Epstein-Barr virus latently infected cells are selectively deleted in simulated-microgravity cultures

Three-Dimensional Rotating Wall Vessel-Derived Cell Culture Models for Studying Virus-Host Interactions

The key to better understanding complex virus-host interactions is the utilization of robust three-dimensional (3D) human cell cultures that effectively recapitulate native tissue architecture and model the microenvironment. A lack of physiologically-relevant animal models for many viruses has limited the elucidation of factors that influence viral pathogenesis and of complex host immune mechanisms. Conventional monolayer cell cultures may support viral infection, but are unable to form the tissue structures and complex microenvironments that mimic host physiology and, therefore, limiting their translational utility. The rotating wall vessel (RWV) bioreactor was designed by the National Aeronautics and Space Administration (NASA) to model microgravity and was later found to more accurately reproduce features of human tissue in vivo. Cells grown in RWV bioreactors develop in a low fluid-shear environment, which enables cells to form complex 3D tissue-like aggregates. A wide variety of human tissues (from neuronal to vaginal tissue) have been grown in RWV bioreactors and have been shown to support productive viral infection and physiological meaningful host responses. The in vivo-like characteristics and cellular features of the human 3D RWV-derived aggregates make them ideal model systems to effectively recapitulate pathophysiology and host responses necessary to conduct rigorous basic science, preclinical and translational studies.

Failure of propagation of human norovirus in intestinal epithelial cells with microvilli grown in three-dimensional cultures

Human noroviruses (HuNoVs) are a leading cause of acute gastroenteritis. Establishment of a cell culture system for in vitro HuNoV growth remains challenging. Replication of HuNoVs in human intestinal cell lines (INT-407 and Caco-2) that differentiate to produce microvilli in rotation wall vessel (RWV) three-dimensional cultures has been reported (Straub et al. in Emerg Infect Dis 13:396-403, 2007; J Water Health 9:225-240, 2011, and Water Sci Technol 67:863-868, 2013). We used a similar RWV system, intestinal cell lines, and the same (Genogroup [G] I.1) plus additional (GII.4 and GII.12) HuNoV strains to test the system's reproducibility and to expand the earlier findings. Apical microvilli were observed on the surface of both cell lines by light and electron microscopy. However, none of the cell types tested resulted in productive viral replication of any of the HuNoV strains, as confirmed by plateau or declining viral RNA titers in the supernatants and cell lysates of HuNoV-infected cells, determined by real-time reverse transcription PCR. These trends were the same when culture supplements were added that have been reported to be effective for replication of other fastidious enteric viruses in vitro. Additionally, by confocal microscopy and orthoslice analysis, viral capsid proteins were mainly observed above the actin filament signals, which suggested that the majority of viral antigens were on the cell surface. We conclude that even intestinal cells displaying microvilli were not sufficient to support HuNoV replication under the conditions tested.

In vitro cell culture infectivity assay for human noroviruses

A 3-dimensional organoid human small intestinal epithelium model was used.

Human noroviruses cause severe, self-limiting gastroenteritis that typically lasts 24–48 hours. Because of the lack of suitable tissue culture or animal models, the true nature of norovirus pathogenesis remains unknown. We show that noroviruses can infect and replicate in a 3-dimensional (3-D), organoid model of human small intestinal epithelium. Cells grown on porous collage-coated beads under fluid shear conditions in rotating wall vessel bioreactors differentiate into 3-D architectures resembling both the morphologic and physiologic function of in vivo tissues. Microscopy, PCR, and fluorescent in situ hybridization provided evidence of norovirus infection. Cytopathic effect and norovirus RNA were detected at each of the 5 cell passages for genogroup I and II viruses. Our results demonstrate that the highly differentiated 3-D cell culture model can support the natural growth of human noroviruses, whereas previous attempts that used differentiated monolayer cultures failed.