A Novel Adenovirus Type 6 (Ad6)-Based Hepatitis C Virus Vector That Overcomes Preexisting Anti-Ad5 Immunity and Induces Potent and Broad Cellular Immune Responses in Rhesus Macaques

Abstract

Success in resolving hepatitis C virus (HCV) infection has been correlated to vigorous, multispecific, and sustained CD8؉ T-cell response in humans and chimpanzees. The efficacy of inducing T-cell-mediated immunity by recombinant serotype 5 adenovirus vector has been proven in many animal models of infectious diseases, but its immunogenicity can be negatively influenced by preexisting immunity against the vector itself. To evaluate the less prevalent adenovirus serotype 6 (Ad6) as an alternative vector for and HCV vaccine development, we have generated serotype 5 and 6 adenoviral vectors directing expression of the nonstructural region of HCV (MRKAd5-NSmut and MRKAd6-NSmut). Immunogenicity studies in mice showed that the two vectors induced comparable T-cell responses but that only MRKAd6-NSmut was not suppressed in the presence of anti-Ad5 immunity. In contrast, preexisting anti-Ad5 immunity dramatically blunted the immunogenicity of the serotype 5-based HCV vector. Furthermore, MRKAd6-NSmut showed equivalent potency, breadth, and longevity of HCV-specific T-cell responses in rhesus macaques as the corresponding Ad5-based vector over a wide range of doses and was capable of boosting DNA-primed animals even if administered at low doses. These data support the use of the MRKAd6-NSmut for anti-HCV immunotherapy and, more generally, for the Ad6 serotype as a better genetic vaccine vehicle than Ad5.

Combined Adenovirus Vector and Hepatitis C Virus Envelope Protein Prime-Boost Regimen Elicits T Cell and Neutralizing Antibody Immune Responses

“…HCV T212 expression cassettes were inserted by homologous recombination into the Ad6 backbone on plasmid pAd6/NSmut (28). PmeI and PacI fragments, respectively, from pNEB/E1F78E2p7 and pNEB/F78E2 662 containing expression cassette and Ad6 E1 flanking regions were recombined to SnaBI-linearized pAd6/NSmut in BJ5183 cells, creating plasmids pAd6/E1F78E2p7 and pAd6/F78E2 662 containing the Ad6 genome with deletions of E1 and E3 genes and with introduced transgenes.…”

Modulation of the Immune Response Induced by Gene Electrotransfer of a Hepatitis C Virus DNA Vaccine in Nonhuman Primates

“…Another group of rhesus macaques (n ϭ 4) received 10 10 viral particle of MRKAd6NSmut at weeks 0 and 4. This schedule and dosage proved to be very effective at inducing a strong cellular immune response in rhesus macaques (17). Serial PBMC samples were collected at periodic intervals after vaccination and tested for the induction of HCV-specific T cells with effector function by IFN-␥ ELISPOT assay.…”

“…Macaques from group C (Table I) were immunized with 10 10 viral particles of MRKAd6NSmut in 1 ml of buffer A105 (17) injected in the deltoid muscle split over two sites (0.5 ml/site).…”

Recent advances inEbolavirusvaccine development

“…Ongoing research evaluating the development of adenovirus serotypes that are not as prevalent in the human population include AdHu12, AdHu35, 126 and AdHu6 which was shown to be immunogenic in NHPs. 127 Current efforts are also ongoing for the development of adenovirus-based vaccines originating from different animal species such as simian, 124 bovine 128 or porcine adenoviruses. Pre-existing immunity was by-passed in animals pre-treated with neutralizing antibodies to AdHu5 and then immunized with a vaccine based on chimpanzee adenovirus (AdC7) expressing ZEBOV GP.…”