Biology subjects

Lim, E. Y.

Publications and source records attributed to Lim, E. Y..

5 recordsLinked to original sources

bioRxiv2022

Antiviral activity of Cytomegalovirus-specific CD4+ T cells against lytically infected non-haemopoietic cells

HCMV establishes a lifelong latent infection in its host, eliciting a broad immune response involving both the innate and adaptive arms of immunity. In immunocompromised individuals, recovery of the HCMV-specific CD4+ T cell response is associated with a lower risk of HCMV reactivation and disease, suggesting that CD4+ T cells contribute significantly to control of viral replication in vivo. However, most prior studies of the HCMV-specific CD4+ T cell response have been performed with the aim of either predicting those at risk for HCMV reactivation and end-organ disease, or identifying markers which are associated with higher risk of HCMV viraemia. Few studies have examined the mechanisms of viral control of CD4+ T cells in response to cells lytically infected with HCMV. In this paper, we show that CD4+ T cells from a HCMV-seropositive donor can prevent viral dissemination in autologous fibroblasts, that the secretome from these cells is also antiviral, and that IFN-{gamma} is a key cytokine in the secretome. We also show that MHC Class II antigen presentation by monocytes was critical to driving this HCMV-specific CD4+ T cell response.

immunology↗

bioRxiv2022

Impaired neuromodulator crosstalk delays vigilance-dependent astroglia Ca2+ activation in mouse models of Alzheimer's disease

Degeneration in neuronal nuclei producing the neuromodulators acetylcholine and norepinephrine is a hallmark of Alzheimers disease (AD). Therapeutic interventions that increase acetylcholine in brain ameliorate AD symptoms in human patients, and augmenting norepinephrine restores cognitive function in mouse models of AD as well as Down Syndrome, the most frequent cause of early onset AD. A prominent cellular target of noradrenergic and potentially cholinergic signaling during states of heightened vigilance are astroglia and recent studies indicate that astroglia Ca2+ dynamics in awake mice contribute to optimal cognitive performance. Here we tested the hypothesis that vigilance-dependent Ca2+ signaling in mouse primary visual cortex astrocytes is altered in mouse models of AD and provide mechanistic insight into upstream neuromodulator signaling that shapes astrocyte Ca2+ dynamics in healthy and AD conditions. In two mouse models of AD (APPswe/PSEN1dE9 and AppNL-F KI), we consistently observed delayed and less coordinated astrocyte Ca2+ elevations in response to locomotion, a well-controlled behavioral paradigm triggering widespread Ca2+ activation in astroglia throughout the brain. Combining pharmacological and genetic manipulations, we found that noradrenergic signaling to astrocytes was facilitated by cholinergic signaling, but this neuromodulator crosstalk was impaired in AppNL-F mice. Pharmacological facilitation of norepinephrine release rescued delayed and less coordinated astrocyte Ca2+ activation in AppNL-F mice and suggests that astrocytes preserve a functional reserve that can be recruited even during late-stage disease. Our findings of delayed and less coordinated astroglia Ca2+ activation predict impaired noradrenergic signaling and may contribute to the cognitive decline in AD.

neuroscience↗

bioRxiv2022

Constraints of vigilance-dependent noradrenergic signaling to mouse cerebellar Bergmann glia

Behavioral state plays an important role in determining astroglia Ca2+ signaling. In particular, locomotion-mediated elevated vigilance has been found to trigger norepinephrine-dependent whole cell Ca2+ elevations in astroglia throughout the brain. For cerebellar Bergmann glia it has recently been found that locomotion-induced transient Ca2+ elevations depend on their 1A-adrenergic receptors. With increasing availability and implementation of locomotion as behavioral parameter it becomes important to understand the constraints of noradrenergic signaling to astroglia. Here we evaluated the effect of speed, duration and interval of locomotion on Ca2+ signals in Bergmann glia as well as cerebellar noradrenergic axon terminals. We found almost no dependence on locomotion speed, but following the initial Ca2+ transient prolonged locomotion events revealed a steady-state Ca2+ elevation. Comparison of time course and recovery of transient Bergmann glia and noradrenergic terminal Ca2+ dynamics suggested that noradrenergic terminal Ca2+ activity determines Bergmann glia Ca2+ activation and does not require noradrenergic receptor desensitization to account for attenuation during prolonged locomotion. Further, analyzing the correlation among Ca2+ dynamics within regions within the field of observation we found that coordinated activity among noradrenergic terminals accounts for fluctuations of steady-state Bergmann glia Ca2+ activity. Together, our findings will help to better understand astroglia Ca2+ dynamics during less controlled awake behavior and may guide the identification of behavioral contexts preferably dependent on astroglia Ca2+ signaling.

neuroscience↗

bioRxiv2020

Targeting the latent human cytomegalovirus reservoir with virus specific nanobodies

Latent reservoirs of viral pathogens are significant barriers to eradication of these viruses. During latency, herpesviruses maintain their genome, with little gene expression, making latent infections refractory to current treatments targeting viral replication. In the case of human cytomegalovirus (HCMV), sporadic reactivation events are well controlled by the immune system. However, in immunocompromised or immunosuppressed individuals, HCMV reactivation often results in morbidity in solid organ and stem cell transplant patients. Clearance of the latent reservoir could lower the incidence and severity of HCMV-associated disease. Here, we develop a virus specific nanobody (VUN100b) that partially inhibits signaling of the viral receptor US28. VUN100b treatment partially reverses latency without fully reactivating the virus. Moreover, VUN100b treatment drives recognition and killing of latently infected monocytes by autologous cytotoxic T lymphocytes from HCMV-seropositive individuals. This study shows the potential of VUN100b as a therapy to clear the HCMV latent reservoir of transplant patients.

microbiology↗

bioRxiv2019

Interferon-responsive genes are targeted during the establishment of human cytomegalovirus latency

Human cytomegalovirus (HCMV) latency is an active process which remodels the latently infected cell to optimise latent carriage and reactivation. This is achieved, in part, through the expression of viral genes, including the G-protein coupled receptor US28. Here, we use an unbiased proteomic screen to assess changes in host proteins induced by US28, revealing that interferon-inducible genes are downregulated by US28. We validate that MHC Class II and two PYHIN proteins, MNDA and IFI16, are downregulated during experimental latency in primary human CD14+ monocytes. We find that IFI16 is targeted rapidly during the establishment of latency in a US28-dependent manner, but only in undifferentiated myeloid cells, a natural site of latent carriage. Finally, by overexpressing IFI16, we show that IFI16 can activate the viral major immediate early promoter and immediate early gene expression during latency via NF-{kappa}B, a function which explains why downregulation of IFI16 during latency is advantageous for the virus.\n\nImportanceHuman cytomegalovirus (HCMV) is a ubiquitous herpesvirus which infects 50-100% of humans worldwide. HCMV causes a lifelong subclinical infection in immunocompetent individuals, but is a serious cause of mortality and morbidity in the immunocompromised and in neonates. In particular, reactivation of HCMV in the transplant setting is a major cause of transplant failure and related disease. Therefore, a molecular understanding of HCMV latency and reactivation could provide insights into potential ways to target the latent viral reservoir in at-risk patient populations.

microbiology↗