Previous Article | Next Article ![]()
Journal of Virology, December 1998, p. 10222-10226, Vol. 72, No. 12
Institute for Human Gene Therapy and
Departments of Molecular and Cellular Engineering and of Medicine,
University of Pennsylvania, and the Wistar Institute, Philadelphia,
Pennsylvania
Received 10 April 1998/Accepted 2 September 1998
Factors relevant to the successful application of adeno-associated
virus (AAV) vectors for liver-directed gene therapy were evaluated.
Vectors with different promoters driving expression of human
The liver is an excellent target for
in vivo gene therapy because hepatocytes are easily accessible to
vectors injected into the circulation through large pores in liver
capillaries (6). Nonviral gene delivery vehicles, based on
liposomes and DNA-protein complexes, target hepatocytes in vivo,
although gene transfer efficiency is low and expression is transient
(20, 24). Recombinant adenoviruses target hepatocytes with
higher efficiency but suffer from destructive cellular and blocking
humoral immune responses (7, 11, 22).
Adeno-associated virus (AAV) has shown promise for in vivo gene therapy
in a number of organs, such as skeletal muscle, central nervous system,
and retina, where expression is efficient, stable, and associated with
little inflammation or cellular immune response (1, 4, 5, 10, 12,
21). Results in the liver have been less consistent, with Snyder
et al. providing the most impressive results by achieving sustained and
therapeutic levels of factor IX in mice from an AAV vector utilizing a
retroviral long terminal repeat (LTR) promoter (18).
The goal of this study was to further evaluate the potential of AAV as
a vector for in vivo gene therapy of the liver. Studies were performed
with human Hepatocytes were transduced in vivo following infusion of
1011 genome equivalents of AAV into the portal
circulation of immunodeficient mice. Figure
1 shows the level of human
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Adeno-Associated Virus as a Vector for
Liver-Directed Gene Therapy
![]()
ABSTRACT
Top
Abstract
Text
References
-1-antitrypsin (
-1AT) were injected into the portal circulation
of immunodeficient mice.
-1AT expression was stable but dependent on
the promoter. Southern analysis of liver DNA revealed approximately 0.1 to 2.0 provirus copies/diploid genome in presumed head-to-tail
concatamers. In situ hybridization and immunohistochemical
analysis revealed expression in approximately 5% of hepatocytes
clustered in the pericentral region. These results support the use of
AAV as a vector for diseases treatable by targeting of hepatocytes.
![]()
TEXT
Top
Abstract
Text
References
-1-antitrypsin (
-1AT) as a reporter gene in murine
models, because it allows quantitation of overall expression of the
transgene through enzyme-linked immunosorbent assay (ELISA) of
-1AT
in serum. Vectors in which
-1AT is driven from one of a number of
promoters were constructed; they included (i) the 5' flanking sequence
and upstream enhancer sequences of the albumin gene (Alb), (ii) the 5'
flanking region of the immediate early gene of cytomegalovirus
(CMV), (iii) the 5' flanking region of the human phosphoglycerate
kinase gene (PGK), (iv) the 5' LTR of the Moloney murine leukemia
virus, and (v) the chicken
-actin promoter fused to the enhancer
region of the CMV immediate early gene (CB). Recombinant stocks of AAV
for each vector were created by a transfection approach that does not
require coinfection with adenovirus.
-1AT in
serum of recipient mice for 18 weeks following gene transfer. The
profile of expression with each vector was essentially the same, with
the concentration of serum
-1AT increasing during the first 6 weeks
and thereafter stabilizing for the duration of the experiment. Total
production of
-1AT was consistent within each group but varied
substantially between the different promoters. The highest expression
was noted with the albumin and LTR constructs, with levels of
-1AT
ranging from 5 to 50 µg/ml. The CMV enhanced
-actin promoter (CB)
yielded intermediate levels of
-1AT (i.e., 1 to 10 µg/ml), whereas
expression from the CMV and PGK promoters was substantially lower, at
approximately 0.1 to 1 µg/ml. Additional experiments conducted with
the albumin construct demonstrated a direct relationship between the
dose of vector and transgene expression over a range of 3 × 108 to 1 × 1011 vector genomes (data not
shown).

View larger version (27K):
[in a new window]
FIG. 1.
Levels of Human
-1AT in serum of mice after
intraportal infusion of AAV vector. RAG-1 mice were injected with
1011 genomes of AAV vector, bearing different
promoters, directly into the portal circulation via the spleen. Vector
constructs contained the EcoRI fragment of pAT85 (from the
American Type Culture Collection), spanning human
-1AT cDNA
fused to the polyadenylation sequence from simian virus 40. Each panel
presents serum
-1AT levels from multiple animals for vectors with
different promoters measured up to 18 weeks after vector infusion.
-1AT was measured by an ELISA with
-1AT antibodies purchased from
Sigma. The different promoters were as follows: CB, chicken
-actin
promoter (
1 to +275) fused to enhancer sequences from the immediate
early gene of CMV (23); CMV, promoter and enhancer of the
immediate early gene of CMV spanning 795 bp of the 5' flanking
sequence; LTR, 2.3-kb Moloney murine leukemia virus LTR promoter
isolated from pBR-MFG containing the LTR and intron (2);
Alb, 2.4-kb murine albumin promoter from pAlbuPA2
(NotI-to-KpnI fragment) containing 300 bp of the
5' flanking sequence and the enhancer region from
8.5 to
10.4
kb (16); PGK, 0.5-kb PGK promoter from PGK-neo (from M. McBurney and K. Jardine). Experiments were repeated with a number of
different vector preparations (CB [n = 1], CMV,
[n = 3], LTR [n = 1], Alb
[n = 5], and PGK [n = 2]), all with
identical results. Recombinant AAV based on AAV serotype 2 was produced
by simultaneously transfecting three plasmids into 293 cells and
purifying vector from the cell lysate by sequential cesium
chloride sedimentation. The three plasmids were vector, pJWX500
(inverted terminal repeats deleted from wild-type AAV and a 500-bp
stuffer inserted between p5 and rep), and PF
13
(the adenovirus [Ad] helper construct created by deleting the
RsrII fragment from pFG140 [Microbix, Toronto, Canada]).
These preparations contained varying levels of replication-competent
AAV (rcAAV), ranging from 1/103 to 1/105 (rcAAV
genomes/vector AAV genomes), and no detectable Ad based on PFU assay
(<1 Ad PFU/1011 vector AAV genomes).
The impact of the promoter on the level of transgene expression, noted in our study, may explain some discrepancies in the literature. Two groups failed to demonstrate significant expression of lacZ in the liver with AAV vectors containing the CMV promoter (3, 17). The performance of the murine leukemia virus LTR is more complex. The high level of activity of the LTR demonstrated in our study is consistent with the data of Snyder et al., who achieved substantial levels of factor IX with a similar vector (18), but is discordant with the results of Koeberl et al., where expression of alkaline phosphatase and factor IX from the LTR was low (13).
Additional studies were performed to evaluate the molecular state of
the AAV genome in recipients. Livers were harvested from selected
animals at 14 weeks after vector infusion and subjected to DNA
hybridization analysis, the results of which are presented in Fig.
2. The total content of proviral DNA in
liver was evaluated by digesting cellular DNA with enzymes that release
an internal 800-bp fragment followed by DNA hybridization with human
-1AT used as a probe (Fig. 2A). Proviral DNA was detected in livers from each animal, ranging from approximately 0.1 to 2 proviral copies
per diploid genome. Undigested DNA produced a smear without a discrete
band (Fig. 2B, lane 1). DNA restricted with endonucleases that contain
a single site within the provirus yielded discrete bands whose apparent
molecular weights were equivalent to that of the provirus (Fig. 2B,
lanes 2 and 3). A smaller band of equal intensity was observed when
total cellular DNA was restricted with two endonucleases that together
release a 3.1-kb internal fragment (Fig. 2B, lane 4). These data
are most consistent with a model in which AAV exists as an integrated
head-to-tail concatamer similar to what is seen with latent
AAV infection (14, 15, 19) and muscle transduced with AAV
vectors (4, 21).
|
A number of histological analyses were performed to evaluate the
frequency and distribution of AAV transduction following intraportal
infusion. Immunohistochemical hybridization analysis with an antibody
to human
-1AT probe revealed staining over ~5% of hepatocytes
throughout the liver (Fig.
3A to E) that was
not found in mock-infected animals (data not shown). More
transgene-expressing cells were clustered around central veins
(Fig. 3B and C) than around portal triads (Fig. 3D and E). Similar
frequency and distribution of transgene-expressing cells were found by
in situ hybridization with a probe to human
-1AT (Fig. 3F to J).
This does not agree with the findings of Snyder et al., who claimed
expression of AAV-encoded tyrosine hydroxylase in cells around
periportal regions (18). In our study, the pericentral
localization of transduction was observed with each promoter, including
the one used by Snyder et al., suggesting that other
differences must play a role (e.g., method of delivery). The
reasons for the observed gradient of transduction are unclear although
not unexpected, considering that many genes demonstrate a gradient of
expression along the portal to the central hepatic axis (9).
|
Data provided in this report and in the report of Snyder et al. (18) clearly support the use of AAV for targeting to hepatocytes genes that encode secreted proteins. What is the potential of AAV for treatment of metabolic diseases where the hepatocyte serves a catabolic or metabolic function, such as in familial hypercholesterolemia or urea cycle disorders? In situ hybridization and immunohistochemistry revealed transduction in 5% of hepatocytes following infusion of 1011 vector genomes of recombinant AAV. Increased catabolic/metabolic capacity would best be achieved if transgene expression was distributed throughout a greater number of hepatocytes. Transgene expression appears to be proportional to dose up to 1011 vector genomes per injection, suggesting that increased doses will lead to more transduced hepatocytes. Direct confirmation of this hypothesis will require improved methods of AAV production to allow injection of higher vector doses.
In summary, AAV appears to be a viable alternative to adenoviruses and nonviral vectors for in vivo gene therapy to the liver. The advantages of immune evasion that attend their use in muscle (8) need to be confirmed in the liver, although preliminary results in immunocompetent mice suggest that elimination of AAV-transduced hepatocytes by cytotoxic T lymphocytes will not be as much of a problem as has been observed with adenoviruses (data not shown). A better understanding of the mechanism and distribution of proviral integration is needed.
| |
ACKNOWLEDGMENTS |
|---|
We acknowledge the Vector and Cell Morphology Cores of the Institute for Human Gene Therapy and the technical support of Marcia Houston-Leslie, Rosalind Barr, Melissa Casey, and Sarah Ehlen-Haecker.
This work was supported by grants from the NIH (P01 HD32649-04 and P30 DK47757-05 [to J. M. Wilson]) and by Genovo, Inc., a company J. M. Wilson founded and has equity in.
| |
FOOTNOTES |
|---|
* Corresponding author. Mailing address: 204 Wistar, 3601 Spruce St., Philadelphia, PA 19104-4268. Phone: (215) 898-3000. Fax: (215) 898-6588. E-mail: wilsonjm{at}mail.med.upenn.edu.
| |
REFERENCES |
|---|
|
|
|---|
| 1. |
Bennett, J.,
D. Duan,
J. Engelhardt, and A. M. Maguire.
1997.
Real-time non-invasive in vivo assessment of adeno-associated virus-mediated retinal transduction.
Investig. Ophthalmol. Vis. Sci.
38:2857-2863 |
| 2. |
Dranoff, G.,
E. Jaffee,
A. Lazenby,
P. Golumbek,
H. Levitsky,
K. Brose,
V. Jackson,
H. Hamada,
D. Pardoll, and R. C. Mulligan.
1993.
Vaccination with irradiated tumor cells engineered to secrete murine granulocyte-macrophage colony-stimulating factor stimulates potent, specific, and long-lasting anti-tumor immunity.
Proc. Natl. Acad. Sci. USA
90:3539-3543 |
| 3. | Fisher, K. J., G.-P. Gao, M. D. Weitzman, R. DeMatteo, J. F. Burda, and J. M. Wilson. 1996. Transduction with recombinant adeno-associated virus for gene therapy is limited by leading-strand synthesis. J. Virol. 70:520-532[Abstract]. |
| 4. | Fisher, K. J., K. Jooss, J. Alston, Y. Yang, S. E. Haecker, K. High, R. Pathak, S. E. Raper, and J. M. Wilson. 1997. Recombinant adeno-associated virus for muscle-directed gene therapy. Nat. Med. 3:306-312[Medline]. |
| 5. |
Flannery, J. G.,
S. Zolotukhin,
M. I. Vaquero,
M. M. LaVail,
N. Muzyczka, and W. W. Hauswirth.
1997.
Efficient photoreceptor-targeted gene expression in vivo by recombinant adeno-associated virus.
Proc. Natl. Acad. Sci. USA
94:6916-6921 |
| 6. | Fraser, R., B. R. Dobbs, and G. W. T. Rogers. 1995. Lipoproteins and the liver sieve: the role of fenestrated sinusoidal endothelium in lipoprotein metabolism, atherosclerosis, and cirrhosis. Hepatology 3:863-874. |
| 7. | Jaffe, H. A., C. Danel, G. Longenecker, M. Metzger, Y. Setoguchi, M. A. Rosenfeld, T. W. Gant, S. S. Thorgeirsson, L. D. Stratford-Perricaudet, M. Perricaudet, A. Pavirani, J.-P. Lecocq, and R. G. Crystal. 1992. Adenovirus-mediated in vivo gene transfer and expression in normal rat liver. Nat. Genet. 1:372-378[Medline]. |
| 8. |
Jooss, K.,
Y. Yang,
K. J. Fisher, and J. M. Wilson.
1998.
Transduction of dendritic cells by DNA viral vectors directs the immune response to transgene products in muscle fibers.
J. Virol.
72:4212-4223 |
| 9. | Jungerman, K. 1995. Zonation of metabolism and gene expression in liver. Histochemistry 103:81-91[Medline]. |
| 10. | Kaplitt, M. G., P. Leone, R. J. Samulski, X. Xiao, D. W. Pfaff, K. L. O'Malley, and M. J. During. 1994. Long-term gene expression and phenotypic correction using adeno-associated virus vectors in the mammalian brain. Nat. Genet. 8:148-154[Medline]. |
| 11. | Kay, M. A., F. Graham, F. Leland, and S. L. C. Woo. 1995. Therapeutic serum concentrations of human alpha-1-antitrypsin after adenoviral-mediated gene transfer into mouse hepatocytes. Hepatology 21:815-819[Medline]. |
| 12. |
Kessler, P. D.,
G. M. Podsakoff,
X. Chen,
S. A. McQuiston,
P. C. Colosi,
L. A. Matelis,
G. J. Kurtzman, and B. J. Byrne.
1996.
Gene delivery to skeletal muscle results in sustained expression and systemic delivery of a therapeutic protein.
Proc. Natl. Acad. Sci. USA
93:14082-14087 |
| 13. |
Koeberl, D. D.,
I. E. Alexander,
C. L. Halbert,
D. W. Russell, and A. D. Miller.
1997.
Persistent expression of human clotting factor IX from mouse liver after intravenous injection of adeno-associated virus vectors.
Proc. Natl. Acad. Sci. USA
94:1426-1431 |
| 14. |
McLaughlin, S. K.,
P. Collis,
P. L. Hermonat, and N. Muzcyzka.
1988.
Adeno-associated virus general transduction vectors: analysis of proviral structures.
J. Virol.
62:1963-1973 |
| 15. | Muzcyzka, N. 1992. Use of adeno-associated virus as a general transduction vector in mammalian cells. Curr. Top. Microbiol. Immunol. 158:97-129[Medline]. |
| 16. |
Pinkert, C. A.,
D. M. Ornitz,
R. L. Brinster, and R. D. Palmiter.
1987.
An albumin enhancer located 10 kb upstream functions along with its promoter to direct efficient, liver-specific expression in transgenic mice.
Genes Dev.
1:268-276 |
| 17. | Ponnazahan, S., P. Mukherjee, M. C. Yoder, X.-S. Wang, S. Z. Zhou, J. Kaplan, S. Wadsworth, and A. Srivastava. 1996. Adeno-associated virus 2-mediated gene transfer in vivo: organ-tropism and expression of transduced sequences in mice. Gene 190:203-210. |
| 18. | Snyder, R. O., C. H. Miao, G. A. Patijn, S. K. Spratt, O. Danos, D. Nagy, A. M. Brown, B. Winther, L. Meuse, L. K. Cohen, A. R. Thompson, and M. A. Kay. 1997. Persistent and therapeutic concentrations of human factor IX in mice after hepatic gene transfer of recombinant AAV vectors. Nat. Genet. 16:270-276[Medline]. |
| 19. |
Tratschin, J.-D.,
I. L. Miller,
M. G. Smith, and B. J. Carter.
1985.
Adeno-associated virus vector for high-frequency integration, expression, and rescue of genes in mammalian cells.
Mol. Cell. Biol.
5:3251-3260 |
| 20. |
Wu, G., and C. H. Wu.
1988.
Receptor-mediated gene delivery and expression in vivo.
J. Biol. Chem.
263:14621-14624 |
| 21. | Xiao, X., J. Li, and R. J. Samulski. 1996. Efficient long-term gene transfer into muscle tissue of immunocompetent mice by adeno-associated virus vectors. J. Virol. 70:8098-8108[Abstract]. |
| 22. |
Yang, Y.,
F. A. Nunes,
K. Berencsi,
E. E. Furth,
E. Gönczöl, and J. M. Wilson.
1994.
Cellular immunity to viral antigens limits E1-deleted adenoviruses for gene therapy.
Proc. Natl. Acad. Sci. USA
91:4407-4411 |
| 23. |
Ye, X.,
M. B. Robinson,
M. L. Batshaw,
E. E. Furth,
I. Smith, and J. M. Wilson.
1996.
Prolonged metabolic correction in adult ornithine transcarbamylase deficient mice with adenoviral vectors.
J. Biol. Chem.
271:3639-3646 |
| 24. |
Zhu, N.,
D. Liggett,
Y. Liu, and R. Debs.
1993.
Systemetric gene expression after intravenous DNA delivery into adult mice.
Science
261:209-211 |
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»