Biology subjects

O'Connell, A. K.

Publications and source records attributed to O'Connell, A. K..

7 recordsLinked to original sources

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↗

bioRxiv2025

Sub-phenotypes of pneumonia defined by pulmonary histopathological features

Establishing sub-phenotypes of pneumonia based on distinct host processes will be a step towards using host-directed therapies (to complement microbe-directed therapies) more rationally and precisely. Although pneumonia is a pulmonary pathophysiology, histological changes within the lungs have not been leveraged for sub-phenotyping. We addressed this by scoring 18 histopathology features (e.g., type 2 cell hyperplasia or necrosis) across rapid autopsy lung samples from 276 elderly subjects with pneumonia. Machine learning algorithms segregated subjects into seven different sub-phenotypes of pneumonia with distinct histopathology signatures. Quantitative immunofluorescence demonstrated associations of macrophages, neutrophils, T cells, and B cells with select histology features and pulmonary pathology sub-phenotypes. Mouse models revealed corollary sub-phenotypes, although some histology features observed in human lungs were never observed in mice. By illuminating this spectrum of histopathologies and discriminating discrete sub-phenotypes of pneumonia, a foundational framework emerges for developing and using host-directed therapies for subsets of pneumonia patients.

immunology↗

bioRxiv2024

3D Multiplexed Immunohistochemistry Using Opal-TSA Amplification for Enhanced Imaging of Pulmonary TB Lesions

Mycobacterium tuberculosis hijacks the host immune system and persists for several years before the onset of active disease. Spatial characterization of epithelial compartments, immune cell populations and bacteria simultaneously within tissue specimens provide significant information about host pathogen interactions. Here, we present a protocol to detect multiple protein markers using Opal-TSA conjugated fluorescent dyes in free floating 10% neutral buffered formalin fixed thick tissue sections (50-100 m), with minimal additional tissue processing not requiring specialized equipment. Use of thick sections provides more information as compared to classic thin microtomy sections (3-10 m), including the capacity for Z stacking and three-dimensional image rendering. Importantly, reduced tissue processing of samples with this method preserves endogenous fluorescent reporter signal. Use of Opal-TSA conjugated fluorescent dyes enhances the sensitivity of low expressing proteins and supports the use of primary antibodies raised in the same species. Before you beginThis protocol describes the specific use of Mtb infected mouse lungs, but is applicable to any tissue type and species of origin. Institutional permissionsObtain institutional permission to perform animal studies and collect tissues under an approved Institutional Animal Care and Use Committee (IACUC) or Institutional Review Board protocol. Our protocol was approved by Boston Universitys Institutional Animal Care and Use Committee (IACUC protocol number PROTO201800218). MiceB6J.C3-Sst1C3HeB/Fej Krmn and B6. Sst1S, ifnb-YFP mice were developed in our laboratory (available from MMRRC stock # 043908-UNC). HighlightsO_LICompatible with Opal-TSA conjugated fluorescent dyes resulting in enhanced signal sensitivity with low background noise C_LIO_LIReduced tissue processing preserves endogenous fluorescent reporter signals C_LIO_LICompatible with primary antibodies raised in the same species C_LIO_LIDoesnt require specialized automated instruments C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=193 SRC="FIGDIR/small/619885v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@3e3439org.highwire.dtl.DTLVardef@1d6ba85org.highwire.dtl.DTLVardef@6f9595org.highwire.dtl.DTLVardef@1c573ae_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2024

Pre-existing H1N1 immunity reduces severe disease with bovine H5N1 influenza virus

The emergence of highly pathogenic H5N1 avian influenza in dairy cattle herds across the United States has caused multiple mild human infections. There is an urgent need to understand the risk of spillover into humans. Here, we show that pre-existing immunity from the 2009 H1N1 pandemic influenza virus provided protection from mortality and severe clinical disease to ferrets intranasally infected with bovine H5N1. H1N1 immune ferrets exhibited a differential tissue tropism with little bovine H5N1 viral dissemination to organs outside the respiratory tract and significantly less H5N1 virus found in nasal secretions and the respiratory tract. Additionally, ferrets with H1N1 prior immunity produced antibodies that cross-reacted with H5N1 neuraminidase protein. Taken together, these results suggest that mild disease in humans may be linked to prior immunity to human seasonal influenza viruses.

microbiology↗

bioRxiv2024

Resolution of SARS-CoV-2 infection in human lung tissues is driven by extravascular CD163+ monocytes

While human autopsy samples have provided insights into pulmonary immune mechanisms associated with severe viral respiratory diseases, the mechanisms that contribute to a clinically favorable resolution of viral respiratory infections remain unclear due to the lack of proper experimental systems. Using mice co-engrafted with a genetically matched human immune system and fetal lung xenograft (fLX), we mapped the immunological events defining successful resolution of SARS-CoV-2 infection in human lung tissues. Viral infection is rapidly cleared from fLX following a peak of viral replication, histopathological manifestations of lung disease and loss of AT2 program, as reported in human COVID-19 patients. Infection resolution is associated with the activation of a limited number of hematopoietic subsets, including inflammatory monocytes and non-canonical double-negative T-cells with cytotoxic functions, which are highly enriched in viral RNA and dissipate upon infection resolution. Activation of specific human fibroblast and endothelial subsets also elicit robust antiviral and monocyte chemotaxis signatures, respectively. Notably, systemic depletion of human CD4+ cells, but not CD3+ cells, abrogates infection resolution in fLX and induces persistent infection, supporting evidence that peripheral CD4+ monocytes are important contributors to SARS-CoV-2 infection resolution in lung tissues. Collectively, our findings unravel a comprehensive picture of the immunological events defining effective resolution of SARS-CoV-2 infection in human lung tissues, revealing markedly divergent immunological trajectories between resolving and fatal COVID-19 cases.

immunology↗

bioRxiv2021

Platelet proteome analysis reveals an early hyperactive phenotype in SARS-CoV-2-infected humanized ACE2 mice

Coronavirus disease-2019 (COVID-19) provokes a hypercoagulable state with increased incidence of thromboembolism and mortality. Platelets are major effectors of thrombosis and hemostasis. Suitable animal models are needed to better understand COVID-19-associated coagulopathy (CAC) and underlying platelet phenotypes. Here, we assessed K18-hACE2 mice undergoing a standardized SARS-CoV-2 infection protocol to study dynamic platelet responses via mass spectrometry-based proteomics. In total, we found significant changes in >1,200 proteins. Strikingly, protein alterations occurred rapidly by 2 days post-infection (dpi) and preceded outward clinical signs of severe disease. Pathway enrichment analysis of 2dpi platelet proteomes revealed that SARS-CoV-2 infection upregulated complement-coagulation networks (F2, F12, CFH, CD55/CD59), platelet activation-adhesion-degranulation proteins (PF4, SELP, PECAM1, HRG, PLG, vWF), and chemokines (CCL8, CXCL5, CXCL12). When mice started to lose weight at 4dpi, pattern recognition receptor signaling (RIG-I/MDA5, CASP8, MAPK3), and interferon pathways (IFIT1/IFIT3, STAT1) were predominant. Interestingly, SARS-CoV-2 spike protein in the lungs was observed by immunohistochemistry, but in platelets was undetected by proteomics. Similar to patients, K18-hACE2 mice during SARS-CoV-2 infection developed progressive lymphohistiocytic interstitial pneumonia with platelet aggregates in the lungs and kidneys. In conclusion, this model recapitulates activation of coagulation, complement, and interferon responses in circulating platelets, providing valuable insight into platelet pathology during COVID-19. Key PointsO_LISARS-CoV-2-infected humanized ACE2 mice recapitulate platelet reprogramming towards activation-degranulation-aggregation. C_LIO_LIComplement/coagulation pathways are dominant in platelets at 2 days post-infection (dpi), while interferon signaling is dominant at 4dpi. C_LI

immunology↗

bioRxiv2021

Macrophages govern antiviral responses in human lung tissues protected from SARS-CoV-2 infection

The majority of SARS-CoV-2 infections among healthy individuals result in asymptomatic to mild disease. However, the immunological mechanisms defining effective lung tissue protection from SARS-CoV-2 infection remain elusive. Unlike mice solely engrafted with human fetal lung xenograft (fLX), mice co-engrafted with fLX and a myeloid-enhanced human immune system (HNFL mice) are protected against SARS-CoV-2 infection, severe inflammation, and histopathology. Effective control of viral infection in HNFL mice associated with significant macrophage infiltration, and the induction of a potent macrophage-mediated interferon response. The pronounced upregulation of the USP18-ISG15 axis (a negative regulator of IFN responses), by macrophages was unique to HNFL mice and represented a prominent correlate of reduced inflammation and histopathology. Altogether, our work shed light on unique cellular and molecular correlates of lung tissue protection during SARS-CoV-2 infection, and underscores macrophage IFN responses as prime targets for developing immunotherapies against coronavirus respiratory diseases. HIGHLIGHTSO_LIMice engrafted with human fetal lung xenografts (fLX-mice) are highly susceptible to SARS-CoV-2. C_LIO_LICo-engraftment with a human myeloid-enriched immune system protected fLX-mice against infection. C_LIO_LITissue protection was defined by a potent and well-balanced antiviral response mediated by infiltrating macrophages. C_LIO_LIProtective IFN response was dominated by the upregulation of the USP18-ISG15 axis. C_LI

microbiology↗