Increased virus dissemination leads to enhanced lung injury but not inflammation during influenza-associated secondary bacterial infection.

Secondary bacterial infections increase influenza-related morbidity and mortality, particularly if acquired after 5-7 d from the viral onset. Synergistic host responses and direct pathogen-pathogen interactions are thought to lead to a state of hyperinflammation, but the kinetics of the lung pathology have not yet been detailed, and identifying the contribution of different mechanisms to disease is difficult because these may change over time. To address this gap, we examined host-pathogen and lung pathology dynamics following a secondary bacterial infection initiated at different time points after influenza within a murine model.

Dynamically linking influenza virus infection kinetics, lung injury, inflammation, and disease severity.

Influenza viruses cause a significant amount of morbidity and mortality. Understanding host immune control efficacy and how different factors influence lung injury and disease severity are critical. We established and validated dynamical connections between viral loads, infected cells, CD8 T cells, lung injury, inflammation, and disease severity using an integrative mathematical model-experiment exchange.

PARAMETER AND UNCERTAINTY ESTIMATION FOR DYNAMICAL SYSTEMS USING SURROGATE STOCHASTIC PROCESSES.

Inference on unknown quantities in dynamical systems via observational data is essential for providing meaningful insight, furnishing accurate predictions, enabling robust control, and establishing appropriate designs for future experiments. Merging mathematical theory with empirical measurements in a statistically coherent way is critical and challenges abound, e.g.

Loss-of-Function RNAi Screen to Identify Necrosis-Signaling Molecules.

Over the recent years, genome-wide RNA interference (RNAi) library screens have been instrumental in the identification of key regulators of various biological pathways. The prolific use of this technique is attributed to its amenability to a high-throughput format. Here, we present the step-by-step method to conduct a siRNA screen to identify genes involved in necroptosis, a nonapoptotic form of proinflammatory cell death.

Influenza Virus Infection Model With Density Dependence Supports Biphasic Viral Decay.

Mathematical models that describe infection kinetics help elucidate the time scales, effectiveness, and mechanisms underlying viral growth and infection resolution. For influenza A virus (IAV) infections, the standard viral kinetic model has been used to investigate the effect of different IAV proteins, immune mechanisms, antiviral actions, and bacterial coinfection, among others. We sought to further define the kinetics of IAV infections by infecting mice with influenza A/PR8 and measuring viral loads with high frequency and precision over the course of infection.

CYLD deubiquitinates RIP1 in the TNFα-induced necrosome to facilitate kinase activation and programmed necrosis.

Background: Necroptosis/programmed necrosis is initiated by a macro-molecular protein complex termed the necrosome. Receptor interacting protein kinase 1 (RIPK1/RIP1) and RIP3 are key components of the necrosome. TNFα is a prototypic inducer of necrosome activation, and it is widely believed that deubiquitination of RIP1 at the TNFR-1 signaling complex precedes transition of RIP1 into the cytosol where it forms the RIP1-RIP3 necrosome.

The RIP1/RIP3 necrosome forms a functional amyloid signaling complex required for programmed necrosis.

RIP1 and RIP3 kinases are central players in TNF-induced programmed necrosis. Here, we report that the RIP homotypic interaction motifs (RHIMs) of RIP1 and RIP3 mediate the assembly of heterodimeric filamentous structures. The fibrils exhibit classical characteristics of β-amyloids, as shown by Thioflavin T (ThT) and Congo red (CR) binding, circular dichroism, infrared spectroscopy, X-ray diffraction, and solid-state NMR.

Viral cell death inhibitor MC159 enhances innate immunity against vaccinia virus infection.

Viral inhibitors of host programmed cell death (PCD) are widely believed to promote viral replication by preventing or delaying host cell death. Viral FLIPs (Fas-linked ICE-like protease [FLICE; caspase-8]-like inhibitor proteins) are potent inhibitors of death receptor-induced apoptosis and programmed necrosis. Surprisingly, transgenic expression of the viral FLIP MC159 from molluscum contagiosum virus (MCV) in mice enhanced rather than inhibited the innate immune control of vaccinia virus (VV) replication.

The molecular regulation of programmed necrotic cell injury.

Proper regulation of cell death is essential for metazoan development and functions. Unlike apoptosis, necrosis is a more inflammatory form of cell death that might contribute to antiviral immunity. Indeed, necrotic cell injury is distinguished from apoptosis by extensive organelle and cell swelling and plasma membrane rupture.

Phosphorylation-driven assembly of the RIP1-RIP3 complex regulates programmed necrosis and virus-induced inflammation.

Programmed necrosis is a form of caspase-independent cell death whose molecular regulation is poorly understood. The kinase RIP1 is crucial for programmed necrosis, but also mediates activation of the prosurvival transcription factor NF-kappaB. We postulated that additional molecules are required to specifically activate programmed necrosis.

The induction of antibody production by IL-6 is indirectly mediated by IL-21 produced by CD4+ T cells.

Interleukin (IL) 6 is a proinflammtory cytokine produced by antigen-presenting cells and nonhematopoietic cells in response to external stimuli. It was initially identified as a B cell growth factor and inducer of plasma cell differentiation in vitro and plays an important role in antibody production and class switching in vivo. However, it is not clear whether IL-6 directly affects B cells or acts through other mechanisms.