Recognition of microbial viability via TLR8 drives TFH cell differentiation and vaccine responses

Live attenuated vaccines are generally highly efficacious and often superior to inactivated vaccines, yet the underlying mechanisms of this remain largely unclear. Here we identify recognition of microbial viability as a potent stimulus for follicular helper T cell (TFH cell) differentiation and vaccine responses. Antigen-presenting cells (APCs) distinguished viable bacteria from dead bacteria through Toll-like receptor 8 (TLR8)-dependent detection of bacterial RNA. In contrast to dead bacteria and other TLR ligands, live bacteria, bacterial RNA and synthetic TLR8 agonists induced a specific cytokine profile in human and porcine APCs, thereby promoting TFH cell differentiation. In domestic pigs, immunization with a live bacterial vaccine induced robust TFH cell and antibody responses, but immunization with its heat-killed counterpart did not. Finally, a hypermorphic TLR8 polymorphism was associated with protective immunity elicited by vaccination with bacillus Calmette-Guérin (BCG) in a human cohort. We have thus identified TLR8 as an important driver of TFH cell differentiation and a promising target for TFH cell–skewing vaccine adjuvants

Tumor Microenvironment in Pancreatic Intraepithelial Neoplasia

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive tumors with a poor prognosis. A characteristic of PDAC is the formation of an immunosuppressive tumor microenvironment (TME) that facilitates bypassing of the immune surveillance. The TME consists of a desmoplastic stroma, largely composed of cancer-associated fibroblasts (CAFs), immunosuppressive immune cells, immunoregulatory soluble factors, neural network cells, and endothelial cells with complex interactions. PDAC develops from various precursor lesions such as pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasms (IPMN), mucinous cystic neoplasms (MCN), and possibly, atypical flat lesions (AFL). In this review, we focus on the composition of the TME in PanINs to reveal detailed insights into the complex restructuring of the TME at early time points in PDAC progression and to explore ways of modifying the TME to slow or even halt tumor progression

Targeting HSP90 dimerization via the C-terminus is effective in imatinib resistant CML and lacks heat shock response

Heat shock protein 90 (HSP90) stabilizes many client proteins including BCR-ABL1 oncoprotein. BCR-ABL1 is the hallmark of CML in which treatment-free remission (TFR) is limited with clinical and economic consequences. Thus, there is an urgent need for novel therapeutics, which synergize with current treatment approaches. Several inhibitors targeting the N-terminal domain (NTD) of HSP90 are under investigation; however, side effects such as induction of heat shock response (HSR) and toxicity have so far precluded their FDA approval. We have developed a novel inhibitor (referred to as aminoxyrone) of HSP90 function by targeting HSP90 dimerization via the C-terminal domain (CTD). This was achieved by structure-based molecular design, chemical synthesis, and functional pre-clinical in vitro and in vivo validation using CML cell lines and patient-derived CML cells. Aminoxyrone (AX) is a promising potential candidate, which induces apoptosis in leukemic stem cells (LSCs) fraction (CD34+CD38-) as well as the leukemic bulk (CD34+CD38+) of primary CML and in TKI-resistant cells. Furthermore, BCR-ABL1 oncoprotein and related pro-oncogenic cellular responses are downregulated and targeting HSP90 C-terminus by AX does not induce HSR in vitro and in vivo. We also probed the potential of AX in other therapy refractory leukemia such as BCR-ABL1+ BCP-ALL, FLT3-ITD+ AML and Ph-like BCP-ALL. Therefore, AX is the first peptidometic C-terminal HSP90 inhibitor with the potential to increase TFR in TKI sensitive and refractory CML patients and also offers a novel therapeutic option for patients with other therapy-refractory leukemia, due to its low toxicity profile and lack of HSR

Infectious stimuli promote malignant B-cell acute lymphoblastic leukemia in the absence of AID

The prerequisite to prevent childhood B-cell acute lymphoblastic leukemia (B-ALL) is to decipher its etiology. The current model suggests that infection triggers B-ALL development through induction of activation-induced cytidine deaminase (AID; also known as AICDA) in precursor B-cells. This evidence has been largely acquired through the use of ex vivo functional studies. However, whether this mechanism governs native non-transplant B-ALL development is unknown. Here we show that, surprisingly, AID genetic deletion does not affect B-ALL development in Pax5-haploinsufficient mice prone to B-ALL upon natural infection exposure. We next test the effect of premature AID expression from earliest pro-B-cell stages in B-cell transformation. The generation of AID off-target mutagenic activity in precursor B-cells does not promote B-ALL. Likewise, known drivers of human B-ALL are not preferentially targeted by AID. Overall these results suggest that infections promote B-ALL through AID-independent mechanisms, providing evidence for a new model of childhood B-ALL development