We report here that the Shigella invasion plasmid antigen (Ipa)B, which is sufficient to induce apoptosis in macrophages, binds to caspase (Casp)-1, but not to Casp-2 or Casp-3. Casp-1 is activated and its specific substrate interleukin-1␤ is cleaved shortly after Shigella infection. Macrophages isolated from Casp-1 knock-out mice are not susceptible to Shigella-induced apoptosis, although they respond normally to other apoptotic stimuli. Shigella kills macrophages from casp-3, casp-11, and p53 knock-out mice as well as macrophages overexpressing Bcl-2. We propose that Shigella induces apoptosis by directly activating Casp-1 through IpaB, bypassing signal transduction events and caspases upstream of Casp-1. Taken together these data indicate that Shigella-induced apoptosis is distinct from other forms of apoptosis and seems uniquely dependent on Casp-1.

Recent studies have demonstrated that exosomal microRNAs (miRNAs) are novel biomarkers and therapeutic targets for various diseases including vascular disease. However, specific exosomal miRNAs expression in stroke patients has not been reported yet. Here, we explored whether circulating exosomal miRNAs can serve as potential biomarkers for the diagnosis of acute ischemic stroke and discussed the potential for clinical application. Blood samples were collected from acute ischemic stroke patients within the first 72 h (n = 50). Circulating exosomes were exacted by Exoquick exosome isolation kit and characterized by transmission electron microscopy. Western blot was performed to assess the expression of exosomal protein makers. Exosomal miRNA-223 (miR-223) was detected by RT-PCR assay. The relationship between the expression levels of miR-223 and National Institutes of Health Stroke Scale (NIHSS) scores, brain infarct volume, and neurological outcomes were analyzed. Circulating exosomes were isolated and the size of vesicles ranged between 30 and 100 nm. The identification of exosomes was further confirmed by the detection of specific exosomal protein markers CD9, CD63, and Tsg101. Exosomal miR-223 in acute ischemic stroke patients was significantly upregulated compared to control group (p < 0.001). Exosomal miR-223 level was positively correlated with NIHSS scores (r = 0.31, p = 0.03). Exosomal miR-223 expression in stroke patients with poor outcomes was higher than those with good outcomes (p < 0.05). Increased exosomal miR-223 was associated with acute ischemic stroke occurrence, stroke severity, and short-term outcomes. Future studies with large sample are needed to assess the clinical application of exosomal miR-223 as a novel biomarker for ischemic stroke diagnosis.

Summary VRC01-class antibodies neutralize diverse HIV-1 strains by targeting the conserved CD4-binding site. Despite extensive investigations, crucial events in the early stage of VRC01 development remain elusive. We demonstrated how VRC01-class antibodies emerged within a Chinese donor by antigen-specific single B cell sorting, structural and functional studies, longitudinal antibody and virus repertoire analyses. A monoclonal antibody DRVIA7 with modest neutralizing breadth was isolated that displayed a subset of VRC01 signatures. Structures revealed a VRC01-like angle of approach, but less favorable interactions between DRVIA7 light chain CDR1 and N-terminus with N276 and V5 glycans on gp120. While the DRVIA7 lineage was unable to acquire broad neutralization, longitudinal analysis revealed a repertoire-encoded VRC01 light chain CDR3 signature and VRC01-like neutralizing heavy chain precursors that rapidly matured within two years. Thus, light chain accommodation of the glycan shield should be taken into account in vaccine design targeting this conserved site of vulnerability.