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Journal of Virology, September 1999, p. 7812-7816, Vol. 73, No. 9
Laboratory of Genetics, The Salk Institute
for Biological Studies, La Jolla, California 92037
Received 5 February 1999/Accepted 3 June 1999
Retinitis pigmentosa (RP) is the most common inherited retinal
disease, in which photoreceptor cells degenerate, leading to blindness.
Mutations in the rod photoreceptor cGMP phosphodiesterase Retinitis pigmentosa (RP) is a
genetically and clinically heterogeneous group of retinal degenerative
diseases, affecting approximately 1 in 3,500 people (29).
Symptoms include night blindness, progressive loss of peripheral visual
field, and eventual loss of central vision caused by degeneration of
photoreceptor cells. There are no adequate therapies for RP at
present. However, increasing numbers of genes responsible for RP have
been identified (11, 33), providing an avenue for gene
therapy in the treatment of RP. Most of the identified genes
responsible for RP are expressed specifically in photoreceptor cells,
and degeneration primarily affects photoreceptor cells. Therefore,
methods for efficient gene transfer into terminally differentiated
photoreceptor cells are essential for gene therapy of RP.
Mutations in the rod photoreceptor cGMP phosphodiesterase
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Rescue from Photoreceptor Degeneration in the
rd Mouse by Human Immunodeficiency Virus Vector-Mediated
Gene Transfer

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ABSTRACT
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Abstract
Text
References
subunit
(PDE
) gene are found in patients with autosomal recessive RP as well
as in the rd mouse. We have recently shown that lentivirus vectors based on human immunodeficiency virus (HIV) type 1 achieve stable and efficient gene transfer into retinal cells. In this study,
we evaluated the potential of HIV vector-mediated gene therapy for RP
in the rd mouse. HIV vectors containing a gene encoding a
hemagglutinin (HA)-tagged PDE
were injected into the subretinal
spaces of newborn rd mouse eyes. One to three rows of
photoreceptor nuclei were observed in the eyes for at least 24 weeks
postinjection, whereas no photoreceptor cells remained in the eyes of
control animals at 6 weeks postinjection. Expression of HA-tagged
PDE
in the rescued photoreceptor cells was confirmed by two-color
confocal immunofluorescence analysis using anti-HA and anti-opsin
antibodies. HIV vector-mediated gene therapy appears to be a promising
means for the treatment of recessive forms of inherited retinal degeneration.
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TEXT
Top
Abstract
Text
References
subunit
(PDE
) gene are found in patients with autosomal recessive RP as well
as in rd mice and rcd1 Irish setters (10,
24, 30, 32). The rd mouse is the best-studied animal
model of RP and is characterized by a rapid photoreceptor degeneration,
although photoreceptor cells develop normally until postnatal day 7. Degeneration first appears in the rod photoreceptor cells between
postnatal days 7 and 9 and is detectable by electron microscopy, and a
majority of photoreceptor cells have degenerated by 30 days (7, 8, 31). As shown in Fig. 1, the
photoreceptor layer in the rd mice has degenerated
completely by 6 weeks of age. Transgenic rd mice that
express a functional bovine PDE
gene showed preservation of
photoreceptor cells, suggesting that somatic gene therapy to prevent
degeneration is also feasible (20). However, therapeutic gene delivery to the rd mouse eye by using adenovirus or
adeno-associated virus (AAV) vectors has been inefficient and could
only delay the degeneration (4, 9, 14, 19, 21).

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FIG. 1.
Light micrographs of retinas collected from normal (a)
and rd (b) mice at 6 weeks of age. Paraffin-embedded
sections of eyes were counterstained with toluidine blue. In the
rd mouse, the photoreceptor layer that includes the outer
segment (OS), the outer nuclear layer (ONL), and the outer plexiform
layer (OPL) has degenerated completely. RPE, retinal pigment
epithelium; INL, inner nuclear layer; IPL, inner plexiform layer; GCL,
ganglion cell layer. Original magnification, ×400.
We have developed a lentivirus vector based on human immunodeficiency virus type 1 (HIV-1) that can transduce nondividing cells in vitro and in vivo (6, 15, 27, 28). Recently, we have shown that HIV vectors can mediate efficient transfer and sustained long-term expression of the transgene in retinal cells, particularly in photoreceptor cells, when gene expression is controlled by the rhodopsin promoter (26). The present study was designed to evaluate the therapeutic potential of HIV vectors for treatment of RP.
HIV vector plasmids containing the murine PDE
cDNA under the
control of the cytomegalovirus (CMV) promoter (CMV-PDE
) or the bovine rhodopsin promoter (Rho-PDE
) were constructed by
replacing the green fluorescent protein (GFP) fragments of pHR'-CMV-GFP and pHR'-Rho-GFP (26), respectively, with the PDE
cDNA fragment of plasmid MPB-71 (2). To detect the
expression of PDE
, the hemagglutinin (HA) epitope tag was fused to
the amino terminus of PDE
. Expression of HA-tagged PDE
in vitro
was confirmed by immunoblot analysis and immunofluorescence microscopy
by using anti-HA antibody in 293T cells transfected with the CMV-PDE
vector plasmid (data not shown).
HIV vectors pseudotyped with vesicular stomatitis virus G glycoprotein
were generated as described previously (27). The titer of
HIV vectors was determined by measuring the amount of HIV-1 p24 antigen
by using enzyme-linked immunosorbent assay. Approximately 5 × 105 infectious units of HIV vectors was injected into the
subretinal space of C3H/HeJ rd/rd mouse eyes between
postnatal days 2 and 5. HIV vector containing the GFP gene under the
control of the rhodopsin promoter (Rho-GFP) was used as a control.
Altogether, 18, 58, and 60 rd mouse eyes were injected with
the Rho-GFP, the CMV-PDE
, and the Rho-PDE
vectors,
respectively. At 6, 12, and 24 weeks postinjection, mice were
sacrificed and eyes were subjected to histological and
immunohistochemical analyses. In control eyes collected at 6 weeks
postinjection, histological analysis of hematoxylin-and-eosin-stained paraffin-embedded sections demonstrated a single row of
photoreceptor-like nuclei (Fig. 2a).
However, as shown in Fig. 3d,
immunohistochemistry with an anti-opsin antibody showed no opsin
immunoreactivity, indicating that these retained cells were not
photoreceptor cells but dislocated cells in the inner nuclear layer. It
is often difficult to distinguish cell nuclei in the inner nuclear
layer from remaining pyknotic photoreceptor nuclei in the degenerated
rd mouse retina (Fig. 2b). Thus, we assessed rescue of
photoreceptor cells from degeneration by immunohistochemistry in this
study.
|
|
In eyes injected with either the Rho-PDE
vector or the CMV-PDE
vector, numerous opsin-positive photoreceptor cells were observed at 6, 12, and 24 weeks postinjection. In contrast, all control eyes injected
with the Rho-GFP vector showed no opsin-positive photoreceptor cells.
Representative results are shown in Fig. 3. Two-color confocal
immunofluorescence analysis using anti-opsin and anti-HA antibodies
indicated that most of the rescued photoreceptor cells expressed
HA-tagged PDE
(Fig. 4). As expected,
HA-tagged PDE
as well as opsin was found localized exclusively in
the outer segments of photoreceptor cells, where it normally exists.
Taken together, these results indicate that HA-tagged PDE
was
functional and that its expression was able to rescue photoreceptor
cells from degeneration. Up to three rows of photoreceptor nuclei were observed with 4',6-diamidino-2-phenylindole (DAPI) staining (Fig. 4e).
Rescued photoreceptor cells expressing PDE
were seen not only around
the injection site but also over the entire retina, suggesting that
virus particles diffused in the subretinal space. This phenomenon has
also been observed in our previous study of rat pups (26).
|
Rescued photoreceptor cells were found in 8 of 22, 10 of 28, and 3 of 8 eyes injected with the CMV-PDE
vector and in 20 of 34, 8 of 18, and
4 of 8 eyes injected with the Rho-PDE
vector at 6, 12, and 24 weeks
postinjection, respectively. Furthermore, the total number of rescued
photoreceptor cells varied greatly from eye to eye. These results were
presumably due to technical variations, since the lens opacity of
newborn mice made it difficult to confirm the successful subretinal
injection by fundus examination. In the most-successfully rescued eyes,
however, there was no significant difference in the numbers of rescued
photoreceptor cells in each group at all the periods evaluated (Fig.
5), although we previously observed that
the rhodopsin promoter was more effective than the CMV promoter in rat
photoreceptor cells (26).
|
The outer segments are continuously shed from the end of each
photoreceptor cell and phagocytosed by cells of the retinal pigment
epithelium. Therefore, constitutive expression of PDE
is required to
prevent photoreceptor degeneration and maintain the outer segments.
Others have shown that adenovirus and AAV vectors can efficiently
transfer a reporter gene to retinal cells (1, 5, 13, 22).
However, when these vectors were applied for gene therapy of RP in the
rd mouse, the therapeutic effect was inefficient and
resulted in only a delay of photoreceptor degeneration until up to 6 weeks after birth (4, 14). A major problem with the
adenovirus vectors is the transient expression of the transgene due to
a cellular immune response(s) against the transduced cells
(16), limiting the use of this vector for long-term gene
therapy. Unsuccessful results obtained with AAV vectors may be due to a
slow onset of transgene expression since it takes more than 3 weeks to
obtain maximum expression (1, 3, 13). In contrast, our
results clearly show that HIV vector-mediated PDE
gene expression
persisted for at least 24 weeks, resulting in significant rescue of
authentic photoreceptor cells detected by anti-opsin antibody. It is
unclear whether more photoreceptor cells survived at earlier time
points as others have reported (4, 9, 14, 19, 21). However,
our goal in the present study was to examine long-term rescue from
photoreceptor degeneration. This is the first study to establish the
therapeutic ability of HIV vectors by using an animal model. Long-term
rescue from photoreceptor degeneration was achieved, although only one
to three rows of photoreceptor nuclei remained in the HIV
vector-injected mice, in contrast with eight to ten rows in normal
mice. However, clinicopathologic studies in humans with RP have
suggested that a single layer of photoreceptor cells is sufficient to
maintain minimal visual function, even though electroretinogram
response is undetectable (23, 34). One possible explanation
for partial rescue from photoreceptor degeneration is that the time of
injection (postnatal days 2 to 5) was too late to rescue all
photoreceptor cells. Although photoreceptor development appears
morphologically normal until postnatal day 7 (7, 31),
degeneration at the molecular level may already be ongoing in the
majority of photoreceptor cells at the time of injection or earlier.
Another possible explanation is that the amount of PDE
provided by
HIV vectors was insufficient to rescue all photoreceptor cells. Half of
the normal expression level of PDE
is sufficient to maintain normal
photoreceptor morphology and visual function, since the RP phenotype in
the rd mouse is inherited as a recessive trait. In any case,
it will be important to ascertain when and how much PDE
is required
to rescue all photoreceptor cells.
RP is an excellent candidate for human gene therapy. Direct access to the target cells, photoreceptor cells, is possible by means of subretinal injection. In comparison with the rd mouse, humans suffering from RP show later onset and slower progression, i.e., typically onset of night blindness in childhood and progression to legal blindness by 60 years of age. In addition, only a small area of the retina, for example, a 500-µm-diameter area of macula, is sufficient to preserve minimal visual function. Thus more successful therapeutic effects could be expected in humans. HIV vector-mediated gene transfer appeared to be safe, as there were no adverse effects on the animals at any time point after injection. However, safety is still a potential concern for clinical application of HIV vectors. In this regard, recent improvements, including self-inactivating vectors (25, 35), packaging constructs eliminating all accessory genes (12, 18, 36), and inducible packaging cell lines (17), could further minimize the risk. Although further studies in animal models are required to determine the efficacy and safety of HIV vectors before human clinical trials are conducted, our results substantiate the feasibility of gene therapy for recessive forms of retinal degenerative disease.
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ACKNOWLEDGMENTS |
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M.T. and H.M. contributed equally to this work.
We thank H. Okuda for hematoxylin and eosin staining, S. Forbes for
care of the mice, and N. Somia for critical reading of the manuscript.
We also thank W. Baehr for providing murine PDE
cDNA plasmid and
C. J. Barnstable for providing mouse anti-opsin antibody.
M.T. was supported by a fellowship from the Nippon Eye Bank Association. H.M. was supported by a fellowship from the Uehara Memorial Foundation. This work was supported by grants from NIH, NIA, NINDS, March of Dimes Foundation, Frances Berger Foundation, and Valley Foundation. I.M.V. is an American Cancer Society Professor of Molecular Biology.
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FOOTNOTES |
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* Corresponding author. Mailing address: Laboratory of Genetics, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Rd., La Jolla, CA 92037. Phone: (619) 453-4100, ext. 1012. Fax: (619) 597-0824. E-mail: fgage{at}salk.edu.
Present address: Department of Ophthalmology and Visual Sciences,
Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606, Japan.
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REFERENCES |
|---|
|
|
|---|
| 1. | Ali, R. R., M. B. Reichel, M. De Alwis, N. Kanuga, C. Kinnon, R. J. Levinsky, D. M. Hunt, S. S. Bhattacharya, and A. J. Thrasher. 1998. Adeno-associated virus gene transfer to mouse retina. Hum. Gene Ther. 9:81-86[Medline]. |
| 2. |
Baehr, W.,
M. S. Champagne,
A. K. Lee, and S. J. Pittler.
1991.
Complete cDNA sequences of mouse rod photoreceptor cGMP phosphodiesterase - and -subunits, and identification of '-, a putative -subunit isozyme produced by alternative splicing of the -subunit gene.
FEBS Lett.
278:107-114[Medline].
|
| 3. |
Bennett, J.,
D. Duan,
J. F. Engelhardt, and A. M. Maguire.
1997.
Real-time, noninvasive in vivo assessment of adeno-associated virus-mediated retinal transduction.
Investig. Ophthalmol. Vis. Sci.
38:2857-2863 |
| 4. | Bennett, J., T. Tanabe, D. Sun, Y. Zeng, H. Kjeldbye, P. Gouras, and A. M. Maguire. 1996. Photoreceptor cell rescue in retinal degeneration (rd) mice by in vivo gene therapy. Nat. Med. 2:649-654[Medline]. |
| 5. |
Bennett, J.,
J. Wilson,
D. Sun,
B. Forbes, and A. Maguire.
1994.
Adenovirus vector-mediated in vivo gene transfer into adult murine retina.
Investig. Ophthalmol. Vis. Sci.
35:2535-2542 |
| 6. | Blomer, U., L. Naldini, T. Kafri, D. Trono, I. M. Verma, and F. H. Gage. 1997. Highly efficient and sustained gene transfer in adult neurons with a lentivirus vector. J. Virol. 71:6641-6649[Abstract]. |
| 7. | Caley, D. W., C. Johnson, and R. A. Liebelt. 1972. The postnatal development of the retina in the normal and rodless CBA mouse: a light and electron microscopic study. Am. J. Anat. 133:179-212[Medline]. |
| 8. |
Carter-Dawson, L. D.,
M. M. LaVail, and R. L. Sidman.
1978.
Differential effect of the rd mutation on rods and cones in the mouse retina.
Investig. Ophthalmol. Vis. Sci.
17:489-498 |
| 9. | Cayouette, M., and C. Gravel. 1997. Adenovirus-mediated gene transfer of ciliary neurotrophic factor can prevent photoreceptor degeneration in the retinal degeneration (rd) mouse. Hum. Gene Ther. 8:423-430[Medline]. |
| 10. | Danciger, M., J. Blaney, Y. Q. Gao, D. Y. Zhao, J. R. Heckenlively, S. G. Jacobson, and D. B. Farber. 1995. Mutations in the PDE6B gene in autosomal recessive retinitis pigmentosa. Genomics 30:1-7[Medline]. |
| 11. | Dryja, T. P., and T. Li. 1995. Molecular genetics of retinitis pigmentosa. Hum. Mol. Genet. 4:1739-1743[Abstract]. |
| 12. |
Dull, T.,
R. Zufferey,
M. Kelly,
R. J. Mandel,
M. Nguyen,
D. Trono, and L. Naldini.
1998.
A third-generation lentivirus vector with a conditional packaging system.
J. Virol.
72:8463-8471 |
| 13. |
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 |
| 14. | Jomary, C., K. A. Vincent, J. Grist, M. J. Neal, and S. E. Jones. 1997. Rescue of photoreceptor function by AAV-mediated gene transfer in a mouse model of inherited retinal degeneration. Gene Ther. 4:683-690[Medline]. |
| 15. | Kafri, T., U. Blomer, D. A. Peterson, F. H. Gage, and I. M. Verma. 1997. Sustained expression of genes delivered directly into liver and muscle by lentiviral vectors. Nat. Genet. 17:314-317[Medline]. |
| 16. |
Kafri, T.,
D. Morgan,
T. Krahl,
N. Sarvetnick,
L. Sherman, and I. Verma.
1998.
Cellular immune response to adenoviral vector infected cells does not require de novo viral gene expression: implications for gene therapy.
Proc. Natl. Acad. Sci. USA
95:11377-11382 |
| 17. |
Kafri, T.,
H. van Praag,
L. Ouyang,
F. H. Gage, and I. M. Verma.
1999.
A packaging cell line for lentivirus vectors.
J. Virol.
73:576-584 |
| 18. |
Kim, V. N.,
K. Mitrophanous,
S. M. Kingsman, and A. J. Kingsman.
1998.
Minimal requirement for a lentivirus vector based on human immunodeficiency virus type 1.
J. Virol.
72:811-816 |
| 19. |
Kumar-Singh, R., and D. B. Farber.
1998.
Encapsidated adenovirus minichromosome-mediated delivery of genes to the retina: application to the rescue of photoreceptor degeneration.
Hum. Mol. Genet.
7:1893-1900 |
| 20. |
Lem, J.,
J. G. Flannery,
T. Li,
M. L. Applebury,
D. B. Farber, and M. I. Simon.
1992.
Retinal degeneration is rescued in transgenic rd mice by expression of the cGMP phosphodiesterase beta subunit.
Proc. Natl. Acad. Sci. USA
89:4422-4426 |
| 21. | Lewin, A. S., K. A. Drenser, W. W. Hauswirth, S. Nishikawa, D. Yasumura, J. G. Flannery, and M. M. LaVail. 1998. Ribozyme rescue of photoreceptor cells in a transgenic rat model of autosomal dominant retinitis pigmentosa. Nat. Med. 4:967-971[Medline]. |
| 22. |
Li, T.,
M. Adamian,
D. J. Roof,
E. L. Berson,
T. P. Dryja,
B. J. Roessler, and B. L. Davidson.
1994.
In vivo transfer of a reporter gene to the retina mediated by an adenoviral vector.
Investig. Ophthalmol. Vis. Sci.
35:2543-2549 |
| 23. | Li, Z. Y., S. G. Jacobson, and A. H. Milam. 1994. Autosomal dominant retinitis pigmentosa caused by the threonine-17-methionine rhodopsin mutation: retinal histopathology and immunocytochemistry. Exp. Eye Res. 58:397-408[Medline]. |
| 24. |
McLaughlin, M. E.,
T. L. Ehrhart,
E. L. Berson, and T. P. Dryja.
1995.
Mutation spectrum of the gene encoding the beta subunit of rod phosphodiesterase among patients with autosomal recessive retinitis pigmentosa.
Proc. Natl. Acad. Sci. USA
92:3249-3253 |
| 25. |
Miyoshi, H.,
U. Blomer,
M. Takahashi,
F. H. Gage, and I. M. Verma.
1998.
Development of a self-inactivating lentivirus vector.
J. Virol.
72:8150-8157 |
| 26. |
Miyoshi, H.,
M. Takahashi,
F. H. Gage, and I. M. Verma.
1997.
Stable and efficient gene transfer into the retina using an HIV-based lentiviral vector.
Proc. Natl. Acad. Sci. USA
94:10319-10323 |
| 27. |
Naldini, L.,
U. Blomer,
F. H. Gage,
D. Trono, and I. M. Verma.
1996.
Efficient transfer, integration, and sustained long-term expression of the transgene in adult rat brains injected with a lentiviral vector.
Proc. Natl. Acad. Sci. USA
93:11382-11388 |
| 28. | Naldini, L., U. Blomer, P. Gallay, D. Ory, R. Mulligan, F. H. Gage, I. M. Verma, and D. Trono. 1996. In vivo gene delivery and stable transduction of nondividing cells by a lentiviral vector. Science 272:263-267[Abstract]. |
| 29. | Pagon, R. A. 1988. Retinitis pigmentosa. Surv. Ophthalmol. 33:137-177[Medline]. |
| 30. |
Pittler, S. J., and W. Baehr.
1991.
Identification of a nonsense mutation in the rod photoreceptor cGMP phosphodiesterase beta-subunit gene of the rd mouse.
Proc. Natl. Acad. Sci. USA
88:8322-8326 |
| 31. | Shiose, Y. 1969. Electron microscopic aspects on early changes of inherited dystrophic mouse retina. Jpn. J. Ophthalmol. 12:181-190. |
| 32. |
Suber, M. L.,
S. J. Pittler,
N. Qin,
G. C. Wright,
V. Holcombe,
R. H. Lee,
C. M. Craft,
R. N. Lolley,
W. Baehr, and R. L. Hurwitz.
1993.
Irish setter dogs affected with rod/cone dysplasia contain a nonsense mutation in the rod cGMP phosphodiesterase beta-subunit gene.
Proc. Natl. Acad. Sci. USA
90:3968-3972 |
| 33. | Sullivan, L. S., and S. P. Daiger. 1996. Inherited retinal degeneration: exceptional genetic and clinical heterogeneity. Mol. Med. Today 2:380-386[Medline]. |
| 34. |
Szamier, R. B., and E. L. Berson.
1977.
Retinal ultrastructure in advanced retinitis pigmentosa.
Investig. Ophthalmol. Vis. Sci.
16:947-962 |
| 35. |
Zufferey, R.,
T. Dull,
R. J. Mandel,
A. Bukovsky,
D. Quiroz,
L. Naldini, and D. Trono.
1998.
Self-inactivating lentivirus vector for safe and efficient in vivo gene delivery.
J. Virol.
72:9873-9880 |
| 36. | Zufferey, R., D. Nagy, R. J. Mandel, L. Naldini, and D. Trono. 1997. Multiply attenuated lentiviral vector achieves efficient gene delivery in vivo. Nat. Biotechnol. 15:871-875[Medline]. |
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