Investigating post-infection anxiety- and depression-like behaviors in a SARS-CoV-2 mouse model

<b>Rationale:</b> The COVID-19 pandemic, driven by SARS-CoV-2, has resulted in a wide range of neuropsychiatric symptoms associated with post-acute sequelae (PASC). However, the mechanisms by which SARS-CoV-2 impacts the brain and leads to persistent behavioral changes remain poorly understood. We hypothesize that SARS-CoV-2 exposure induces neuroinflammation and microglial activation, leading to anxiety- and depression-like behaviors in mice. <b>Methods:</b> We established a SARS-CoV-2 mouse model using the virulent SARS2-N501Y_MA30 strain to investigate its impact on the central nervous system (CNS). We assessed neuroinvasion via immunostaining of dsRNA and markers for neuronal, astrocyte, and microglia in brain slices. Behavioral changes were evaluated at 2 weeks, 2 months, and 4 months post-infection. Molecular and cellular analyses included bulk RNA-seq, Golgi-Cox staining, field excitatory postsynaptic potential (fEPSP) recordings, immunofluorescence, and quantitative real-time PCR (qRT-PCR) to assess gene expression, neuronal morphology, and microglial activation in the brain. <b>Results</b>: We demonstrated that intranasal inoculation of SARS2-N501Y_MA30 results in viral dissemination to multiple brain regions, including the amygdala and the prefrontal cortex (PFC). Behavioral assays indicated a marked elevation in anxiety- and depression-like behaviors post-infection. A comparative analysis of RNA expression profiles disclosed alterations in the post-infected brains. Additionally, we observed dendritic spine remodeling on neurons within the amygdala after infection. Infection with SARS2-N501Y_MA30 was associated with microglial activation and a subsequent increase in microglia-dependent neuronal activity in the amygdala. Transcriptomic analysis of infected brains revealed the upregulation of inflammatory and cytokine-related pathways, implicating neuroinflammation in the pathogenesis of neuronal hyperactivity and behavioral abnormality. <b>Conclusion:</b> Our findings provide evidence that SARS-CoV-2 neuroinvasion plays a critical role in the development of lasting behavioral sequelae observed in PASC. These data provide critical insights into the neurological consequences of SARS-CoV-2 infection and underscore microglia as a potential therapeutic target for ameliorating virus-induced neurobehavioral abnormalities.