Enhanced and Sustained CD8+ T Cell Responses with an Adenoviral Vector-Based Hepatitis C Virus Vaccine Encoding NS3 Linked to the MHC Class II Chaperone Protein Invariant Chain

Abstract

Potent and broad cellular immune responses against the nonstructural (NS) proteins of hepatitis C virus (HCV) are associated with spontaneous viral clearance. In this study, we have improved the immunogenicity of an adenovirus (Ad)-based HCV vaccine by fusing NS3 from HCV (Strain J4; Genotype 1b) to the MHC class II chaperone protein invariant chain (Ii). We found that, after a single vaccination of C57BL/6 or BALB/c mice with Ad-IiNS3, the HCV NS3-specific CD8+ T cell responses were significantly enhanced, accelerated, and prolonged compared with the vaccine encoding NS3 alone. The AdIiNS3 vaccination induced polyfunctional CD8+ T cells characterized by coproduction of IFN-γ, TNF-α and IL-2, and this cell phenotype is associated with good viral control. The memory CD8+ T cells also expressed high levels of CD27 and CD127, which are markers of long-term survival and maintenance of T cell memory. Functionally, the AdIiNS3-vaccinated mice had a significantly increased cytotoxic capacity compared with the AdNS3 group. The AdIiNS3-induced CD8+ T cells protected mice from infection with recombinant vaccinia virus expressing HCV NS3 of heterologous 1b strains, and studies in knockout mice demonstrated that this protection was mediated primarily through IFN-γ production. On the basis of these promising results, we suggest that this vaccination technology should be evaluated further in the chimpanzee HCV challenge model.

Adenovirus-Based Vaccine against Listeria monocytogenes: Extending the Concept of Invariant Chain Linkage

“…These constructs have a previously documented in vivo protective capacity against viral infection, regardless of whether perforin or IFN-g represents the major antiviral effector mechanism (20,21). Through challenge of vaccinated mice with a recombinant strain of L. monocytogenes modified to secrete part of LCMV GP (Lm-GP33), we obtained basic proof-of-concept for the hypothesis that the adenovirus-based vaccine strategy will confer protection against an intracellular bacterial infection like L. monocytogenes and that protection might be improved by tethering of the target Ag to Ii.…”

Harnessing the Potential of Adenovirus Vectored Vaccines

“…Surprisingly, this strategy improved not only CD4+ T cell responses, but also the kinetics, breadth, magnitude and stability of the CD8+ T cell response via increased MHC class I presentation and independently of MHC class II . We have since then confirmed these findings with a variety of antigens and are able to conclude that the level of antigen presentation on the adenovirus transduced cell is a limiting factor with regard to the speed and breadth of CD8+ T cell responses (Hoegh-Petersen et al, 2009;Mikkelsen et al, 2011;Sorensen et al, 2009). Given the apparent dichotomy of fast hematopoietic and chronic nonhematopoietic antigen presentation in adenoviral vaccination, this is highly consistent with the hypothesis that the above described strategies work at least in part to increase the first wave of antigen presentation mediated by dendritic cells directly transduced by the vector (see figure 2).…”

Vaccine Targeting of Subdominant CD8+ T Cell Epitopes Increases the Breadth of the T Cell Response upon Viral Challenge, but May Impair Immediate Virus Control

“…Absence of a dominant epitope in an Ii-linked construct may dramatically increase subdominant responses Linking the vaccine Ag expressed from an adenoviral vector to the MHC class II-associated Ii has proved successful in eliciting increased numbers of Ag-specific CD8 + T cells in several studies (29,30,(35)(36)(37). However, the effect of Ii linkage varies with the selected Ag, and we have previously observed that the NP of LCMV does not seem to benefit from Ii linkage in terms of numbers of NP396 (dominant epitope)-specific CD8 + T cells and protection from LCMV infection (24) (Supplemental Fig.…”

“…Bishop (Oxford University, Oxford, U.K.) via Annette Oxenius (Swiss Federal Institute of Technology, Zurich, Switzerland) and grown on CV-1 cells at low multiplicity of infection; quantification was performed as described previously (30). Mice were infected i.p.…”

“…Adenoviral vectors have been extensively studied as potential vaccine candidates for a number of diseases in which the induction of a robust and long-lasting CD8 + T cell response is considered pivotal (25)(26)(27)(28). We have previously shown that linkage of the vaccine Ag to the MHC class II invariant chain (Ii) can broaden and enhance the Ag-specific CD8 + T response, resulting in improved antiviral protection (29,30). Based on these observations and a review of the existing literature, we speculated that removal of the dominant epitope from the Ii-linked Ag might further broaden and enhance responses toward subdominant epitopes, and thus create a vaccine suitable for targeting viruses with a high mutation rate where a broad CD8 + T cell repertoire is likely to be important.…”