Biology subjects

Spector, S. N.

Publications and source records attributed to Spector, S. N..

4 recordsLinked to original sources

bioRxiv2024

La Crosse virus reassortants highlight genomic determinants of infection and pathogenesis

The genomic determinants that contribute to orthobunyavirus infection and pathogenesis are not well-defined. In this study, we harnessed the process of reassortment to understand which viral factors drive change in the replication and pathogenesis of La Crosse virus (LACV). We systematically reassorted the genomic segments of two genetically similar Lineage I LACV isolates into six unique reassortants. Despite the parental isolates having high levels of RNA and protein consensus, the reassortants demonstrate how minimal changes in RNA and protein structure can have significant changes in viral growth and reproduction in vitro in mammalian and insect models. We observed that swapping the S segment between isolates led to differences in replication and assembly resulting in one non-rescuable reassortant and one viable reassortant that exhibited an increase in viral growth dynamics. Switching the M segment led to changes in viral plaque phenotype and growth kinetics. L segment reassortants similarly differed in changes in viral growth dynamics. We further explored the M segment reassortants in a neonate mouse model and observed a role for the M segment in neuroinflammation and virulence. Through reassortment of the La Crosse virus genomic segments, we are able to further understand how genomic determinants of infection and pathogenesis operate in orthobunyaviruses. Future investigations will focus on identifying the specific molecular elements that govern the observed phenotypes in vitro and in vivo. ImportanceLa Crosse virus is the leading cause of pediatric arboviral encephalitis in the United States, yet it is largely unknown how each of the three genomic segments contribute to pathogenesis and disease. Our study utilizes genomic reassortment between two similar Lineage I LACV isolates to understand genomic determinants for differences in infection and pathogenesis phenotypes in vitro and in vivo. By identifying roles for each segment in observed outcomes, we are able to plan further studies for molecular characterization of these phenotypes. Additionally, it is imperative to continue to characterize orthobunyavirus function since climate change will expand the range and prevalence of arthropod-borne diseases such as LACV in the United States.

microbiology↗

bioRxiv2023

The chikungunya virus E1 glycoprotein fusion loop and hinge alter glycoprotein dynamics leading to cell and host specific changes in infectivity.

Alphaviruses infect both mammals and insects, yet the distinct mechanisms that alphaviruses use to infect different hosts are not well defined. In this study, we characterize CHIKV E1 variants in the fusion loop (E1-M88L) and hinge region (E1-N20Y) in vitro and in vivo to understand how these regions of the E1 glycoprotein contribute to host-specific infection. Through cell culture assays, we found that CHIKV E1-N20Y enhanced infectivity in mosquito cells while the CHIKV E1-M88L variant enhanced virus binding and infectivity in both BHK-21 and C6/36 cells, and led to changes in the virus cholesterol-dependence in BHK-21 cells. Given these in vitro results and that residue E1-M88L is in a defined Mxra8 interacting domain, we hypothesized that this residue may be important for receptor usage. However, while the CHIKV E1-M88L variant increased replication in Mxra8-deficient mice compared to WT CHIKV, it was attenuated in vitro in mouse fibroblasts, suggesting that residue E1-M88 may function in a cell-type dependent manner to alter entry. Finally, using molecular dynamics to understand how potential changes in the E1 glycoprotein may impact the CHIKV glycoprotein E1-E2 complex, we found that E1-M88L and other E1 domain II variants lead to changes in both E1 and E2 dynamics. Taken together, these studies show that key residues in the CHIKV E1 fusion loop and hinge region function through changes in E1-E2 dynamics to facilitate cell- and host-dependent entry. ImportanceArthropod-borne viruses (arboviruses) are significant global public health threats, and their continued emergence around the world highlights the need to understand how these viruses replicate at the molecular level. The alphavirus class II glycoproteins are critical for virus entry in mosquitoes and mammals, yet how these proteins function is not completely understood. Therefore, to address these gaps in our knowledge, it is critical to dissect how distinct glycoprotein domains function in vitro and in vivo. Here, we show that changes in the CHIKV E1 fusion loop and hinge contribute to host-specific entry and E1-E2 dynamics, furthering our knowledge of how alphaviruses infect mammals and insects.

microbiology↗

bioRxiv2023

The La Crosse virus class II fusion glycoprotein ij loop contributes to infectivity and cholesterol-dependent entry.

Arthropod-borne viruses (arboviruses) are an emerging and evolving global public health threat with little to no antiviral treatments. La Crosse virus (LACV) from the Bunyavirales order is responsible for pediatric encephalitis cases in the United States, yet little is known about the infectivity of LACV. Given the structural similarities between class II fusion glycoproteins of LACV and chikungunya virus (CHIKV), an alphavirus from the Togaviridae family, we hypothesized that LACV would share similar entry mechanisms to CHIKV. To test this hypothesis, we performed cholesterol-depletion and repletion assays and used cholesterol modulating compounds to study LACV entry and replication. We found that LACV entry was cholesterol-dependent while replication was less affected by cholesterol manipulation. In addition, we generated single point mutants in the LACV ij loop that corresponded to known CHIKV residues important for virus entry. We found that a conserved histidine and alanine residue in the Gc ij loop impaired virus infectivity and attenuate LACV in vitro and in vivo. Finally, we took an evolution-based approach to explore how the LACV glycoprotein evolution in mosquitoes and mice. We found multiple variants that cluster in the Gc glycoprotein head domain, supporting the Gc glycoprotein as a target for LACV adaptation. Together, these results begin to characterize the mechanisms of LACV infectivity and how the LACV glycoprotein contributes to infectivity and pathogenesis. ImportanceVector-borne arboviruses are significant health threats leading to devastating disease worldwide. This emergence and the fact that there are little to no vaccines or antivirals targeting these viruses highlights the need to study how arboviruses replicate at the molecular level. One potential antiviral target is the class II fusion glycoprotein. Alphaviruses, flaviviruses, and bunyaviruses encode a class II fusion glycoprotein that contain strong structural similarities in the tip of domain II. Here we show that the bunyavirus La Crosse virus uses similar mechanisms to entry as the alphavirus chikungunya virus and residues in the ij loop are important for virus infectivity. These studies show that genetically diverse viruses use similar mechanisms through concerned structure domains, suggesting these may be a target for broad-spectrum antivirals to multiple arbovirus families.

microbiology↗

bioRxiv2022

Type I interferon and MAVS signaling restricts chikungunya virus heart infection and cardiac tissue damage

Chikungunya virus (CHIKV) infection has been associated with severe cardiac manifestations, yet, how CHIKV infection leads to heart disease remains unknown. Here, we leveraged both mouse models and human primary cells to define the mechanisms of CHIKV heart infection. We found that CHIKV actively replicates in cardiac fibroblasts and is cleared without significant tissue damage through the induction of a local type-I interferon response from both infected and non-infected cardiac cells. Importantly, signaling through the mitochondrial antiviral-signaling protein (MAVS) is required for viral clearance from the heart. In the absence of MAVS, persistent infection leads to focal myocarditis and major vessel vasculitis persisting for up to 60 days post-infection, suggesting CHIKV can lead to vascular inflammation and potential long-lasting cardiovascular complications. This study provides a model of CHIKV cardiac infection and mechanistic insight into CHIKV-induced heart disease, underscoring the importance of monitoring cardiac function in patients with CHIKV infections.

microbiology↗