Host factor PLAC8 is required for pancreas infection by SARS-CoV-2 (preprint)

Although mounting evidence demonstrated that pancreas is infected by SARS-CoV-2 the severity and pathophysiology of pancreatic COVID-19 disease are still unclear. Here we investigated the consequences of SARS-CoV-2 infection of the pancreas and the role of Placenta-associated protein-8 (PLAC8). Our data showed pancreatic damage in patients who died from COVID-19. Notably, circulating pancreatic enzymes stratified patients according to COVID-19 severity and outcome. PLAC8 expression was associated with SARS-CoV-2 infection in postmortem analysis of COVID-19 patients and functional assays demonstrated the requirement of PLAC8 in SARS-CoV-2 pancreatic infection. Full SARS-CoV-2 infectious virus revealed a requirement of PLAC8 for efficient viral infection of pancreatic cell lines. Finally, we observed colocalization of PLAC8 and SARS-CoV-2 in the pancreas of deceased patients. In conclusion, our data confirm the human pancreas as a SARS-CoV-2 target and demonstrate the requirement of PLAC8 for SARS-CoV-2 pancreatic infection thereby opening new target opportunities for COVID-19-associated pancreatic pathogenesis.

Spike mutation T403R allows bat coronavirus RaTG13 to use human ACE2 (preprint)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of the COVID-19 pandemic, most likely emerged from bats. A prerequisite for this devastating zoonosis was the ability of the SARS-CoV-2 Spike (S) glycoprotein to use human angiotensin-converting enzyme 2 (ACE2) for viral entry. Although the S protein of the closest related bat virus, RaTG13, shows high similarity to the SARS-CoV-2 S protein it does not efficiently interact with the human ACE2 receptor. Here, we show that a single T403R mutation allows the RaTG13 S to utilize the human ACE2 receptor for infection of human cells and intestinal organoids. Conversely, mutation of R403T in the SARS-CoV-2 S significantly reduced ACE2-mediated virus infection. The S protein of SARS-CoV-1 that also uses human ACE2 also contains a positive residue (K) at this position, while the S proteins of CoVs utilizing other receptors vary at this location. Our results indicate that the presence of a positively charged amino acid at position 403 in the S protein is critical for efficient utilization of human ACE2. This finding could help to predict the zoonotic potential of animal coronaviruses.

IFITM proteins promote SARS-CoV-2 infection and are targets for virus inhibition (preprint)

Interferon-induced transmembrane proteins (IFITMs 1, 2 and 3) are thought to restrict numerous viral pathogens including severe acute respiratory syndrome coronaviruses (SARS-CoVs). However, most evidence comes from single-round pseudovirus infection studies of cells that overexpress IFITMs. Here, we verified that artificial overexpression of IFITMs blocks SARS-CoV-2 infection. Strikingly, however, endogenous IFITM expression was essential for efficient infection of genuine SARS-CoV-2 in human lung cells. Our results indicate that the SARS-CoV-2 Spike protein interacts with IFITMs and hijacks them for efficient viral entry. IFITM proteins were expressed and further induced by interferons in human lung, gut, heart and brain cells. Intriguingly, IFITM-derived peptides and targeting antibodies inhibited SARS-CoV-2 entry and replication in human lung cells, cardiomyocytes and gut organoids. Our results show that IFITM proteins are important cofactors for SARS-CoV-2 infection of human cell types representing in vivo targets for viral transmission, dissemination and pathogenesis and suitable targets for therapeutic approaches.

SARS-CoV-2 infects cells of the human exocrine and endocrine pancreas and interferes with beta-cell function (preprint)

Preexisting diabetes increases the risk of a severe course of the pandemic coronavirus disease 2019 (COVID-19). Vice versa, exacerbations of a preexisting diabetes as well as new-onset diabetes have been reported upon SARS-CoV-2 infection. Thus, there is an imperative need to clarify whether human pancreatic endocrine cells organized within an islet of Langerhans are permissive for and affected by SARS-CoV-2 infection, and to elucidate the mechanisms underlying the development of diabetes upon COVID-19. Here, we (i) defined ACE2 and TMPRSS2 expression patterns in human pancreatic endocrine and exocrine cell types, (ii) employed human pancreatic islet cultures to demonstrate susceptibility to SARS-CoV-2 infection and to viral replication in β-cells, (iii) showed that SARS-CoV-2 attenuates glucose-stimulated insulin secretion, and (iv) tested remdesivir as eventually effective to prevent β-cell failure. In addition, we (v) visualized viral particles replicating in endocrine pancreatic cells and define their subcellular localization patterns via transmission electron microscopy, and finally (vi) present examples of cell type specific pancreatic infection patterns of COVID-19 deceased patients. Overall, our data demonstrate that SARS-CoV-2 can infect both the exocrine and endocrine compartments of the pancreas and can perturb β-cell integrity, which might lead to an increased risk for diabetes.

IFITM proteins promote SARS-CoV-2 infection in human lung cells (preprint)

Interferon-induced transmembrane proteins (IFITMs 1, 2 and 3) restrict numerous viral pathogens and are thought to prevent infection by severe acute respiratory syndrome coronaviruses (SARS-CoVs). However, most evidence comes from single-round pseudoparticle infection of cells artificially overexpressing IFITMs. Here, we confirmed that overexpression of IFITMs blocks pseudoparticle infections mediated by the Spike proteins of {beta}-coronaviruses including pandemic SARS-CoV-2. In striking contrast, however, endogenous IFITM expression promoted genuine SARS-CoV-2 infection in human lung cells both in the presence and absence of interferon. IFITM2 was most critical for efficient entry of SARS-CoV-2 and enhanced virus production from Calu-3 cells by several orders of magnitude. IFITMs are expressed and further induced by interferons in the lung representing the primary site of SARS-CoV-2 infection as well as in other relevant tissues. Our finding that IFITMs enhance SARS-CoV-2 infection under conditions approximating the in vivo situation shows that they may promote viral invasion during COVID-19. HIGHLIGHTSO_LIOverexpression of IFITM1, 2 and 3 restricts SARS-CoV-2 infection C_LIO_LIEndogenous IFITM1, 2 and 3 boost SARS-CoV-2 infection of human lung cells C_LIO_LIIFITM2 is critical for efficient entry of SARS-CoV-2 in Calu-3 cells C_LI

Remdesivir but not famotidine inhibits SARS-CoV-2 replication in human pluripotent stem cell-derived intestinal organoids (preprint)

Gastrointestinal symptoms in COVID-19 are associated with prolonged symptoms and increased severity. We employed human intestinal organoids derived from pluripotent stem cells (PSC-HIOs) to analyze SARS-CoV-2 pathogenesis and to validate efficacy of specific drugs in the gut. Certain, but not all cell types in PSC-HIOs express SARS-CoV-2 entry factors ACE2 and TMPRSS2, rendering them susceptible to SARS-CoV-2 infection. Remdesivir, a promising drug to treat COVID-19, effectively suppressed SARS-CoV-2 infection of PSC-HIOs. In contrast, the histamine-2-blocker famotidine showed no effect. Thus, PSC-HIOs provide an interesting platform to study SARS-CoV-2 infection and to identify or validate drugs.