Reits, E. E. | bioRxiv Science

bioRxiv2021

Lipid and nucleocapsid N-protein accumulation in COVID-19 patient lung and infected cells

The pandemic of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global outbreak and prompted an enormous research effort. Still, the subcellular localization of the corona virus in lungs of COVID-19 patients is not well understood. Here, the localization of the SARS-CoV-2 proteins is studied in postmortem lung material of COVID-19 patients and in SARS- CoV-2 infected Vero cells, processed identically. Correlative light and electron microscopy on semi- thick cryo-sections, demonstrated induction of electron-lucent, lipid filled compartments after SARS- CoV-2 infection in both lung and cell cultures. In lung tissue, the non-structural protein 4 and the stable nucleocapsid N-protein, were detected on these novel lipid filled compartments. The induction of such lipid filled compartments and the localization of the viral proteins in lung of patients with fatal COVID-19, may explain the extensive inflammatory response and provide a new hallmark for SARS- Cov-2 infection at the final, fatal stage of infection.

microbiology↗

bioRxiv2020

Both adaptive immunity and IL-1R1 dependent signals improve clearance of cytosolic virulent mycobacteria in vivo

Mycobacterium tuberculosis infections claim more than a million lives each year and better treatments or vaccines are required. A crucial pathogenicity factor is translocation from the phago-lysosomes to the cytosol upon phagocytosis by macrophages. The translocation from the phago-lysosome into the cytosol is an ESX-1 dependent process as previously shown in vitro. Here we show that in vivo, mycobacteria also translocate to the cytosol but mainly when host immunity is compromised. We observed only low numbers of cytosolic bacilli in mice, armadillo, zebrafish and patient material infected with M. tuberculosis, M. marinum or M. leprae. In contrast, when innate or adaptive immunity was compromised, as in SCID or IL-1R1 deficient mice, a significant number of cytosolic M. tuberculosis bacilli were detected in lungs of infected mice. Taken together, M. tuberculosis infection is controlled by adaptive immune responses as well as IL-1R1-mediated signals that result in clearance of cells containing cytosolic mycobacteria in vivo. ImportanceFor decades, Mycobacterium tuberculosis is one of the deathliest pathogens known. Despite infecting approximately one third of the human population, no effective treatment or vaccine is available. A crucial pathogenicity factor is the subcellular localization, as M. tuberculosis can translocate from the phago-lysosome to the cytosol in macrophages. The situation in vivo is more complicated. In this study we establish that high level cytosolic escape of mycobacteria can indeed occur in vivo, but mainly when host resistance is compromised. The IL-1 pathway is crucial for the control of the number of cytosolic mycobacteria. The establishment that immune signals result in clearance of cells containing cytosolic mycobacteria, connects two important fields: cell-biology and immunology which is vital for the understanding of the pathology of M. tuberculosis.

cell biology↗