Murine astrovirus tropism for goblet cells and enterocytes facilitates an IFN-λ response in vivo and in enteroid cultures

Abstract

Although they globally cause viral gastroenteritis in children, astroviruses are understudied due to the lack of well-defined animal models. While murine astroviruses (muAstVs) chronically infect immunodeficient mice, a culture system and understanding of their pathogenesis is lacking. Here, we describe a platform to cultivate muAstV using air-liquid interface (ALI) cultures derived from mouse enteroids, which support apical infection and release. Chronic muAstV infection occurs predominantly in the small intestine and correlates with higher interferon-lambda (IFN-λ) expression. MuAstV stimulates IFN-λ production in ALI, recapitulating our in vivo findings. We demonstrate that goblet cells and enterocytes are targets for chronic muAstV infection in vivo , and that infection is enhanced by parasite coinfection or type 2 cytokine signaling. Depletion of goblet cells from ALI limits muAstV infection in vitro. During chronic infection, muAstV stimulates IFN-λ production in infected cells and induces ISGs throughout the intestinal epithelium in an IFN-λ-receptor dependent manner. Collectively, our study provides insights into the cellular tropism and innate immune responses to muAstV and establishes an enteroid-based culture system to propagate muAstV in vitro .

Experimental Methods to Study the Pathogenesis of Human Enteric RNA Viruses

“…Importantly, genetic modifications of HIEs have been successfully performed using CRISPR-Cas9 approaches to explore FUT2 requirements and IFN regulation of HuNoV [ 32 , 33 ]; this capacity to genetically modify HIEs is likely to be increasingly applied to enteric viral cultivation studies ( Figure 1 ). HIEs also permit efficient replication of HAstV, with HIEs derived from all intestinal segments supporting the growth of representative strains from all three clades [ 43 , 45 , 46 ]. These studies have shown that HAstV can infect multiple cell types such as goblet cells, mature enterocytes, and intestinal progenitor cells [ 43 , 45 , 46 ], and have revealed the importance of IFN-mediated antiviral responses against HAstV [ 45 ].…”

“…HIEs also permit efficient replication of HAstV, with HIEs derived from all intestinal segments supporting the growth of representative strains from all three clades [ 43 , 45 , 46 ]. These studies have shown that HAstV can infect multiple cell types such as goblet cells, mature enterocytes, and intestinal progenitor cells [ 43 , 45 , 46 ], and have revealed the importance of IFN-mediated antiviral responses against HAstV [ 45 ].…”

“…More recently, murine astrovirus (muAstV) was identified as a small animal model for HAstVs [ 213 , 214 ]. MuAstV has been shown to mediate viral interference against other enteric viruses in immunodeficient hosts [ 215 ], and its tropism for mucus-secreting goblet cells may also permit muAstV to regulate enteric bacterial pathogens [ 46 , 216 ]. Although mouse models of viral infection may not reflect all clinical outcomes of human enteric viruses, their importance in interrogating and defining key aspects of viral regulation in vivo cannot be denied.…”

Intra- and Cross-Species Transmission of Astroviruses

“…For example, the mechanisms of cell entry and cell tropism have not been well characterized. While some light has been shed recently on the tropism of enteric human and murine AstVs [68][69][70], the tropism for AstVs in general-especially AAstVs-remains to be determined. In this review, we summarize the current understanding of the mechanisms of transmission, mutation and recombination, cross-species transmission, and highlight areas of future research in AstV transmission.…”

Beyond the Gastrointestinal Tract: The Emerging and Diverse Tissue Tropisms of Astroviruses

“…However, murine astroviruses have not been clearly associated with a specific disease in mice, as uninfected mice excrete virus in their stool but do not develop diarrhea or systemic signs upon infection [ 53 , 54 ]. Murine astrovirus infection has been localized to goblet cells in mice leading to alterations in mucus production and subsequently, the gut microbiome, but these changes do not appear to cause a clear phenotype [ 55 , 56 ]. Interestingly, murine astroviruses may also play an important role in shaping immunity of the GI tract.…”