Neurological Consequences of Viral Encephalitis: Behavioral Deficits, Neuronal Restructuring, and Therapeutic Interventions

Abstract

Viral infections may lead to persistent neurological symptoms that can mimic or potentially trigger the onset of neurodegenerative disorders linked with aging. Neuronal degeneration, a hallmark of neurodegenerative diseases and viral neuropathologies, involves the progressive loss of neuronal structure and function, often leading to memory dysfunction, motor impairments, and chronic inflammation. We study the cognitive effects of Venezuelan equine encephalitis virus (VEEV), a neuroinvasive alphavirus that causes severe neurological symptoms, including seizures and encephalitis, with no available treatments or vaccines. Despite its significant public health implications, including its potential as a biological weapon, VEEV remains understudied, particularly regarding its chronic effects on memory and neuronal function. Therefore, this work bridges the gap to identify critical features of neuron loss and neuron restructuring that lead to neurobehavioral deficits and explore two avenues of broad-spectrum antiviral and neuroprotective therapeutics.

First, we investigate the acute and chronic neurological consequences of VEEV infection using a murine model, focusing on behavioral, neuropathological, and transcriptomic changes. Mice displayed decreased anxiety-like behavior, decreased recognition memory and altered neuromuscular functions during chronic disease. Single-cell transcriptomic analysis showed that innate immune and inflammatory responses were activated at an acute time post-infection and neurological signaling was dampened during chronic disease. VEEV infection resulted in chronic activation of microglia and astrocytes and chronic neuron loss in the hippocampus, which correlated with the altered transcriptomic profile observed in the hippocampus.

A key therapeutic focus of this study is the tumor suppressor protein p53, a pivotal regulator of apoptosis and cellular stress responses. Activating p53 using the small molecule inhibitor NVP-CGM097 resulted in significant inhibition of VEEV infectious titers. Secondly, we investigated the therapeutic potential of Pifithrin-μ (PFT-μ), an inhibitor of the autophagy-associated chaperone HSP70. PFT-μ treatment resulted in a significant reduction in viral replication for VEEV and related alphaviruses. In mice, PFT-μ treatment reduced weight loss, neurological symptoms, and alternations in anxiety-like behaviors and neuromuscular functions.

Together, these insights bridge cell biology, virology, and neuropathology and offers innovative strategies to understand and combat alphavirus-induced neuronal damage. It provides a valuable framework for developing antiviral therapies and neuroprotective interventions, with broader implications for understanding viral impacts on cellular function and neurodegeneration.