Sex, Obesity, Immunometabolism, and Viral Persistence in Post-Acute Sequelae of SARS-CoV-2 Infection

Introduction: Despite the burden of Long COVID (LC), its underlying mechanisms and biomarkers have not been definitively identified. We investigated immune and metabolic dysregulation correlating with specific post-acute sequelae of SARS-CoV-2 (PASC) symptoms through our cross-disciplinary team with expertise in virology, immunity, cutting edge tissue-based viral assays, COVID-19 animal models, infectious disease diagnostics, high-dimensional single cell data analysis, and sex-based differences in respiratory viral infection.

Objective: We investigated correlations between immune cells, immune proteins, or persistent virus and LC using human samples complemented by a small animal model to assess mechanisms based on sex and BMI.

Methods: In Aim 1, we have used immune-metabolic high-dimensional flow cytometry, targeted metabolic gene expression profiling and functional assays, and single cell RNA sequencing to dissect the metabolic and immune programs driving differentiation and function of these unique populations in longitudinal samples from individuals with distinct PASC symptoms and sequelae and those with complete recovery from COVID-19. In Aim 2, we have investigated whether specific symptoms and sequelae of PASC are associated with prolonged evolution of SARS-CoV-2-specific B and T cell responses suggestive of viral antigen or RNA persistence and are facilitated by obesity. In Aim 3, we have used our novel mouse model of SARS-CoV-2 to evaluate sex differences in the persistence of SARS-CoV-2 RNA or antigen in multiple organs to determine if that leads to immune-metabolic dysregulation in tissues and correlate with behavioral signs of PASC in mice.

Results: Multiple chemokines/cytokines, eosinophil counts, mean corpuscular hemoglobin, and anti-spike IgG and IgA levels distinguished people with complete recovery (Never-LC), current LC, and recovery from previous LC. In older individuals, LC had lower frequencies of SARS-CoV-2-specific CD4+ T cells than Never-LC individuals. Mouse models of LC revealed greater frequencies and activation of inflammatory monocytes, macrophages, and microglia in females than males associated with memory deficits. Sex differences in memory loss during LC were caused by having two X chromosomes, with infection-induced upregulation of X-linked genes Xist and Tlr7 correlated with outcomes.

Conclusion/Discussion: Immune profiling identified differences between people with quick recovery, people with current Long COVID and people who recovered from Long COVID. Development and interrogation of novel mouse models of Long COVID revealed genetic and immunological mechanisms that cause greater female risk of Long COVID.

Key Topics:

• Assay and in vitro studies to gain mechanistic insights
• Biomarker, in-depth phenotyping assays and in vitro studies using tissue and other biospecimens
• Chronic immune dysfunction
• Clinical manifestations of chronic viral infections, biological pathways, immune-autoimmune disorders, systems, organs, or diseases
• Collaborative and systems biology approaches
• Long COVID and other chronic conditions
• Nonhuman primate (NHP) and/or other animal models
• Remaining gaps in tissue-specific manifestations of Long COVID
• Viral persistence/reactivation