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- Immunology
Senescent-like Microglia Limit Remyelination Through the Senescence Associated Secretory Phenotype
Gross et al., Nature Communications. 2025.
https://www.nature.com/articles/s41467-025-57632-w
Multiple sclerosis (MS) is a chronic, immune-mediated demyelinating disease in which immune cells infiltrate the central nervous system and promote deterioration of myelin and neurodegeneration. The capacity to regenerate myelin in the central nervous system diminishes with age. In this study, researchers used 2- to 3-month-old (young), 12-month-old (middle-aged), and 18- to 22-month-old (aged) C57BL/6 male and female mice. Results showed an upregulation of the senescence marker P16ink4a (P16) in microglial and macrophage cells within demyelinated lesions. Notably, treatment of senescent cells using genetic and pharmacological senolytic methods leads to enhanced remyelination in young and middle-aged mice but fails to improve remyelination in aged mice. These results suggest that therapeutic targeting of senescence-associated secretory phenotype components may improve remyelination in aging and MS. Supported by ORIP (R24OD036199), NIA, NINDS, and NIMH.
A Switch from Glial to Neuronal Gene Expression Alterations in the Spinal Cord of SIV-Infected Macaques on Antiretroviral Therapy
Mulka et al., Journal of Neuroimmune Pharmacology. 2024.
https://pubmed.ncbi.nlm.nih.gov/38862787/
Up to one-third of patients with HIV experience HIV-associated peripheral neuropathy, affecting sensory pathways in the spinal cord. Spinal cord sampling is limited in people with HIV. Researchers examined gene expression alterations in the spinal cords of simian immunodeficiency virus (SIV)-infected male pigtail macaques with and without antiretroviral therapy (ART), using RNA sequencing at key time points throughout infection. Results indicate a shift from glial cell-associated pathways to neuronal pathways in SIV-infected animals receiving ART. These findings suggest that neurons, rather than glia, are predominantly involved in ART-related neurotoxicity and offer new insights into therapeutic strategies for maintaining synaptic homeostasis. Supported by ORIP (U42OD013117, T32OD011089) and NINDS.
SIV-Specific Antibodies Protect Against Inflammasome-Driven Encephalitis in Untreated Macaques
Castell et al., Cell Reports. 2024.
https://pmc.ncbi.nlm.nih.gov/articles/PMC11552693
Viral infections are the most common infectious cause of encephalitis, and simian immunodeficiency virus (SIV)–infected macaques are a well-established model for HIV. Researchers investigated the protective effects of SIV-specific antibodies against inflammation-driven encephalitis in using untreated, SIV-infected, male and female pigtail and rhesus macaques. Findings indicate that these antibodies reduce neuroinflammation and encephalitis, highlighting the importance of antibodies in controlling neuroimmune responses, especially in the absence of antiretroviral therapy. This study provides insight into immune-modulatory approaches to combating inflammation-driven encephalopathies. Supported by ORIP (U42OD013117, T32OD011089), NIDA, NHLBI, NIAID, NINDS, and NIMH.
RNA Landscapes of Brain and Brain-Derived Extracellular Vesicles in Simian Immunodeficiency Virus Infection and Central Nervous System Pathology
Huang et al., The Journal of Infectious Diseases. 2024.
https://pubmed.ncbi.nlm.nih.gov/38079216/
Brain tissue–derived extracellular vesicles (bdEVs) act locally in the central nervous system (CNS) and may indicate molecular mechanisms in HIV CNS pathology. Using brain homogenate (BH) and bdEVs from male pigtailed macaques, researchers identified dysregulated RNAs in acute and chronic infection. Most dysregulated messenger RNAs (mRNAs) in bdEVs reflected dysregulation in source BH, and these mRNAs are disproportionately involved in inflammation and immune responses. Additionally, several circular RNAs were differentially abundant in source tissue and might be responsible for specific differences in small RNA levels in bdEVs during simian immunodeficiency virus (SIV) infection. This RNA profiling shows potential regulatory networks in SIV infection and SIV-related CNS pathology. Supported by ORIP (U42OD013117), NCI, NIAID, NIDA, NIMH, and NINDS.
Synthetic Protein Circuits for Programmable Control of Mammalian Cell Death
Xia et al., Cell. 2024.
https://pubmed.ncbi.nlm.nih.gov/38657604/
Natural cell-death pathways have been shown to eliminate harmful cells and shape immunity. Researchers used synthetic protein-level cell-death circuits, collectively termed “synpoptosis” circuits, to proteolytically regulate engineered executioner proteins and mammalian cell death. They show that the circuits direct cell death modes, respond to combinations of protease inputs, and selectively eliminate target cells. This work provides a foundation for programmable control of mammalian cell death. Future studies could focus on programmable control of cell death in various contexts, including cancer, senescence, fibrosis, autoimmunity, and infection. Supported by ORIP (F30OD036190) and NIBIB.
Lymphoid Tissues Contribute to Plasma Viral Clonotypes Early After Antiretroviral Therapy Interruption in SIV-Infected Rhesus Macaques
Solis-Leal et al., Science Translational Medicine. 2023.
https://pubmed.ncbi.nlm.nih.gov/38091409/
Researchers are interested in better understanding the sources, timing, and mechanisms of HIV rebound that occurs after interruption of antiretroviral therapy (ART). Using rhesus macaques (sex not specified), investigators tracked barcoded simian immunodeficiency virus (SIV) clonotypes over time and among tissues. Among the tissues studied, mesenteric lymph nodes, inguinal lymph nodes, and spleen contained viral barcodes detected in plasma. Additionally, the authors reported that CD4+ T cells harbored the most viral RNA after ART interruption. These tissues are likely to contribute to viral reactivation and rebound after ART interruption, but further studies are needed to evaluate the relative potential contributions from other tissues and organs. Supported by ORIP (P51OD011104, P51OD011133, S10OD028732, S10OD028653), NCI, NIMH, and NINDS.
Very-Long-Chain Fatty Acids Induce Glial-Derived Sphingosine-1-Phosphate Synthesis, Secretion, and Neuroinflammation
Chung et al., Cell Metabolism. 2023.
https://pubmed.ncbi.nlm.nih.gov/37084732/
Very-long-chain fatty acids (VLCFAs) are the most abundant fatty acids in myelin. During age‑associated degeneration of myelin, glia are exposed to increased levels of VLCFAs. Investigators previously described a novel phenotype in patients that harbors a novel variant in the peroxisomal enzyme ACOX1. Here, they report that that glial loss of ACOX1 leads to an increase of VLCFAs, which results in a concomitant increase in sphingosine-1-phosphate (S1P). They found that suppressing S1P function attenuates the pathological phenotypes caused by excess VLCFAs. This work suggests that lowering of VLCFAs and S1P could be applied as a treatment avenue for multiple sclerosis. Supported by ORIP (R24OD022005, R24OD031447, P40OD018537), NINDS, and NICHD
HIV-1 Remission: Accelerating the Path to Permanent HIV-1 Silencing
Lyons et al., c. 2023.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10674359/
Current HIV treatment strategies are focused on forced proviral reactivation and elimination of reactivated cells with immunological or toxin-based technologies. Researchers have proposed the use of a novel “block-lock-stop” approach, which entails the long-term durable silencing of viral expression and permanent transcriptional deactivation of the latent provirus. In the present study, the authors present this approach and its rationale. More research is needed to understand the (1) epigenetic architecture of integrated provirus, (2) cell types and epigenetic cell states that favor viral rebound, (3) molecular functions of Tat (a protein that controls transcription of HIV) and host factors that prevent permanent silencing, (4) human endogenous retrovirus silencing in the genome, and (5) approaches to generate defective proviruses. Additionally, community engagement is crucial for this effort. Supported by ORIP (K01OD031900), NIAID, NCI, NIDA, NIDDK, NHLBI, NIMH, and NINDS.
Interferon Regulatory Factor 7 Modulates Virus Clearance and Immune Responses to Alphavirus Encephalomyelitis
Troisi et al., Journal of Virology. 2023.
https://pubmed.ncbi.nlm.nih.gov/37772825/
Interferon regulatory factor 7 (IRF7)–deficient mice develop fatal paralysis after CNS infection with Sindbis virus, while wild-type mice recover. Irf7-/- mice produce low levels of IFN-α but high levels of IFN-β with induction of IFN-stimulated genes, so the reason for this difference is not understood. The current study shows that Irf7-/- mice developed inflammation earlier but failed to clear virus from motor neuron–rich regions of the brainstem and spinal cord. Therefore, IRF7 is either necessary for the neuronal response to currently identified mediators of clearance or enables the production of additional antiviral factor(s) needed for clearance. Supported by ORIP (T32OD011089, R01OD01026529) NINDS, and NIAID.
Timing of Initiation of Anti-Retroviral Therapy Predicts Post-Treatment Control of SIV Replication
Pinkevych et al., PLOS Pathogens. 2023.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10558076/
Researchers are interested in approaches to reducing viral rebound following interruption of antiretroviral therapy, but more work is needed to understand major factors that determine the viral “setpoint” level. Researchers previously assessed how timing of treatment can affect the frequency of rebound from latency. In the current study, the authors analyzed data from multiple studies of simian immunodeficiency virus (SIV) infection in rhesus macaques to further explore the dynamics and predictors of post-treatment viral control. They determined that the timing of treatment initiation was a major predictor of both the level and the duration of post-rebound SIV control. These findings could help inform future treatments. Supported by ORIP (U42OD011023, P51OD011132, P51OD011092), NIAID, NCI, NIDA, NIDDK, NHLBI, NIMH, and NINDS