Abstract | BACKGROUND: Adeno-associated vectors (rAAV) have been used to attain long-term liver gene expression. In humans, the cellular immune response poses a serious obstacle for transgene persistence while neutralizing humoral immunity curtails re-administration. Porphobilinogen deaminase (PBGD) haploinsufficiency ( acute intermittent porphyria) benefits from liver gene transfer in mouse models and clinical trials are about to begin. In this work, we sought to study in non-human primates the feasibility of repeated gene-transfer with intravenous administration of rAAV5 vectors under the effects of an intensive immunosuppressive regimen and to analyze its ability to circumvent T-cell immunity and thereby prolong transgene expression. METHODS: Three female Macaca fascicularis were intravenously injected with 1 x 10(13) genome copies/kg of rAAV5 encoding the human PBGD. Mycophenolate mofetil (MMF), anti-thymocyte immunoglobulin, methylprednisolone, tacrolimus and rituximab were given in combination during 12 weeks to block T- and B-cell mediated adaptive immune responses in two macaques. Immunodeficient and immunocompetent mice were intravenously injected with 5 x 10(12) genome copies/kg of rAAV5-encoding luciferase protein. Forty days later MMF, tacrolimus and rituximab were daily administrated to ascertain whether the immunosuppressants or their metabolites could interfere with transgene expression. RESULTS: Macaques given a rAAV5 vector encoding human PBGD developed cellular and humoral immunity against viral capsids but not towards the transgene. Anti-AAV humoral responses were attenuated during 12 weeks but intensely rebounded following cessation of the immunosuppressants. Accordingly, subsequent gene transfer with a rAAV5 vector encoding green fluorescent protein was impossible. One macaque showed enhanced PBGD expression 25 weeks after rAAV5-pbgd administration but overexpression had not been detected while the animal was under immunosuppression. As a potential explanation, MMF decreases transgene expression in mouse livers that had been successfully transduced by a rAAV5 several weeks before MMF onset. Such a silencing effect was independent of AAV complementary strand synthesis and requires an adaptive immune system. CONCLUSIONS: These results indicate that our transient and intensive pharmacological immunosuppression fails to improve AAV5-based liver gene transfer in non-human primates. The reasons include an incomplete restraint of humoral immune responses to viral capsids that interfere with repeated gene transfer in addition to an intriguing MMF-dependent drug-mediated interference with liver transgene expression.
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Authors | Carmen Unzu, Sandra Hervás-Stubbs, Ana Sampedro, Itsaso Mauleón, Uxua Mancheño, Carlos Alfaro, Rafael Enríquez de Salamanca, Alberto Benito, Stuart G Beattie, Harald Petry, Jesús Prieto, Ignacio Melero, Antonio Fontanellas |
Journal | Journal of translational medicine
(J Transl Med)
Vol. 10
Pg. 122
(Jun 15 2012)
ISSN: 1479-5876 [Electronic] England |
PMID | 22704060
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Antigens, Viral
- DNA, Viral
- Immunosuppressive Agents
- Mycophenolic Acid
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Topics |
- Animals
- Antigens, Viral
(immunology)
- Capsid
(immunology)
- DNA, Viral
(blood)
- Dependovirus
(drug effects, metabolism)
- Female
- Gene Transfer Techniques
- Genetic Vectors
(administration & dosage, genetics)
- Humans
- Immunity
(drug effects)
- Immunity, Humoral
(drug effects, immunology)
- Immunosuppression Therapy
- Immunosuppressive Agents
(administration & dosage, pharmacology)
- Injections, Intravenous
- Liver
(drug effects, metabolism)
- Macaca fascicularis
(immunology)
- Mice
- Mice, Transgenic
- Mycophenolic Acid
(analogs & derivatives, pharmacology)
- Serotyping
- Transgenes
(genetics)
- Treatment Failure
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