Anti-adenovirus immune responses in rats are enhanced by interleukin 4 but not interleukin 10 produced by recombinant adenovirus

Expression of heme oxygenase-1 in neural stem/progenitor cells as a potential mechanism to evade host immune response

Besides their therapeutic benefit as cell source, neural stem/progenitor cells (NSPCs) exhibit immunosuppressive properties of great interest for modulating immune response in the central nervous system. To decipher the mechanisms of NSPC-mediated immunosuppression, activated T cells were exposed to NSPCs isolated from fetal rat brains. Analyses revealed that NSPCs inhibited T-cell proliferation and interferon-gamma production in a dose-dependent manner. A higher proportion of helper T cells (CD4+ T cells) was found in the presence of NSPCs, but analyses of FoxP3 population indicated that T-cell suppression was not secondary to an induction of suppressive regulatory T cells (FoxP3+ CD4+ CD25+). Conversely, induction of the high affinity interleukin-2 (IL-2) receptor (CD25) and the inability of IL-2 to rescue T-cell proliferation suggest that NSPCs display immunosuppressive activity without affecting T-cell activation. Cultures in Transwell chambers or addition of NSPC-conditioned medium to activated T cells indicated that part of the suppressive activity was not contact dependent. We therefore searched for soluble factors that mediate NSPC immunosuppression. We found that NSPCs express several immunosuppressive molecules, but the ability of these cells to inhibit T-cell proliferation was only counteracted by heme oxygenase (HO) inhibitors in association or not with nitric oxide synthase inhibitors. Taken together, our findings highlight a dynamic crosstalk between NSPCs and T lymphocytes and provide the first evidence of an implication of HO-1 in mediating the immunosuppressive effects of the NSPCs.

Anti-CD28 antibodies modify regulatory mechanisms and reinforce tolerance in CD40Ig-treated heart allograft recipients

Blockade of CD40-CD40 ligand (CD40L) costimulation has been shown to synergize with that of CTLA4/CD28-B7 to promote transplant tolerance. To date, however, CD28-B7 interactions have been prevented using B7-blocking reagents like CTLA4-Ig that inhibit CD28-B7 together with CTLA4-B7 interactions. In this study, we have tested anti-CD28 Abs to prevent selectively CD28-B7 interactions while preserving CTLA4-B7 in addition to CD40-CD40L blockade. In the LEW.1W to LEW.1A rat combination, interfering with CD40-CD40L interactions by CD40Ig administration through gene transfer resulted in indefinite heart allograft survival due to the appearance of clonotypic CD8+CD45RClow regulatory T cells that were capable of transferring the tolerant state to naive animals. However, cardiac transplants in these recipients systematically developed chronic rejection lesions. Whereas anti-CD28 Ab monotherapy only delayed acute rejection and failed to induce tolerance, coadministration of anti-CD28 Abs and CD40Ig resulted in the long-term acceptation of allografts without chronic rejection lesions in 60% of the recipients, reduced the level of intragraft mRNA transcripts for cytokines and immune factors, and fully abrogated alloantibody production. In addition, the nature of regulatory cells was modified: the CD8+CD45RClow clonotypic T cells described in the CD40Ig-treated animals could not be found in cotreated animals, and the other CD8+CD45RClow cells had no regulatory activity and a different cytokine expression profile. Instead, in cotreated recipients we found IDO-dependent non-T cells with regulatory activity in vitro. Thus, the addition of a short-term anti-CD28 treatment with CD40Ig resulted in decreased heart allograft chronic rejection lesions, complete inhibition of Ab production, and modified regulatory mechanisms.

Dual role of interleukin-4 (IL-4) in pulmonary paracoccidioidomycosis: endogenous IL-4 can induce protection or exacerbation of disease depending on the host genetic pattern

Resistance to paracoccidioidomycosis, the most important endemic mycosis in Latin America, is thought to be primarily mediated by cellular immunity and the production of gamma interferon. To assess the role of interleukin-4 (IL-4), a Th2 cytokine, pulmonary paracoccidioidomycosis in IL-4-depleted susceptible (B10.A) and intermediate (C57BL/6) mice was studied. Two different protocols were used to neutralize endogenous IL-4 in B10.A mice: 1 mg of anti-IL-4 monoclonal antibody (MAb)/week and 8 mg 1 day before intratracheal infection with 10(6) Paracoccidioides brasiliensis yeast cells. Unexpectedly, both protocols enhanced pulmonary infection but did not alter the levels of pulmonary cytokines and specific antibodies. Since in a previous work it was verified that C57BL/6 mice genetically deficient in IL-4 were more resistant to P. brasiliensis infection, we also investigated the effect of IL-4 depletion in this mouse strain. Treatment with the MAb at 1 mg/week led to less severe pulmonary disease associated with impaired synthesis of Th2 cytokines in the lungs and liver of control C57BL/6 mice. Conversely, in IL-4-depleted C57BL/6 mice, increased levels of tumor necrosis factor alpha and IL-12 were found in the lungs and liver, respectively. In addition, higher levels of immunoglobulin G2a (IgG2a) and lower levels of IgG1 antibodies were produced by IL-4-depleted mice than by control mice. Lung pathologic findings were equivalent in IL-4-depleted and untreated B10.A mice. In IL-4-depleted C57BL/6 mice, however, smaller and well-organized granulomas replaced the more extensive lesions that developed in untreated mice. These results clearly showed that IL-4 can have a protective or a disease-promoting effect in pulmonary paracoccidioidomycosis depending on the genetic background of the host.

The role of TNF-related activation-induced cytokine-receptor activating NF-kappa B interaction in acute allograft rejection and CD40L-independent chronic allograft rejection

We analyzed the role of TNF-related activation-induced cytokine (TRANCE), a member of the TNF family expressed on activated T cells that shares functional properties with CD40L, and its receptor-activating NF-kappaB (RANK) which is mostly expressed on mature dendritic cells, during allogenic responses in vivo using a rodent heart allograft model. TRANCE mRNA was strongly up-regulated in acutely rejected allografts on days 4 and 5 posttransplantation whereas RANK was detected as early as day 1 but did not show further up-regulation during the first week. Immunofluoresence analyses of heart allografts showed that 80 and 100% of TRANCE and RANK-expressing cells were T cells and APCs, respectively. We show for the first time that short-term TRANCE blockade using a mouse RANKIg fusion molecule can significantly prolong heart allograft survival in both rat and mouse models. Similarly, rat heart allografts transduced with a RANKIg encoding recombinant adenovirus exhibited a significant prolongation of survival (14.3 vs 7.6 days, p < 0.0001). However, TRANCE blockade using RANKIg did not appear to inhibit allogeneic T and B cell priming humoral responses against RANKIg. Interestingly, TRANCE blockade induced strong up-regulation of CD40 ligand (CD40L) mRNA in allografts. Combined CD40L and TRANCE blockade resulted in significantly decreased chronic allograft rejection lesions as well as allogeneic humoral responses compared with CD40L blockade alone. We conclude that TRANCE-RANK interactions play an important role during acute allograft rejection and that CD40L-independent allogeneic immune responses can be, at least in part, dependent on the TRANCE pathway of costimulation.

Suppression of experimental crescentic glomerulonephritis by interleukin-10 gene transfer

BACKGROUND

Investigated were effects of overexpression of interleukin-10 (IL-10) on the outcome and progression of crescentic glomerulonephritis in Wistar-Kyoto (WKY) rats.

METHODS

Rats were singly or simultaneously injected with antiglomerular basement membrane (a-GBM) antibody and adenoviral vector encoding rat IL-10 (Ad-rIL-10) or LacZ (Ad-LacZ) (3 x 1010 pfu/rat) intravenously, and were sacrificed at day 7. Their kidneys and other organs were isolated and examined by histology and immunohistochemistry. The In vivo expression of IL-10 mRNA in the liver of Ad-rIL-10-injected rats was confirmed by both reverse transcription-polymerase chain reaction (RT-PCR) and ribonuclease protection assay analysis and its translated protein was measured in the serum by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The exogenous IL-10 mRNA was strongly expressed in the liver in a dose-dependent manner and was intense at days 4 and 7 but was less intense at day 14. Ad-rIL-10 treatment significantly reduced the incidence of glomerular crescent formation from 67%+/- 1.9% in a-GBM antibody-treated group or 69.8%+/- 1.9% in a-GBM antibody + Ad-LacZ-treated group to 21.6%+/- 1.8% (P < 0.001), the glomerular infiltration of macrophages from 35.7 +/- 6.3 cell s/gcs (a-GBM antibody) or 37.6 +/- 8.6 cells/gcs (both a-GBM antibody + Ad-LacZ) to 17.9 +/- 5.5 cells/gcs (P < 0.001), that of major histocompatibility complex (MHC) class II-positive cells from 14.4 +/- 5.3 cells/gcs (a-GBM antibody) or 15 +/- 4.6 cells/gcs (a-GBM antibody + Ad-LacZ) to 5.7 +/- 2.3 cells/gcs (P < 0.0001) at day 7, the glomerular and immune tissue expression of IL-1beta mRNA, as well as the proteinuria from 159.0 +/- 22.7 mg/24 hours (a-GBM antibody) or 166 +/- 28 mg/24 hours (a-GBM antibody + Ad-LacZ) to 42.2 +/- 35.2 mg/24 hours (P < 0.01) at day 7. The serum creatinine and blood urea nitrogen levels were also reduced from 2.8 +/- 0.1 mg/dL (a-GBM antibody) or 2.8 +/- 0.1 mg/dL (a-GBM antibody + Ad-LacZ) to 1.0 +/- 0.1 mg/dL (P < 0.001) and from 63.2 +/- 8.9 mg/dL (a-GBM antibody) or 61.3 +/- 5.2 mg/dL (a-GBM antibody + Ad-LacZ) to 27.0 +/- 4.5 mg/dL (P < 0.001), respectively. However, the glomerular accumulation of CD8+ T cells was unaffected: 5.4 +/- 1.1 cells/gcs (a-GBM antibody + Ad-rIL-10), 5.9 +/- 1.5 cells/gcs (a-GBM antibody), and 5.8 +/- 1.1 cells/gcs (a-GBM antibody + Ad-LacZ) (P= NS).

CONCLUSION

IL-10 gene transfer significantly attenuated the glomerular lesions and injury in the anti-GBM crescentic glomerulonephritis of WKY rats.

Adenoviral delivery of soluble VEGF receptor 1 (sFlt-1) abrogates disease activity in murine collagen-induced arthritis

The angiogenic factor VEGF promotes synovitis and bone erosion in rheumatoid arthritis (RA). Previously, we have demonstrated that VEGF expression correlates with disease severity in RA patients and in murine collagen-induced arthritis (CIA). In this study, we adopted an adenoviral gene delivery system expressing soluble VEGF receptor 1 (sFlt-1) to further study the role of VEGF in CIA. Arthritis was induced in DBA/1 mice by injection of bovine collagen. Adenoviruses expressing human soluble VEGF receptor 1 (AdvsFlt-1), or without transgene (Adv0), were injected intravenously on the first day of arthritis. We found that disease severity and paw swelling were significantly suppressed in mice receiving AdvsFlt-1, when compared to untreated or Adv0-treated mice. Expression of sFlt-1 peaked 24 h after injection, with protein detectable in the liver, synovial issue and serum, but rapidly decreased by 72 h. The effect of sFlt-1 expression on signs of disease was paralleled by reduced joint destruction and decreased expression of the vascular marker von Willebrand factor. In summary, adenoviral delivery of human soluble VEGF receptor type 1 significantly suppressed disease activity in CIA. The actions of AdvsFlt-1 are likely to be mediated by reduced synovial neovascularization, and these results support the concept that VEGF blockade may be an effective therapeutic adjunct for the treatment of RA.

CTLA4Ig adenoviral gene transfer induces long-term islet rat allograft survival, without tolerance, after systemic but not local intragraft expression

Genetic engineering using recombinant adenoviruses offers an opportunity to modify islet grafts in order to prevent allograft rejection. We have used an adenovirus coding for CTLA4Ig to compare its efficacy in preventing islet rejection depending on local or systemic production after gene transfer either into the islets or intramuscularly, respectively. Islet allograft survival was also evaluated using recombinant CTLA4Ig administered intraperitoneally or incubated ex vivo with islets prior to transplantation. Transduction of islets with 10(3) or 10(4) plaque-forming units (pfu) per islets of AdCTLA4Ig prolonged islet survival (mean +/- standard deviation [SD] days = 19.5 +/- 5.8 and 19.5 +/- 5.6, respectively, vs. 10.6 +/- 2.4 in control islets, p < 0.001), with low levels of circulating CTLA4Ig. In contrast, long-term survival (>60 days) was obtained after intramuscular injection of AdCTLA4Ig that resulted in sustained high levels of circulating CTLA4Ig. Islets incubated in vitro with CTLA4Ig did not show prolonged survival (10.3 +/- 2.5 days). Graft rejection was delayed after one injection of CTLA4Ig (23 +/- 7.6 days, p < 0.003 vs. control). Recipients of long-term surviving grafts after intramuscular AdCTLA4Ig gene transfer were not tolerant because second islet grafts of donor origin were rejected. These recipients also had a strong inhibition of humoral responses against nominal antigens, whereas animals receiving transduced islets showed normal responses. These data demonstrate that local production of CTLA4Ig after gene transfer was as efficient as a single injection of CTLA4Ig in preventing graft rejection. Furthermore, intramuscular gene transfer of CTLA4Ig was the most efficient way to induce long-term islet graft survival but no donor-specific tolerance was induced.

Bone-marrow-derived macrophages genetically modified to produce IL-10 reduce injury in experimental glomerulonephritis

Macrophages are intimately involved in the development of immune-mediated inflammation, including glomerulonephritis. We have transduced primary cultures of macrophages to express IL-10 and tested the ability of these cells to control rat nephrotoxic nephritis (NTN), a model of human glomerulonephritis. Ad-IL-10-transduced bone-marrow-derived macrophages (BMDM) produced large amounts of IL-10 in culture, and their TNF-alpha production was decreased in response to interferon-gamma and LPS. Transduced macrophages were injected into the renal artery of rats, 6 h after the induction of NTN, where they localized efficiently to inflamed rat glomeruli. Delivery of IL-10-expressing macrophages to nephritic rats produced a marked reduction in albuminuria compared with unmodified NTN or injection of Ad-null-transduced BMDM. IL-10 treatment decreased the number of glomerular ED1- and ED3-positive cells, MHC class II expression, and the number of fibrinoid lesions. Interestingly, anti-inflammatory changes in the Ad-IL-10-injected kidney were mirrored by changes in the contralateral kidney. These results highlight that Ad-IL-10-transduced macrophages infiltrate inflamed glomeruli and reduce the severity of glomerular inflammation, emphasizing the value of local delivery of genetically modified macrophages in the manipulation of inflammatory disease.

Gene transfer of heme oxygenase-1 and carbon monoxide delivery inhibit chronic rejection

The hallmark of chronic rejection is the occlusion of the artery lumen by intima hyperplasia as a consequence of leukocyte infiltration and vascular smooth muscle cell (VSMC) migration and proliferation. Heme oxygenase-1 (HO-1) is a tissue protective molecule which degrades heme into carbon monoxide (CO), free iron and biliverdin. We analyzed the effects of HO-1 gene transfer into the vessel wall using an adenoviral vector (AdHO-1) and of CO delivery in a model of chronic allogeneic aorta rejection in rats. Carbon monoxide treatment was achieved by a new pharmacological approach in transplantation using methylene chloride (MC), which releases CO after degradation. AdHO-1-mediated gene transfer into aorta endothelial cells (ECs) or CO delivery resulted in a significant reduction in intimal thickness compared to untreated or noncoding adenovirus-treated controls. Aortas transduced with AdHO-1 or treated with CO showed a reduction in the number of leukocytes as well as in the expression of adhesion molecules, costimulatory molecules and cytokines, with the gene transfer treatment displaying a more pronounced effect than the CO treatment. Conversely, CO inhibited VSMC accumulation in the intima more efficiently than AdHO-1 treatment. Gene transfer of HO-1 and pharmacological manipulation of CO are novel approaches to the analysis and treatment of chronic rejection.

lacZ transgenic rats tolerant for beta-galactosidase: recipients for gene transfer studies using lacZ as a reporter gene

Gene transfer of reporter genes may trigger immune responses against the heterologous protein resulting in shortening of gene expression and inflammation. We generated transgenic rats expressing the lacZ gene under the control of the human immunodeficiency virus type 1 (HIV-1) long-terminal repeat (LTR) (HIV-lacZ) to obtain rats with undetectable transgene expression using histologic methods, thus avoiding interference with beta-galactosidase (beta-gal) expression from gene transfer, and displaying immune tolerance toward beta-gal. LacZ transgenic mice with tolerance toward beta-gal have already been used for gene transfer but rats constitute unique animal models with several advantages compared to mice. Two transgenic lines displayed low levels of beta-gal mRNA in most organs tested, as detected only by reverse transcription-polymerase chain reaction (RT-PCR). The protein was undetectable by immunohistology and was only detected in the thymus and spleen using a sensitive enzyme-linked immunosorbent assay (ELISA). HIV-lacZ transgenic rats displayed immune tolerance to beta-gal because immunization with beta-gal resulted in markedly lower cellular and antibody responses compared to wild-type controls, whereas immunization with a nonrelated antigen, keyhole limpet hemocyanin (KLH), resulted in comparable immune responses. The usefulness of this model in gene transfer was tested using a retroviral vector, which does not elicit destructive immune responses against transduced cells. Retroviral-mediated nlslacZ gene transfer in the liver resulted in nuclear beta-gal expression for longer than 12 months in HIV-lacZ transgenic rats, whereas wild-type controls showed nuclear beta-gal expression for less than 1 month. After gene transfer of nlslacZ to the liver, antibodies, cytotoxic T lymphocytes (CTLs), and proliferation against beta-gal were detected in wild-type controls but not in HIV-lacZ transgenic rats. In conclusion, HIV-lacZ transgenic rats displaying low beta-gal expression and immune tolerance toward beta-gal are a useful tool to analyze the spatial and temporal expression of the beta-gal protein in gene transfer experiments using lacZ as a reporter gene.

Prolonged blockade of CD40-CD40 ligand interactions by gene transfer of CD40Ig results in long-term heart allograft survival and donor-specific hyporesponsiveness, but does not prevent chronic rejection

Previous work on blockade of CD40-CD40 ligand interaction in mice and primates with anti-CD40 ligand mAbs has resulted in a moderate prolongation of allograft survival without the development of true allograft tolerance. In this study, we show in rats that adenovirus-mediated gene transfer of CD40Ig sequences into the graft resulted in prolonged (>200 days) expression of CD40Ig and in long-term (>300 days) survival. Recipients expressing CD40Ig displayed strongly (>90%) inhibited mixed leukocyte reactions and alloantibody production at early (days 5 and 17) and late time points (>100 day) after transplantation, but showed limited inhibition of leukocyte infiltration and cytokine production as evaluated by immunohistology at early time points (day 5). Recipients of long-surviving hearts showed donor-specific hyporesponsiveness since acceptance of second cardiac allografts was donor specific. Nevertheless, long-term allografts (>100 days) displayed signs of chronic rejection vasculopathy. Occluded vessels showed leukocyte infiltration, mainly composed of CD4(+) and CD8(+) cells, macrophages, and mast cells. These recipients also showed antidonor CTL activity. Recipients expressing CD40Ig did not show nonspecific immunosuppression, as they were able to mount anticognate immune responses that were partially inhibited at early time points and were normal thereafter. We conclude that gene transfer-mediated expression of CD40Ig resulted in a highly efficient inhibition of acute heart allograft rejection in rats. This treatment induced donor-specific inhibition of certain alloreactive mechanisms in the short-, but not the long-term, which resulted in long-term survival of allografts concomitant with the development of chronic rejection.

Pattern of alloimmune response in second same donor allografts after induction of tolerance using CTLA4Ig

BACKGROUND

The pattern of allograft acceptance in the presence of costimulatory blockade is manifested by the sequential appearance of Th1 cells, followed by Th2 cells. The aim of this study was to examine whether this phenomenon repeats itself after second same donor allotransplantation, hoping to determine whether acceptance in this setting provokes a predominance of the Th2 response.

METHODS

Tolerance was achieved by transplantation of CTLA4Ig-transduced ACI liver allografts in Lewis recipients. Recipient long-term survivors received a second transplant, consisting of a cervical heterotopic heart from the same ACI donor strain. Animals were sacrificed at predetermined intervals following the second transplant and the heart and liver were processed for histology and cytokine mRNA expression.

RESULTS

Recipients of CTLA4Ig-transduced livers survived indefinitely. Rechallenge with same donor strain second allograft was manifested by an anergic immune response in the second cardiac allograft, and a very mild transient infiltrate within the first accepted liver graft. Cardiac function was maintained with resolution of all infiltrates. The cytokine cascade was activated within the allografts; however, the pattern of acceptance was not associated with predominance of a specific Th subtype.

CONCLUSIONS

The pattern of acceptance of an allograft following CTLA4Ig-mediated costimulatory blockade is not related to long-term predominance of Th2 cells, a phenomenon that may be unique to the setting of a tolerant liver. It may be likely that the infiltrating lymphocytes that are dominant in the second graft are suppressed by other memory mechanisms.

The prevention and treatment of murine colitis using gene therapy with adenoviral vectors encoding IL-10

IL-10-deficient (IL-10(-/-)) mice develop colitis with many similarities to Crohn's disease. Daily IL-10 injections have a short systemic half-life and are unable to induce complete remission in IL-10(-/-) mice with established disease. In this paper, we investigate the duration, potency, and immunogenicity of gene therapy using an adenoviral vector encoding murine IL-10 (AdvmuIL-10). A single systemic injection of AdvmuIL-10 was sufficient not only to prevent the onset of colitis for at least 10 wk but also to induce clinical and histological remission in mice with established disease. In addition, AdvmuIL-10 diminished the systemic manifestations of disease, including elevated acute-phase proteins, as well as the local consequences of inflammation such as raised stool IL-1beta concentrations. Both IL-10 protein and the effects of secreted IL-10 were detectable for 10 wk after AdvmuIL-10 injection. Furthermore, the immunoregulatory effect of a single AdvmuIL-10 injection was manifest both by a reduction in TNF-alpha, IFN-gamma, and RANTES release from stimulated splenocyte cultures, and also by a change in the proportion of CD45RB(high/low) lymphocytes in the spleen compared with control mice. The delivery of AdvmuIL-10 resulted in a significantly diminished host antiadenoviral response compared with control adenoviral vectors. Thus, gene therapy strategies using adenoviral vectors encoding immunoregulatory and antiinflammatory cytokines may prove to be a potent approach for the treatment of chronic inflammatory disease. Antiinflammatory cytokine expression protects against immune responses directed at gene vectors.

Paradoxical effects of tissue inhibitor of metalloproteinases 1 gene transfer in collagen-induced arthritis

OBJECTIVE

The imbalance between matrix metalloproteinases (MMPs) 1, 3, and 9 and their specific inhibitor, tissue inhibitor of metalloproteinases 1 (TIMP-1), is a critical step in cartilage injury and angiogenesis in arthritis. To explore the therapeutic potential of TIMP-1 gene transfer in erosive arthritis, the effects of an adenoviral vector (Ad-TIMP-1) were assessed in DBA/1 mice with collagen-induced arthritis (CIA).

METHODS

DBA/1 mice with CIA received an intravenous injection of replication-deficient adenovirus containing the human TIMP-1 gene or a control LacZ gene on day 28 postimmunization. The efficiency of gene transfer was determined by serum TIMP-1 detection, measurements of paw swelling, as well as radiologic and histologic examination of the paws.

RESULTS

A single administration of Ad-TIMP-1 resulted in detectable serum levels of the exogenous protein for at least 13 days. The incidence and onset of arthritis were not statistically modified after human TIMP-1 gene transfer in DBA/1 mice compared with control mice. However, the severity of inflammation was statistically significantly increased in Ad-TIMP-1-treated mice and a similar trend was observed in the histologic and radiologic scores. With regard to the mechanisms of the worsened effect in the Ad-TIMP-1-treated mice, we observed 1) higher serum levels of anti-type II collagen IgG2a, 2) a significant increase in endogenous soluble tumor necrosis factor receptor I (TNFRI) in sera, and 3) increased labeling of mouse tumor necrosis factor alpha and TNFRI within arthritic joints.

CONCLUSION

These findings show that overexpression of TIMP-1 does not prevent osteochondral injury in a mouse model of arthritis. Since MMPs have overlapping properties in terms of their roles in extracellular matrix degradation, angiogenesis, and shedding of cell surface adhesion molecules, cytokines, and cytokine receptors, the paradoxical results obtained suggest that TIMP-1 is probably not the main inhibitor to target.

Lethal hepatitis after gene transfer of IL-4 in the liver is independent of immune responses and dependent on apoptosis of hepatocytes: a rodent model of IL-4-induced hepatitis

The putative role of IL-4 in human and animal models of hepatitis has not yet been directly determined. We now report that direct expression of IL-4 in the liver of rats or mice using recombinant adenoviruses coding for rat or mouse IL-4 (AdrIL-4 and AdmIL-4, respectively) results in a lethal, dose-dependent hepatitis. The hepatitis induced by IL-4 was characterized by hepatocyte apoptosis and a massive monocyte/macrophage infiltrate. IL-4-induced hepatitis was independent of T cell-mediated immune responses. Hepatitis occurred even after gene transfer of IL-4 into nude rats, CD8-depleted rats, cyclosporine A-treated rats, or recombinase-activating gene 2(-/-) immunodeficient mice. Peripheral depletion of leukocytes using high doses of cyclophosphamide, and/or the specific depletion of liver macrophages with liposome-encapsulated dichloromethylene diphosphonate in rats did not block lethal IL-4-induced hepatitis. Direct transduction of hepatocytes with adenoviruses was not essential, since injection of AdrIL-4 into the hind limb induced an identical hepatitis. Finally, primary rat hepatocytes in culture also showed apoptosis when cultured in the presence of rIL-4. IL-4-dependent hepatitis was associated with increases in the intrahepatic levels of IFN-gamma, TNF-alpha, and Fas ligand. Administration of AdmIL-4 to IFN-gamma, TNF-alpha receptor type I, or TNF-alpha receptor type II knockout mice also resulted in lethal hepatitis, whereas a moderate protection was observed in Fas-deficient lpr mice. IL-4-dependent hepatocyte apoptosis could be abolished by treatment with caspase inhibitory peptides. Our results thus demonstrate that IL-4 causes hepatocyte apoptosis, which is only partially dependent on the activation of Apo-1-Fas signaling and is largely independent of any immune cells in the liver.

Tolerance to cardiac allografts via local and systemic mechanisms after adenovirus-mediated CTLA4Ig expression

Blockade of the CD28/B7 T cell costimulatory pathway prolongs allograft survival and induces tolerance in some animal models. We analyzed the efficacy of a CTLA4Ig-expressing adenovirus in preventing cardiac allorejection in rats, the mechanisms underlying heart transplant acceptance, and whether the effects of CTLA4Ig were restricted to the graft microenvironment or were systemic. CTLA4Ig gene transfer into the myocardium allowed indefinite graft survival (>100 days vs 9 +/- 1 days for controls) in 90% of cases, whereas CTLA4Ig protein injected systemically only prolonged cardiac allograft survival (by up to 22 days). CTLA4Ig could be detected in the graft and in the serum for at least 1 year after gene transfer. CTLA4Ig gene transfer induced local intragraft immunomodulation at day 5 after transplantation, as shown by decreased expression of the IL-2R and MHC II Ags; decreased levels of mRNA encoding for IFN-gamma, inducible NO synthase, and TGF-beta; and inhibited proliferative responses of graft-infiltrating cells. Systemic immune responses were also down-modulated, as shown by the suppression of Ab production against donor alloantigens and cognate Ags, up to at least 120 days after gene transfer. Alloantigenic and mitogenic proliferative responses of graft-infiltrating cells and total splenocytes were inhibited and were not reversed by IL-2. In contrast, lymph node cells and T cells purified from splenocytes showed normal proliferation. Recipients of long-term grafts treated with adenovirus coding for CTLA4Ig showed organ and donor-specific tolerance. These data show that expression of CTLA4Ig was high and long lasting after adenovirus-mediated gene transfer. This expression resulted in down-modulation of responses against cognate Ags, efficient suppression of local and systemic allograft immune responses, and ultimate induction of donor-specific tolerance.

Interleukin-10 produced by recombinant adenovirus prolongs survival of cardiac allografts in rats

Interleukin-10 (IL-10) and interleukin-4 (IL-4), two Th2-derived cytokines, are molecules with anti-inflammatory and immunodeviating properties whose direct expression in allografts may prolong graft survival. Recombinant adenoviruses represent efficient vectors for gene transfer in quiescent cells in vivo. Adenoviral vectors encoding rat IL-10 (AdIL-10), rat IL-4 (AdIL-4) or beta-galactosidase (AdlacZ) or without transgene (Addl324) were injected directly into rat hearts at the time of transplantation in order to test their potential to prolong heart allograft survival. Expression of vectorized sequences was confirmed in heart biopsies, and kinetic analysis of beta-galactosidase showed transient expression. Cardiac allograft survival was significantly prolonged after administration of 10(9) p.f.u. of AdIL-10 (16.6 +/- 3.2 days, P < 0.05), but not AdIL-4 (9.8 +/- 1.6 days), compared with Addl324-treated (9.3 +/- 3.3 days) or untreated groups (7.8 +/- 1.5 days). Immunohistochemical analysis of allografts after gene transfer of IL-10 showed that leukocyte infiltration was quantitatively equivalent to that seen in control groups but with a strong tendency towards lower levels of CD8+ cells. Importantly, adenovirus-derived IL-10 modified the functional status of leukocytes by inducing a significant decrease in IFN-gamma production but significantly increased transforming-growth factor beta 1 (TGF-beta 1) expression within the grafts compared with those treated with Addl324. These results show that expression of IL-10 by rat hearts after gene transfer mediated by an adenoviral vector decreases allogeneic immune responses and allows prolongation of allograft survival.

Adenoviral-mediated gene transfer to mouse salivary glands

Adenoviral vectors effectively transfer genes to rat salivary glands. However, potent immune responses limit their use in vivo. Mice offer more opportunities than rats for the study of these immune processes. We first established conditions for infection of mouse salivary glands, with an adenoviral vector. The effects of time, viral dose, viral diluent buffer volume, and dexamethasone on expression of a transgene, luciferase, were determined by means of the recombinant vector AdCMVluc. Optimal luciferase expression was observed when the vector was suspended in 50 microL of buffer. This volume completely filled the gland parenchyma and slightly distended the capsule. Dexamethasone increased immediate transgene expression and reduced the acute inflammation one day following viral administration, but did not alter subsequent mononuclear inflammation or transgene expression 14 or 28 days later. An adenoviral vector encoding either anti-inflammatory cytokine IL-4 or IL-10 was co-administered with AdCMVluc to increase transgene expression at 14 and 28 days. While this strategy did not extend the duration of luciferase expression, co-administration of AdCMVIL-10 with AdCMVluc almost completely eliminated the chronic inflammatory infiltrate in the glands after 28 days. This study demonstrates that adenoviral-mediated gene transfer to mouse submandibular glands is possible by intraductal cannulation and that reduction of either the acute or chronic inflammatory infiltrates was insufficient to increase long-term transgene expression in this tissue.

TNF-alpha receptor signaling and IL-10 gene therapy regulate the innate and humoral immune responses to recombinant adenovirus in the lung

Recombinant adenovirus-mediated gene therapy has demonstrated great promise for the delivery of genes to the pulmonary epithelium. However, dose-dependent inflammation and local immune responses abbreviate transgene expression. The purpose of these studies was to determine the role of TNF-alpha and individual TNF receptor signaling to adenovirus clearance and immune responses, and whether coexpression of human IL-10 could reduce inflammation and extend the duration of transgene expression in the lung. beta-Galactosidase expression in mice receiving intratracheal instillation of Adv/beta-gal (adenovirus construct expressing beta-galactosidase) was transient (less than 14 days), but a significant early increase of beta-galactosidase expression was seen in mice lacking either or both TNF-alpha receptors. Absence of TNF-alpha or the p55 receptor significantly attenuated the Ab response to both adenovirus and beta-galactosidase. Human IL-10 expression in the lung suppressed local TNF-alpha production following AdV/hIL-10 (adenovirus construct expressing human IL-10) delivery, but did not lead to increased or prolonged transgene expression when coexpressed with beta-galactosidase. Expression of human IL-10 following AdV/hIL-10 instillation extended at least 14 days, was nonimmunogenic, and suppressed the development of neutralizing Abs against adenoviral proteins as well as against human IL-10. We conclude that TNF-alpha signaling through both the p55 and p75 receptor plays important roles in the clearance of adenoviral vectors and the magnitude of the humoral immune response. Additionally, although coexpression of human IL-10 with beta-galactosidase had only modest effects on transgene expression, we demonstrate that AdV/hIL-10 is well tolerated, has extended expression compared with beta-galactosidase, and is nonimmunogenic in the lung.