, A. Satishchandran, R. Draghia-Akli, and D. B. Weiner. 2008. Intradermal/subcutaneous immunization by electroporation improves plasmid vaccine delivery and potency in pigs and rhesus macaques. Vaccine 26:440-448.[CrossRef][Medline]
18 - Hooper, J. W., J. W. Golden, A. M. Ferro, and A. D. King. 2007. Smallpox DNA vaccine delivered by novel skin electroporation device protects mice against intranasal poxvirus challenge. Vaccine 25:1814-1823.[CrossRef][Medline]
19 - Kutzler, M. A., T. M. Robinson, M. A. Chattergoon, D. K. Choo, A. Y. Choo, P. Y. Choe, M. P. Ramanathan, R. Parkinson, S. Kudchodkar, Y. Tamura, M. Sidhu, V. Roopchand, J. J. Kim, G. N. Pavlakis, B. K. Felber, T. A. Waldmann, J. D. Boyer, and D. B. Weiner. 2005. Coimmunization with an optimized IL-15 plasmid results in enhanced function and longevity of CD8 T cells that are partially independent of CD4 T cell help. J. Immunol. 175:112-123.[Abstract/Free Full Text]
20 - Li, Z., H. Zhang, X. Fan, Y. Zhang, J. Huang, Q. Liu, T. E. Tjelle, I. Mathiesen, R. Kjeken, and S. Xiong. 2006. DNA electroporation prime and protein boost strategy enhances humoral immunity of tuberculosis DNA vaccines in mice and non-human primates. Vaccine 24:4565-4568.[CrossRef][Medline]
21 - Liu, J., B. A. Ewald, D. M. Lynch, A. Nanda, S. M. Sumida, and D. H. Barouch. 2006. Modulation of DNA vaccine-elicited CD8+ T-lymphocyte epitope immunodominance hierarchies. J. Virol. 80:11991-11997.[Abstract/Free Full Text]
22 - Luckay, A., M. K. Sidhu, R. Kjeken, S. Megati, S. Y. Chong, V. Roopchand, D. Garcia-Hand, R. Abdullah, R. Braun, D. C. Montefiori, M. Rosati, B. K. Felber, G. N. Pavlakis, I. Mathiesen, Z. R. Israel, J. H. Eldridge, and M. A. Egan. 2007. Effect of plasmid DNA vaccine design and in vivo electroporation on the resulting vaccine-specific immune responses in rhesus macaques. J. Virol. 81:5257-5269.[Abstract/Free Full Text]
23 - Luxembourg, A., C. F. Evans, and D. Hannaman. 2007. Electroporation-based DNA immunization: translation to the clinic. Expert Opin. Biol. Ther. 7:1647-1664.[CrossRef][Medline]
24 - MacGregor, R. R., J. D. Boyer, K. E. Ugen, K. E. Lacy, S. J. Gluckman, M. L. Bagarazzi, M. A. Chattergoon, Y. Baine, T. J. Higgins, R. B. Ciccarelli, L. R. Coney, R. S. Ginsberg, and D. B. Weiner. 1998. First human trial of a DNA-based vaccine for treatment of human immunodeficiency virus type 1 infection: safety and host response. J. Infect. Dis. 178:92-100.[Medline]
25 - Mathiesen, I. 1999. Electropermeabilization of skeletal muscle enhances gene transfer in vivo. Gene Ther. 6:508-514.[CrossRef][Medline]
26 - McKay, P. F., D. H. Barouch, S. Santra, S. M. Sumida, S. S. Jackson, D. A. Gorgone, M. A. Lifton, and N. L. Letvin. 2004. Recruitment of different subsets of antigen-presenting cells selectively modulates DNA vaccine-elicited CD4+ and CD8+ T lymphocyte responses. Eur. J. Immunol. 34:1011-1020.[CrossRef][Medline]
27 - Otten, G. R., M. Schaefer, B. Doe, H. Liu, J. Z. Megede, J. Donnelly, D. Rabussay, S. Barnett, and J. B. Ulmer. 2006. Potent immunogenicity of an HIV-1 gag-pol fusion DNA vaccine delivered by in vivo electroporation. Vaccine 24:4503-4509.[CrossRef][Medline]
28 - Rizzuto, G., M. Cappelletti, D. Maione, R. Savino, D. Lazzaro, P. Costa, I. Mathiesen, R. Cortese, G. Ciliberto, R. Laufer, N. La Monica, and E. Fattori. 1999. Efficient and regulated erythropoietin production by naked DNA injection and muscle electroporation. Proc. Natl. Acad. Sci. USA 96:6417-6422.[Abstract/Free Full Text]
29 - Shiver, J. W., T. M. Fu, L. Chen, D. R. Casimiro, M. E. Davies, R. K. Evans, Z. Q. Zhang, A. J. Simon, W. L. Trigona, S. A. Dubey, L. Huang, V. A. Harris, R. S. Long, X. Liang, L. Handt, W. A. Schleif, L. Zhu, D. C. Freed, N. V. Persaud, L. Guan, K. S. Punt, A. Tang, M. Chen, K. A. Wilson, K. B. Collins, G. J. Heidecker, V. R. Fernandez, H. C. Perry, J. G. Joyce, K. M. Grimm, J. C. Cook, P. M. Keller, D. S. Kresock, H. Mach, R. D. Troutman, L. A. Isopi, D. M. Williams, Z. Xu, K. E. Bohannon, D. B. Volkin, D. C. Montefiori, A. Miura, G. R. Krivulka, M. A. Lifton, M. J. Kuroda, J. E. Schmitz, N. L. Letvin, M. J. Caulfield, A. J. Bett, R. Youil, D. C. Kaslow, and E. A. Emini. 2002. Replication-incompetent adenoviral vaccine vector elicits effective anti-immunodeficiency-virus immunity. Nature 415:331-335.[CrossRef][Medline]
30 - Sumida, S. M., P. F. McKay, D. M. Truitt, M. G. Kishko, J. C. Arthur, M. S. Seaman, S. S. Jackson, D. A. Gorgone, M. A. Lifton, N. L. Letvin, and D. H. Barouch. 2004. Recruitment and expansion of dendritic cells in vivo potentiate the immunogenicity of plasmid DNA vaccines. J. Clin. Investig. 114:1334-1342.[CrossRef][Medline]
31 - Takahashi, H., Y. Nakagawa, C. D. Pendleton, R. A. Houghten, K. Yokomuro, R. N. Germain, and J. A. Berzofsky. 1992. Induction of broadly cross-reactive cytotoxic T cells recognizing an HIV-1 envelope determinant. Science 255:333-336.[Abstract/Free Full Text]
32 - Tjelle, T. E., R. Salte, I. Mathiesen, and R. Kjeken. 2006. A novel electroporation device for gene delivery in large animals and humans. Vaccine 24:4667-4670.[CrossRef][Medline]
33 - Wang, R., D. L. Doolan, T. P. Le, R. C. Hedstrom, K. M. Coonan, Y. Charoenvit, T. R. Jones, P. Hobart, M. Margalith, J. Ng, W. R. Weiss, M. Sedegah, C. de Taisne, J. A. Norman, and S. L. Hoffman. 1998. Induction of antigen-specific cytotoxic T lymphocytes in humans by a malaria DNA vaccine. Science 282:476-480.[Abstract/Free Full Text]
34 - Widera, G., M. Austin, D. Rabussay, C. Goldbeck, S. W. Barnett, M. Chen, L. Leung, G. R. Otten, K. Thudium, M. J. Selby, and J. B. Ulmer. 2000. Increased DNA vaccine delivery and immunogenicity by electroporation in vivo. J. Immunol. 164:4635-4640.[Abstract/Free Full Text]
35 - Wolff, J. A., R. W. Malone, P. Williams, W. Chong, G. Acsadi, A. Jani, and P. L. Felgner. 1990. Direct gene transfer into mouse muscle in vivo. Science 247:1465-1468.[Abstract/Free Full Text]
Journal of Virology, June 2008, p. 5643-5649, Vol. 82, No. 11
0022-538X/08/$08.00+0 doi:10.1128/JVI.02564-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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