Late Endosomal Trafficking of Alternative Serotype Adenovirus Vaccine Vectors Augments Antiviral Innate Immunity

Abstract

Adenovirus (Ad) vaccine vectors have found widespread use as vaccine platforms against multiple infections and cancers, and multiple serotypes have been shown to differ significantly in their biological properties and immune phenotypes. Our laboratory and others have previously described differential innate immune stimulation elicited by various Ad serotypes. Here, we show that Ad serotype 5 (Ad5) traffics rapidly to the nucleus following infection, whereas Ad35 and Ad26 accumulate in late endosomes 2 to 8 h postinfection. Innate immune cytokine elicitation by all Ad serotypes was abrogated by blockade of endosomal acidification, cathepsin B, and caspase 1, suggesting that virus interactions with acid-dependent sensors, such as Toll-like receptor-and cathepsin-dependent inflammasome activation in late endosomes, may trigger innate immunity. These data suggest a mechanism by which Ad vectors from various serotypes differentially trigger innate antiviral pathways via distinct intracellular trafficking to late endosomes. IMPORTANCEAdenoviruses (Ad) are widely used for vaccination and gene therapy applications. Importantly, Ad vectors have been shown to differ significantly in their innate immune profiles both in vivo and in vitro. The molecular mechanism that underlies these observed differences has important implications for the development of improved vaccines. In this study, we propose a mechanism in which the degree of late endosomal trafficking of Ad vectors results in differential stimulation of late endosomal pattern recognition receptors.

The Amphipathic Helix of Adenovirus Capsid Protein VI Contributes to Penton Release and Postentry Sorting

“…Thus, differences in capsid stability may be the primary determinant of entry-associated sorting for all AdVs, allowing endosomal escape in very early endocytic compartments (as observed for species C AdVs) or after prolonged sorting from the late endosomal/lysosomal compartment, as was suggested for species B viruses (28,63). In contrast, premature protein VI release (e.g., PVI-L40Q) or failure to release protein VI at all (PRO-P137L) would result in noninfectious virions.…”

Unabated Adenovirus Replication following Activation of the cGAS/STING-Dependent Antiviral Response in Human Cells

“…Similarly, differences in antiviral innate immune activation may have consequences for vaccine strategies when vectors are based on different viral backbones. Recent reports identified serotype-specific innate immune responses in the in vivo murine model (16). Suggestions that differences in immune potency correlate with genome sequence have been made (42).…”

“…Most Ads bind to the coxsackievirus-adenovirus receptor (CAR) (12), but CD46 is the high-affinity receptor targeted by subgroup 1 species B viruses (13), and desmoglein-2 binds fiber of the subgroup 2 species B viruses (14). Recent studies have indicated that differences in fiber/receptor binding influence the viral endocytic import pathway (15) and antiviral activation levels (16).…”

Integrin Receptors Play a Key Role in the Regulation of Hepatic CYP3A

“…IL-12 levels in samples obtained 6 hours after administration of AdDRGD were three times lower than those from mice given AdlacZ (392.1 6 26.1 pg/ml); however, the concentration of this cytokine was significantly higher than that detected in the AdlacZ group at the 24-hour (247.6 6 30.3 pg/ml) and 48-hour (270.0 6 18.6 pg/ml) time points. This finding was somewhat unexpected; however, early studies with AdDRGD and the native wild-type virus described notable differences in intracellular trafficking and endosomal escape patterns (Shayakhmetov et al, 2005a), processes that significantly affect development of the innate immune response to the virus (Leopold and Crystal, 2007;Teigler et al, 2014). Other studies in which AdDRGD was given to mice in the same manner as described in our studies have reported notable suppression of a variety of proinflammatory cytokines (Di Paolo et al, 2009); however, levels of cytokines with dual inflammatory and protective roles after administration of the virus have not previously been described.…”