C. Dillen

Human NACHT, LRR, and PYD domain–containing protein 3 (NLRP3) inflammasome activity is regulated by and potentially targetable through Bruton tyrosine kinase

Background: The Nod‐like receptor NACHT, LRR, and PYD domain–containing protein 3 (NLRP3) and Bruton tyrosine kinase (BTK) are protagonists in innate and adaptive immunity, respectively. NLRP3 senses exogenous and endogenous insults, leading to inflammasome activation, which occurs spontaneously in patients with Muckle‐Wells syndrome; BTK mutations cause the genetic immunodeficiency X‐linked agammaglobulinemia (XLA). However, to date, few proteins that regulate NLRP3 inflammasome activity in human primary immune cells have been identified, and clinically promising pharmacologic targeting strategies remain elusive. Objective: We sought to identify novel regulators of the NLRP3 inflammasome in human cells with a view to exploring interference with inflammasome activity at the level of such regulators. Methods: After proteome‐wide phosphoproteomics, the identified novel regulator BTK was studied in human and murine cells by using pharmacologic and genetic BTK ablation. Results: Here we show that BTK is a critical regulator of NLRP3 inflammasome activation: pharmacologic (using the US Food and Drug Administration–approved inhibitor ibrutinib) and genetic (in patients with XLA and Btk knockout mice) BTK ablation in primary immune cells led to reduced IL‐1&bgr; processing and secretion in response to nigericin and the Staphylococcus aureus toxin leukocidin AB (LukAB). BTK affected apoptosis‐associated speck‐like protein containing a CARD (ASC) speck formation and caspase‐1 cleavage and interacted with NLRP3 and ASC. S aureus infection control in vivo and IL‐1&bgr; release from cells of patients with Muckle‐Wells syndrome were impaired by ibrutinib. Notably, IL‐1&bgr; processing and release from immune cells isolated from patients with cancer receiving ibrutinib therapy were reduced. Conclusion: Our data suggest that XLA might result in part from genetic inflammasome deficiency and that NLRP3 inflammasome–linked inflammation could potentially be targeted pharmacologically through BTK. Graphical abstract Figure. No Caption available.

Clonally expanded γδ T cells protect against Staphylococcus aureus skin reinfection

The mechanisms that mediate durable protection against Staphylococcus aureus skin reinfections are unclear, as recurrences are common despite high antibody titers and memory T cells. Here, we developed a mouse model of S. aureus skin reinfection to investigate protective memory responses. In contrast with WT mice, IL-1&bgr;–deficient mice exhibited poor neutrophil recruitment and bacterial clearance during primary infection that was rescued during secondary S. aureus challenge. The &ggr;&dgr; T cells from skin-draining LNs utilized compensatory T cell–intrinsic TLR2/MyD88 signaling to mediate rescue by trafficking and producing TNF and IFN-&ggr;, which restored neutrophil recruitment and promoted bacterial clearance. RNA-sequencing (RNA-seq) of the LNs revealed a clonotypic S. aureus–induced &ggr;&dgr; T cell expansion with a complementarity-determining region 3 (CDR3) aa sequence identical to that of invariant V&ggr;5+ dendritic epidermal T cells. However, this T cell receptor &ggr; (TRG) aa sequence of the dominant CDR3 sequence was generated from multiple gene rearrangements of TRGV5 and TRGV6, indicating clonotypic expansion. TNF- and IFN-&ggr;–producing &ggr;&dgr; T cells were also expanded in peripheral blood of IRAK4-deficient humans no longer predisposed to S. aureus skin infections. Thus, clonally expanded &ggr;&dgr; T cells represent a mechanism for long-lasting immunity against recurrent S. aureus skin infections.

Noninvasive optical and nuclear imaging of Staphylococcus-specific infection with a human monoclonal antibody-based probe

ABSTRACT Staphylococcus aureus infections are a major threat in healthcare, requiring adequate early-stage diagnosis and treatment. This calls for novel diagnostic tools that allow noninvasive in vivo detection of staphylococci. Here we performed a preclinical study to investigate a novel fully-human monoclonal antibody 1D9 that specifically targets the immunodominant staphylococcal antigen A (IsaA). We show that 1D9 binds invariantly to S. aureus cells and may further target other staphylococcal species. Importantly, using a human post-mortem implant model and an in vivo murine skin infection model, preclinical feasibility was demonstrated for 1D9 labeled with the near-infrared fluorophore IRDye800CW to be applied for direct optical imaging of in vivo S. aureus infections. Additionally, 89Zirconium-labeled 1D9 could be used for positron emission tomography imaging of an in vivo S. aureus thigh infection model. Our findings pave the way towards clinical implementation of targeted imaging of staphylococcal infections using the human monoclonal antibody 1D9.