Unali, G. | Search bioRxiv

bioRxiv2025

A Mouse Model of SARS-CoV-2-Driven Acute Maladaptive Responses and Chronic Systemic Diseases

Our understanding of SARS-CoV-2 acute and post-acute pathogenesis is hindered by the lack of adequate small animal models. We present RAB/6N, a mouse model prone to severe disease after exposure to SARS-CoV-2 clinical isolates, with lethal cases showing no widespread brain infection typical of the widely used K18-hACE2 mouse model. Lung viral replication in RAB/6N mice remains steady for several days before a decline in viral titers. Delayed initiation of infection clearance is marked by increased lung T-cell extravasation and type-2 immune responses, leading to maladaptive lung consolidation. While systemic antiviral cytokine responses only correlate with SARS-CoV-2 brain infection in K18-hACE2 mice, they are concomitant with pulmonary immune dynamics in infected RAB/6N mice. Convalescent RAB/6N mice display systemic inflammation and decreased antibody titers against SARS-CoV-2 spike RBD, persistent viral RNA and prolonged lymphoid infiltration in the lungs. These animals also exhibit signatures of multi-organ dysfunction, cognitive impairment, cardiac inflammation, hyper- immunoglobulin production, and various autoimmune disorders, illuminating the molecular correlates of various pathologies associated with post-acute sequelae of COVID-19 (PASC). RAB/6N mice pave the way for dissecting the molecular drivers underlying SARS-CoV-2-induced acute maladaptive responses and subsequent post-acute systemic diseases. This preclinical platform also opens opportunities for the exploration of therapeutic interventions against systemic PASC and for anticipating the emergence of PASC-associated comorbidities. One-sentence summaryWe generated a hACE2-transgenic mouse model that develops maladaptive lung immune responses upon acute SARS-CoV-2 infection, leading to fatal outcomes or post-acute systemic disease syndromes in convalescent animals.

microbiology↗

bioRxiv2021

The lysine-rich intracellular loop and cell type-specific co-factors are required for IFITM3 antiviral immunity in hematopoietic stem cells

The interferon-induced transmembrane protein 3 (IFITM3) inhibits lentiviral gene therapy vector entry into hematopoietic stem cells and can be overcome by Cyclosporine H (CsH), but underlying mechanisms remain unclear. Here, we show that mutating the evolutionarily conserved lysines of the IFITM3 intracellular loop abolishes its antiviral activity without affecting either its localization or its degradation by CsH through non-canonical lysosomal pathways. When confined to the plasma membrane, the lysine-competent IFITM3 lost restriction against VSV-G pseudotyped viral vectors but gained antiviral activity against vectors that fuse directly at the plasma membrane. Interestingly, altering the lysines did not alter IFITM3 homodimerization but impacted higher-order protein complex formation, suggesting loss of interaction with cellular co-factors. In agreement, IFITM3 expression was not sufficient to restrict viral vectors in myeloid K562 cells as opposed to promonocytic THP1 or primary HSC. We exclude the involvement of previously identified factors affecting IFITM3 biology and propose a novel model for IFITM3 restriction that depends on the presence of cellular co-factor(s) that may interact with IFITM3 through the intracellular loop lysine residues. Overall, our work provides significant insight into the mechanisms of action of IFITM3 and CsH that can be exploited for improved gene therapies and broadly acting antiviral strategies.

microbiology↗