Canine Adenovirus Vectors for Lung-Directed Gene Transfer: Efficacy, Immune Response, and Duration of Transgene Expression Using Helper-Dependent Vectors

Abstract

A major hurdle to the successful clinical use of some viral vectors relates to the innate, adaptive, and memory immune responses that limit the efficiency and duration of transgene expression. Some of these drawbacks may be circumvented by using vectors derived from nonhuman viruses such as canine adenovirus type 2 (CAV-2). Here, we evaluated the potential of CAV-2 vectors for gene transfer to the respiratory tract. We found that CAV-2 transduction was efficient in vivo in the mouse respiratory tract, and ex vivo in well-differentiated human pulmonary epithelia. Notably, the in vivo and ex vivo efficiency was poorly inhibited by sera from mice immunized with a human adenovirus type 5 (HAd5, a ubiquitous human pathogen) vector or by human sera containing HAd5 neutralizing antibodies. Following intranasal instillation in mice, CAV-2 vectors also led to a lower level of inflammatory cytokine secretion and cellular infiltration compared to HAd5 vectors. Moreover, CAV-2 transduction efficiency was increased in vitro in human pulmonary cells and in vivo in the mouse respiratory tract by FK228, a histone deacetylase inhibitor. Finally, by using a helper-dependent CAV-2 vector, we increased the in vivo duration of transgene expression to at least 3 months in immunocompetent mice without immunosuppression. Our data suggest that CAV-2 vectors may be efficient and safe tools for long-term clinical gene transfer to the respiratory tract.

Contrasting Effects of Human, Canine, and Hybrid Adenovirus Vectors on the Phenotypical and Functional Maturation of Human Dendritic Cells: Implications for Clinical Efficacy

“…CAV-2 immunogenicity. We previously found that ⌬E1 CAV-2 vectors were less immunogenic than ⌬E1/E3 HAd5 vectors in the immunologically naïve rodent CNS and respiratory tract (38,74). In the rat CNS, we detected fewer infiltrating CD4 ϩ and CD8 ϩ cells at an equivalent number of injected particles (74).…”

“…We hypothesized that this was due to a combination of factors: the lack of transduction of CNS immune mediator cells (micro-and macroglia) (2), the dispersion of the vector from the site of injection via axoplasmic retrograde transport, and possibly a lower innate immune response due to the lack of an integrin-interacting motif in the CAV-2 virion (10,71). Following intranasal instillation in mice, CAV-2 vectors also led to a lower level of TNF-␣ secretion than HAd5 vectors (38). The data presented here are consistent with our previous data and may provide a partial explanation for the reduced adaptive immune response in some tissues: poor DC transduction and maturation lead to a lower adaptive response in naïve hosts.…”

“…In the central nervous sys-tems (CNS) of several species, CAV-2 vectors preferentially transduce neurons and lead to an efficient level of axoplasmic transport (73). Helper-dependent (HD) CAV-2 vectors also lead to long-term transgene expression in the CNS (74) and respiratory tracts (38) of immunocompetent rodents without immunosuppression. Our data and those from studies using HD human adenovirus (HAd) vectors (3) suggest that HD CAV-2 vectors could be used for the long-term treatment of some global neurodegenerative disorders (40,54).…”

Lentivirus Vector Can Be Readministered to Nasal Epithelia without Blocking Immune Responses

“…Preexisting immunity against either Ad or AAV may also present a significant barrier to initial use of these vectors (14,46). More recently, helper-dependent Ads have shown promise for prolonged expression (22), and perhaps readministration (24). In addition, the ability to switch Ad or AAV capsid serotypes (serotype switching) may offer at least a temporary solution (28,33).…”

Three-Dimensional Structure of Canine Adenovirus Serotype 2 Capsid

“…We previously showed that CAV-2 vectors could lead to preferential transduction of neurons in vivo (49), long-term (Ͼ1 yr) expression in the brain (50), and a lower cellular immune response (27,49). The majority of donors in a random cohort harbored no or only low levels of anti-CAV-2 neutralizing antibodies (30,37), and less than half of this cohort harbored anti-CAV-2 memory T cells (38).…”