Abstract
Dendritic cells (DC) are central to the initiation of immune responses, and various approaches have been used to target vaccines to DC in order to improve immunogenicity. Cannulation of lymphatic vessels allows for the collection of DC that migrate from the skin. These migrating DC are involved in antigen uptake and presentation following vaccination. Human replication-deficient adenovirus (AdV) 5 is a promising vaccine vector for delivery of recombinant antigens. Although the mechanism of AdV attachment and penetration has been extensively studied in permissive cell lines, few studies have addressed the interaction of AdV with DC. In this study, we investigated the interaction of bovine skin-migrating DC and replication-deficient AdV-based vaccine vectors. We found that, despite lack of expression of Coxsackie B–Adenovirus Receptor and other known adenovirus receptors, AdV readily enters skin-draining DC via an actin-dependent endocytosis. Virus exit from endosomes was pH independent, and neutralizing antibodies did not prevent virus entry but did prevent virus translocation to the nucleus. We also show that combining adenovirus with adjuvant increases the absolute number of intracellular virus particles per DC but not the number of DC containing intracellular virus. This results in increased trans-gene expression and antigen presentation. We propose that, in the absence of Coxsackie B–Adenovirus Receptor and other known receptors, AdV5-based vectors enter skin-migrating DC using actin-dependent endocytosis which occurs in skin-migrating DC, and its relevance to vaccination strategies and vaccine vector targeting is discussed.
Highlights
Vaccines based on replication-incompetent adenovirus (AdV) vectors are safe and highly immunogenic, capable of inducing a full spectrum of adaptive humoral and cellmediated immune responses and of inducing protective immunity in a number of animal species including man (Dicks et al, 2015; Green et al, 2015; Taylor et al, 2015).Human adenovirus 5 (AdV5 and sometimes referred to as HAdV-C5), a species C adenovirus, is the most commonly studied adenovirus vector for both gene therapy and vaccination and, it is the most studied in terms of cell entry, host responses and gene expression (Smith et al., 2010)
In the absence of Coxsackie B–Adenovirus Receptor and other known receptors, AdV5-based vectors enter skinmigrating Dendritic cells (DC) using actin-dependent endocytosis which occurs in skin-migrating DC, and its relevance to vaccination strategies and vaccine vector targeting is discussed
We have previously shown that AdV5 injected subcutaneously or intramuscularly above the site of cannulation is internalized by migrating DC between 4 and 12 h post-inoculation and that, in vitro, up to 40 % of afferent lymph dendritic cells (ALDC) can be transduced by AdV5 using a multiplicity of infection (MOI) of
Summary
Vaccines based on replication-incompetent adenovirus (AdV) vectors are safe and highly immunogenic, capable of inducing a full spectrum of adaptive humoral and cellmediated immune responses and of inducing protective immunity in a number of animal species including man (Dicks et al, 2015; Green et al, 2015; Taylor et al, 2015).Human adenovirus 5 (AdV5 and sometimes referred to as HAdV-C5), a species C adenovirus, is the most commonly studied adenovirus vector for both gene therapy and vaccination and, it is the most studied in terms of cell entry, host responses and gene expression (Smith et al., 2010). It is generally accepted that the first step in AdV5 entry to its target cell is the binding of the virus’ fibre protein to CAR (Coxsackie B–Adenovirus Receptor), followed by the binding of the RGD motif on the penton base to cellular integrins (avb and avb). It is generally accepted that the first step in AdV5 entry to its target cell is the binding of the virus’ fibre protein to CAR (Coxsackie B–Adenovirus Receptor), followed by the binding of the RGD motif on the penton base to cellular integrins (avb and avb5) This promotes virus endocytosis into clathrin-coated vesicles and triggers the first step of the uncoating program (Burckhardt et al, 2011). The virus exits endosomal vesicles to the cytosol, where it utilizes microtubule motors to traffic to the nuclear membrane (Bremner et al, 2009) and deliver its DNA through the nuclear pore (Puntener et al, 2011)
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