Lucio Pastore

Use of a liver-specific promoter reduces immune response to the transgene in adenoviral vectors.

Previous studies using adenoviral (Ad) vectors expressing human alpha1-antitrypsin (hAAT) under the control of ubiquitous promoters (RSV, mPGK) elicited the production of antibodies to hAAT in some mouse strains (C3H/HeJ and BALB/c) but not in others (C57BL/6J). In contrast, when a helper-dependent Ad vector (AdSTK109) with all viral coding sequences deleted and expressing hAAT from human genomic DNA with the endogenous promoter was used, C3H/HeJ mice failed to develop antibodies and demonstrated long-term expression. These results suggested that promoter choice and/or properties of the vector itself might influence the host immune response to the transgene product. Direct comparison of first-generation vectors expressing the hAAT cDNA from a ubiquitous mouse PGK promoter rather than from a liver-specific mouse albumin promoter demonstrated that an antibody response to hAAT occurred with the mPGK promoter but not with the albumin promoter in C3H/HeJ mice. As expected, neither vector elicits an antibody response in C57BL/6J mice. Coinjection of the two first-generation vectors containing the mPGK and albumin promoter in C3H/HeJ mice induced an antibody response with resulting loss of detectable hAAT from the sera of the injected mice in 3-4 weeks. From these data, we conclude that under certain conditions, the choice of promoter with its associated liver-specific expression can modulate the host immune response to the transgene independent of viral backbone.

Long-Term Stable Correction of Low-Density Lipoprotein Receptor–Deficient Mice With a Helper-Dependent Adenoviral Vector Expressing the Very Low-Density Lipoprotein Receptor

Background — Familial hypercholesterolemia (FH) that results from LDL receptor (LDLR) deficiency affects ≈1 in 500 persons in the heterozygous state and ≈1 in 1 million persons in the homozygous state. We tested a novel gene therapy strategy for the treatment of FH in a mouse model. Methods and Results — We delivered the VLDL receptor (VLDLR) to the liver of LDLR-deficient mice and compared the effect of a helper-dependent adenoviral vector with all viral coding sequences deleted (HD-Ad-mVLDLR) with a first-generation vector (FG-Ad-mVLDLR), an HD-Ad (HD-Ad-0) that contained no expression cassette, and dialysis buffer (DB). A single intravenous injection of HD-Ad-mVLDLR led to a lowering of plasma cholesterol that lasted ≥6 months. Acute liver toxicity (as measured with liver enzyme elevation) occurred after FG-Ad-mVLDLR but not after HD-Ad-mVLDLR, HD-Ad-0, or DB treatment. At 6 months, VLDLR was detected in the liver with Western blotting and with immunofluorescence staining only in HD-Ad-mVLDLR–treated mice. Aortic atherosclerosis was almost completely prevented in these animals. Conclusions — HD-Ad–mediated intravenous delivery of VLDLR to hepatocytes is well tolerated. It produces long-term lowering of plasma cholesterol and prevents atherosclerosis development in LDLR-deficient mice. These data provide support for the feasibility and safety of this approach for therapy of human subjects.

Long-term stable expression of human apolipoprotein A-I mediated by helper-dependent adenovirus gene transfer inhibits atherosclerosis progression and remodels atherosclerotic plaques in a mouse model of familial hypercholesterolemia

Background—Epidemiologic studies and transgenic mouse experiments indicate that high plasma HDL and apolipoprotein (apo) A-I protect against atherosclerosis. We used helper-dependent adenovirus (HD-Ad) gene transfer to examine the effect of long-term hepatic apoA-I expression on atherosclerotic lesion progression and remodeling in a mouse model of familial hypercholesterolemia. Methods and Results—We treated LDL receptor–deficient (LDLR−/−) mice maintained on a high-cholesterol diet for 6 weeks with either a HD-Ad containing human apoA-I gene (HD-Ad-AI) or saline (control). HD-Ad-AI treatment did not affect plasma liver enzymes but induced the appearance of plasma human apoA-I at or above human levels for the duration of the study. Substantial amounts of human apoA-I existed in lipid-free plasma. Compared with controls, HDLs from treated mice were larger and had a greater inhibitory effect on tumor necrosis factor-&agr;–induced vascular cellular adhesion molecule-1 expression in cultured endothelial cells. Twenty-four weeks after injection, aortic atherosclerotic lesion area in saline-treated mice progressed ≈700%; the rate of progression was reduced by >50% by HD-Ad-AI treatment. The lesions in HD-Ad-AI–treated mice contained human apoA-I that colocalized mainly with macrophages; they also contained less lipid, fewer macrophages, and less vascular cellular adhesion molecule-1 immunostaining but more smooth muscle cells (&agr;-actin staining) and collagen. Conclusions—HD-Ad-AI treatment of LDLR−/− mice leads to long-term overexpression of apoA-I, retards atherosclerosis progression, and remodels the lesions to a more stable-appearing phenotype. HD-Ad–mediated transfer of apoA-I may be a useful clinical approach for protecting against atherosclerosis progression and stabilizing atherosclerotic lesions associated with dyslipidemia in human patients.

S100B Induces the Release of Pro-Inflammatory Cytokines in Alveolar Type I-like Cells

S100B, a 21kDa cytosolic calcium-binding protein of the EF-hand type, present in high abundance in the brain, stimulates inflammatory responses in different cellular types inside and outside the central nervous system. Most of extracellular S100B effects are mediated by Receptor for Advanced Glycation End-products (RAGE). RAGE is highly expressed in lung by Alveolar Type-I (AT-I) cells and its activation contributes to ALI/ARDS pathogenesis. In this in-vitro study, we tested the hypothesis that S100B (0.002μg/L, 0.02μg/L, 0.5μg/L, 5μg/L) stimulates an ATI-derived cell line (R3/1) to secrete inflammatory mediators involved in lung inflammation. Our main result is that S100B stimulates R3/1 cells to secrete TNF-alpha and IL-6 (well-known pro-inflammatory cytokines in lung inflammation and neurogenic pulmonary edema), but not sICAM-1, CINC-1 or CINC-3. Soluble RAGE (sRAGE) reduced SlOOB-dependent secretion of TNF-alpha but did not decrease S100B-dependent secretion of IL-6. Moreover, in absence of S100B, sRAGE enhanced IL-6 release. This study demonstrates that in vitro S100B dose-dependently stimulated R3/1 cells, to enhance the secretion of TNF-alpha and IL-6; S100B pro-inflammatory activity might be mediated at least in part by RAGE. Besides acting as decoy receptor, sRAGE could have pro-inflammatory properties.

Adenovirus Mediated Gene Therapy in Citrullinemia: Clinical Correlations of in vivo Nitrogen Flux Measurements in Neontal Bovine Citrullinemia and in Urea Cycle Patients • 723

Adenovirus Mediated Gene Therapy in Citrullinemia: Clinical Correlations of in vivo Nitrogen Flux Measurements in Neontal Bovine Citrullinemia and in Urea Cycle Patients • 723