The IL-1 family cytokines are regulated on transcriptional and posttranscriptional levels. Pattern recognition and cytokine receptors control pro-IL-1β transcription whereas inflammasomes regulate the proteolytic processing of pro-IL-1β. The NLRP3 inflammasome, however, assembles in response to extracellular ATP, pore-forming toxins, or crystals only in the presence of proinflammatory stimuli. How the activation of gene transcription by signaling receptors enables NLRP3 activation remains elusive and controversial. In this study, we show that cell priming through multiple signaling receptors induces NLRP3 expression, which we identified to be a critical checkpoint for NLRP3 activation. Signals provided by NF-κB activators are necessary but not sufficient for NLRP3 activation, and a second stimulus such as ATP or crystal-induced damage is required for NLRP3 activation.

In many human infections, hosts and pathogens coexist for years or decades. Important examples include HIV, herpes viruses, tuberculosis, leprosy, and malaria. With the exception of intensively studied viral infections such as HIV͞AIDs, little is known about the extent to which the clonal expansion that occurs during long-term infection by pathogens involves important genetic adaptations. We report here a detailed, whole-genome analysis of one such infection, that of a cystic fibrosis (CF) patient by the opportunistic bacterial pathogen Pseudomonas aeruginosa. The bacteria underwent numerous genetic adaptations during 8 years of infection, as evidenced by a positive-selection signal across the genome and an overwhelming signal in specific genes, several of which are mutated during the course of most CF infections. Of particular interest is our finding that virulence factors that are required for the initiation of acute infections are often selected against during chronic infections. It is apparent that the genotypes of the P. aeruginosa strains present in advanced CF infections differ systematically from those of ''wild-type'' P. aeruginosa and that these differences may offer new opportunities for treatment of this chronic disease.chronic infection ͉ positive selection ͉ virulence ͉ antibiotic resistance M ost cystic fibrosis (CF) patients acquire chronic Pseudomonas aeruginosa infections by their teenage years, if not earlier, and these respiratory infections are responsible for much of the morbidity and mortality caused by CF (1, 2). It has been established that most of these infections are clonal (3), and even among groups of CF patients treated in specific clinics the infections are acquired independently, presumably from diverse environmental reservoirs (4). Previous studies, particularly of the O-antigen biosynthetic locus and the transcriptional regulator mucA, indicate that some P. aeruginosa genes commonly incur loss-of-function mutations as the infections progress (5-7). Mutator phenotypes also arise frequently (8).The overall picture is reminiscent of typical cancers: a clone of cells, albeit in this instance one of exogenous origin, experiences selection for an accumulation of genetic variants that promote long-term survival and clonal expansion. Our data validate this model for P. aeruginosa infections in CF and provide strong evidence for the role of selection in shaping the genotypes of the bacteria that are present during the late, life-threatening phase of the infections. Our data also focus attention on particular aspects of P. aeruginosa metabolism that are premier targets of selection, both in the patient we studied in most detail and in other, independently evolving, P. aeruginosa infections in additional CF patients.

Autosomal recessive interleukin-1 receptor-associated kinase (IRAK)-4 and myeloid differentiation factor (MyD)88 deficiencies impair Toll-like receptor (TLR)- and interleukin-1 receptor-mediated immunity. We documented the clinical features and outcome of 48 patients with IRAK-4 deficiency and 12 patients with MyD88 deficiency, from 37 kindreds in 15 countries. The clinical features of IRAK-4 and MyD88 deficiency were indistinguishable. There were no severe viral, parasitic, and fungal diseases, and the range of bacterial infections was narrow. Noninvasive bacterial infections occurred in 52 patients, with a high incidence of infections of the upper respiratory tract and the skin, mostly caused by Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The leading threat was invasive pneumococcal disease, documented in 41 patients (68%) and causing 72 documented invasive infections (52.2%). P. aeruginosa and Staph. aureus documented invasive infections also occurred (16.7% and 16%, respectively, in 25% and 25% of patients). Systemic signs of inflammation were usually weak or delayed. The first invasive infection occurred before the age of 2 years in 53 (88.3%) and in the neonatal period in 19 (32.7%) patients. Multiple or recurrent invasive infections were observed in most survivors (n = 36/50, 72%).