Ad5:Ad48 Hexon Hypervariable Region Substitutions Lead to Toxicity and Increased Inflammatory Responses Following Intravenous Delivery

Abstract

The development of adenoviral vectors for intravascular delivery will require improvements to their in vivo safety and efficacy. The hypervariable regions of the Ad5 hexon are a target for neutralizing antibodies, but also interact with FX, facilitating hepatocyte transduction. Ad48, a species D adenovirus, does not bind FX and has low seroprevalence. Therefore, it has been suggested that Ad5HVR48(1-7), a hexon-chimeric vector featuring the seven HVRs from Ad48, should display advantageous properties for gene therapy, by evading pre-existing Ad5 immunity and blocking FX interactions. We investigated the in vivo biodistribution of Ad5, Ad5HVR48(1-7) and Ad48 following iv delivery. Ad5HVR48(1-7) displayed reduced hepatocyte transduction and accumulation in Kupffer cells, but triggered a robust pro-inflammatory response, even at relatively low doses of vector. We detected elevated serum transaminases (48h) and increased numbers of peri-portal CD11b+/Gr-1+ cells in the livers of Ad5HVR48(1-7)-treated animals following intravascular, but not intramuscular, delivery. In contrast, Ad48 did not elevate transaminases or result in the accumulation of CD11b+/Gr-1+ cells. Collectively, these findings suggest that substantial hexon modifications can lead to unexpected properties which cannot be predicted from parental viruses. Therefore, refined mutations may be preferential for the successful development of targeted vector systems which require intravascular administration.

Hexon Hypervariable Region-Modified Adenovirus Type 5 (Ad5) Vectors Display Reduced Hepatotoxicity but Induce T Lymphocyte Phenotypes Similar to Ad5 Vectors

“…Notably, our results contrast with those of a prior study that reported unexpected hepatotoxicity of Ad5HVR48 compared with that of Ad5 and Ad48 (27,29). Our data show substantial hepatotoxicity with Ad5 vectors in MF1 mice but no detectable hepatotoxicity with Ad5HVR48 and Ad48 vectors, likely reflecting the lack of liver tropism of Ad5HVR48 and Ad48 (29).…”

“…Our data show substantial hepatotoxicity with Ad5 vectors in MF1 mice but no detectable hepatotoxicity with Ad5HVR48 and Ad48 vectors, likely reflecting the lack of liver tropism of Ad5HVR48 and Ad48 (29). Moreover, innate cytokine profiles with Ad5HVR48 were intermediate between Ad5 and Ad48.…”

“…The mice (C57BL/6 or MF1; n ϭ 3 to 4/group) were inoculated intravenously (i.v.) with 3 ϫ 10 10 or 1 ϫ 10 11 viral particles (vp) of Ad5, Ad5HVR48, or Ad48 vectors, consistent with procedures in prior studies (29). Serum samples were collected 6 h after vaccination, and systemic levels of cytokines and chemokines were assessed by Luminex analyses.…”

“…Furthermore, studies from our laboratory and others have described marked differences in vaccine-elicited innate and adaptive immune responses following Ad5 or Ad48 immunization (4,27,28). While Ad5HVR48 has shown a lack of vector-induced toxicity in both nonhuman primates (NHP) and humans, a previous report suggested that Ad5HVR48 may exhibit unexpected hepatotoxic and inflammatory responses in mice that are greater than those observed with Ad5 or Ad48 vectors (29). Understanding the impact of HVR modifications on the toxicity and innate and adaptive immune phenotypes elicited by Ad vectors is important for future clinical development of HVR-chimeric Ad vectors.…”

CD46-Mediated Transduction of a Species D Adenovirus Vaccine Improves Mucosal Vaccine Efficacy

“…While these alternative viral vectors may have a lower seroprevalence, the differences in their biology as compared with Ad5 have started to come into question. It is a risky assumption to assume that all Ads share the same phenotype (Coughlan et al, 2012). In this study we show that there is a significant degree of difference in phenotypes even within the same species of Ad.…”