Multiple innate signaling pathways cooperate with CD40 to induce potent, CD70-dependent cellular immunity

Abstract

We have previously shown that Toll-like receptor (TLR) agonists cooperate with CD40 to generate CD8 T cell responses exponentially larger than the responses generated with traditional vaccine formulations. We have also shown that combined TLR agonist/anti-CD40 immunization uniquely induces the upregulation of CD70 on antigen bearing dendritic cells (DCs). In contrast, immunization with either a TLR agonist or a CD40 stimulus alone does not significantly increase CD70 expression on DCs. Furthermore, the CD8+ T cell response generated by combined TLR agonist/anti-CD40 immunization is dependent on the expression of CD70 by DCs, as CD70 blockade following immunization dramatically decreases the CD8 T cell response. Here we show that other innate pathways, independent of the TLRs, can also cooperate with CD40 to induce potent, CD70 dependent, CD8 T cell responses. These innate stimuli include Type I IFN (IFN) and αgalactosylceramide (αGalCer) or αC-GalCer, glycolipids that are presented by a nonclassical class I MHC molecule, CD1d, and are able to activate NKT cells. Furthermore, this combined IFN/antiCD40 immunization generates protective memory against bacterial challenge with Listeria monocytogenes. Together these data indicate the importance of assessing CD70 expression on DCs as a marker for the capacity of a given vaccine formulation to potently activate cellular immunity. Our data indicate that optimal induction of CD70 expression requires a coordinated stimulation of both innate (TLR, IFN, αGalCer) and adaptive (CD40) signaling pathways.

Human Anti-CD40 Antibody and Poly IC:LC Adjuvant Combination Induces Potent T Cell Responses in the Lung of Nonhuman Primates

“…CD11c+ myeloid DCs (MDCs) maturation was most pronounced in the αCD40Ab/poly IC:LC group (Figure 1D). We have previously shown that CD70, a co-stimulatory receptor on APCs that binds to CD27 on T cells (8, 25–27), was required for enhancement of CD4+ and CD8+ T cell responses in mice following immunization with αCD40Ab in combination with TLR agonists (8, 9, 28). In our NHP model, administration of αCD40Ab alone also induced high levels of IL-12p40/p70 in the serum at 6–48 hrs, which returned back to baseline by day 8 (Figure 1E).…”

IL-27 is required for shaping the magnitude, affinity distribution, and memory of T cells responding to subunit immunization

“…This failure to recapitulate the magnitude of the T-cell response to Poly I:C/αCD40 indicates that IL-27 cannot completely replicate the complex inflammatory environment instigated by the TLR agonist. We and others previously published on an important role for CD70-CD27 interactions in the T-cell response to combined TLR/ CD40 immunization (24,25,54) as well as to infectious challenge/ vaccination (55)(56)(57)(58). Because IL-27 and CD27 separately are required for maximal T-cell responses after subunit vaccination, neither alone is therefore sufficient for maximal T-cell expansion.…”

T Cell Vaccinology: Beyond the Reflection of Infectious Responses

“…Much like the B cell response, the use of either of these single adjuvants typically produces around 10–50,000 total antigen specific CD8+ T cells [2], a number that is non-protective with respect to T cell responses [13]. In contrast, after a single exposure, the combined innate/CD40 adjuvant can produce a similar number of antigen specific T cells (~1–3 million antigen specific T cells), and in the same time frame (7 days), as the infectious challenge [2, 10, 13, 44, 45]. As a result of the potency of this vaccine adjuvant, we and others [46–48] have spent years studying its underlying mechanisms in mice and have recently shown its capacity to produce robust CD8 and CD4 responses in non-human primates [49].…”

“…In hindsight, we should not have been surprised to find that rather than revealing secrets of the hidden infectious process, we identified signals central only to the efficacy of subunit vaccine adjuvants. Thus far, two signaling pathways have stood out as critical to vaccine-elicited CD8+ T cell responses; CD27 [10, 12, 13, 45] and (coincidently) IL-27 [2]. While the “27s” also influence and modulate the infectious response, their role in the infection is far more qualitative and nuanced than in vaccination where they dictate (in a necessary-but-not-sufficient manner) the magnitude of the primary response and the function of the memory response.…”