Biology subjects

Klein, R. S.

Publications and source records attributed to Klein, R. S..

9 recordsLinked to original sources

bioRxiv2026

NOD2 activation reprograms infiltrating inflammatory monocytes in the Zika virus infected CNS to maintain neural correlates of learning and memory

Zika virus (ZIKV) encephalitis induces cytokine-mediated cognitive deficits which persist long-term. Here, we determined if NOD2-mediated conversion of monocytes from Ly6CHi inflammatory to Ly6CLo anti-inflammatory phenotypes during ZIKV encephalitis preserves neural correlates of learning and memory within the hippocampus. Short-term administration of the NOD2 agonist, muramyl dipeptide (MDP), during peak ZIKV infection prevents synapse elimination and loss of adult hippocampal neurogenesis, without impacting CNS virologic control. Transcriptomic analyses of forebrain immune cells in MDP-treated mice revealed functional modulation of infiltrated monocytes and T cells, reducing their expression of pro-inflammatory cytokines, with limited effects on microglia, compared to controls. Notably, NOD2 activation in peripheral immune cells alone balances innate immune signals, preserving synapses, and increasing macrophage phagocytic capacities that do not target synapses. Our findings identify infiltrating Ly6CHi monocytes as key drivers of long-term cognitive dysfunction following ZIKV encephalitis and as potential therapeutic targets for limiting synapse loss. HighlightsO_LINOD2 activation via MDP phenotypically shifts monocyte subsets from inflammatory to anti-inflammatory during the acute phase of ZIKV encephalitis. C_LIO_LIShort-term MDP administration increases phagocytic machinery and reduces inflammatory cytokine/chemokine production within macrophage populations. C_LIO_LISynapse elimination is attenuated within the hippocampus of ZIKV-infected animals treated with MDP. C_LIO_LIMDP derived effects are mediated through peripherally derived immune cells. C_LI

immunology↗

bioRxiv2024

CCR2 limits inflammatory functions of CD8 TRM cells that impair recognition memory during recovery from WNV encephalitis

Central nervous system (CNS) resident memory CD8 T cells (TRM) that express IFN-{gamma} contribute to neurodegenerative processes, including synapse loss, leading to memory impairments. Here, we show that CCR2 signalling in CD8 TRM that persist within the hippocampus after recovery from CNS infection with West Nile virus (WNV) significantly prevents the development of memory impairments. Using CCR2-deficient mice, we determined that CCR2 expression is not essential for CNS T cell recruitment or virologic control during acute WNV infection. However, transcriptomic analyses of forebrain CCR2+ versus CCR2- CD8 TRM during WNV recovery reveal that CCR2 signalling significantly regulates hippocampal CD8 TRM phenotype and function via extrinsic and intrinsic effects, decreasing the expression of CD103 and granzyme A and IFN-{gamma}, respectively. Consistent with this, WNV-recovered Cd8acreCcr2fl/fl mice exhibit decreased recognition memory. Our findings highlight a neuroprotective role for CCR2 in limiting CD8 T cell-mediated neuroinflammation and cognitive deficits, providing insights into potential therapeutic targets for CNS infections.

immunology↗

bioRxiv2023

Myeloid cell activation during Zika virus encephalitis predicts recovery of functional cortical connectivity

Neurologic complications of Zika virus (ZIKV) infection across the lifespan have been described during outbreaks in Southeast Asia, South America, and Central America since 2016. In the adult CNS ZIKV tropism for neurons is tightly linked to its effects, with neuronal loss within the hippocampus during acute infection and protracted synapse loss during recovery, which is associated with cognitive deficits. The effects of ZIKV on cortical networks have not been evaluated. Although animal behavior assays have been used previously to model cognitive impairment, in vivo brain imaging can provide orthogonal information regarding the health of brain networks in real time, providing a tool to translate findings in animal models to humans. In this study, we use widefield optical imaging to measure cortical functional connectivity (FC) in mice during acute infection with, and recovery from, intracranial infection with a mouse-adapted strain of ZIKV. Acute ZIKV infection leads to high levels of myeloid cell activation, with loss of neurons and presynaptic termini in the cerebral cortex and associated loss of FC primarily within the somatosensory cortex. During recovery, neuron numbers, synapses and FC recover to levels near those of healthy mice. However, hippocampal injury and impaired spatial cognition persist. The magnitude of activated myeloid cells during acute infection predicted both recovery of synapses and the degree of FC recovery after recovery from ZIKV infection. These findings suggest that a robust inflammatory response may contribute to the health of functional brain networks after recovery from infection. Significance StatementDetermining the long-term cognitive impact of infections is clinically challenging. We found that the degree of myeloid cell activation correlated with the degree of recovery of functional connectivity after recovery from ZIKV encephalitis. Using functional cortical connectivity, we demonstrate that interhemispheric cortical connectivity is decreased in individuals with acute ZIKV encephalitis. This correlates with decreased presynaptic terminals in the somatosensory cortex. During recovery from ZIKV infection, presynaptic terminals recover, which is associated with recovered interhemispheric connectivity. This suggests a role for activated myeloid cells in maintenance of cognition and further supports the contribution of synapses in the cortex to functional networks in the brain, which can be detected by widefield optical imaging. These findings also suggest neuroinflammation may play a neuroprotective role in addition to aiding in local virologic control.

biophysics↗

bioRxiv2023

Post-exposure intranasal IFNα suppresses replication and neuroinvasion of Venezualen Equine Encephalitis virus within olfactory sensory neurons

Venezuelan Equine Encephalitis virus (VEEV) may enter the central nervous system (CNS) within olfactory sensory neurons (OSN) that originate in the nasal cavity after intranasal exposure. While it is known that VEEV has evolved several mechanisms to inhibit type I interferon (IFN) signaling within infected cells, whether this inhibits virologic control during neuroinvasion along OSN has not been studied. Here, we utilized an established murine model of intranasal infection with VEEV to assess the cellular targets and IFN signaling responses after VEEV exposure. We found that immature OSN, which express higher levels of the VEEV receptor LDLRAD3 than mature OSN, are the first cells infected by VEEV. Despite rapid VEEV neuroinvasion after intranasal exposure, olfactory neuroepithelium (ONE) and olfactory bulb (OB) IFN responses, as assessed by evaluation of expression of interferon signaling genes (ISG), are delayed for up to 48 hours during VEEV neuroinvasion, representing a potential therapeutic window. Indeed, a single intranasal dose of recombinant IFN triggers early ISG expression in both the nasal cavity and OB. When administered at the time of or early after infection, IFN treatment delayed onset of sequelae associated with encephalitis and extended survival by several days. VEEV replication after IFN treatment was also transiently suppressed in the ONE, which inhibited subsequent invasion into the CNS. Our results demonstrate a critical and promising first evaluation of intranasal IFN for the treatment of human encephalitic alphavirus exposures. AUTHOR SUMMARYVenezuelan Equine Encephalitis virus (VEEV) may enter the brain through the nasal cavity upon intranasal exposure. The nasal cavity normally displays brisk antiviral immune responses, thus it is unclear why this type of exposure leads to fatal VEEV infection. Using an established murine model of intranasal infection with VEEV we identified the initial targets of infection within the nasal cavity and found that antiviral immune responses to virus at this site and during brain infection are delayed for up to 48 hours. Thus, administration of a single intranasal dose of recombinant IFN at the time of or early after infection improved early antiviral immune responses and suppressed viral replication, which delayed onset of brain infection and extended survival by several days. VEEV replication after IFN treatment was also transiently suppressed in the nasal cavity, which inhibited subsequent invasion into the CNS. Our results demonstrate a critical and promising first evaluation of intranasal IFN for the treatment of human VEEV exposures.

immunology↗

bioRxiv2021

Single-cell RNA transcriptome analysis reveals CXCL16/CXCR6 as maintenance factors for CNS tissue resident T cells that drive synapse elimination during viral recovery

BackgroundEmerging RNA viruses that target the central nervous system (CNS) lead to cognitive sequelae in survivors. Studies in humans and mice infected with West Nile virus (WNV), a re-emerging RNA virus associated with learning and memory deficits, revealed microglial-mediated synapse elimination within the hippocampus. Moreover, CNS resident memory T (TRM) cells activate microglia, limiting synapse recovery and inducing spatial learning defects in WNV-recovered mice. The signals involved in T cell-microglia interactions are unknown. MethodsHere, we examined the murine WNV-recovered forebrain using single-cell RNA sequencing to identify putative ligand-receptor pairs involved in intercellular communication between T cells and microglia. Clustering and differential gene analyses were followed by protein validation, genetic and antibody-based approaches utilizing an established murine model of WNV recovery in which microglia and complement promote ongoing hippocampal synaptic loss. ResultsProfiling of host transcriptome at 25 days post-infection revealed a shift in forebrain homeostatic microglia to activated subpopulations with transcriptional signatures that have previously been observed in studies of neurodegenerative diseases. Importantly, CXCL16/CXCR6, a chemokine signaling pathway involved in TRM cell biology, was identified as critically regulating CXCR6 expressing CD8+ TRM cell numbers within the WNV-recovered forebrain. We demonstrate that CXCL16 is highly expressed by all myeloid cells, and its unique receptor, CXCR6, is highly expressed on all CD8+ T cells. Using genetic and pharmacological approaches, we demonstrate that CXCL16/CXCR6 is required not only for the maintenance of WNV-specific, CD8 TRM cells in the post-infectious CNS, but also contributes to their expression of TRM cell markers. Moreover, CXCR6+CD8+ T cells are required for glial activation and ongoing synapse elimination. ConclusionsWe provide a comprehensive assessment of the role of CXCL16/CXCR6 as an interaction link between microglia and CD8+ T cells that maintains forebrain TRM cells, microglial and astrocyte activation, and ongoing synapse elimination in virally recovered animals. We also show that therapeutic targeting of CXCL16 during recovery may reduce CNS CD8+ TRM cells.

immunology↗

bioRxiv2021

Targeting interferon-{lambda} signaling promotes recovery from central nervous system autoimmunity

Type III interferons (IFNLs) are newly discovered cytokines, acting at epithelial and other barriers, that exert immunomodulatory functions in addition to their primary roles in antiviral defense. Here we define a role for IFNLs in maintaining autoreactive T cell effector function and limiting recovery in a murine model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE). Genetic or antibody-based neutralization of the IFNL receptor (IFNLR) resulted in lack of disease maintenance during EAE, with loss of CNS Th1 effector responses and limited axonal injury. Phenotypic effects of IFNLR signaling were traced to increased antigen presenting cell (APC) function, with associated increase in T cell production of IFN{gamma} and GM-CSF. Consistent with this, IFNL levels within lesions of CNS tissues derived from MS patients were elevated compared to MS normal appearing white matter (NAWM). Furthermore, expression of IFNLR was selectively elevated in MS active lesions compared to inactive lesions or NAWM. These findings suggest IFNL signaling as a potential therapeutic target to prevent chronic autoimmune neuroinflammation.

immunology↗

bioRxiv2021

CCR2-dependent monocyte-derived cells restrict SARS-CoV-2 infection

SARS-CoV-2 has caused a historic pandemic of respiratory disease (COVID-19) and current evidence suggests severe disease is associated with dysregulated immunity within the respiratory tract. However, the innate immune mechanisms that mediate protection during COVID-19 are not well defined. Here we characterize a mouse model of SARS-CoV-2 infection and find that early CCR2-dependent infiltration of monocytes restricts viral burden in the lung. We find that a recently developed mouse-adapted MA-SARS-CoV-2 strain, as well as the emerging B. 1.351 variant, trigger an inflammatory response in the lung characterized by expression of pro-inflammatory cytokines and interferon-stimulated genes. scRNA-seq analysis of lung homogenates identified a hyper-inflammatory monocyte profile. Using intravital antibody labeling, we demonstrate that MA-SARS-CoV-2 infection leads to increases in circulating monocytes and an influx of CD45+ cells into the lung parenchyma that is dominated by monocyte-derived cells. We utilize this model to demonstrate that mechanistically, CCR2 signaling promotes infiltration of classical monocytes into the lung and expansion of monocyte-derived cells. Parenchymal monocyte-derived cells appear to play a protective role against MA-SARS-CoV-2, as mice lacking CCR2 showed higher viral loads in the lungs, increased lung viral dissemination, and elevated inflammatory cytokine responses. These studies have identified a CCR2-monocyte axis that is critical for promoting viral control and restricting inflammation within the respiratory tract during SARS-CoV-2 infection.

immunology↗

bioRxiv2020

A single intranasal or intramuscular immunization with chimpanzee adenovirus vectored SARS-CoV-2 vaccine protects against pneumonia in hamsters.

The development of an effective vaccine against SARS-CoV-2, the etiologic agent of COVID-19, is a global priority. Here, we compared the protective capacity of intranasal and intramuscular delivery of a chimpanzee adenovirus-vectored vaccine encoding a pre-fusion stabilized spike protein (ChAd-SARS-CoV-2-S) in Golden Syrian hamsters. While immunization with ChAd-SARS-CoV-2-S induced robust spike protein specific antibodies capable or neutralizing the virus, antibody levels in serum were higher in hamsters immunized by an intranasal compared to intramuscular route. Accordingly, ChAd-SARS-CoV-2-S immunized hamsters were protected against a challenge with a high dose of SARS-CoV-2. After challenge, ChAd-SARS-CoV-2-S-immunized hamsters had less weight loss and showed reductions in viral RNA and infectious virus titer in both nasal swabs and lungs, and reduced pathology and inflammatory gene expression in the lungs, compared to ChAd-Control immunized hamsters. Intranasal immunization with ChAd-SARS-CoV-2-S provided superior protection against SARS-CoV-2 infection and inflammation in the upper respiratory tract. These findings support intranasal administration of the ChAd-SARS-CoV-2-S candidate vaccine to prevent SARS-CoV-2 infection, disease, and possibly transmission.

microbiology↗

bioRxiv2019

Encephalitic alphaviruses exploit caveolae-mediated transcytosis at the blood-brain barrier for CNS entry

Venezuelan and Western equine encephalitis viruses (VEEV and WEEV) invade the CNS early during infection, via neuronal and hematogenous routes (1, 2). While viral replication mediates host-shut off, including expression of type I interferons (IFN) (3, 4), few studies have addressed how alphaviruses gain access to the CNS during established infection or the mechanisms of viral crossing at the blood-brain barrier (BBB). Here, we show that hematogenous dissemination of VEEV and WEEV into the CNS occurs via caveolin (Cav)-1-mediated transcytosis (Cav-MT) across an intact BBB, which is impeded by IFN and inhibitors of RhoA GTPase. Use of reporter and non-replicative strains also demonstrates that IFN signaling mediates viral restriction within cells comprising the neurovascular unit (NVU), differentially rendering brain endothelial cells, pericytes and astrocytes permissive to viral replication. Transmission and immunoelectron microscopy revealed early events in virus internalization and Cav-1-association within brain endothelial cells. Cav-1-deficient mice exhibit diminished CNS VEEV and WEEV titers during early infection, whereas viral burdens in peripheral tissues remained unchanged. Our findings show that alphaviruses exploit Cav-MT to enter the CNS, and that IFN differentially restricts this process at the BBB.\n\nImportanceVEEV, WEEV and EEEV are emerging infectious diseases in the Americas, and they have caused several major outbreaks in the human and horse population during the past few decades. Shortly after infection, these viruses can infect the CNS, resulting in severe long-term neurological deficits or death. Neuroinvasion has been associated with virus entry into the CNS directly from the blood-stream, however the underlying molecular mechanisms have remained largely unknown. Here we demonstrate that following peripheral infection alphavirus augments vesicular formation/trafficking at the BBB and utilizes Cav-MT to cross an intact BBB, a process regulated by activators of Rho GTPAses within brain endothelium. In vivo examination of early viral entry in Cav-1-deficient mice revealed significantly lower viral burdens than in similarly infected wild-type animals. These studies identify a potentially targetable pathway to limit neuroinvasion by alphaviruses.

microbiology↗