Biology subjects

Maples, R. W.

Publications and source records attributed to Maples, R. W..

5 recordsLinked to original sources

bioRxiv2026

Circadian Clock Programming of Anticipatory Antiviral Immunity Gates Enteric Virus Infection Susceptibility

Susceptibility to viral infection varies widely but is not fully explained by genetics, immune status, or exposure level. We show that time of day strongly influences infection outcome, with up to 100-fold differences in enteric viral burden depending on infection timing. This temporal gating is abolished in mice lacking a functional circadian clock. We identify the antiviral transcription factor IRF1 as a direct target of the circadian transcription factor BMAL1, resulting in rhythmic expression of a basal antiviral gene program prior to infection. Loss of IRF1 eliminates this program and abrogates time-of-day-dependent differences in viral replication. This circuit operates within intestinal myeloid cells, establishing a preexisting antiviral state. These findings indicate that the circadian clock programs host susceptibility in the intestine, before infection occurs.

immunology↗

bioRxiv2026

A single-cell atlas of intestinal immune cells across the day-night cycle reveals dynamic populations

The small intestine houses an array of immune cells that receive diverse inputs from food intake, microbiota, and other cues that vary by time of day. However, how diurnal variation influences intestinal immune cell proportions and functions is unclear. Here, we use flow cytometry and single cell RNA sequencing to establish an atlas of 815,073 mouse small intestine immune cells at four times across the day-night cycle. These data suggest possible temporal coordination of dendritic cell antigen processing and subsequent T cell antigen recognition. Most cells express circadian clock genes and have intrinsic oscillatory transcriptomes. However, differentiated antibody-producing plasma cells have minimal circadian gene expression and instead may receive extrinsic oscillatory cues from other cell types. Finally, certain populations of B cells are extremely dynamic, with broad transcriptional changes within a six hour time span. This dataset provides insight into the circadian dynamics of intestinal immunity. SummaryO_LIAn atlas of 815,073 small intestine immune cells across four time-points reveals a large proportion of naive B and T cells. C_LIO_LIGene expression profiles suggest coordination of antigen processing in dendritic cells prior to antigen recognition by T cells. C_LIO_LITh17 and innate lymphoid cells have high expression of circadian clock genes and most immune cells have rhythmic gene expression. C_LIO_LIPopulations of certain B cell subtypes, including transitional B cells and centrocytes, are extremely dynamic with large shifts over a six hour time frame. C_LIO_LITerminally differentiated antibody-producing plasma cells have minimal circadian gene expression and few oscillatory genes. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/701519v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@162f451org.highwire.dtl.DTLVardef@1960711org.highwire.dtl.DTLVardef@a9fd4aorg.highwire.dtl.DTLVardef@341f42_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Egress-enhancing mutation reveals inefficiency of non-enveloped virus cell exit

Viruses encounter a range of selective pressures, but inefficiencies during replication can be masked. To uncover factors that limit viral replication, we used forward genetics to enrich for a murine norovirus (MNV) mutant with faster replication. We sequentially harvested the earliest progeny in cultured cells and identified a single amino acid change in the viral NS3 protein, K40R, that was sufficient to enhance replication speed. We found that the NS3-K40R virus induced earlier cell death and viral egress compared with wild-type virus. Mechanistically, NS3-K40R protein disrupted membranes more efficiently than wild-type NS3 protein, potentially contributing to increased mitochondrial dysfunction and cell death. Mice infected with NS3-K40R virus had increased titers, suggesting that increasing egress did not reduce fitness in vivo. Overall, by using a forward genetic approach, we identified a previously unknown inefficiency in norovirus egress and provide new insights into selective pressures that influence viral replication and evolution.

microbiology↗

bioRxiv2024

A Single Mutation in an Enteric Virus Alters Tropism and Sensitivity to Microbiota

Many enteric viruses benefit from the microbiota, and depletion of the microbiota reduces infection of noroviruses and picornaviruses in mice. However, Reovirales viruses are outliers among enteric viruses. Rotavirus infection is inhibited by bacteria, and we determined that several reovirus strains have enhanced replication following microbiota depletion. We found that an isogenic pair of reoviruses have opposing infection outcomes after microbiota depletion. Microbiota depletion reduces infection of reovirus strain T3SA+ but increases infection of strain T3SA-. These strains differ by a single amino acid polymorphism in the {sigma}1 attachment protein, which confers sialic acid binding to T3SA+. Sialic acid binding facilitates T3SA+ infection of intestinal endothelial cells, while T3SA- inefficiently infects intestinal epithelial cells due to restriction by microbiota-driven, host-derived type III interferon responses. This study enhances an understanding of the complex interactions of enteric viruses, the microbiota, intestinal tropism, and antiviral responses. HighlightsO_LIMicrobiota enhance infection of a sialic acid (SA)-binding reovirus strain but inhibit infection of an isogenic non-SA-binding reovirus strain that differs by a single amino acid change. C_LIO_LISA binding facilitates viral infection of intestinal endothelial cells in a microbiota-dependent manner. C_LIO_LIA non-SA-binding reovirus strain inefficiently infects intestinal epithelial cells due to microbiota-driven type III interferon responses. C_LI

microbiology↗

bioRxiv2024

Murine norovirus mutants adapted to replicate in human cells reveal a post-entry restriction

RNA viruses lack proofreading in their RNA polymerases and therefore exist as genetically diverse populations. By exposing these diverse viral populations to selective pressures, viruses with mutations that confer fitness advantages can be enriched. To examine factors important for viral tropism and host restriction, we passaged murine norovirus (MNV) in a human cell line, HeLa cells, to select for mutant viruses with increased fitness in non-murine cells. A major determinant of host range is expression of the MNV receptor CD300lf on mouse cells, but additional host factors may limit MNV replication in human cells. We found that viruses passaged six times in HeLa cells had enhanced replication compared with the parental virus. The passaged viruses had several mutations throughout the viral genome, which were primarily located in the viral non-structural coding regions. While viral attachment was not altered for the passaged viruses, their replication was higher than the parental virus when entry was bypassed, suggesting the mutant viruses overcame a post-entry block in human cells. Three mutations in the viral NS1 protein were sufficient for enhanced post-entry replication in human cells. We found that the human cell-adapted MNV variants had reduced fitness in mouse BV2 cells. Although the mutant viruses had increased fitness in HeLa cells, they did not have increased fitness in mice. Overall, this work suggests that MNV tropism is not only determined by the presence of the viral receptor but also post-entry factors. ImportanceViruses infect specific species and cell types, which is dictated by expression of host factors required for viral entry as well as downstream replication steps. Murine norovirus (MNV) infects mouse cells, but not human cells. However, human cells expressing the murine CD300lf receptor support MNV replication, suggesting receptor expression is a major determinant of MNV tropism. To determine whether other factors influence MNV tropism, we selected for variants with enhanced replication in human cells. We identified mutations that enhance MNV replication in human cells and demonstrated that these mutations enhance infection at a post-entry replication step. Therefore, MNV infection of human cells is restricted at both entry and post-entry stages. These results shed new light on factors that influence viral tropism and host range.

microbiology↗