Inflammatory damage following first-generation replication-defective adenovirus controlled by anti-LFA-1

Adeno-associated virus serotype 9-mediated overexpression of extracellular superoxide dismutase improves recovery from surgical hind-limb ischemia in BALB/c mice

OBJECTIVE

Neovascularization is a physiologic repair process that partly depends on nitric oxide. Extracellular superoxide dismutase (EcSOD) is the major scavenger of superoxide. It is an important regulator of nitric oxide bioavailability and thus protects against vascular dysfunction. We hypothesized that overexpression of EcSOD in skeletal muscle would improve recovery from hind-limb ischemia.

METHODS

Adeno-associated virus serotype 9 (AAV9) vectors expressing EcSOD or luciferase (control) from the cytomegalovirus promoter were cross-packaged into AAV9 capsids and injected intramuscularly into the hind-limb muscles (1 × 10(11) viral genomes/limb) of 12-week-old mice. Ischemia was induced after intramuscular injections. Laser Doppler was used to measure limb perfusion on days 0, 7, and 14 after injection. Values were expressed as a ratio relative to the nonischemic limb. EcSOD expression was measured by Western blotting. Capillary density was documented by immunohistochemical staining for platelet endothelial cell adhesion molecule. Apoptosis was assessed by terminal deoxynucleotide transferase-mediated biotin-deoxy uridine triphosphate nick-end labeling and necrosis was visually evaluated daily.

RESULTS

EcSOD expression was twofold upregulated in EcSOD treated vs control ischemic muscles at day 14. Capillary density (capillaries/fiber) was 1.9-fold higher in treated (1.65 ± 0.02) vs control muscle (0.78 ± 0.17, P < .05). Recovery of perfusion ratio at day 14 after ischemia was 1.5-fold greater in EcSOD vs control mice (P < .05). The percentage of apoptotic nuclei was 1.3% ± 0.4% in EcSOD-treated mice compared with 4.2% ± 0.2% in controls (P < .001). Limb necrosis was also significantly lower in EcSOD vs control mice.

CONCLUSION

AAV9-mediated overexpression of EcSOD in skeletal muscle significantly improves recovery from hind-limb ischemia in mice, consistent with improved capillary density and perfusion ratios in treated mice.

Neo-vascularization and bone formation mediated by fetal mesenchymal stem cell tissue-engineered bone grafts in critical-size femoral defects

Tissue-engineered bone grafts (TEBG) require highly osteogenic cell sources for use in fracture repair applications. Compared to other sources of mesenchymal stem cells (MSC), human fetal MSC (hfMSC) have recently been shown to be more proliferative and osteogenic. We studied the functional performance of hfMSC-mediated TEBG in 7 mm rat femoral critical-sized bone defects (CSD). Dynamically-cultured and osteogenically-primed hfMSC seeded onto macroporous poly-epsilon-caprolactone tri-calcium phosphate scaffolds were transplanted into CSDs. After 12 weeks, hfMSC-mediated TEBG induced 2.1x more new bone formation (43.3+/-10.5 vs. 21.0+/-7.4 mm(3), p<0.05), with greater compact and woven bone, and a 9.8x increase in stiffness (3.9+/-1.7 vs. 0.4+/-0.3 mNm/degree, p<0.05) compared to acellular scaffolds, such that only animals transplanted with TEBG underwent full fracture repair of the CSD. Although hfMSC survived for <4 weeks, by 4 weeks they were associated with a 3.9x larger vasculature network in the defect area (35.2+/-11.1 vs. 6.5+/-3.6 mm(3)p<0.05), suggesting an important role for hfMSC in the promotion of neo-vasculogenesis. We speculate that hfMSC-mediated healing of the CSD by stimulating neo-vascularization through as yet undetermined mechanisms. This proof-of-principle study demonstrates the utility of primitive MSC for bone regeneration, and may be of relevance to vascularization in other areas of regenerative medicine.

Specific inhibition of interferon signal transduction pathways by adenoviral infection

Adenoviral evolution has generated strategies to resist host cell antiviral systems, but molecular mechanisms for evasion of interferon (IFN) effects by adenoviruses during late-phase infection are poorly defined. In this study, we examined adenovirus type 5 (AdV) effects on IFN-gamma-dependent gene expression and Janus family kinase-signal transducer and activator of transcription signaling components in human tracheobronchial epithelial cells. We found that AdV infection specifically inhibited IFN-gamma-dependent gene expression in airway epithelial cells without evidence of epithelial cell injury or generation of a soluble extracellular inhibitor. Furthermore, infection with AdV for 18-24 h blocked phosphorylation/activation of the Stat1 transcription factor that regulates IFN-gamma-dependent genes. Although AdV also inhibited IFN-alpha-dependent phosphorylation of Stat1 and Stat2, interleukin-4-dependent phosphorylation of the related transcription factor Stat6 was not affected, indicating that the virus selectively affected specific signaling pathways. Our results indicate that AdV inhibition of the IFN-gamma signal transduction cascade occurs through loss of ligand-induced receptor complex assembly and consequent component phosphorylation and suggest that lack of complex assembly is due to decreased expression of the IFN-gammaR2 chain of the IFN-gamma receptor. IFN-gammaR2 is required at an early step in Janus family kinase-signal transducer and activator of transcription pathway activation and is expressed at low levels in airway epithelial cells, supporting the concept that adenoviral down-regulation of the level of this IFN-gamma receptor component allows for persistent modulation of IFN-gamma-dependent gene expression.

Infection of Endothelium With E1 − E4 + , but Not E1 − E4 − , Adenovirus Gene Transfer Vectors Enhances Leukocyte Adhesion and Migration by Modulation of ICAM-1, VCAM-1, CD34, and Chemokine Expression

Abstract —Intravascular introduction of replication-deficient adenoviral vectors (Advectors) provides an ideal model of delivery of transgenes for the treatment of various vascular abnormalities. On the basis of the knowledge that Advectors can induce inflammatory responses after intravascular administration, we speculated that cellular activation by Advector infection could directly modulate the endothelial cell (EC) adhesion molecule/chemokine expression repertoire. Infection of human umbilical vein ECs or bone marrow microvascular ECs with an E1 − E4 + Advector resulted in the upregulation of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and CD34, but not E-selectin, P-selectin, CD36, CD13, CD44, HLA-DR or PECAM. Upregulation of ICAM-1, VCAM-1, and CD34 was apparent 12 hours after infection and persisted for weeks after infection. Selective induction of adhesion molecules was mediated by the presence of the E4 gene in the Advector, because infection of ECs with an E1 − E4 − Advector had no effect on adhesion molecule expression. ECs infected with E1 − E4 + Advector, but not those infected with E1 − E4 − Advector, supported the adhesion of leukocytes. Monoclonal antibodies to ICAM-1 and VCAM-1 inhibited adhesion of leukocytes to E1 − E4 + -infected ECs. Infection of the ECs with E1 − E4 + Advector, but not E1 − E4 − Advector, resulted in downregulation of expression of chemocytokines, including interleukin-8, MCP-1, RANTES, and GM-CSF. Nonetheless, a large number of leukocytes migrated through ECs infected with E1 − E4 + , but not those infected with E1 − E4 l− , in response to exogenous chemokines. These results demonstrate that infection of ECs with E1 − E4 + Advectors, but not E1 − E4 − Advectors, may directly augment inflammatory responses by upregulating expression of adhesion molecules and enhancing migration through Advector-infected ECs and suggest that E1 − E4 − Advectors may be a better choice for gene-transfer strategies directed to the ECs.

Gene transfer into inflamed glomeruli using macrophages transfected with adenovirus

In vivo gene transfer to sites of inflammatory disease provides a novel method both for studying the effects of cytokines and growth factors, and for therapeutic intervention. Macrophages play a pivotal role in the development and control of inflammation and are therefore logical cells to use for genetic modification and in vivo gene delivery. In this study we show that macrophages (both cell lines and primary cultures) can be transfected by recombinant adenoviruses expressing beta-galactosidase, that the macrophages become activated by the transfection process as determined by generation of nitric oxide and can be easily manipulated to localise to inflamed glomeruli after direct injection into the renal artery of rats with an experimentally induced glomerular inflammation caused by nephrotoxic nephritis. The injection of transfected macrophages reduces the severity of injury in this model of glomerulonephritis as shown by a reduction in the degree of albuminuria. This approach provides a favourable system for gene delivery in inflammatory disease and shows that both the functional properties of the transfected macrophage as well the transgene it is engineered to produce are relevant for in vivo gene transfer. Gene Therapy (2000) 7, 263-270.

Variability of human systemic humoral immune responses to adenovirus gene transfer vectors administered to different organs

Administration of adenovirus (Ad) vectors to immunologically naive experimental animals almost invariably results in the induction of systemic anti-Ad neutralizing antibodies. To determine if the human systemic humoral host responses to Ad vectors follow a similar pattern, we evaluated the systemic (serum) anti-Ad serotype 5 (Ad5) neutralizing antibodies in humans after administration of first generation (E1(-) E3(-)) Ad5-based gene transfer vectors to different hosts. AdGVCFTR.10 (carrying the normal human cystic fibrosis [CF] transmembrane regulator cDNA) was sprayed (8 x 10(7) to 2 x 10(10) particle units [PU]) repetitively (every 3 months or every 2 weeks) to the airway epithelium of 15 individuals with CF. AdGVCD.10 (carrying the Escherichia coli cytosine deaminase gene) was administered (8 x 10(8) to 8 x 10(9) PU; once a week, twice) directly to liver metastasis of five individuals with colon cancer and by the intradermal route (8 x 10(7) to 8 x 10(9) PU, single administration) to six healthy individuals. AdGVVEGF121.10 (carrying the human vascular endothelial growth factor 121 cDNA) was administered (4 x 10(8) to 4 x 10(9.5) PU, single administration) directly to the myocardium of 11 individuals with ischemic heart disease. Ad vector administration to the airways of individuals with CF evoked no or minimal serum neutralizing antibodies, even with repetitive administration. In contrast, intratumor administration of an Ad vector to individuals with metastatic colon cancer resulted in a robust antibody response, with anti-Ad neutralizing antibody titers of 10(2) to >10(4). Healthy individuals responded to single intradermal Ad vector variably, from induction of no neutralizing anti-Ad antibodies to titers of 5 x 10(3). Likewise, individuals with ischemic heart disease had a variable response to single intramyocardial vector administration, ranging from minimal neutralizing antibody levels to titers of 10(4). Evaluation of the data from all trials showed no correlation between the peak serum neutralizing anti-Ad response and the dose of Ad vector administered (P > 0.1, all comparisons). In contrast, there was a striking correlation between the peak anti-Ad5 neutralizing antibody levels evoked by vector administration and the level of preexisting anti-Ad5 antibodies (P = 0.0001). Thus, unlike the case for experimental animals, administration of Ad vectors to humans does not invariably evoke a systemic anti-Ad neutralizing antibody response. In humans, the extent of the response is dictated by preexisting antibody titers and modified by route of administration but is not dose dependent. Since the extent of anti-Ad neutralizing antibodies will likely modify the efficacy of administration of Ad vectors, these observations are of fundamental importance in designing human gene therapy trials and in interpreting the efficacy of Ad vector-mediated gene transfer.

Direct suppression of Stat1 function during adenoviral infection

The action of adenoviral E1A oncoprotein on host immune-response genes has been attributed to interaction with p300/CBP-type transcriptional coactivators in competition with endogenous transcription factors such as signal transducer and activator of transcription (STAT) proteins. However, we show that mutant forms of E1A that no longer bind p300/CBP can still interact directly with Stat1 (via E1A N-terminal and Stat1 C-terminal residues) and block IFNgamma-driven, Stat1-dependent gene activation and consequent function during early-phase infection in the natural host cell. The results provide a distinct and more specific mechanism for E1A-mediated immune suppression and an alternative model of IFNgamma-driven enhanceosome formation that may allow for other adaptors (in addition to p300/CBP) to link Stat1 to the basal transcription complex.