Profiling Patient Exosomes as Key Regulators of Neurological Symptoms in Coronavirus Disease 2019 (COVID-19)
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) pandemic, also known as coronavirus disease 2019 (COVID-19), has ignited the most significant world-wide health crisis of the 21st century. While acute COVID-19 infection has potentially lethal outcomes, there are also cases of post-acute sequelae of COVID-19 (PASC) infections, commonly known as 'long-haul' COVID-19. In these long-haul cases, individuals experience prolonged neurologic symptoms including loss of taste and smell, altered level of consciousness, weakness, and chronic fatigue, months after acute COVID-19 infection has subsided. Currently, more than half of COVID-19 survivors present with at least one long-haul COVID-19 symptom. Additionally, there are no effective treatments for these complex neurological symptoms due to lack of sufficient knowledge of the mechanisms in which COVID-19 affects brain function and contributes to long-haul COVID-19 symptoms. Exosomes are extracellular vesicles (EVs) containing genetic material, protein, metabolites and lipids, which mirror their cell of origin. The physiologic role of exosomes has yet to be clearly defined, but it is widely speculated that these EVs play a fundamental role in cell-cell communication. Virally infected cells are able to release EVs that interact with distant cells and alter their typical biological functions. Similar to other neurotropic viruses, EVs have been isolated and characterized in samples from patients with COVID-19. A recent respiratory virus mimetic experiment has demonstrated the ability of EVs to enter the brain and collect in microglial cells. Based on this current research, we suspect exosomes are contributing to the development of chronic neurological symptoms seen in individuals with long-haul COVID-19. We hypothesize that there are differences in exosomes isolated from individuals with and without neurological symptoms following COVID-19 infection. Exosomes were isolated from nasal swabs of COVID-19 patients using ultra-centrifugation, and separated from viral particles using density gradient purification with 20% sucrose buffer. Exosomal small RNAs were isolated, and then identified using RNA sequencing. Sequencing data was compared to both human and COVID-19 genomes using bioinformatics to determine expression levels and known functions of the small RNAs that are present. The exosomal RNAs characterized in this study will guide our future aims to identify the effects these EVs have on different neuronal cells. Differentially expressed cellular or viral RNAs could regulate long-haul COVID-19 neurological outcomes. We hope to gain an understanding of the role these EVs play in COVID-19 infections, as well as provide insight into potential therapeutic targets for individuals living with long-haul symptoms. Funding: This work was supported by US4 MD006882 from the National Institute on Minority Health and Health Disparities.