Intradermal Immunization with rAAV1 Vector Induces Robust Memory CD8+ T Cell Responses Independently of Transgene Expression in DCs

Abstract

Recombinant adeno-associated viral (rAAV) vectors exhibit interesting properties as vaccine carriers for their ability to induce long-lasting antibody responses. However, rAAV-based vaccines have been suggested to trigger functionally impaired long-term memory CD8 T cell responses, in part due to poor dendritic cell (DC) transduction. Such results, albeit limited to intramuscular immunization, undermined the use of rAAV as vaccine vehicles against intracellular pathogens. We report here that intradermal immunization with a model rAAV2/1-based vaccine drives the development of bona fide long-term memory CD8 T cell responses. The intradermal route of immunization and the presence of potent major histocompatibility complex (MHC) class II responses showed synergistic effects on the overall quantity and quality of systemic long-term effector memory transgene-specific CD8 T cells being generated against the transgene. Of key interest, we found that the induction of memory cytotoxic T lymphocytes (CTLs) following intradermal immunization was solely dependent on the cross-presentation of skin-expressed transgene products, which appeared highly enhanced as compared to muscle-expressed transgene products. Overall our results highlight key tissue-specific differences in transgene presentation pathway requirements of importance for the design of rAAV-based T cell-inducing vaccines.

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

“…As previously published (34), no significant differences could be seen in the frequencies of OVA 257 -specific CD8 ϩ T cells in the peripheral blood of intramuscularly and intradermally immunized female mice up to 60 days postimmunization ( Fig. 1A).…”

“…The addition of four repeats of the miR142-3p target sequence downstream of the mOVAHY transgene inhibits its expression in DCs (34), in line with the prevalent miR142-3p expression found in all hematopoietic cells (37). Interestingly, similar numbers of skin resident OVA 257 ϩ CD8 ϩ T cells could be recovered from immunized female mice with both wild-type (WT) (mOVAHY) and miR142-3p-regulated constructs (mOVAHY-miR) (Fig.…”

“…Interestingly, a significant OVA 257 -specific CD8 ϩ T cell population could still be detected in both the dermis and epidermis of intradermally, but not intramuscularly, immunized female mice by day 60 ( Fig. 1B and C), at a time when transgene expression is undetectable (34). On average, around 10 4 OVA 257 ϩ CD8 ϩ T cells could be recovered per injected ear, representing a 300-fold increase in OVA 257 ϩ CD8 ϩ T cell numbers compared to ears of mice injected intramuscularly or to control vector-injected ears.…”

“…Intradermal immunization with rAAV2/1 vector induces transgene-specific skin resident memory CD8 ؉ T cells. We have previously described in detail the generation of systemic anti-transgene effector (T EM ) and central memory (T CM ) CD8 ϩ T cells following both intramuscular and intradermal immunization with an rAAV2/1 vector (34). To further investigate whether intradermal immunization also gave rise to tissue resident memory CD8 ϩ T cell responses at the site of immunization, we used the same rAAV2/1 vector, which encodes a full-length membrane-bound form of the ovalbumin model antigen fused to the UTY 246 and DBY 608 male HY antigen epitopes (rAAV2/1-mOVA-HY).…”

“…All experiments described so far were performed in female mice. The strong anti-transgene DBY 608 -specific CD4 ϩ T cell response that can be seen in female hosts significantly boosts systemic antitransgene CD8 ϩ T cell responses following rAAV2/1 intradermal immunization (34). Additionally, previous studies have clearly shown that pseudotyped rAAV vector are not all equal regarding dendritic cell transduction.…”