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Hematopoietic stem and progenitor cell (HSPC)-based ex vivo gene therapy has demonstrated clinical success for X-linked severe combined immunodeficiency (SCID-X1) patients who lack a suitable donor for HSPC transplantation. Nevertheless, this form of treatment is associated with an increased risk of infectious disease complications and genotoxicity mainly due to the conditioning regimen. In addition, ex vivo gene therapy approaches require sophisticated facilities to manufacture gene-modified cells and to care for the patients after chemotherapy. Considering these impediments, we have developed an in vivo gene therapy approach to treat canine SCID-X1 after HSPC mobilization and systemic delivery of the therapeutic vector. Here, we investigated the use of the cocal envelope to pseudotype a lentiviral (LV) vector expressing a functional gammaC gene. The cocal envelope is resistant to serum inactivation compared with the commonly used vesicular stomatitis virus envelope glycoprotein (VSV-G) envelope and thus well suited for systemic delivery. Two SCID-X1 neonatal canines treated with this approach achieved long-term therapeutic immune reconstitution with no prior conditioning. Therapeutic levels of gene-corrected CD3(+) T cells were demonstrated for at least 16 months, and all other correlates of T cell functionality were within normal range. Retroviral integration-site analysis demonstrated polyclonal T cell reconstitution. Comparative analysis of integration profiles of foamy viral (FV) vector and cocal LV vector after in vivo gene therapy found distinct integration-site patterns. These data demonstrate that clinically relevant and durable correction of canine SCID-X1 can be achieved with in vivo delivery of cocal LV. Since manufacturing of cocal LV is similar to VSV-G LV, this approach is easily translatable to a clinical setting, thus providing for a highly portable and accessible gene therapy platform for SCID-X1.

Foamy viruses (FVs) are nonpathogenic retroviruses that infect various animals including bovines, felines, nonhuman primates (NHPs), and can be transmitted to humans through zoonotic infection. Due to their non-pathogenic nature, broad tissue tropism and relatively safe integration profile, FVs have been engineered as novel vectors (foamy virus vector, FVV) for stable gene transfer into different cells and tissues. FVVs have emerged as an alternative platform to contemporary viral vectors (e.g., adeno associated and lentiviral vectors) for experimental and therapeutic gene therapy of a variety of monogenetic diseases. Some of the important features of FVVs include the ability to efficiently transduce hematopoietic stem and progenitor cells (HSPCs) from humans, NHPs, canines and rodents. We have successfully used FVV for proof of concept studies to demonstrate safety and efficacy following in-vivo delivery in large animal models. In this review, we will comprehensively discuss FVV based in-vivo gene therapy approaches established in the X-linked severe combined immunodeficiency (SCID-X1) canine model.

Autophagy (ATG) is the process of bulk degradation and recycling of long-lived proteins, macromolecular aggregates, and damaged intracellular organelles. Cellular homeostasis requires continuous removal of worn-out components and replacement with newly synthesized ones. Studies in yeast and other mammalian systems have increased our knowledge of the molecular mechanism of autophagy and the role of autophagy in various pathological conditions. Discovery of the genes involved in the process of autophagy has provided insight into the involvement of various molecular pathways. Growing evidence has indicated that diminished autophagic activity may play a pivotal role in the aging process. Cellular aging is characterized by a progressive accumulation of nonfunctional cellular components owing to oxidative damage and a decline in turnover rate and housekeeping mechanisms. Lysosomes are key organelles in the aging process due to their involvement in both macroautophagy and other housekeeping mechanisms. Autophagosomes themselves have limited degrading capacity and rely on fusion with lysosomes. Accumulation of defective mitochondria also appears to be critical in the progression of aging. Inefficient removal of nonfunctional mitochondria by lysosomes constitutes a major issue in the aging process. Autophagy has been associated with a growing number of pathological conditions, including cancer, myopathies, and neurodegenerative disorders. In this review, we discuss the cellular and molecular mechanisms involved in autophagy, the mechanisms of aging, and the possible role of autophagy in this process. Understanding the mechanisms by which autophagy impacts aging may provide useful molecular targets for pharmaceuticals designed to delay aging or correct conditions of premature aging.

Autophagy is an intracellular catabolic process that responds with great sensitivity to nutrient availability, implying that certain macro- or micro-nutrients are involved. We found that retinoic acid promotes autophagosome maturation through a pathway independent from the classic nuclear retinoid receptors. Retinoic acid redistributes the cation-independent mannose-6-phosphate receptor from the trans-Golgi region to maturing autophagosomal structures inducing their acidification. Manipulation of the autophagic activity by retinoids could have enormous health implications, since they are essential dietary components and frequently used pharmaceuticals.