COVID-19 Pathology in the Lung, Kidney, Heart and Brain: The Different Roles of T-Cells, Macrophages, and Microthrombosis.

Here, we aim to describe COVID-19 pathology across different tissues to clarify the disease's pathophysiology. Lungs, kidneys, hearts, and brains from nine COVID-19 autopsies were compared by using antibodies against SARS-CoV-2, macrophages-microglia, T-lymphocytes, B-lymphocytes, and activated platelets. Alzheimer's Disease pathology was also assessed. PCR techniques were used to verify the presence of viral RNA. COVID-19 cases had a short clinical course (0-32 days) and their mean age was 77.4 y/o. Hypoxic changes and inflammatory infiltrates were present across all tissues. The lymphocytic component in the lungs and kidneys was predominant over that of other tissues (p < 0.001), with a significantly greater presence of T-lymphocytes in the lungs (p = 0.020), which showed the greatest presence of viral antigens. The heart showed scant SARS-CoV-2 traces in the endothelium-endocardium, foci of activated macrophages, and rare lymphocytes. The brain showed scarce SARS-CoV-2 traces, prominent microglial activation, and rare lymphocytes. The pons exhibited the highest microglial activation (p = 0.017). Microthrombosis was significantly higher in COVID-19 lungs (p = 0.023) compared with controls. The most characteristic pathological features of COVID-19 were an abundance of T-lymphocytes and microthrombosis in the lung and relevant microglial hyperactivation in the brainstem. This study suggests that the long-term sequelae of COVID-19 derive from persistent inflammation, rather than persistent viral replication.

COVID-19 patients and Dementia: Frontal cortex transcriptomic data.

Since the association of SARS-Cov-2 infection with Nervous System (NS) manifestations, we performed RNA-sequencing analysis in Frontal Cortex of COVID-19 positive or negative individuals and affected or not by Dementia individuals. We examined gene expression differences in individuals with COVID-19 and Dementia compared to Dementia only patients by collecting transcript counts in each sample and performing Differential Expression analysis. We found eleven genes satisfying our significance criteria, all of them being protein coding genes. These data are suitable for integration with supplemental samples and for analysis according to different individuals' classification. Also, differential expression evaluation may be implemented with other scientific purposes, such as research of unannotated genes, mRNA splicing and genes isoforms. The analysis of Differential Expressed genes in COVID-19 positive patients compared to non-COVID-19 patients is published in: S. Gagliardi, E.T. Poloni, C. Pandini, M. Garofalo, F. Dragoni, V. Medici, A. Davin, S.D. Visonà, M. Moretti, D. Sproviero, O. Pansarasa, A. Guaita, M. Ceroni, L. Tronconi, C. Cereda, Detection of SARS-CoV-2 genome and whole transcriptome sequencing in frontal cortex of COVID-19 patients., Brain. Behav. Immun. (2021). https://doi.org/10.1016/j.bbi.2021.05.012.

COVID-19-related neuropathology and microglial activation in elderly with and without dementia.

The actual role of SARS-CoV-2 in brain damage remains controversial due to lack of matched controls. We aim to highlight to what extent is neuropathology determined by SARS-CoV-2 or by pre-existing conditions. Findings of 9 Coronavirus disease 2019 (COVID-19) cases and 6 matched non-COVID controls (mean age 79 y/o) were compared. Brains were analyzed through immunohistochemistry to detect SARS-CoV-2, lymphocytes, astrocytes, endothelium, and microglia. A semi-quantitative scoring was applied to grade microglial activation. Thal-Braak stages and the presence of small vessel disease were determined in all cases. COVID-19 cases had a relatively short clinical course (0-32 days; mean: 10 days), and did not undergo mechanical ventilation. Five patients with neurocognitive disorder had delirium. All COVID-19 cases showed non-SARS-CoV-2-specific changes including hypoxic-agonal alterations, and a variable degree of neurodegeneration and/or pre-existent SVD. The neuroinflammatory picture was dominated by ameboid CD68 positive microglia, while only scant lymphocytic presence and very few traces of SARS-CoV-2 were detected. Microglial activation in the brainstem was significantly greater in COVID-19 cases (p = 0.046). Instead, microglial hyperactivation in the frontal cortex and hippocampus was clearly associated to AD pathology (p = 0.001), regardless of the SARS-CoV-2 infection. In COVID-19 cases complicated by delirium (all with neurocognitive disorders), there was a significant enhancement of microglia in the hippocampus (p = 0.048). Although higher in cases with both Alzheimer's pathology and COVID-19, cortical neuroinflammation is not related to COVID-19 per se but mostly to pre-existing neurodegeneration. COVID-19 brains seem to manifest a boosting of innate immunity with microglial reinforcement, and adaptive immunity suppression with low number of brain lymphocytes probably related to systemic lymphopenia. Thus, no neuropathological evidence of SARS-CoV-2-specific encephalitis is detectable. The microglial hyperactivation in the brainstem, and in the hippocampus of COVID-19 patients with delirium, appears as a specific topographical phenomenon, and probably represents the neuropathological basis of the "COVID-19 encephalopathic syndrome" in the elderly.

Detection of SARS-CoV-2 genome and whole transcriptome sequencing in frontal cortex of COVID-19 patients.

SARS-Cov-2 infection is frequently associated with Nervous System manifestations. However, it is not clear how SARS-CoV-2 can cause neurological dysfunctions and which molecular processes are affected in the brain. In this work, we examined the frontal cortex tissue of patients who died of COVID-19 for the presence of SARS-CoV-2, comparing qRT-PCR with ddPCR. We also investigated the transcriptomic profile of frontal cortex from COVID-19 patients and matched controls by RNA-seq analysis to characterize the transcriptional signature. Our data showed that SARS-CoV-2 could be detected by ddPCR in 8 (88%) of 9 examined samples while by qRT-PCR in one case only (11%). Transcriptomic analysis revealed that 11 genes (10 mRNAs and 1 lncRNA) were differential expressed when frontal cortex of COVID-19 patients were compared to controls. These genes fall into categories including hypoxia, hemoglobin-stabilizing protein, hydrogen peroxide processes. This work demonstrated that the quantity of viral RNA in frontal cortex is minimal and it can be detected only with a very sensitive method (ddPCR). Thus, it is likely that SARS-CoV-2 does not actively infect and replicate in the brain; its topography within encephalic structures remains uncertain. Moreover, COVID-19 may have a role on brain gene expression, since we observed an important downregulation of genes associated to hypoxia inducting factor system (HIF) that may inhibit the capacity of defense system during infection and oxigen deprivation, showing that hypoxia, well known multi organ condition associated to COVID-19, also marked the brain.

Prevalence and prognostic value of Delirium as the initial presentation of COVID-19 in the elderly with dementia: An Italian retrospective study.

BACKGROUND: Delirium may be one of the presenting symptoms of COVID-19, complicating diagnosis and care of elderly patients with dementia. We aim to identify the prevalence and prognostic significance of delirium as the sole onset manifestation of COVID-19. METHODS: This is a retrospective single-centre study based on review of medical charts, conducted during the outbreak peak (March 27-April 18, 2020) in a Lombard dementia facility, including 59 elderly subjects with dementia and laboratory-confirmed COVID-19. FINDINGS: Of the 59 residents, 57 (96⋅6%) tested positive (mean age: 82⋅8; women: 66⋅7%). Comorbidities were present in all participants, with 18/57 (31⋅6%) having three or more concomitant diseases. Delirium-Onset COVID-19 (DOC) was observed in 21/57 (36⋅8%) subjects who were chiefly older (mean age: 85⋅4 y/o) and with multiple comorbidities. Eleven/21 DOC patients (52⋅4%) had hypoactive delirium, while hyperactive delirium occurred in ten/21 (47⋅6%). Lymphopenia was present in almost all subjects (median: 1⋅3 × 109/L). Overall mortality rate was 24⋅6% (14/57) and dementia severity per se had no impact on short-term mortality due to COVID-19. DOC was strongly associated with higher mortality (p<0⋅001). Also, DOC and male gender were independently associated with increased risk of mortality (OR: 17⋅0, 95% CI: 2⋅8-102⋅7, p = 0⋅002 and 13⋅6, 95% CI: 2⋅3-79⋅2, p = 0⋅001 respectively). INTERPRETATION: Delirium occurrence in the elderly with dementia may represent a prodromal phase of COVID-19, and thus deserves special attention, especially in the presence of lymphopenia. Hypoxia and a severe inflammatory state may develop subsequently. DOC cases have higher short-term mortality rate. FUNDING: None.