Long-term, high-level hepatic secretion of acid α-glucosidase for Pompe disease achieved in non-human primates using helper-dependent adenovirus.

Pompe disease (glycogen storage disease type II (GSD-II)) is a myopathy caused by a genetic deficiency of acid α-glucosidase (GAA) leading to lysosomal glycogen accumulation causing muscle weakness, respiratory insufficiency and death. We previously demonstrated in GSD-II mice that a single injection of a helper-dependent adenovirus (HD-Ad) expressing GAA resulted in at least 300 days of liver secretion of GAA, correction of the glycogen storage in cardiac and skeletal muscles and improved muscle strength. Recent reports suggest that gene therapy modeling for lysososomal storage diseases in mice fails to predict outcomes in larger animal models. We therefore evaluated an HD-Ad expressing GAA in non-human primates. The baboons not only tolerated the procedure well, but the results also confirmed that a single dose of the HD-Ad allowed the livers of the treated animals to express and secrete large amounts of GAA for at least 6 months, at levels similar to those achieved in mice. Moreover, we detected liver-derived GAA in the heart, diaphragm and skeletal muscles of the treated animals for the duration of the study at levels that corrected glycogen accumulation in mice. This work validates our proof-of-concept studies in mice, and justifies future efforts using Ad-based vectors in Pompe disease patients.

CR1/2 is an important suppressor of Adenovirus-induced innate immune responses and is required for induction of neutralizing antibodies.

Human complement receptors 1 and 2 are well described as important regulators of innate and adaptive immune responses, having pivotal roles in regulating complement activation (CR1) and B-cell maturation/survival. In contrast, the role of the murine homologs of CR1 and CR2 (mCR1/2) have been primarily defined as modulating activation of the adaptive immune system, with very little evidence available about the role of mCR1/2 in regulating the innate immune responses to pathogens. In this paper, we confirm that mCR1/2 plays an important role in regulating both the innate and adaptive immune responses noted after Adenovirus (Ad)-mediated gene transfer. Our results uncovered a novel role of mCR1/2 in downregulating several complement-dependent innate immune responses. We also unveiled the mechanism underlying the complement-dependent induction of neutralizing antibodies to Ad capsids as a CR1/2-dependent phenomenon that correlates with B-cell activation. These results confirm that Ad interactions with the complement system are pivotal in understanding how to maximize the safety or potency of Ad-mediated gene transfer for both gene therapy and vaccine applications.

Improved cytotoxic T-lymphocyte immune responses to a tumor antigen by vaccines co-expressing the SLAM-associated adaptor EAT-2.

The signaling lymphocytic activation molecule-associated adaptor Ewing's sarcoma's-activated transcript 2 (EAT-2) is primarily expressed in dendritic cells, macrophages and natural killer cells. Including EAT-2 in a vaccination regimen enhanced innate and adaptive immune responses toward pathogen-derived antigens, even in the face of pre-existing vaccine immunity. Herein, we investigate whether co-vaccinations with two recombinant Ad5 (rAd5) vectors, one expressing the carcinoembryonic antigen (CEA) and one expressing EAT-2, can induce more potent CEA-specific cytotoxic T lymphocyte (CTL) and antitumor activity in the therapeutic CEA-expressing MC-38 tumor model. Our results suggest that inclusion of EAT-2 significantly alters the kinetics of Th1-biasing proinflammatory cytokine and chemokine responses, and enhances anti-CEA-specific CTL responses. As a result, rAd5-EAT2-augmented rAd5-CEA vaccinations are more efficient in eliminating CEA-expressing target cells as measured by an in vivo CTL assay. Administration of rAd5-EAT2 vaccines also reduced the rate of growth of MC-38 tumor growth in vivo. Also, an increase in MC-38 tumor cell apoptosis (as measured by hematoxylin and eosin staining, active caspase-3 and granzyme B levels within the tumors) was observed. These data provide evidence that more efficient, CEA-specific effector T cells are generated by rAd5 vaccines expressing CEA, when augmented by rAd5 vaccines expressing EAT-2, and this regimen may be a promising approach for cancer immunotherapy in general.