Feline immunodeficiency virus-mediated viral interleukin-10 gene transfer prolongs non-vascularized cardiac allograft survival

Gene transfer of heme oxygenase-1 using an adeno-associated virus serotype 6 vector prolongs cardiac allograft survival

Introduction. Allograft survival can be prolonged by overexpression of cytoprotective genes such as heme oxygenase-1 (HO-1). Modifications in vector design and delivery have provided new opportunities to safely and effectively administer HO-1 into the heart prior to transplantation to improve long-term graft outcome. Methods. HO-1 was delivered to the donor heart using an adeno-associated virus vector (AAV) with a pseudotype 6 capsid and vascular endothelial growth factor (VEGF) to enhance myocardial tropism and microvascular permeability. Survival of mouse cardiac allografts, fully or partially mismatched at the MHC, was determined with and without cyclosporine A. Intragraft cytokine gene expression was examined by PCR. Results. The use of AAV6 to deliver HO-1 to the donor heart, combined with immunosuppression, prolonged allograft survival by 55.3% when donor and recipient were completely mismatched at the MHC and by 94.6% if partially mismatched. The combination of gene therapy and immunosuppression was more beneficial than treatment with either AAV6-HO-1 or CsA alone. IL-17a, b, e and f were induced in the heart at rejection. Conclusions. Pretreatment of cardiac allografts with AAV6-HO-1 plus cyclosporine A prolonged graft survival. HO-1 gene therapy represents a beneficial adjunct to immunosuppressive therapy in cardiac transplantation.

Immunotherapy of viral infections

Among the microorganisms that cause diseases of medical or veterinary importance, the only group that is entirely dependent on the host, and hence not easily amenable to therapy via pharmaceuticals, is the viruses. Since viruses are obligate intracellular pathogens, and therefore depend a great deal on cellular processes, direct therapy of viral infections is difficult. Thus, modifying or targeting nonspecific or specific immune responses is an important aspect of intervention of ongoing viral infections. However, as a result of the unavailability of effective vaccines and the extended duration of manifestation, chronic viral infections are the most suitable for immunotherapies. We present an overview of various immunological strategies that have been applied for treating viral infections after exposure to the infectious agent.

Gene therapy in transplantation

Gene therapy is an exciting and novel technology that offers the prospect of improving transplant outcomes beyond those achievable with current clinical protocols. This review explores both the candidate genes and ways in which they have been deployed to overcome both immune and non-immune barriers to transplantation success in experimental models. Finally, the major obstacles to implementing gene therapy in the clinic are considered.

Lentiviral Gene Transfer of the Chemokine Antagonist RANTES 9-68 Prolongs Heart Graft Survival

BACKGROUND

Allograft tolerance might be achieved by expressing immunomodulatory proteins through gene therapy. We have evaluated the possibility of promoting significantly allograft survival in a vascularized cardiac allograft model by performing ex vivo gene transfer. We used a lentiviral vector encoding the chemokine antagonist RANTES 9-68 that is capable of competing with native RANTES.

METHODS

The Fisher donor/Lewis recipient rat strain combinations were used and all animals received for the first 5 days posttransplantation a subtherapeutic dose of cyclosporine A (1.5 mg/kg). Ex vivo gene transfer into heart allograft was performed by multiple injections of the SIN.cPPT lentiviral vector, which corresponds to the multiply attenuated, self-inactivating lentivector derived from the human immunodeficiency virus (HIV)-1.

RESULTS

About 6% of the cardiac tissue had integrated lentiviral vector, which closely matches the mean in vivo RANTES antagonist expression of 5% obtained by immunohistochemistry. In vivo RANTES 9-68 expression has significantly prolonged graft survival (median [25%-75%]: 20 [17-26] days), compared to the control 15 ([14-15] days; P=0.0007). Furthermore, hearts transduced with RANTES 9-68 showed a significant (P<0.05) reduction in cell infiltration and intragraft expression of TNF-alpha, IFN-gamma, endogenous RANTES, and TGF-beta.

CONCLUSION

Lentiviral gene transfer of RANTES 9-68 antagonist attenuates significantly the inflammatory response and delays allograft rejection, despite low levels of transduction. Future improvement of heart transduction by lentiviral vectors, as it has been achieved with other vectors, might become an attractive alternative therapy for treating allografts that require sustained gene expression for better organ preservation.

Allo-specific T-cells encoding for viral IL-10 exert strong immunomodulatory effects in vitro but fail to prevent graft rejection

Recently, we demonstrated the capacity of allo-specific gene-engineered T lymphocytes as transport vehicle for therapeutic transgenes into allografts. In this study, the influence of viral IL-10 as therapeutic transgene was addressed. Lewis rat T-cell lines specific for DA rat alloantigens were engineered to express vIL-10 by using a retroviral gene expression system. Like T regulatory 1 cells, vIL-10 transgenic T lymphocytes express the phenotype CD4(+)25(+) and secrete, in addition to vIL-10, rat IL-10 and IFN-gamma but no IL-4. First, the capacity of vIL-10 transgenic T-cell lines to modulate alloantigen-specific immune responses was evaluated in vitro. In comparison to control MLR with no transgenic cells or equal numbers of control T(EGFP)-lymphocytes, the proliferation as well as production of IFN-gamma by naive responder cells were significantly diminished. Despite this regulatory capacity in vitro, T(vIL-10)-lymphocytes were not able, either alone or in combination with suboptimal doses of Cyclosporine A, to prolong the survival of either DA rat cardiac or renal allografts in Lewis rat recipients. These data demonstrate that intra-graft IL-10 over-expression is not sufficient to prolong allograft survival in a high-responder strain combination and that the regulatory capacity of T cells in vitro does not predict their in vivo efficiency.

Viral interleukin-10-engineered autologous hematopoietic stem cell therapy: a novel gene therapy approach to prevent graft rejection

The Epstein-Barr virus-encoded protein BCRF1 (viral interleukin [vIL]-10) is a biologically active homologue of cellular interleukin (IL)-10. In this study, a novel gene therapy approach to prolong allograft survival was designed. Autologous (syngeneic) hematopoietic progenitor/stem cell-enriched (HSC; lineage(-ve)) population derived from CBA/J mouse bone marrow were transduced with retrovirus encoding vIL-10 gene (vIL-10-HSC), ex vivo; vIL-10-HSC were injected (4-6 x 10(6) cells intravenously) into lethally (9.5 Gy) or sublethally (4 Gy) irradiated CBA/J mice. Six weeks after vIL-10-HSC administration, vascular heterotopic heart (C57BL/6) transplantation was performed. Ex vivo, the vIL-10-HSC produced 5.4 +/- 0.5 ng of vIL-10 protein/2 x 10(5) cells per 24 hr. In vivo, serum vIL-10 production was 187 +/- 205 pg/ml during 3-10 weeks after vIL-10-HSC administration. Cardiac allograft survival was prolonged (p < 0.004) in lethally (71 +/- 40 days) and sublethally (114 +/- 15 days) irradiated mice that received vIL-10-HSC compared to controls that received unengineered (UE) HSC or vector DNA-engineered HSC (12-16 days). However, secondary skin graft (C57BL/6) survival was not prolonged in cardiac allograft-tolerant animals. In the vIL-10-HSC-administered group, graft histopathology demonstrated mild arteritis/venulitis (grade 0.7) and rejection (grade 1.0). Intragraft expression of costimulatory molecules (B7.1, B7.2), cytokines (IL-2, IL-4, mIL-10, interferon [IFN]-gamma), and inducible nitric oxide synthase (iNOS) molecules was markedly lower in vIL-10-HSC-treated tolerant grafts that survived more than 100 days compared to vector DNA-HSC- or UE-HSC-treated controls. Furthermore, T lymphocytes derived from vIL-10-HSC-treated tolerant recipients demonstrated hyporeactivity to donor antigens in mixed lymphocyte cultures. Administration of autologous vIL-10-engineered HSC prior to organ transplantation prolonged cardiac allograft survival significantly.

Secreted Immunomodulatory Viral Proteins as Novel Biotherapeutics

Many viruses have learned to evade or subvert the host antiviral immune responses by encoding and expressing immunomodulatory proteins that protect the virus from attack by elements of the innate and acquired immune systems. Some of these viral anti-immune regulators are expressed as secreted proteins that engage specific host immune targets in the extracellular environment, where they exhibit potent anti-immune properties. We review here viral immunomodulatory proteins that have been tested as anti-inflammatory reagents in animal models of disease caused by excessive inflammation or hyperactivated immune pathways. The potential for such viral molecules for the development of novel drugs to treat immune-based or inflammatory disorders is discussed.

Therapeutic manipulation of T cell chemotaxis in transplantation

T cell migration and trafficking are regulated by the well defined cellular processes of rolling, activation, tight adhesion, arrest and diapedesis. These processes are, in turn, controlled by molecular events involving integrins, selectins, chemokines and chemokine receptors. Recent studies have shown that sphingosine 1-phosphate receptors and their ligands are also important molecular modulators of migration and trafficking. Many of these molecules are appropriate targets for preventing allograft rejection or for achieving tolerance. Studies of migration and trafficking have also shown that the anatomic choreography of alloantigen presentation and T cell encounter with alloantigen and immunosuppression, are over-riding determinants of T cell priming versus tolerization.