Biology subjects

Pfeiffer, J. K.

Publications and source records attributed to Pfeiffer, J. K..

At least 19 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

P. aeruginosa rhamnolipids stabilize human rhinovirus 14 virions

Many mammalian viruses encounter bacteria and bacterial molecules over the course of infection. Previous work has shown that the microbial ecology of the gut plays an integral role in poliovirus and coxsackievirus infection, where bacterial glycans can facilitate virus-receptor interactions, enhance viral replication, and stabilize viral particles. However, how airway bacteria alter respiratory viral infection is less understood. Therefore, we investigated whether a panel of airway bacteria affect rhinovirus stability. We found that Pseudomonas aeruginosa, an opportunistic airway pathogen, protects human rhinovirus 14 from acid or heat inactivation. Further investigation revealed that P. aeruginosa rhamnolipids, glycolipids with surfactant properties, are necessary and sufficient for stabilization of rhinovirus virions. Taken together, this work demonstrates that specific molecules produced by an opportunistic airway pathogen can influence a respiratory virus. ImportanceBacteria can enhance viral stability and infection for enteric members of the Picornaviridae such as poliovirus and coxsackievirus; however, whether bacteria influence respiratory picornaviruses is unknown. In this study, we examined impacts of airway bacteria on rhinovirus, a major etiological agent of the common cold. We found that P. aeruginosa protects human rhinovirus 14 from both acid and heat inactivation through rhamnolipids. Overall, this work demonstrates bacterial effects on respiratory virus through specific bacterial molecules.

microbiology↗

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↗

bioRxiv2022

CDKL5 regulates p62-mediated selective autophagy and host antiviral defense

Virophagy, the selective autophagosomal engulfment and degradation of viral components, is crucial for antiviral immunity. However, the mechanisms leading to viral antigen recognition and autophagy induction remain poorly understood. Here, we identify a novel kinase, Cyclin-dependent kinase-like 5 (CDKL5), as an essential regulator of virophagy. Deletion of CDKL5 or abrogation of its kinase activity reduced virophagy of Sindbis virus (SINV), a neurotropic RNA virus, and increased intracellular accumulation of SINV capsid proteins and cellular cytotoxicity. Mechanistically, through direct phosphorylation of the selective autophagy receptor p62, CDKL5 promoted formation of p62 inclusion bodies that bound capsid. Loss of CDKL5 disrupted the capsid-p62 interaction, and a p62 phosphomimetic mutant rescued the interaction. CDKL5 knockout mice demonstrated increased neuronal cell death after SINV infection and enhanced lethality after infection with several human viruses. Overall, these findings identify a cell-autonomous innate immune mechanism for autophagy activation to clear toxic viral capsid aggregates during infection.

microbiology↗

bioRxiv2022

Bacteria-mediated stabilization of murine norovirus

Enteric viruses encounter various bacteria in the host which can impact infection outcomes. The interactions between noroviruses and enteric bacteria are not well understood. Previous work determined that murine norovirus (MNV), a model norovirus, had decreased replication in antibiotic-treated mice compared with conventional mice. Although this suggests that microbiota promote MNV infection, the mechanisms are not completely understood. Additionally, prior work with other enteric viruses such as poliovirus and coxsackievirus B3 demonstrated that virions bind bacteria, and exposure to bacteria stabilizes viral particles and limits premature RNA release. Therefore, we examined interactions between MNV and specific bacteria and the consequences of these interactions. We found that the majority of Gram-positive bacteria tested stabilized MNV, while Gram-negative bacteria did not stabilize MNV. Both Gram-positive and Gram-negative bacteria bound to MNV. However, bacterial binding alone was not sufficient for virion stabilization since Gram-negative bacteria bound MNV but did not stabilize virions. Additionally, we found that bacterial conditioned media also stabilized MNV and this stabilization may be due to a small heat stable molecule. Overall this work identifies specific bacteria and bacterial components that stabilize MNV and may impact virion stability in the environment. ImportanceEnteric viruses are exposed to a wide variety of bacteria in the intestine, but effects of bacteria on viral particles are incompletely understood. We found that murine norovirus (MNV) virion stability is enhanced in the presence of several Gram-positive bacterial strains. Virion stabilizing activity was also present in bacterial culture medium, and activity was retained upon heat or protease treatment. These results suggest that certain bacteria and bacterial products may promote MNV stability in the environment, which could influence viral transmission.

microbiology↗

bioRxiv2021

STING mediates immune responses in a unicellular choanoflagellate

Animals have evolved unique repertoires of innate immune genes and pathways that provide their first line of defense against pathogens. To reconstruct the ancestry of animal innate immunity, we have developed the choanoflagellate Monosiga brevicollis, one of the closest living relatives of animals, as a model for studying mechanisms underlying pathogen recognition and immune response. We found that M. brevicollis is killed by exposure to Pseudomonas aeruginosa bacteria. Moreover, M. brevicollis expresses STING, which, in animals, activates innate immune pathways in response to cyclic dinucleotides during pathogen sensing. M. brevicollis STING increases the susceptibility of M. brevicollis to P. aeruginosa-induced cell death and is required for responding to the cyclic dinucleotide 23 cGAMP. Furthermore, similar to animals, autophagic signaling in M. brevicollis is induced by 23 cGAMP in a STING-dependent manner. This study provides evidence for a pre-animal role for STING in antibacterial immunity and establishes M. brevicollis as a model system for the study of immune responses.

microbiology↗

bioRxiv2021

Tradeoffs for a viral mutant with enhanced replication speed

RNA viruses exist as genetically heterogeneous populations due to high mutation rates and many of these mutations reduce fitness and/or replication speed. However, it is unknown whether mutations can increase replication speed of a virus already well adapted to replication in cultured cells. By sequentially passaging coxsackievirus B3 in cultured cells and collecting the very earliest progeny, we selected for increased replication speed. We found that a single mutation in a viral capsid protein, VP1-F106L, was sufficient for the fast-replication phenotype. Characterization of this mutant revealed quicker genome release during entry compared to wild-type virus, highlighting a previously unappreciated infection barrier. However, this mutation also reduced capsid stability in vitro and reduced replication and pathogenesis in mice. These results reveal a tradeoff between overall replication speed and fitness. Importantly, this approach-- selecting for the earliest viral progeny--could be applied to a variety of viral systems and has the potential to reveal unanticipated inefficiencies in viral replication cycles. SignificanceViruses have characteristic replication speeds within a given cell type. Many factors can slow the rate of viral replication, including attenuating mutations and host antiviral responses. However, it has been unclear whether it would be possible to "speed up" a virus that already replicates efficiently in a specific cell type. Here, we selected for a mutant coxsackievirus with enhanced replication speed by sequentially harvesting the very earliest progeny in multiple rounds of selection. A single mutation conferred the fast replication phenotype. While this mutant virus has enhanced replication in cultured cells due to faster genome uncoating, it was attenuated in mice. These results highlight selective pressures that shape viral populations in different environments.

microbiology↗

bioRxiv2020

Microbiota-Independent Antiviral Effects of Antibiotics on Enteric Viruses

Coxsackieviruses primarily infect the gastrointestinal tract of humans, but they can disseminate systemically and cause severe disease. Using antibiotic treatment regimens to deplete intestinal microbes in mice, several groups have shown that bacteria promote oral infection with a variety of enteric viruses. However, it is unknown whether antibiotics have microbiota-independent antiviral effects for enteric viruses or whether antibiotics influence extra-intestinal, systemic infection. Here, we examined the effects of antibiotics on systemic enteric virus infection by performing intraperitoneal injections of either coxsackievirus B3 (CVB3) or poliovirus followed by quantification of viral titers. We found that antibiotic treatment reduced systemic infection for both viruses. Interestingly, antibiotics reduced CVB3 titers in germ-free mice, suggesting that antibiotic treatment alters CVB3 infection through a microbiota-independent mechanism. Overall, these data provide further evidence that antibiotics can have noncanonical effects on viral infection.

microbiology↗

bioRxiv2019

Use of a glycan library reveals a new model for enteric virus oligosaccharide binding and virion stabilization

Enteric viruses infect the gastrointestinal tract and bacteria can promote replication and transmission of several enteric viruses. Viruses can be inactivated by exposure to heat or bleach, but poliovirus, coxsackievirus B3, and reovirus can be stabilized by bacteria or bacterial polysaccharides, limiting inactivation and aiding transmission. We previously demonstrated that certain N-acetylglucosamine (GlcNAc)-containing polysaccharides can stabilize poliovirus. However, the detailed virus-glycan binding specificity and glycan chain length requirements, and thus the mechanism of virion stabilization, has been unclear. A previous limitation was our lack of defined-length glycans to probe mechanisms and consequences of virus-glycan interactions. Here, we generated a panel of polysaccharides and oligosaccharides to determine the properties required for binding and stabilization of poliovirus. Poliovirus virions are non-enveloped icosahedral 30 nm particles with 60 copies of each of four capsid proteins, VP1-4. VP1 surrounds the fivefold axis and our past work indicates that this region likely contains the glycan binding site. We found that relatively short GlcNAc oligosaccharides, such as a six unit GlcNAc oligomer, can bind poliovirus but fail to enhance virion stability. Virion stabilization required binding of long GlcNAc polymers of greater than 20 units. Our data suggest a model where GlcNAc polymers greater than 20 units bind and bridge adjacent fivefold axes, thus aiding capsid rigidity and stability. This study provides a deeper understanding of enteric virus-bacterial glycan interactions, which is important for virion environmental stability and transmission.\n\nImportanceEnteric viruses are transmitted through the fecal-oral route, but how enteric viruses survive in the environment is unclear. Previously, we found that bacterial polysaccharides enhance poliovirus stability against heat or bleach inactivation, but the specific molecular requirements have been unknown. Here we showed that certain short chain oligosaccharides can bind to poliovirus but do not increase virion stability. Long chain polysaccharides bind and may bridge adjacent sites on the viral surface, thus increasing capsid rigidity and stability. This work defines the unique interactions of poliovirus and glycans, which provides insight into virion environmental stability and transmission.

microbiology↗

bioRxiv2019

Rapid dissemination and monopolization of viral populations in mice revealed using a panel of barcoded viruses

The gastrointestinal tract presents a formidable barrier for pathogens to initiate infection. Despite this barrier, enteroviruses, including coxsackievirus B3 (CVB3), successfully penetrate the intestine to initiate infection and spread systemically prior to shedding in stool. However, the effect of the gastrointestinal barrier on CVB3 population dynamics is relatively unexplored, nor are the selective pressures acting on CVB3 in the intestine well-characterized. To examine viral population dynamics in orally infected mice, we produced over one hundred CVB3 viruses harboring unique nine nucleotide \"barcodes.\" Using this collection of barcoded viruses, we found diverse viral populations throughout each mouse within the first day post-infection, but by 48 hours the viral populations were dominated by less than three barcoded viruses in intestinal and extra-intestinal tissues. Using light-sensitive viruses to track replication status, we found diverse viruses had replicated prior to loss of diversity. Sequencing whole viral genomes from samples later in infection did not reveal detectable viral adaptations. Surprisingly, orally inoculated CVB3 was detectable in pancreas and liver as soon as 20 minutes post inoculation, indicating rapid systemic dissemination. These results suggest rapid dissemination of diverse viral populations, followed by a major restriction in population diversity and monopolization in all examined tissues. These results underscore a complex dynamic between dissemination and clearance for an enteric virus.\n\nImportanceEnteric viruses initiate infection in the gastrointestinal tract but can disseminate to systemic sites. However, the dynamics of viral dissemination are unclear. In this study, we created a library of 135 barcoded coxsackieviruses to examine viral population diversity across time and space following oral inoculation of mice. Overall, we found that the broad population of viruses disseminates early, followed by monopolization of mouse tissues with three or fewer pool members at later time points. Interestingly, we detected virus in systemic tissues such as pancreas and liver just 20 minutes post-oral inoculation. These results suggest rapid dissemination of diverse viral populations, followed by a major restriction in population diversity and monopolization in all examined tissues.

microbiology↗

bioRxiv2019

Related enteric viruses have different requirements for host microbiota in mice

Accumulating evidence suggests that intestinal bacteria promote enteric virus infection in mice. For example, previous work demonstrated that antibiotic treatment of mice prior to oral infection with poliovirus reduced viral replication and pathogenesis. Here we examined the effect of antibiotic treatment on infection with coxsackievirus B3 (CVB3), a picornavirus closely related to poliovirus. We treated mice with a mixture of five antibiotics to deplete host microbiota and examined CVB3 replication and pathogenesis following oral inoculation. We found that, like poliovirus, CVB3 shedding and pathogenesis were reduced in antibiotic-treated mice. While treatment with just two antibiotics, vancomycin and ampicillin, was sufficient to reduce CVB3 replication and pathogenesis, this treatment had no effect on poliovirus. Quantity and composition of bacterial communities were altered by treatment with the five antibiotic cocktail and by treatment with vancomycin and ampicillin. To determine whether more subtle changes in bacterial populations impact viral replication, we examined viral infection in mice treated with milder antibiotic regimens. Mice treated with one-tenth the concentration of the normal antibiotic cocktail supported replication of poliovirus but not CVB3. Importantly, a single dose of one antibiotic, streptomycin, was sufficient to reduce CVB3 shedding and pathogenesis, while having no effect on poliovirus shedding and pathogenesis. Overall, replication and pathogenesis of CVB3 is more sensitive to antibiotic treatment than poliovirus, indicating that closely related viruses may differ in their reliance on microbiota.\n\nImportanceRecent data indicate that intestinal bacteria promote intestinal infection of several enteric viruses. Here we show that coxsackievirus, an enteric virus in the picornavirus family, also relies on microbiota for intestinal replication and pathogenesis. Relatively minor depletion of the microbiota was sufficient to decrease coxsackievirus infection, while poliovirus infection was unaffected. Surprisingly, a single dose of one antibiotic was sufficient to reduce coxsackievirus infection. Therefore, these data indicate that microbiota can influence enteric virus infection through distinct mechanisms, even for closely related viruses.

microbiology↗

bioRxiv2018

The Antibiotic Neomycin Enhances Coxsackievirus Plaque Formation

Coxsackievirus typically infects humans via the gastrointestinal tract, which has a large number of microorganisms collectively referred to as the microbiota. To study how the intestinal microbiota influence enteric virus infection, several groups have used an antibiotic regimen in mice to deplete bacteria. These studies have shown that bacteria promote infection with several enteric viruses. However, very little is known about whether antibiotics influence viruses in a microbiota-independent manner. Here, we sought to determine the effects of antibiotics on coxsackievirus B3 (CVB3) using an in vitro cell culture model in the absence of bacteria. We determined that an aminoglycoside antibiotic, neomycin, enhanced plaque size of CVB3-Nancy strain. Neomycin treatment did not alter viral attachment, translation, or replication. However, we found that the positive charge of neomycin and other positively charged compounds enhanced viral diffusion by overcoming the negative inhibitory effect of sulfated polysaccharides present in agar overlays. Overall, these data lend further evidence that antibiotics can play non-canonical roles in viral infections and that this should be considered when studying enteric virus-microbiota interactions.\n\nImportanceCoxsackieviruses primarily infect the gastrointestinal tract of humans, but they can disseminate systemically and cause severe disease. Using antibiotic treatment regimens to deplete intestinal microbes in mice, several groups have shown the bacteria promote infection with a variety of enteric viruses. However, it is possible that antibiotics have microbiota-independent effects on viruses. Here, we show that an aminoglycoside antibiotic, neomycin, can influence quantification of coxsackievirus in cultured cells in absence of bacteria.

microbiology↗

bioRxiv2018

Bacteria-mediated stabilization of a panel of Picornaviruses

Several viruses encounter various bacterial species within the host and in the environment. Despite these close encounters, the effects of bacteria on picornaviruses specifically is not completely understood. Previous work determined that poliovirus (PV), an enteric virus, has enhanced virion stability when exposed to bacteria or bacterial surface polysaccharides such as lipopolysaccharide. Virion stabilization by bacteria may be important for inter-host transmission since a mutant PV with reduced bacterial binding had a fecal-oral transmission defect in mice. Therefore, we investigated whether bacteria broadly enhance stability of picornaviruses from three different genera: Enterovirus (PV and coxsackievirus B3 (CVB3)), Kobuvirus (Aichi virus) and Cardiovirus (Mengo virus). Furthermore, to delineate strain-specific effects, we examined two strains of CVB3 and a PV mutant with enhanced thermal stability. We determined that specific bacterial strains enhance thermal stability of PV and CVB3, while Mengo virus and Aichi virus are stable at high temperatures in the absence of bacteria. Additionally, we determined that bacteria or lipopolysaccharide can stabilize PV, CVB3, Aichi virus, and Mengo virus during exposure to bleach. These effects are likely mediated through direct interactions with bacteria since viruses bound to bacteria in a pull-down assay. Overall, this work reveals shared and distinct effects of bacteria on a panel of picornaviruses.\n\nIMPORTANCERecent studies have shown that bacteria promote infection and stabilization of poliovirus particles, but the breadth of these effects on other members of the Picornaviridae family is unknown. Here, we compared the effect of bacteria on four distinct members of the Picornaviridae family. We found that bacteria reduced inactivation of all of the viruses during bleach treatment, but not all viral strains were stabilized by bacteria during heat treatment. Overall, our data provide insight into how bacteria play differential roles on picornavirus stability.

microbiology↗

bioRxiv2018

Characterization of a thermal stable poliovirus mutant reveals distinct mechanisms of virion stabilization

Enteric viruses, including poliovirus, are spread by the fecal-oral route. In order to persist and transmit to a new host, enteric virus particles must remain stable once they are in the environment. Environmental stressors such as heat and disinfectants can inactivate virus particles and prevent viral transmission. It has been previously demonstrated that bacteria or bacterial surface glycans can enhance poliovirus virion stability and limit inactivation from heat or bleach. While investigating the mechanisms underlying bacterial-enhanced virion thermal stability, we identified and characterized a poliovirus mutant with increased resistance to heat inactivation. This poliovirus mutant, M132V, harbors a single amino acid change in the VP1 capsid-coding that is sufficient to confer heat resistance. M132V was comparable to wild-type virus for replication in vitro, as well as for replication and pathogenesis in orally-inoculated mice. Although the M132V virus was stable in the absence of bacteria or feces at most temperatures, M132V virus was stabilized by feces at very high temperatures. Additionally, the M132V virus does not have enhanced stability during bleach treatment, suggesting that thermal and bleach inactivation mechanisms are separable. Our results suggest that different mechanisms underlie virion stabilization by bacteria and the M132V mutation. Overall, this work sheds light on factors that influence virion stability.\n\nIMPORTANCEViruses spread by the fecal-oral route need to maintain viability in the environment to ensure transmission. Previous work indicated that bacteria and bacterial surface polysaccharides can stabilize viral particles and enhance transmission. To explore factors that influence viral particle stability, we isolated a mutant poliovirus that is heat resistant. This mutant virus does not require feces for stability at most temperatures, but can be stabilized by feces at very high temperatures. Even though the mutant virus is heat resistant, it is susceptible to inactivation by treatment with bleach. This work provides insight into how viral particles maintain infectivity in the environment.

microbiology↗

bioRxiv2017

Bacteria facilitate viral co-infection of mammalian cells and promote genetic recombination

Intestinal bacteria promote infection of several mammalian enteric viruses, but the mechanisms and consequences are unclear. We screened a panel of 41 bacterial strains as a platform to determine how different bacteria impact enteric viruses. We found that most bacterial strains bound poliovirus, a model enteric virus. Given that each bacterium bound multiple virions, we hypothesized that bacteria may deliver multiple viral genomes to a mammalian cell even when very few virions are present, such as during the first replication cycle after inter-host transmission. We found that exposure to certain bacterial strains increased viral co-infection even when the ratio of virus to host cells was low. Bacteria-mediated viral co-infection correlated with bacterial adherence to cells. Importantly, bacterial strains that induced viral co-infection facilitated viral fitness restoration through genetic recombination. Thus, bacteria-virus interactions may increase viral fitness through viral recombination at initial sites of infection, potentially limiting abortive infections.

microbiology↗