Biology subjects

Baldridge, M. T.

Publications and source records attributed to Baldridge, M. T..

3 recordsLinked to original sources

bioRxiv2021

Rotavirus susceptibility of antibiotic-treated mice ascribed to diminished expression of interleukin-22

The commensal microbiota regulates susceptibility to enteric pathogens by fine-tuning mucosal innate immune responses, but how susceptibility to enteric viruses is shaped by the microbiota remains incompletely understood. Past reports have indicated that commensal bacteria may either promote or repress rotavirus replication in the small intestine of mice. We now report that rotavirus replicated more efficiently in the intestines of germ-free and antibiotic-treated mice compared to animals with an unmodified microbiota. Antibiotic treatment also facilitated rotavirus replication in type I and type III interferon (IFN) receptor-deficient mice, revealing IFN-independent proviral effects. Expression of interleukin-22 (IL-22) was strongly diminished in the intestine of antibiotic-treated mice. Treatment with exogenous IL-22 blocked rotavirus replication in microbiota-depleted wild-type and Stat1-/- mice, demonstrating that the antiviral effect of IL-22 in animals with altered microbiome is not dependent on IFN signaling. In antibiotic-treated animals, IL-22-induced a specific set of genes including Fut2, encoding fucosyl-transferase 2 that participates in the biosynthesis of fucosylated glycans which can mediate rotavirus binding. Interestingly, IL-22 also blocked rotavirus replication in antibiotic-treated Fut2-/- mice. Furthermore, IL-22 inhibited rotavirus replication in antibiotic-treated mice lacking key molecules of the necroptosis or pyroptosis pathways of programmed cell death. Taken together, our results demonstrate that IL-22 determines rotavirus susceptibility of antibiotic-treated mice, yet the IL-22-induced effector molecules conferring rotavirus resistance remain elusive.

immunology↗

bioRxiv2020

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

Noroviruses are a leading cause of gastrointestinal infection in humans and mice. Understanding human norovirus (HuNoV) cell tropism has important implications for our understanding of viral pathogenesis. Murine norovirus (MNoV) is extensively used as a surrogate model for HuNoV. We previously identified CD300lf as the receptor for MNoV. Here, we generated a Cd300lf conditional knockout (CD300lfF/F) mouse to elucidate the cell tropism of persistent and non-persistent strains of murine norovirus. Using this mouse model, we demonstrate that CD300lf expression on intestinal epithelial cells (IECs), and on tuft cells in particular, is essential for transmission of the persistent MNoV strain CR6 (MNoVCR6) in vivo. In contrast, the nonpersistent MNoV strain CW3 (MNoVCW3) does not require CD300lf expression on IECs for infection. However, deletion of CD300lf in myelomonocytic cells (LysM Cre+) partially reduces CW3 viral load in lymphoid and intestinal tissues. Disruption of CD300lf expression on B cells (CD19 Cre), neutrophils (Mrp8 Cre), and dendritic cells (CD11c Cre) did not affect CW3 viral RNA levels. Finally, we show that the transcription factor STAT1, which is critical for the innate immune response, partially restricts the cell tropism of MNoVCW3 to LysM+ cells. Taken together, these data demonstrate that CD300lf expression on tuft cells is essential for MNoVCR6, that myelomonocytic cells are a major, but not exclusive, target cell of MNoVCW3, and that STAT1 signaling restricts the cellular tropism of MNoVCW3. This provides the first genetic system to study the cell type-specific role of CD300lf in norovirus pathogenesis. IMPORTANCEHuman noroviruses (HuNoVs) are a leading cause of gastroenteritis resulting in up to 200,000 deaths each year. The receptor and cell tropism of HuNoV in immunocompetent humans are unclear. We use murine norovirus (MNoV) as a model for HuNoV. We recently identified CD300lf as the sole physiologic receptor for MNoV. Here, we leverage this finding to generate a Cd300lf conditional knockout mouse to decipher the contributions of specific cell types to MNoV infection. We demonstrate that persistent MNoVCR6 requires CD300lf expression on tuft cells. In contrast, multiple CD300lf+ cell types, dominated by myelomonocytic cells, are sufficient for non-persistent MNoVCW3 infection. CD300lf expression on epithelial cells, B cells, neutrophils, and dendritic cells is not critical for MNoVCW3 infection. Mortality associated with MNoVCW3 strain in Stat1-/- mice does not require CD300lf expression on LysM+ cells, highlighting that both CD300lf receptor expression and innate immunity regulate MNoV cell tropism in vivo.

microbiology↗

bioRxiv2019

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

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 bona fide 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 in vitro. Here we explored whether CD300lf is the sole physiologic receptor in vivo 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 in vitro. We further demonstrate that CD300lf is essential for both oral and parenteral MNoV infection and to elicit anti-MNoV humoral responses in vivo. In mice deficient in STAT1 signaling, CD300lf is required for MNoV-induced lethality. However, after high dose intraperitoneal challenge with MNoV in Cd300lf-/-Stat1-/- mice a single amino acid mutation in the MNoV capsid protein emerged. This substitution did not alter receptor utilization in vitro. 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. Author SummaryHuman 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 in vitro. 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 its 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.

microbiology↗