Neurological complications are common in COVID-19. Although SARS-CoV-2 has been detected in patients' brain tissues, its entry routes and resulting consequences are not well understood. Here, we show a pronounced upregulation of interferon signaling pathways of the neurovascular unit in fatal COVID-19. By investigating the susceptibility of human induced pluripotent stem cell (hiPSC)-derived brain capillary endothelial-like cells (BCECs) to SARS-CoV-2 infection, we found that BCECs were infected and recapitulated transcriptional changes detected in vivo. While BCECs were not compromised in their paracellular tightness, we found SARS-CoV-2 in the basolateral compartment in transwell assays after apical infection, suggesting active replication and transcellular transport of virus across the blood-brain barrier (BBB) in vitro. Moreover, entry of SARS-CoV-2 into BCECs could be reduced by anti-spike-, anti-angiotensin-converting enzyme 2 (ACE2)-, and anti-neuropilin-1 (NRP1)-specific antibodies or the transmembrane protease serine subtype 2 (TMPRSS2) inhibitor nafamostat. Together, our data provide strong support for SARS-CoV-2 brain entry across the BBB resulting in increased interferon signaling.

The transport and Golgi organization 1 (TANGO1) proteins play pivotal roles in the secretory pathway. Full length TANGO1 is a transmembrane protein localised at endoplasmic reticulum (ER) exit sites, where it binds bulky cargo within the ER lumen and recruits membranes from the ER Golgi intermediate compartment to create an exit route for their export. Here we report the first TANGO1-associated syndrome in humans. A synonymous substitution that results in exon eight skipping in most mRNA molecules, ultimately leading to a truncated TANGO1 protein was identified as disease-causing mutation. The four homozygously affected sons of a consanguineous family display severe dentinogenesis imperfecta, short stature, various skeletal abnormalities, insulin-dependent diabetes mellitus, sensorineural hearing loss, and mild intellectual disability. Functional studies in HeLa and U2OS cells revealed that the corresponding truncated TANGO1 protein is dispersed in the ER and its expression in cells with intact endogenous TANGO1 impairs cellular collagen I secretion.

Merkel cell carcinoma (MCC), an aggressive neuroendocrine skin tumor, is a polyomavirus‐induced human cancer. To study the causal relationship of MCC carcinogenesis with the integrated Merkel cell polyomavirus (MCPyV) in detail, well‐characterized MCC cell lines are needed. Consequently, in the current study, we established and characterized six MCPyV‐positive MCC cell lines. Microarray‐based comparative genomic hybridization revealed a stable genome carrying only a limited number of chromosomal gains and deletions. All cell lines expressed MCC markers Keratin‐20 and neuron‐specific enolase as well as truncated MCPyV‐encoded large T antigen (LT). For five cell lines, we were able to identify the MCPyV‐integration sites in introns of different genes. The LT‐truncating stop codon mutations and integration sites were affirmed in the respective clinical patient samples. Inverse PCR suggested that three of the cell lines contained MCPyV genomes as concatemers. This notion was confirmed for the two cell lines with known integration sites. Importantly, our observation of distinct stop codon mutations in cell lines with concatemeric MCPyV integration indicates that these LT‐truncating mutations occur before integration. In summary, we provide the detailed characterization of six MCPyV‐positive MCC cell lines, which are likely to serve as valuable tools in future MCC research.

In 2019, the novel highly infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak rapidly led to a global pandemic with more than 346 million confirmed cases worldwide, resulting in 5.5 million associated deaths (January 2022). Entry of all SARS-CoV-2 variants is mediated by the cellular angisin-converting enzyme 2 (ACE2). The virus abundantly replicates in the epithelia of the upper respiratory tract. Beyond vaccines for immunization, there is an imminent need for novel treatment options in COVID-19 patients. So far, only a few drugs have found their way into the clinics, often with modest success. Specific gene silencing based on small interfering RNA (siRNA) has emerged as a promising strategy for therapeutic intervention, preventing/limiting SARS-CoV-2 entry into host cells or interfering with viral replication. Here, we pursued both strategies. We designed and screened nine siRNAs (siA1-9) targeting the viral entry receptor ACE2. SiA1, (siRNA against exon1 of ACE2 mRNA) was most efficient, with up to 90% knockdown of the ACE2 mRNA and protein for at least six days. In vitro, siA1 application was found to protect Vero E6 and Huh-7 cells from infection with SARS-CoV-2 with an up to ∼92% reduction of the viral burden indicating that the treatment targets both the endosomal and the viral entry at the cytoplasmic membrane. Since the RNA-encoded genome makes SARS-CoV-2 vulnerable to RNA interference (RNAi), we designed and analysed eight siRNAs (siV1-8) directly targeting the Orf1a/b region of the SARS-CoV-2 RNA genome, encoding for non-structural proteins (nsp). As a significant hallmark of this study, we identified siV1 (siRNA against leader protein of SARS-CoV-2), which targets the nsp1-encoding sequence (a.k.a. ‘host shutoff factor’) as particularly efficient. SiV1 inhibited SARS-CoV-2 replication in Vero E6 or Huh-7 cells by more than 99% or 97%, respectively. It neither led to toxic effects nor induced type I or III interferon production. Of note, sequence analyses revealed the target sequence of siV1 to be highly conserved in SARS-CoV-2 variants. Thus, our results identify the direct targeting of the viral RNA genome (ORF1a/b) by siRNAs as highly efficient and introduce siV1 as a particularly promising drug candidate for therapeutic intervention.

A prospective, randomized, double-blind and placebo-controlled study was conducted to assess the effectiveness of i.v. administration of 6% hydroxyethyle starch solution (HES) in preventing moderate and severe ovarian hyperstimulation syndrome (OHSS) in patients in an in-vitro fertilization programme. A total of 101 women who had serum oestradiol concentrations >1500 pg/ml and/or more than 10 follicles on day of human chorionic gonadotrophin (HCG) administration were recruited into two groups: HES group (n = 51) received 1000 ml 6% HES; and the placebo group (n = 50) received 1000 ml of sodium chloride 0.9% solution at the time shortly after embryo transfer. Follow-up examinations 7 +/- 1 and 14 +/- 1 days after embryo transfer included transvaginal ultrasound (diameters of each ovary and maximum cysts, number of cysts, ascites), blood tests (serum oestradiol, progesterone, beta-HCG, C-reactive protein, blood count, plasma proteins, electrolytes, kidney function tests) and evaluation of abdominal pain, nausea, diarrhoea, abdominal swelling and weight gain. Only one moderate OHSS developed in the HES group whereas seven moderate-severe cases were observed in the placebo group (P = 0.031). Furthermore, serum oestradiol concentration, leukocyte count, increase in abdominal circumference and weight gain 14 days after embryo transfer were significantly higher in the placebo group. There were no differences between the two groups in terms of age, oestradiol concentration and number of follicles at time of HCG injection. Administration of 6% HES prevents the development of moderate-severe OHSS in risk patients.