Vaccines Expressing the Innate Immune Modulator EAT-2 Elicit Potent Effector Memory T Lymphocyte Responses despite Pre-Existing Vaccine Immunity

Abstract

The mixed results from recent vaccine clinical trials targeting HIV-1 justify the need to enhance the potency of HIV-1 vaccine platforms in general. Use of first-generation recombinant adenovirus serotype 5 (rAd5) platforms failed to protect vaccinees from HIV-1 infection. One hypothesis is that the rAd5-based vaccine failed due to the presence of pre-existing Ad5 immunity in many vaccines. We recently confirmed that EAT-2–expressing rAd5 vectors uniquely activate the innate immune system and improve cellular immune responses against rAd5-expressed Ags, inclusive of HIV/Gag. In this study, we report that use of the rAd5-EAT-2 vaccine can also induce potent cellular immune responses to HIV-1 Ags despite the presence of Ad5-specific immunity. Compared to controls expressing a mutant SH2 domain form of EAT-2, Ad5 immune mice vaccinated with an rAd5-wild-type EAT-2 HIV/Gag-specific vaccine formulation significantly facilitated the induction of several arms of the innate immune system. These responses positively correlated with an improved ability of the vaccine to induce stronger effector memory T cell-biased, cellular immune responses to a coexpressed Ag despite pre-existing anti-Ad5 immunity. Moreover, inclusion of EAT-2 in the vaccine mixture improves the generation of polyfunctional cytolytic CD8+ T cell responses as characterized by enhanced production of IFN-γ, TNF-α, cytotoxic degranulation, and increased in vivo cytolytic activity. These data suggest a new approach whereby inclusion of EAT-2 expression in stringent human vaccination applications can provide a more effective vaccine against HIV-1 specifically in Ad5 immune subjects.

Improved cytotoxic T-lymphocyte immune responses to a tumor antigen by vaccines co-expressing the SLAM-associated adaptor EAT-2

“…20,33,34 To investigate whether the enhanced innate immune responses promoted by Ad-mediated expression of EAT-2 could also influence the adaptive immune responses to a non-pathogen-derived self-antigen such as CEA; we co-immunized C57BL/6 mice with rAd5-based vectors expressing CEA alongside rAd5 vectors expressing-EAT2, or as, a control, rAd5 vectors expressing GFP (rAd5-GFP). We performed initial dose curve studies to identify the appropriate dose of rAd5-CEA that can be used in our studies in the C57BL/6 mice (Figure 2).…”

“…Fourteen days after vaccination, the two groups of mice were then injected with CFSE-labeled syngeneic splenocytes pulsed with either nonspecific or CEA-derived peptides, as described in the Materials and methods section and also previously. 20,33,34 The elimination of the peptide-pulsed splenocytes (CFSE high ) in the control or experimental animals was then examined by a flow cytometry-based CTL assay. CEA-specific CTL activities induced in mice co-immunized with rAd5-CEA and rAd5-EAT2 were significantly ( P <0.01) higher, as compared with mice injected with the rAd5-CEA and rAd5-GFP controls (Figure 6).…”

“…29 We have shown previously that EAT-2 expression from Ad5-based vaccine platforms positively regulates effector and regulatory functions of innate immune cells inclusive of macrophage, DCs and NK cells. 20,34 EAT-2 overexpression also enhances the production of several proinflammatory cytokines and chemokines immediately subsequent to vaccination with Ad vectors expressing EAT-2. 20,34 Innate immune responses enhanced by EAT-2 delivery also resulted in improved induction of beneficial cellular immune responses to co-administered pathogen-derived antigens, 20,33,34 and in this report, self-human antigens such as CEA.…”

“…Ad5 vectors expressing the EAT-2 adaptor are superior to conventional Ad5 vectors. 20,33,34 Specifically, we found that administration of a recombinant Ad5 vector-expressing EAT-2 (rAd5-EAT2) improved early activation of innate immune responses, responses that are characterized by increased activation of innate immune cells (NK cells, NK T cells), enhanced maturation of APCs (DCs and macrophages) and enhanced production of beneficial cytokines and chemokines. 20,34 As a result of the enhanced innate immune profile prompted by expression of EAT-2, EAT-2-expressing Ad vaccines also improved the induction of adaptive immune responses generated against co-expressed target antigens, including the induction of superior effector memory (T EM )-biased T-lymphocyte immune responses.…”

“…20,34 As a result of the enhanced innate immune profile prompted by expression of EAT-2, EAT-2-expressing Ad vaccines also improved the induction of adaptive immune responses generated against co-expressed target antigens, including the induction of superior effector memory (T EM )-biased T-lymphocyte immune responses. 34 …”