Cholesterol homeostasis is required for the replication of many viruses, including Ebola virus, hepatitis C virus, and human immunodeficiency virus-1. Niemann-Pick C1 (NPC1) is an endosomal-lysosomal membrane protein involved in cholesterol trafficking from late endosomes and lysosomes to the endoplasmic reticulum. We identified NPC1 in CRISPR and RNA interference screens as a putative host factor for infection by mammalian orthoreovirus (reovirus). Following internalization via clathrin-mediated endocytosis, the reovirus outer capsid is proteolytically removed, the endosomal membrane is disrupted, and the viral core is released into the cytoplasm where viral transcription, genome replication, and assembly take place. We found that reovirus infection is significantly impaired in cells lacking NPC1, but infection is restored by treatment of cells with hydroxypropyl-β-cyclodextrin, which binds and solubilizes cholesterol. Absence of NPC1 did not dampen infection by infectious subvirion particles, which are reovirus disassembly intermediates that bypass the endocytic pathway for infection of target cells. NPC1 is not required for reovirus attachment to the plasma membrane, internalization into cells, or uncoating within endosomes. Instead, NPC1 is required for delivery of transcriptionally active reovirus core particles from endosomes into the cytoplasm. These findings suggest that cholesterol homeostasis, ensured by NPC1 transport activity, is required for reovirus penetration into the cytoplasm, pointing to a new function for NPC1 and cholesterol homeostasis in viral infection.

Background: Influenza (flu) and COVID-19 vaccination rates are subpar across the US, especially in racial and/or socioeconomic minority groups who are understudied in public health literature. Objective: The objective of this study was to elucidate the attitudes of Turtle Creek patients towards flu and COVID-19 vaccines, with the goal of establishing targetable vaccine education gaps and ultimately increasing vaccine uptake in the community. Design/Patients: This study was conducted as a retrospective cross-sectional analysis. Authors completed 123 patient phone surveys of patients cared for at the Turtle Creek Primary Care Center inquiring about flu and COVID-19 infection status and vaccination uptake (August 26 - October 10, 2021). Approach/Key Results: Our data revealed a significant association between COVID-19 and flu vaccine acceptance. Additionally, we found a strong association between vaccine acceptance and age, with older patients being more likely to be vaccinated against COVID-19. Using multivariable logistic regression models, we assessed how flu and COVID-19 vaccine acceptance was affected by informational sources participants trusted most. In the COVID-19 models, those who cited trusting medical professionals had higher odds of vaccine acceptance while participants who cited trusting social media had significantly decreased odds of vaccine acceptance. Conclusion: Our study revealed significant trends for flu and COVID-19 vaccine acceptance by sociodemographic factors and trust in the medical system. Using these data, we can create future interventions to overcome vaccine hesitancy.

Respiratory viral infections remain a leading cause of morbidity and mortality. Using a murine model of human metapneumovirus (HMPV), we identified recruitment of a C1q-producing inflammatory monocyte population concomitant with viral clearance by adaptive immune cells. Genetic ablation of C1q led to reduced CD8+ T cell function. Production of C1q by a myeloid lineage was sufficient to enhance CD8+ T cell function. Activated and dividing CD8+ T cells expressed a putative C1q receptor, gC1qR. Perturbation of gC1qR signaling led to altered CD8+ T cell IFN-γ production and metabolic capacity. Autopsy specimens from fatal respiratory viral infections in children demonstrated diffuse production of C1q by an interstitial population. Humans with severe COVID-19 infection also demonstrated upregulation of gC1qR on activated and rapidly dividing CD8+ T cells. Collectively, these studies implicate C1q production from monocytes as a critical regulator of CD8+ T cell function following respiratory viral infection.

Human metapneumovirus (HMPV) is a leading cause of respiratory tract infection in pediatric, elderly, and immunocompromised populations. All individuals have been exposed to HMPV by the age of 5, but humoral immunity does not fully protect against reinfection of adults. Despite the clinical burden, there are currently no FDA-approved vaccines or therapeutics for HMPV. T cell responses are important for protection and viral clearance. The aim of this study was to better understand the human T cell response to HMPV and guide vaccine development. To accomplish these goals, we sought to identify HLA class I-restricted viral epitopes. In this study, 5 transgenic mouse strains that express human HLA-A*01:03, HLA-A*24:01, HLA-B*35:01, HLA-B*15:02, or HLA-Cw*07:01 were used to map HMPV-specific epitopes and characterize HMPV-specific CD8+ T cells. We used ELISpot screening of overlapping peptides and predictopes to discover several epitopes and generate MHC-I tetramers for each genetic background. We found that human CD8+ T cells of subjects expressing the same HLA types could recognize viral epitopes by ELISpot and tetramer staining. Our results suggest that the transgenic mouse is a useful model to identify HLA-restricted viral-specific epitopes and novel targets for vaccination against HMPV. Supported by grants from NIH (R01 AI085062)