Cross-Presentation of Skin-Targeted Recombinant Adeno-associated Virus 2/1 Transgene Induces Potent Resident Memory CD8 ⁺ T Cell Responses

Abstract

A key aspect to consider for vaccinal protection is the induction of a local line of defense consisting of nonrecirculating tissue-resident memory T cells (TRM), in parallel to the generation of systemic memory CD8+ T cell responses. The potential to induce TRM has now been demonstrated for a number of pathogens and viral vectors. This potential, however, has never been tested for recombinant adeno-associated virus (rAAV) vectors, which are weakly inflammatory and poor transducer of dendritic cells. Using a model rAAV2/1-based vaccine, we determined that a single intradermal immunization with rAAV2/1 vectors in mice induces fully functional TRM at the local site of immunization. The optimal differentiation of rAAV-induced transgene-specific skin TRM was dependent on local transgene expression and additional CD4+ T cell help. Transgene expression in dendritic cells, however, appeared to be dispensable for the priming of transgene-specific skin TRM, suggesting that this process solely depends on the cross-presentation of transgene products. Overall, this study provides needed information to properly assess rAAV vectors as T cell-inducing vaccine carriers. IMPORTANCE rAAVs display numerous characteristics that could make them extremely attractive as vaccine carriers, including an excellent safety profile in humans and great flexibility regarding serotypes and choice of target tissue. Studies addressing the ability of rAAV to induce protective T cell responses, however, are scarce. Notably, the potential to induce a tissue-resident memory T cell response has never been described for rAAV vectors, strongly limiting further interest for their use as vaccine carriers. Using a model rAAV2/1 vaccine delivered to the skin, our study demonstrated that rAAV vectors can induce bona fide skin resident TRM and provides additional clues regarding the cellular mechanisms underlying this process. These results will help widen the field of rAAV applications.

An Engineered AAV6-Based Vaccine Induces High Cytolytic Anti-Tumor Activity by Directly Targeting DCs and Improves Ag Presentation

“…Several studies highlighted the usefulness of certain AAV serotypes for immunomodulation and cancer vaccines, depending on capsid configuration, dose, and route of administration in a mouse model 14, 15, 16, 17, 18, 19. Among other serotypes, AAV6 is able to transduce the cells of myeloid origin in general 39 , 69 and DCs in particular 25 , 35 .…”

“…Several studies highlighted the usefulness of certain AAV serotypes for immunomodulation and cancer vaccines, depending on capsid configuration, dose, and route of administration in a mouse model. [14][15][16][17][18][19] Among other serotypes, AAV6 is able to transduce the cells of myeloid origin in general 39,69 and DCs in particular. 25,35 Thus, AAV6-based vectors with Ova as a model Ag as described here are a highly attractive platform for developing anti-tumor vaccines.…”

“…Second, recent data obtained from clinical studies changed the paradigm about low AAV immunogenicity 13 . Several natural and engineered AAV serotypes can induce strong cellular immune responses against an encoded transgene, an important feature needed for vaccine development, and showed protective anti-cancer immune response in mouse animal models 14, 15, 16, 17, 18, 19. Third, much research was done to understand the interaction of AAV with DCs and improve AAV infectivity by modifying the viral capsid to overcome intracellular obstacles such as proteasomal degradation 20 , 21 and vector uncoating 22 …”

“…13 Several natural and engineered AAV serotypes can induce strong cellular immune responses against an encoded transgene, an important feature needed for vaccine development, and showed protective anti-cancer immune response in mouse animal models. [14][15][16][17][18][19] Third, much research was done to understand the interaction of AAV with DCs and improve AAV infectivity by modifying the viral capsid to overcome intracellular obstacles such as proteasomal degradation 20,21 and vector uncoating. 22 DCs, as professional antigen-presenting cells (APCs), can present Ags either by direct presentation of a gene delivered into DCs or by crosspresentation of Ags released from transduced tissue and taken up by un-transfected DCs.…”

Tumor antigen-loaded AAV vaccine drives protective immunity in a melanoma animal model

“… 15 , 16 Other groups have shown that the AAV1 serotype can be used for vaccine development. 13 , 17 , 18 While AAV1 is generally a poor transducer of APCs, the intradermal route of immunization activates cross-presenting APCs against transgenes expressed in mouse skin. The combination of intradermal injection and fusion of Ag with male HY Ag epitopes, which additionally provides CD4 + T helper cells in female mice, ensured the generation of functional Ag-specific cytotoxic T cells against model Ag ovalbumin (OVA).…”