Strain-specific rate of shutdown of CMV enhancer activity in murine liver confirmed by use of persistent [E1(-), E2b(-)] adenoviral vectors.

The systemic delivery of [E1(-)] adenoviral (Ad) vectors encoding a transgene results in efficient viral uptake and abundant transgene expression in the liver. However, [E1(-)]Ad vector persistence is transient due to cytotoxic T lymphocyte (CTL)-mediated loss of the Ad-infected cells. Our laboratory has previously demonstrated that additional modifications to the [E1(-)]Ad vector genome, by deletion of the Ad E2b genes, significantly decreased virus-genome-derived gene expression and simultaneously improved the long-term performance of the resultant [E1(-), E2b(-)]Ad vector. In this study, we confirmed that [E1(-), E2b(-)]Ad vector genomes could persist equally well in C57Bl/6 or Balb/c mouse hepatocytes. Despite vector genome persistence, we observed a strain-dependent variability in the duration of CMV enhancer/promoter-driven transgene expression in the liver. While Balb/c mice rapidly shut down [E1(-), E2b(-)]Ad-derived transgene expression, C57Bl/6 mice allowed for prolonged transgene expression. This occurred even when both strains were crossed into a severe combined immune-deficient background, demonstrating that host adaptive immune responses are not responsible for the phenomenon. Furthermore, differential methylation of the CMV enhancer/promoter was also not demonstrated in either strain of mouse, eliminating this mechanism as causative. Thus, alternative mechanisms for this phenomenon are discussed.

Liver toxicities typically induced by first-generation adenoviral vectors can be reduced by use of E1, E2b-deleted adenoviral vectors.

Adenoviral vectors from which the E1 region has been deleted ([E1(-)] Ad) are known to induce strong immune responses after systemic delivery. In this study we have evaluated liver toxicities in mice after intravenous injection with high doses of [E1(-)] or modified [E1(-), E2b(-)] Ad vectors (both expressing the bacterial beta-galactosidase [lacZ] marker gene) in C57BL/6, BALB/c, and SCID mice. Our data demonstrate a marked reduction in maximal liver toxicities and pathologies (typically noted at 21 days postinjection) with the use of the [E1(-), E2b(-)] modified vector in all strains of mice tested. Our data also demonstrated that despite the use of the [E1(-), E2b(-)] Ad vector, significant liver toxicities were still observed. To address this issue and the fact that the lacZ gene was perceived as a foreign antigen in the immune-competent C57BL/6 and BALB/c mice, we similarly injected mice tolerant of LacZ (lacZ-TG). In contrast to our studies in C57BL/6 and BALB/c mice, LacZ-TG mice exhibited virtually no evidence of hepatotoxicity after intravenous injection with the [E1(-), E2b(-)] vector, in contrast to use of the [E1(-)] Ad vector. Our results demonstrate that the [E1(-), E2b(-)] Ad vector class can reduce liver toxicities typically ascribed to Ad vector-mediated gene transfer after transfer of a highly immunogenic or foreign gene, whereas transfer of a transgene that is perceived as nonforeign by the host can be delivered with virtually no evidence of toxicity. On the basis of a careful review of the literature, these improvements in vector safety rival those noted with other, more significantly modified Ad vectors described to date.

Multiple muscles in the AMD quail can be "cross-corrected" of pathologic glycogen accumulation after intravenous injection of an [E1-, polymerase-] adenovirus vector encoding human acid-alpha-glucosidase.

BACKGROUND: Previously, in murine models of acid maltase deficiency (AMD), we demonstrated that intravenous administration of an improved adenovirus (Ad) vector encoding human acid alpha glucosidase (hGAA) resulted in liver transduction, followed by high-level hepatocyte-mediated secretion of hGAA into the plasma space. The hGAA secreted by the liver was taken up and targeted to muscle cell lysosomes. The levels of hGAA achieved by this approach resulted in clearance of lysosomal glycogen accumulations; in some muscle tissues the effect was prolonged (>6 months). We next wished to demonstrate whether this approach could be generalized across divergent species. To accomplish this goal, we determined whether a similar approach would also result in efficacy, but in a quail model of AMD. METHODS: An [E1-, E2b-]Ad vector encoding hGAA was intravenously injected into AMD quails. At several time points thereafter, plasma, liver, and multiple muscle tissues were assayed for evidence of hGAA gene expression, liver-mediated hGAA secretion, uptake of hGAA by skeletal muscles, and evidence of glycogen correction in AMD skeletal muscles. These results were compared with those obtained from mock-injected AMD or wild-type quails. RESULTS: Intravenous [E1-, E2b-]Ad/hGAA vector injection resulted in high-level liver transduction and hepatic secretion of precursor forms of hGAA. The hepatically secreted hGAA was found to not only be efficiently taken up by cardiac and skeletal muscles, but was also proteolytically cleaved and processed equivalently to the quail-GAA protein detected in wild-type quails. The observations suggest that the signals regulating muscle cell uptake (but not proteolytic cleavage) of lysosomal enzymes are conserved and recognized across divergent species of vertebrates. Importantly, once localized to skeletal muscle lysosomes, the hGAA was able to effectively clear the glycogen accumulations present in AMD quail muscles. CONCLUSIONS: Adenovirus-mediated transduction of the hGAA gene, followed by hepatic secretion, uptake, and cross-correction of the pathologic glycogen accumulation noted in multiple muscles of both the AMD mouse and AMD quail, adds support to the notion that gene transfer strategies (Ad-mediated or other agents) targeting liver tissues with the hGAA gene are likely to be highly efficacious in humans affected by AMD.

Long-term efficacy after [E1-, polymerase-] adenovirus-mediated transfer of human acid-alpha-glucosidase gene into glycogen storage disease type II knockout mice.

Glycogen storage disease type II (GSD-II) is a lethal, autosomal recessive metabolic myopathy caused by a lack of acid-alpha-glucosidase (GAA) activity in the cardiac and skeletal muscles. Absence of adequate intralysosomal GAA activity results in massive amounts of glycogen accumulation in multiple muscle groups, resulting in morbidity and mortality secondary to respiratory embarrassment and/or cardiomyopathy. In a mouse model of GSD-II, we demonstrate that infection of the murine liver with a modified adenovirus (Ad) vector encoding human GAA (hGAA) resulted in long-term persistence of the vector in liver tissues for at least 6 months. Despite both a rapid shutdown of hGAA mRNA expression from the vector, as well as the elicitation of anti-hGAA antibody responses (hGAA is a foreign antigen in this model), the hGAA secreted by the liver was taken up by all muscle groups analyzed and, remarkably, persisted in them for at least 6 months. The persistence of the protein also correlated with long-term correction of pathologic intramuscular glycogen accumulations in all muscle groups tested, but most notably the cardiac tissues, which demonstrated a significantly decreased glycogen content for at least 190 days after a single vector injection. The results suggest that gene therapy strategies may have the potential to significantly improve the clinical course for GSD-II patients.

Adenovirus vectors with the 100K gene deleted and their potential for multiple gene therapy applications.

The 100K protein has a number of critical roles vital for successful completion of the late phases of the adenovirus (Ad) life cycle. We hypothesized that the introduction of deletions within the 100K gene would allow for the production of a series of new classes of Ad vector, including one that is replication competent but blocked in the ability to carry out many late-phase Ad functions. Such a vector would have potential for several gene therapy applications, based upon its ability to increase the copy number of the transgene encoded by the vector (via genome replication) while decreasing the side effects associated with Ad late gene expression. To efficiently produce 100K-deleted Ad ([100K-]Ad) vectors, an E1- and 100K-complementing cell line (K-16) was successfully isolated. Transfection of an [E1-,100K-]Ad vector genome into the K-16 cells readily yielded high titers of the vector. After infection of noncomplementing cells, we demonstrated that [100K-]Ad vectors have a significantly decreased ability to express several Ad late genes. Additionally, if the E1 gene was present in the infected noncomplementing cells, [100K-]Ad vectors were capable of replicating their genomes to high copy number, but were significantly blocked in their ability to efficiently encapsidate the replicated genomes. Injection of an [E1-,100K-]Ad vector in vivo also correlated with significantly decreased hepatotoxicity, as well as prolonged vector persistence. In summary, the unique properties of [100K-]Ad vectors suggest that they may have utility in a variety of gene therapy applications.

Immune responses in goats to caprine arthritis-encephalitis virus.

In this study, goats were experimentally infected with caprine arthritis-encephalitis virus (CAEV). Anti-CAEV antibodies were detected in vivo using indirect enzyme-linked immunosorbent assay (ELISA) and Western blot assays. The results showed that the sensitivity of detection of anti-CAEV antibodies using indirect ELISA was relatively high, whereas Western blotting was very sensitive for detection of P28 anti-CAEV antibody as 4 days postinfection. Apparently, because of high immunogenicity of P28 antigen, the detection of antibodies specific for this viral protein may represent a valuable assay to detect early infection. CAEV related to other lentiviruses may be useful in studies of human immunodeficiency virus (HIV) and related viruses in animal models.