Local adenoviral expression of Fas ligand upregulates pro-inflammatory immune responses in the CNS

Inflammation, apoptosis, and necrosis induced by neoadjuvant fas ligand gene therapy improves survival of dogs with spontaneous bone cancer

Fas ligand (FasL) gene therapy for cancer has shown promise in rodents; however, its efficacy in higher mammals remains unknown. Here, we used intratumoral FasL gene therapy delivered in an adenovirus vector (Ad-FasL) as neoadjuvant to standard of care in 56 dogs with osteosarcoma. Tumors from treated dogs had greater inflammation, necrosis, apoptosis, and fibrosis at day 10 (amputation) compared to pretreatment biopsies or to tumors from dogs that did not receive Ad-FasL. Survival improvement was apparent in dogs with inflammation or lymphocyte-infiltration scores >1 (in a 3-point scale), as well as in dogs that had apoptosis scores in the top 50th percentile (determined by cleaved caspase-3). Survival was no different than that expected from standard of care alone in dogs with inflammation scores ≤1 or apoptosis scores in the bottom 50th percentile. Reduced Fas expression by tumor cells was associated with prognostically advantageous inflammation, and this was seen only in dogs that received Ad-FasL. Together, the data suggest that Ad-FasL gene therapy improves survival in a subset of large animals with naturally occurring tumors, and that at least in some tumor types like osteosarcoma, it is most effective when tumor cells fail to express Fas.

Th1 cytokines are upregulated by adenoviral vectors in the brains of primed mice

A major disadvantage of first generation adenoviral vectors for gene therapy in the brain is the immune response they elicit. Human adenovirus is a common respiratory virus and earlier exposure to it has important implications for gene therapy. We show that the immune response against E1-deleted adenoviral vectors in the brain is more deleterious in animals previously exposed to the virus. Analysis of cytokine mRNA revealed enhanced and prolonged upregulation of the Th1 proinflammatory cytokines, IFN-gamma, TNF-alpha and IL-12 whereas, effects on Th2 cytokines were negligible. This was associated with reduced reporter gene expression, decreased expression of the dopamine transporter protein and demyelination. This knowledge of the molecular regulation of the immune response provides insight into targets, which could be manipulated to reduce inflammation in immunologically primed animals.

IL4 gene delivery to the CNS recruits regulatory T cells and induces clinical recovery in mouse models of multiple sclerosis

Central nervous system (CNS) delivery of anti-inflammatory cytokines, such as interleukin 4 (IL4), holds promise as treatment for multiple sclerosis (MS). We have previously shown that short-term herpes simplex virus type 1-mediated IL4 gene therapy is able to inhibit experimental autoimmune encephalomyelitis (EAE), an animal model of MS, in mice and non-human primates. Here, we show that a single administration of an IL4-expressing helper-dependent adenoviral vector (HD-Ad) into the cerebrospinal fluid (CSF) circulation of immunocompetent mice allows persistent transduction of neuroepithelial cells and long-term (up to 5 months) CNS transgene expression without toxicity. Mice affected by chronic and relapsing EAE display clinical and neurophysiological recovery from the disease once injected with the IL4-expressing HD-Ad vector. The therapeutic effect is due to the ability of IL4 to increase, in inflamed CNS areas, chemokines (CCL1, CCL17 and CCL22) capable of recruiting regulatory T cells (CD4+CD69-CD25+Foxp3+) with suppressant functions. CSF delivery of HD-Ad vectors expressing anti-inflammatory molecules might represent a valuable therapeutic option for CNS inflammatory disorders.

Absence of an intrathecal immune reaction to a helper-dependent adenoviral vector delivered into the cerebrospinal fluid of non-human primates

Inflammation and immune reaction, or pre-existing immunity towards commonly used viral vectors for gene therapy severely impair long-term gene expression in the central nervous system (CNS), impeding the possibility to repeat the therapeutic intervention. Here, we show that injection of a helper-dependent adenoviral (HD-Ad) vector by lumbar puncture into the cerebrospinal fluid (CSF) of non-human primates allows long-term (three months) infection of neuroepithelial cells, also in monkeys bearing a pre-existing anti-adenoviral immunity. Intrathecal injection of the HD-Ad vector was not associated with any sign of systemic or local toxicity, nor by signs of a CNS-specific immune reaction towards the HD-Ad vector. Injection of HD-Ad vectors into the CSF circulation may thus represent a valuable approach for CNS gene therapy allowing for long-term expression and re-administration.