CD300lf is the primary physiologic receptor of murine norovirus but not human norovirus

Abstract

<jats:title>Abstract</jats:title><jats:p>Murine norovirus (MNoV) is an important model of human norovirus (HNoV) and mucosal virus infection more broadly. Viral receptor utilization is a major determinant of cell tropism, host range, and pathogenesis. The <jats:italic>bona fide</jats:italic> receptor for HNoV is unknown. Recently, we identified CD300lf as a proteinaceous receptor for MNoV. Interestingly, its paralogue CD300ld was also sufficient for MNoV infection <jats:italic>in vitro</jats:italic>. Here we explored whether CD300lf is the sole physiologic receptor <jats:italic>in vivo</jats:italic> and whether HNoV can use a CD300 ortholog as an entry receptor. We report that both CD300ld and CD300lf are sufficient for infection by diverse MNoV strains <jats:italic>in vitro</jats:italic>. We further demonstrate that CD300lf is essential for both oral and parenteral MNoV infection and to elicit anti-MNoV humoral responses <jats:italic>in vivo</jats:italic>. In mice deficient in STAT1 signaling, CD300lf is required for MNoV-induced lethality. However, after high dose intraperitoneal challenge with MNoV in <jats:italic>Cd300lf</jats:italic><jats:sup>−/−</jats:sup><jats:italic>Stat1</jats:italic><jats:sup>−/−</jats:sup> mice a single amino acid mutation in the MNoV capsid protein emerged. This substitution did not alter receptor utilization <jats:italic>in vitro</jats:italic>. Finally, we demonstrate that human CD300lf (huCD300lf) is not essential for HNoV infection, nor does huCD300lf inhibit binding of HNoV virus-like particles to glycans. Thus, we report huCD300lf is not a receptor for HNoV.</jats:p><jats:sec><jats:title>Author Summary</jats:title><jats:p>Human norovirus is the leading cause of non-bacterial gastroenteritis causing up to 200,000 deaths each year. How human norovirus enters cells is unknown. Because human norovirus is difficult to grow in the laboratory and in small animals, we use mouse or murine norovirus as a model system. We recently discovered that murine norovirus can use the either CD300ld or CD300lf as a receptor <jats:italic>in vitro</jats:italic>. We also showed that CD300lf deficient mice were resistant to oral challenge with a single virus strain. Here we determined that CD300lf is essential for infection of diverse murine norovirus strains in cell lines and in mice with normal immune systems demonstrating it’s the primary physiologic receptor for diverse murine norovirus strains independent of infection route. However, in immunodeficient mice injected with high dose virus directly into the abdominal cavity, we observed a norovirus mutant that enabled CD300lf-independent infection. Finally, we demonstrated that human CD300lf is not the elusive receptor for human norovirus.</jats:p></jats:sec>

CD300LF Polymorphisms of Inbred Mouse Strains Confer Resistance to Murine Norovirus Infection in a Cell Type-Dependent Manner

“…While these attachment factors have been shown to enhance attachment for several different noroviruses, none of them are required for MNV infection. In contrast, recent clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 screens uncovered CD300LF, a type I integral membrane protein containing a single immunoglobulin-like domain, as an indispensable host factor for MNV attachment and entry ( 9 , 10 , 15 ). In fact, expression of murine CD300LF alone was sufficient to confer MNV susceptibility to otherwise resistant host cells, including those from other species, such as human 293T and HeLa cells ( 9 , 10 ).…”

“…Additional receptor molecules and attachment factors have been identified for closely related members of the Caliciviridae family, including feline junctional adhesion molecule A (fJAM-A) as the receptor for feline calicivirus, which has been used historically as a surrogate for HNV ( 16 – 23 ). As understanding the mechanisms by which viruses enter susceptible host cells is integral to understanding the viral life cycle, recent studies on MNV entry have significantly advanced our understanding of norovirus biology ( 9 , 10 , 15 , 24 – 26 ). Nevertheless, the modulation of norovirus entry factors and their mode of interaction with the viruses are still unclear, and it remains to be determined how these factors underlie norovirus host cell tropism.…”

CD300lf Conditional Knockout Mouse Reveals Strain-Specific Cellular Tropism of Murine Norovirus

“…Though genetically similar, minor genetic variants in these MNoV strains confer distinct in vivo phenotypes (25,26,28,29). The viral determinants of infection have been mapped to the viral capsid protein VP1 and the viral non-structural protein NS1 (25)(26)(27)30).…”

“…Variants in NS1 enable MNoV CR6 to antagonize type III interferon and establish persistent enteric infection (25,31). The host determinants of infection include both the MNoV receptor CD300lf and the innate immune system (23,27,28). CD300lf is a type I integral membrane protein that binds phospholipids on dead and dying cells and can induce proor anti-inflammatory signals depending on the specific context (32).…”

CD300lf conditional knockout mouse reveals strain-specific cellular tropism for murine norovirus

“…Though genetically similar, minor genetic variants in these MNoV strains confer distinct in vivo phenotypes (25,26,28,29). The viral determinants of infection have been mapped to the viral capsid protein VP1 and the viral non-structural protein NS1 (25)(26)(27)30).…”