SARS-CoV-2 drives NLRP3 inflammasome activation in human microglia through spike protein.

Coronavirus disease-2019 (COVID-19) is primarily a respiratory disease, however, an increasing number of reports indicate that SARS-CoV-2 infection can also cause severe neurological manifestations, including precipitating cases of probable Parkinson's disease. As microglial NLRP3 inflammasome activation is a major driver of neurodegeneration, here we interrogated whether SARS-CoV-2 can promote microglial NLRP3 inflammasome activation. Using SARS-CoV-2 infection of transgenic mice expressing human angiotensin-converting enzyme 2 (hACE2) as a COVID-19 pre-clinical model, we established the presence of virus in the brain together with microglial activation and NLRP3 inflammasome upregulation in comparison to uninfected mice. Next, utilising a model of human monocyte-derived microglia, we identified that SARS-CoV-2 isolates can bind and enter human microglia in the absence of viral replication. This interaction of virus and microglia directly induced robust inflammasome activation, even in the absence of another priming signal. Mechanistically, we demonstrated that purified SARS-CoV-2 spike glycoprotein activated the NLRP3 inflammasome in LPS-primed microglia, in a ACE2-dependent manner. Spike protein also could prime the inflammasome in microglia through NF-κB signalling, allowing for activation through either ATP, nigericin or α-synuclein. Notably, SARS-CoV-2 and spike protein-mediated microglial inflammasome activation was significantly enhanced in the presence of α-synuclein fibrils and was entirely ablated by NLRP3-inhibition. Finally, we demonstrate SARS-CoV-2 infected hACE2 mice treated orally post-infection with the NLRP3 inhibitory drug MCC950, have significantly reduced microglial inflammasome activation, and increased survival in comparison with untreated SARS-CoV-2 infected mice. These results support a possible mechanism of microglial innate immune activation by SARS-CoV-2, which could explain the increased vulnerability to developing neurological symptoms akin to Parkinson's disease in COVID-19 infected individuals, and a potential therapeutic avenue for intervention.

SARS-CoV-2 triggers complement activation through interactions with heparan sulfate.

Objectives: To determine whether SARS-CoV-2 can trigger complement activation, the pathways that are involved and the functional significance of the resultant effect. Methods: SARS-CoV-2 was inoculated into a human lepirudin-anticoagulated whole blood model, which contains a full repertoire of complement factors and leukocytes that express complement receptors. Complement activation was determined by measuring C5a production with an ELISA, and pretreatment with specific inhibitors was used to identify the pathways involved. The functional significance of this was then assessed by measuring markers of C5a signalling including leukocyte C5aR1 internalisation and CD11b upregulation with flow cytometry. Results: SARS-CoV-2 inoculation in this whole blood model caused progressive C5a production over 24 h, which was significantly reduced by inhibitors for factor B, C3, C5 and heparan sulfate. However, this phenomenon could not be replicated in cell-free plasma, highlighting the requirement for cell surface interactions with heparan sulfate. Functional analysis of this phenomenon revealed that C5aR1 signalling and CD11b upregulation in granulocytes and monocytes was delayed and only occurred after 24 h. Conclusion: SARS-CoV-2 is a noncanonical alternative pathway activator that progressively triggers complement activation through interactions with heparan sulfate.

COVID-19: Complement, Coagulation, and Collateral Damage.

Coronavirus disease of 2019 (COVID-19) is a highly contagious respiratory infection that is caused by the severe acute respiratory syndrome coronavirus 2. Although most people are immunocompetent to the virus, a small group fail to mount an effective antiviral response and develop chronic infections that trigger hyperinflammation. This results in major complications, including acute respiratory distress syndrome, disseminated intravascular coagulation, and multiorgan failure, which all carry poor prognoses. Emerging evidence suggests that the complement system plays a key role in this inflammatory reaction. Indeed, patients with severe COVID-19 show prominent complement activation in their lung, skin, and sera, and those individuals who were treated with complement inhibitors all recovered with no adverse reactions. These and other studies hint at complement's therapeutic potential in these sequalae, and thus, to support drug development, in this review, we provide a summary of COVID-19 and review complement's role in COVID-19 acute respiratory distress syndrome and coagulopathy.

Complement: Bridging the innate and adaptive immune systems in sterile inflammation.

The complement system is a collection of soluble and membrane-bound proteins that together act as a powerful amplifier of the innate and adaptive immune systems. Although its role in infection is well established, complement is becoming increasingly recognized as a key contributor to sterile inflammation, a chronic inflammatory process often associated with noncommunicable diseases. In this context, damaged tissues release danger signals and trigger complement, which acts on a range of leukocytes to augment and bridge the innate and adaptive immune systems. Given the detrimental effect of chronic inflammation, the complement system is therefore well placed as an anti-inflammatory drug target. In this review, we provide a general outline of the sterile activators, effectors, and targets of the complement system and a series of examples (i.e., hypertension, cancer, allograft transplant rejection, and neuroinflammation) that highlight complement's ability to bridge the 2 arms of the immune system.

Inactivation of Salmonella in organic soil by cinnamaldehyde, eugenol, Ecotrol, and Sporan.

Salmonella can survive in soil for months to years; consequently, soil can be a preharvest source of contamination of produce. Elimination of Salmonella with natural products and processes such as essential oils is important to prevent infection among consumers. Essential oils (distilled extract from plants) have been mainly evaluated in liquid medium and foods in which minimum inhibitory concentration is determined. However, there are no reports describing the impact of essential oils in soil, especially organic soil. We evaluated essential oils for controlling Salmonella enterica serovars in organic soil. Two essential oils (cinnamaldehyde and eugenol), two bio-pesticides (Ecotrol and Sporan), and an organic acid (20% acetic acid) at 0.5%, 1.0%, 1.5%, and 2.0% were mixed with organic sandy soil and inoculated with six different serovars of S. enterica separately. Soils were incubated at room temperature, and samples obtained at 1, 7, and 28 days were enumerated to determine survival. The bactericidal effect of cinnamaldehyde was evident at 0.5%, 1.0%, 1.5%, and 2.0% and during all times of incubation. Overall, Salmonella Negev was the most sensitive strain to oils resulting in significant reductions compared with other strains. Increases in oil concentration resulted in further reduction of Salmonella with all oils used in the study. Up to six log reductions in Salmonella serovars Typhimurium, Negev, and Newport were found after 1 day when cinnamaldehyde, Ecotrol, eugenol, Sporan, or acetic acid was used at 2% level. This study shows the potential use of essential oils to effectively reduce Salmonella populations in soil. The significant reduction of Salmonella could greatly reduce potential contamination of fresh organic produce inadvertently contaminated by soil.

Transport of Mars-crossing asteroids from the quasi-Hilda region.

We employ set oriented methods in combination with graph partitioning algorithms to identify key dynamical regions in the Sun-Jupiter-particle three-body system. Transport rates from a region near the 3:2 Hilda resonance into the realm of orbits crossing Mars' orbit are computed. In contrast to common numerical approaches, our technique does not depend on single long term simulations of the underlying model. Thus, our statistical results are particularly reliable since they are not affected by a dynamical behavior which is almost nonergodic (i.e., dominated by strongly almost invariant sets).

Geometric mechanics and the dynamics of asteroid pairs.

The purpose of this paper is to describe the general setting for the application of techniques from geometric mechanics and dynamical systems to the problem of asteroid pairs. The paper also gives some preliminary results on transport calculations and the associated problem of calculating binary asteroid escape rates. The dynamics of an asteroid pair, consisting of two irregularly shaped asteroids interacting through their gravitational potential is an example of a full-body problem or FBP in which two or more extended bodies interact. One of the interesting features of the binary asteroid problem is that there is coupling between their translational and rotational degrees of freedom. General FBPs have a wide range of other interesting aspects as well, including the 6-DOF guidance, control, and dynamics of vehicles, the dynamics of interacting or ionizing molecules, the evolution of small body, planetary, or stellar systems, and almost any other problem in which distributed bodies interact with each other or with an external field. This paper focuses on the specific case of asteroid pairs using techniques that are generally applicable to many other FBPs. This particular full two-body problem (F2BP) concerns the dynamical evolution of two rigid bodies mutually interacting via a gravitational field. Motivation comes from planetary science, where these interactions play a key role in the evolution of asteroid rotation states and binary asteroid systems. The techniques that are applied to this problem fall into two main categories. The first is the use of geometric mechanics to obtain a description of the reduced phase space, which opens the door to a number of powerful techniques, such as the energy-momentum method for determining the stability of equilibria and the use of variational integrators for greater accuracy in simulation. Second, techniques from computational dynamic systems are used to determine phase space structures that are important for transport phenomena and dynamic evolution.

Statistical theory of asteroid escape rates.

Transition states in phase space are identified and shown to regulate the rate of escape of asteroids temporarily captured in circumplanetary orbits. The transition states, similar to those occurring in chemical reaction dynamics, are then used to develop a statistical semianalytical theory for the rate of escape of asteroids temporarily captured by Mars. Theory and numerical simulations are found to agree to better than 1%. These calculations suggest that further development of transition state theory in celestial mechanics, as an alternative to large-scale numerical simulations, will be a fruitful approach to mass transport calculations.

Heteroclinic connections between periodic orbits and resonance transitions in celestial mechanics.

In this paper we apply dynamical systems techniques to the problem of heteroclinic connections and resonance transitions in the planar circular restricted three-body problem. These related phenomena have been of concern for some time in topics such as the capture of comets and asteroids and with the design of trajectories for space missions such as the Genesis Discovery Mission. The main new technical result in this paper is the numerical demonstration of the existence of a heteroclinic connection between pairs of periodic orbits: one around the libration point L(1) and the other around L(2), with the two periodic orbits having the same energy. This result is applied to the resonance transition problem and to the explicit numerical construction of interesting orbits with prescribed itineraries. The point of view developed in this paper is that the invariant manifold structures associated to L(1) and L(2) as well as the aforementioned heteroclinic connection are fundamental tools that can aid in understanding dynamical channels throughout the solar system as well as transport between the "interior" and "exterior" Hill's regions and other resonant phenomena. (c) 2000 American Institute of Physics.