DDX17 is an essential mediator of sterile NLRC4 inflammasome activation by retrotransposon RNAs.

Detection of microbial products by multiprotein complexes known as inflammasomes is pivotal to host defense against pathogens. Nucleotide-binding domain leucine-rich repeat (NLR) CARD domain containing 4 (NLRC4) forms an inflammasome in response to bacterial products; this requires their detection by NLR family apoptosis inhibitory proteins (NAIPs), with which NLRC4 physically associates. However, the mechanisms underlying sterile NLRC4 inflammasome activation, which is implicated in chronic noninfectious diseases, remain unknown. Here, we report that endogenous short interspersed nuclear element (SINE) RNAs, which promote atrophic macular degeneration (AMD) and systemic lupus erythematosus (SLE), induce NLRC4 inflammasome activation independent of NAIPs. We identify DDX17, a DExD/H box RNA helicase, as the sensor of SINE RNAs that licenses assembly of an inflammasome comprising NLRC4, NLR pyrin domain­containing protein 3, and apoptosis-associated speck-like protein­containing CARD and induces caspase-1 activation and cytokine release. Inhibiting DDX17-mediated NLRC4 inflammasome activation decreased interleukin-18 release in peripheral blood mononuclear cells of patients with SLE and prevented retinal degeneration in an animal model of AMD. Our findings uncover a previously unrecognized noncanonical NLRC4 inflammasome activated by endogenous retrotransposons and provide potential therapeutic targets for SINE RNA­driven diseases.

Voluntary Exercise Suppresses Choroidal Neovascularization in Mice.

Purpose: To determine the effect of voluntary exercise on choroidal neovascularization (CNV) in mice. Methods: Age-matched wild-type C57BL/6J mice were housed in cages equipped with or without running wheels. After four weeks of voluntary running or sedentariness, mice were subjected to laser injury to induce CNV. After surgical recovery, mice were placed back in cages with or without exercise wheels for seven days. CNV lesion volumes were measured by confocal microscopy. The effect of wheel running only in the seven days after injury was also evaluated. Macrophage abundance and cytokine expression were quantified. Results: In the first study, exercise-trained mice exhibited a 45% reduction in CNV volume compared to sedentary mice. In the replication study, a 32% reduction in CNV volume in exercise-trained mice was observed (P = 0.029). Combining these two studies, voluntary exercise was found to reduce CNV by 41% (P = 0.0005). Exercise-trained male and female mice had similar CNV volumes (P = 0.99). The daily running distance did not correlate with CNV lesion size. Exercise only after the laser injury without a preconditioning period did not reduce CNV size (P = 0.41). CNV lesions of exercise-trained mice also exhibited significantly lower F4/80+ macrophage staining and Vegfa and Ccl2 mRNA expression. Conclusions: These findings provide the first experimental evidence that voluntary exercise improves CNV outcomes. These studies indicate that exercise before laser treatment is required to improve CNV outcomes.

IL-15 regulates susceptibility of CD4+ T cells to HIV infection.

HIV integrates into the host genome to create a persistent viral reservoir. Stimulation of CD4+ memory T lymphocytes with common γc-chain cytokines renders these cells more susceptible to HIV infection, making them a key component of the reservoir itself. IL-15 is up-regulated during primary HIV infection, a time when the HIV reservoir established. Therefore, we investigated the molecular and cellular impact of IL-15 on CD4+ T-cell infection. We found that IL-15 stimulation induces SAM domain and HD domain-containing protein 1 (SAMHD1) phosphorylation due to cell cycle entry, relieving an early block to infection. Perturbation of the pathways downstream of IL-15 receptor (IL-15R) indicated that SAMHD1 phosphorylation after IL-15 stimulation is JAK dependent. Treating CD4+ T cells with Ruxolitinib, an inhibitor of JAK1 and JAK2, effectively blocked IL-15-induced SAMHD1 phosphorylation and protected CD4+ T cells from HIV infection. Using high-resolution single-cell immune profiling using mass cytometry by TOF (CyTOF), we found that IL-15 stimulation altered the composition of CD4+ T-cell memory populations by increasing proliferation of memory CD4+ T cells, including CD4+ T memory stem cells (TSCM). IL-15-stimulated CD4+ TSCM, harboring phosphorylated SAMHD1, were preferentially infected. We propose that IL-15 plays a pivotal role in creating a self-renewing, persistent HIV reservoir by facilitating infection of CD4+ T cells with stem cell-like properties. Time-limited interventions with JAK1 inhibitors, such as Ruxolitinib, should prevent the inactivation of the endogenous restriction factor SAMHD1 and protect this long-lived CD4+ T-memory cell population from HIV infection.

Maternal antibody responses to the 52-kd SSA/RO p200 peptide and the development of fetal conduction defects.

OBJECTIVE: To identify a finer level of antibody specificity for risk of congenital heart block (CHB) than reactivity to 52-kd SSA/Ro (Ro 52). METHODS: Serum from mothers enrolled in the Research Registry for Neonatal Lupus and the observational PR Interval and Dexamethasone Evaluation (PRIDE) study was evaluated for reactivity against peptide aa200-239 of Ro 52 (p200), recently reported to be associated with a higher risk of CHB. RESULTS: The majority of 156 Ro 52-positive sera tested were reactive with p200 (>3 SD above control), irrespective of the clinical status of the child. Optical density (OD) values of p200 did not differ significantly among mothers of children with CHB (mean +/- SD 0.187 +/- 0.363), mothers of children with rash (mean +/- SD 0.176 +/- 0.356), and mothers of children without neonatal lupus (mean +/- SD 0.229 +/- 0.315). Reactivity against p200 was found in 80 of 104 mothers of children with CHB (77%), 24 of 30 mothers of children with rash (80%), and 21 of 22 mothers who delivered healthy children and had no children with neonatal lupus (95%) (P not significant for all comparisons). Sera from 4 mothers of children with CHB with varied p200 titers (OD range 0.025-1.818) bound to the surface of non-permeabilized apoptotic, but not proliferating, human fetal cardiocytes. In 32 Ro 52-positive women who completed the PRIDE study (22 with no child with neonatal lupus, 7 with a child with CHB, and 3 with a child with rash) in whom p200 levels were determined during pregnancy, the correlation between level of p200 (OD range 0.000-1.170) and maximal fetal PR interval (range 115-168 msec) was not significant (rho = 0.107, P = 0.58). CONCLUSION: Reactivity to p200 is a dominant but not uniform anti-Ro 52 response in women whose children have CHB. Since exposure to this antibody specificity was observed with a similar frequency in children without CHB born to mothers with anti-Ro 52, additional factors are necessary to convert risk to disease expression.