High-throughput drug screen identifies calcium and calmodulin inhibitors that reduce JCPyV infection

JC polyomavirus (JCPyV) is a nonenveloped, double-stranded DNA virus that infects the majority of the population. Immunocompetent individuals harbor infection in their kidneys, while severe immunosuppression can result in JCPyV spread to the brain, causing the neurodegenerative disease progressive multifocal leukoencephalopathy (PML). Due to a lack of approved therapies to treat JCPyV and PML, the disease results in rapid deterioration, and is often fatal. In order to identify potential antiviral treatments for JCPyV, a high-throughput, large-scale drug screen was performed using the National Institutes of Health Clinical Collection (NCC). Drugs from the NCC were tested for inhibitory effects on JCPyV infection, and drugs from various classes that reduced JCPyV infection were identified, including receptor agonists and antagonists, calcium signaling modulators, and enzyme inhibitors. Given the role of calcium signaling in viral infection including Merkel cell polyomavirus and simian virus 40 polyomavirus (SV40), calcium signaling inhibitors were further explored for the capacity to impact JCPyV infection. Calcium and calmodulin inhibitors trifluoperazine (TFP), W-7, tetrandrine, and nifedipine reduced JCPyV infection, and TFP specifically reduced viral internalization. Additionally, TFP and W-7 reduced infection by BK polyomavirus, SV40, and SARS-CoV-2. These results highlight specific inhibitors, some FDA-approved, for the possible treatment and prevention of JCPyV and several other viruses, and further illuminate the calcium and calmodulin pathway as a potential target for antiviral drug development.

Dynamics and Patterning of 5-Hydroxytryptamine 2 Subtype Receptors in JC Polyomavirus Entry

The organization and dynamics of plasma membrane receptors are a critical link in virus-receptor interactions, which finetune signaling efficiency and determine cellular responses during infection. Characterizing the mechanisms responsible for the active rearrangement and clustering of receptors may aid in developing novel strategies for the therapeutic treatment of viruses. Virus-receptor interactions are poorly understood at the nanoscale, yet they present an attractive target for the design of drugs and for the illumination of viral infection and pathogenesis. This study utilizes super-resolution microscopy and related techniques, which surpass traditional microscopy resolution limitations, to provide both a spatial and temporal assessment of the interactions of human JC polyomavirus (JCPyV) with 5-hydroxytrypamine 2 receptors (5-HT₂Rs) subtypes during viral entry. JCPyV causes asymptomatic kidney infection in the majority of the population and can cause fatal brain disease, and progressive multifocal leukoencephalopathy (PML), in immunocompromised individuals. Using Fluorescence Photoactivation Localization Microscopy (FPALM), the colocalization of JCPyV with 5-HT₂ receptor subtypes (5-HT_2A, 5-HT_2B, and 5-HT_2C) during viral attachment and viral entry was analyzed. JCPyV was found to significantly enhance the clustering of 5-HT₂ receptors during entry. Cluster analysis of infected cells reveals changes in 5-HT₂ receptor cluster attributes, and radial distribution function (RDF) analyses suggest a significant increase in the aggregation of JCPyV particles colocalized with 5-HT₂ receptor clusters in JCPyV-infected samples. These findings provide novel insights into receptor patterning during viral entry and highlight improved technologies for the future development of therapies for JCPyV infection as well as therapies for diseases involving 5-HT₂ receptors.

The MAPK/ERK Pathway and the Role of DUSP1 in JCPyV Infection of Primary Astrocytes

JC polyomavirus (JCPyV) is a neuroinvasive pathogen causing a fatal, demyelinating disease of the central nervous system (CNS) known as progressive multifocal leukoencephalopathy (PML). Within the CNS, JCPyV predominately targets two cell types: oligodendrocytes and astrocytes. The underlying mechanisms of astrocytic infection are poorly understood, yet recent findings suggest critical differences in JCPyV infection of primary astrocytes compared to a widely studied immortalized cell model. RNA sequencing was performed in primary normal human astrocytes (NHAs) to analyze the transcriptomic profile that emerges during JCPyV infection. Through a comparative analysis, it was validated that JCPyV requires the mitogen-activated protein kinase, extracellular signal-regulated kinase (MAPK/ERK) pathway, and additionally requires the expression of dual-specificity phosphatases (DUSPs). Specifically, the expression of DUSP1 is needed to establish a successful infection in NHAs, yet this was not observed in an immortalized cell model of JCPyV infection. Additional analyses demonstrated immune activation uniquely observed in NHAs. These results support the hypothesis that DUSPs within the MAPK/ERK pathway impact viral infection and influence potential downstream targets and cellular pathways. Collectively, this research implicates DUSP1 in JCPyV infection of primary human astrocytes, and most importantly, further resolves the signaling events that lead to successful JCPyV infection in the CNS.

Human DNA Virus Exploitation of the MAPK-ERK Cascade

The extracellular signal-regulated kinases (ERKs) comprise a particular branch of the mitogen-activated protein kinase cascades (MAPK) that transmits extracellular signals into the intracellular environment to trigger cellular growth responses. Similar to other MAPK cascades, the MAPK-ERK pathway signals through three core kinases—Raf, MAPK/ERK kinase (MEK), and ERK—which drive the signaling mechanisms responsible for the induction of cellular responses from extracellular stimuli including differentiation, proliferation, and cellular survival. However, pathogens like DNA viruses alter MAPK-ERK signaling in order to access DNA replication machineries, induce a proliferative state in the cell, or even prevent cell death mechanisms in response to pathogen recognition. Differential utilization of this pathway by multiple DNA viruses highlights the dynamic nature of the MAPK-ERK pathway within the cell and the importance of its function in regulating a wide variety of cellular fates that ultimately influence viral infection and, in some cases, result in tumorigenesis.

High-Throughput Characterization of Viral and Cellular Protein Expression Patterns During JC Polyomavirus Infection

JC polyomavirus (JCPyV) is a ubiquitous human pathogen and the causative agent of a fatal demyelinating disease in severely immunocompromised individuals. Due to the lack of successful pharmacological interventions, the study of JCPyV infection strategies in a rapid and highly sensitive manner is critical for the characterization of potential antiviral therapeutics. Conventional methodologies for studying viral infectivity often utilize the detection of viral proteins through immunofluorescence microscopy-based techniques. While these methodologies are well established in the field, they require significant time investments and lack a high-throughput modality. Scanning imager-based detection methods like the In-cell Western (ICW)^TM have been previously utilized to overcome these challenges incurred by traditional microscopy-based infectivity assays. This automated technique provides not only rapid detection of viral infection status, but can also be optimized to detect changes in host-cell protein expression during JCPyV challenge. Compared to traditional manual determinations of infectivity through microscopy-based techniques, the ICW provides an expeditious and robust determination of JCPyV infection. The optimization of the ICW for the detection of viral and cellular proteins during JCPyV infection provides significant time and cost savings by diminishing sample preparation time and increasing resource utilization. While the ICW cannot provide single-cell analysis information and is limited in the detection of quantitation of low-expressing proteins, this assay provides a high-throughput system to study JCPyV, previously unavailable to the field. Thus, the high-throughput nature and dynamic experimental range of the ICW can be applied to the study of JCPyV infection.