here is increasing evidence that SARS-CoV-2 not only affects the respiratory tract but also impacts the CNS, resulting in neurological symptoms such as loss of smell and taste, headache , fatigue, nausea and vomiting in more than one-third of individuals with COVID-19 (refs. 1,2). Moreover, acute cerebrovascular disease and impaired consciousness have been reported 3. While Olfactory transmucosal SARS-CoV-2 invasion as a port of central nervous system entry in individuals with COVID-19

Idiopathic infantile arterial calcification (IIAC; OMIM 208000) is characterized by calcification of the internal elastic lamina of muscular arteries and stenosis due to myointimal proliferation. We analyzed affected individuals from 11 unrelated kindreds and found that IIAC was associated with mutations that inactivated ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1). This cell surface enzyme generates inorganic pyrophosphate (PP(i)), a solute that regulates cell differentiation and serves as an essential physiologic inhibitor of calcification.

A paper published in Science identifies how certain opportunistic pathogens including Pseudomonas aeruginosa-attenuate the host innate immune response with C12, a quorum-sensing and immunomodulatory compound synthesized by certain bacteria. 1 Although the host receptor for C12 remains unknown, the group at The Scripps Research Institute did show that the molecule disrupts NF-κB signaling.

Innate immune system receptors function as sensors of infection and trigger the immune responses through ligand-specific signaling pathways. These ligands are pathogen-associated products, such as components of bacterial walls and viral nuclear acids. A common response to such ligands is the activation of mitogen-activated protein kinase p38, whereas doublestranded viral RNA additionally induces the phosphorylation of eukaryotic translation initiation factor 2␣ (eIF2␣). Here we have shown that p38 and eIF2␣ phosphorylation represent two biochemical markers of the effects induced by N-(3-oxo-acyl)homoserine lactones, the secreted products of a number of Gramnegative bacteria, including the human opportunistic pathogen Pseudomonas aeruginosa. Furthermore, N-(3-oxo-dodecanoyl)homoserine lactone induced distension of mitochondria and the endoplasmic reticulum as well as c-jun gene transcription. These effects occurred in a wide variety of cell types including alveolar macrophages and bronchial epithelial cells, requiring the structural integrity of the lactone ring motif and its natural stereochemistry. These findings suggest that N-(3-oxo-acyl)homoserine lactones might be recognized by receptors of the innate immune system. However, we provide evidence that N-(3-oxo-dodecanoyl)homoserine lactone-mediated signaling does not require the presence of the canonical innate immune system receptors, Toll-like receptors, or two members of the NLR/Nod/Caterpillar family, Nod1 and Nod2. These data offer a new understanding of the effects of N-(3-oxo-dodecanoyl)homoserine lactone on host cells and its role in persistent airway infections caused by P. aeruginosa.

Autologous retinal pigment epithelium (RPE) grafts derived from induced pluripotent stem cells (iPSCs) may be used to cure blinding diseases in which RPE dysfunction results in photoreceptor degeneration. Four, two, and one factor-derived iPS (4F-, 2F-, and 1F-iPSCs, respectively) were differentiated into fully functional cuboidal shaped pigmented cells in polarized monolayers that express RPE-specific markers. 1F-iPS-RPE strongly resemble primary human fetal RPE (hfRPE) based on proteomic and untargeted metabolomic analyses, and, utilizing novel in vivo imaging technology coupled with electroretinography, we demonstrate that 1F-iPS-RPE mediate anatomical and functional rescue of photoreceptors after transplantation in an animal model of RPE-mediated retinal degeneration. 1F-iPS-RPE cells were injected subretinally as a suspension and formed a monolayer dispersed between host RPE cells. Furthermore, 1F-iPS-RPE do not simply provide trophic support to rescue photoreceptors as previously speculated, but actually phagocytose photoreceptor outer segments in vivo and restore visual cycling (based on high-resolution mass spectrometry based detection of recycled photoreceptor protein and lipid end products and electron microscopic analysis). Thus, 1F-iPS-RPE grafts may be superior to conventional iPS-RPE for clinical use since 1F-iPS-RPE closely resemble hfRPE, mediate anatomical and functional photoreceptor rescue in vivo and are generated using a reduced number of potentially oncogenic reprogramming factors.

The SARS-CoV-2 pandemic has so far claimed over three and a half million lives worldwide. Though the SARS-CoV-2 mediated disease COVID-19 has first been characterized by an infection of the upper airways and the lung, recent evidence suggests a complex disease including gastrointestinal symptoms. Even if a direct viral tropism of intestinal cells has recently been demonstrated, it remains unclear, whether gastrointestinal symptoms are caused by direct infection of the gastrointestinal tract by SARS-CoV-2 or whether they are a consequence of a systemic immune activation and subsequent modulation of the mucosal immune system. To better understand the cause of intestinal symptoms we analyzed biopsies of the small intestine from SARS-CoV-2 infected individuals. Applying qRT-PCR and immunohistochemistry, we detected SARS-CoV-2 RNA and nucleocapsid protein in duodenal mucosa. In addition, applying imaging mass cytometry and immunohistochemistry, we identified histomorphological changes of the epithelium, which were characterized by an accumulation of activated intraepithelial CD8+ T cells as well as epithelial apoptosis and subsequent regenerative proliferation in the small intestine of COVID-19 patients. In summary, our findings indicate that intraepithelial CD8+ T cells are activated upon infection of intestinal epithelial cells with SARS-CoV-2, providing one possible explanation for gastrointestinal symptoms associated with COVID-19.

Our case series is limited by the absence of a control group and the retrospective analysis that was conducted. Large-scale prospective studies and pharmacovigilance monitoring are warranted to clarify the risks of VZV reactivation for all available SARS-CoV-2 vaccines. It should be determined whether all SARS-CoV-2 share a similar risk for this adverse reaction and should some of them be relatively safer in this regard, consideration should be given when choosing a vaccine for individuals most at risk for VZV reactivation (e.g. elderly, immunosuppression).

Bacillus anthracis lethal toxin (LT) is a key virulence factor of anthrax and contributes significantly to the in vivo pathology. The enzymatically active component is a Zn2+-dependent metalloprotease that cleaves most isoforms of mitogen-activated protein kinase kinases (MKKs). Using ex vivo differentiated human lung epithelium we report that LT destroys lung epithelial barrier function and wound healing responses by immobilizing the actin and microtubule network. Long-term exposure to the toxin generated a unique cellular phenotype characterized by increased actin filament assembly, microtubule stabilization, and changes in junction complexes and focal adhesions. LT-exposed cells displayed randomly oriented, highly dynamic protrusions, polarization defects and impaired cell migration. Reconstitution of MAPK pathways revealed that this LT-induced phenotype was primarily dependent on the coordinated loss of MKK1 and MKK2 signaling. Thus, MKKs control fundamental aspects of cytoskeletal dynamics and cell motility. Even though LT disabled repair mechanisms, agents such as keratinocyte growth factor or dexamethasone improved epithelial barrier integrity by reducing cell death. These results suggest that co-administration of anti-cytotoxic drugs may be of benefit when treating inhalational anthrax.