Biology subjects

Seibert, B.

Publications and source records attributed to Seibert, B..

6 recordsLinked to original sources

bioRxiv2025

Multi-System Dysregulation in Placental Malaria Contributes to Adverse Perinatal Outcomes in Mice

Sequestration of Plasmodium parasites in the placental vasculature causes increased morbidity and mortality in pregnant compared to non-pregnant patients in malaria- endemic regions. In this study, outbred pregnant CD1 mice with semi allogeneic fetuses were infected with transgenic Plasmodium berghei or mock-inoculated by mosquito bite at either embryonic day (E) 6 (first trimester-equivalent) or 10 (second trimester- equivalent) and compared with non-pregnant females. P. berghei-infected mosquitoes had greater biting avidity for E10 dams than uninfected mosquitoes, which was not apparent for E6 dams nor non-pregnant females. Infected E10 dams had greater numbers of parasites than E6 dams in the uterus and spleen, but not in the blood or liver. While parasites were found in placentas, no parasites were present in fetuses. Maternal infection at E6 caused greater maternal morbidity, with greater rates of fetal reabsorption and stillbirths than at E10. Infection at E10 caused adverse offspring outcomes, including growth restriction. To identify possible mechanisms of adverse offspring outcomes, E10 dams were euthanized during peak parasitemia (8 days post infection), and outcomes were compared with mock-infected dams. P. berghei caused significant systemic maternal immune activation with elevated circulating lymphocytes, eosinophils, and neutrophils and splenic cytokine concentrations. P. berghei infection at E10 increased corticosterone and decreased progesterone concentrations, which could contribute to adverse perinatal outcomes through immunomodulation. There were limited changes in the maternal fecal microbiome after P. berghei infection. Mosquito bite infection of outbred dams with P. berghei causes placental malaria and provides a novel, tractable model to investigate therapeutic treatments.

microbiology↗

bioRxiv2024

Air-Liquid Interface Model for Influenza Aerosol Exposure In Vitro

Airborne transmission is an essential mode of infection and spread of influenza viruses among humans. However, most studies use liquid inoculum for virus infection. To better replicate natural airborne infections in vitro, we generated a calm-aerosol settling chamber system designed to examine the aerosol infectivity of influenza viruses in different cell types. Aerosol inoculation was characterized for multiple influenza A virus (FLUAV) subtypes, including a pandemic 2009 H1N1, a seasonal swine H3N2, and an avian H9N2 using this exposure system. While each FLUAV strain displayed high infectivity within MDCK cells via liquid inoculation, differences in infectivity were observed during airborne inoculation. This was further observed in recently developed immortalized differentiated human airway epithelial cells (BCi-NS1.1) cultured in an air-liquid interface. The airborne infectious dose 50 for each virus was based on the exposure dose per well. Our findings indicate that this system has the potential to enhance our understanding of the factors influencing influenza transmission via the airborne route. This could be invaluable for conducting risk assessments, potentially reducing the reliance on extensive and costly in vivo animal studies. ImportanceThis study presents a significant advancement in influenza research by developing a novel in vitro system to assess aerosol infectivity, a crucial aspect of influenza transmission. The systems ability to differentiate between mammalian-adapted and avian-adapted influenza viruses based on their aerosol infectivity offers a valuable tool for pre-screening the pandemic potential of different strains. This could potentially streamline the risk assessment process and inform public health preparedness strategies. Moreover, the systems capacity to examine aerosol infectivity in human airway epithelial cells provides a more relevant model for studying virus-host interactions in natural airborne infections. Overall, this study provides an accessible platform for investigating aerosol infectivity, which could significantly contribute to our understanding of influenza transmission and pandemic preparedness.

microbiology↗

bioRxiv2024

Dispersal of influenza virus populations within the respiratory tract shapes their evolutionary potential

Viral infections are characterized by dispersal from an initial site to secondary locations within the host. How the resultant spatial heterogeneity shapes within-host genetic diversity and viral evolutionary pathways is poorly understood. Here we show that dispersal within and between the nasal cavity and trachea maintains diversity and is therefore conducive to adaptive evolution, whereas dispersal to the lungs is stochastic and gives rise to population heterogeneity. We infected ferrets either intranasally or by aerosol with a barcoded influenza A/California/07/2009 (H1N1) virus. At 1, 2 or 4 days post infection, dispersal was assessed by collecting 52 samples from throughout the respiratory tract of each animal. Irrespective of inoculation route, barcode compositions across the nasal turbinates and trachea were similar and highly diverse, revealing little constraint on the establishment of infection in the nasal cavity and descent through the trachea. By comparison, infection of the lungs produced genetically distinct viral populations. Lung populations were pauci-clonal, suggesting that each seeded location received relatively few viral genotypes. While aerosol inoculation gave distinct populations at every lung site sampled, within-host dispersal after intranasal inoculation produced larger patches, indicative of local expansion following seeding of the lungs. Throughout the respiratory tract, barcode diversity declined over time, but new diversity was generated through mutation. De novo variants were often unique to a given location, indicating that localized replication following dispersal resulted in population divergence. In summary, dispersal within the respiratory tract operates differently between regions and contributes to the potential for viral evolution to proceed independently in multiple within-host subpopulations.

microbiology↗

bioRxiv2022

Epistasis reduces fitness costs of influenza A virus escape from stem-binding antibodies

The hemagglutinin (HA) stem region is a major target of universal influenza vaccine efforts owing to the presence of highly conserved epitopes across multiple influenza A virus strains and subtypes. To explore the potential impact of vaccine-induced immunity targeting the HA stem, we examined the fitness effects of viral escape from stem-binding broadly neutralizing antibodies (stem-bnAbs). Recombinant viruses containing each individual antibody escape substitution showed diminished replication compared to wild-type virus, indicating that stem-bnAb escape incurred fitness costs. A second-site mutation in the HA head domain (N133D) reduced the fitness effects observed in primary cell cultures and likely enabled the selection of escape mutations. This putative permissive mutation was not, however, sufficient to ease fitness costs in a ferret transmission model. Taken together, these data suggest that viral escape from stem-bnAbs is costly but highlight the potential for epistatic interactions to enable evolution within the functionally constrained HA stem domain.

microbiology↗

bioRxiv2022

Pathobiology and dysbiosis of the respiratory and intestinal microbiota in 14 months old Golden Syrian hamsters infected with SARS-CoV-2

The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS2) affected the geriatric population. Among research models, Golden Syrian hamsters (GSH) are one of the most representative to study SARS2 pathogenesis and host responses. However, animal studies that recapitulate the effects of SARS2 in the human geriatric population are lacking. To address this gap, we inoculated 14 months old GSH (resembling people over 60 years old) with a prototypic ancestral strain of SARS2 and studied the effects on virus pathogenesis, virus shedding, and respiratory and gastrointestinal microbiome changes. SARS2 infection led to high vRNA loads in the nasal turbinates (NT), lungs, and trachea as well as higher pulmonary lesions scores later in infection. Dysbiosis throughout SARS2 disease progression was observed in the pulmonary microbial dynamics with the enrichment of opportunistic pathogens (Haemophilus, Fusobacterium, Streptococcus, Campylobacter, and Johnsonella) and microbes associated with inflammation (Prevotella). Changes in the gut microbial community also reflected an increase in multiple genera previously associated with intestinal inflammation and disease (Helicobacter, Mucispirillum, Streptococcus, unclassified Erysipelotrichaceae, and Spirochaetaceae). Influenza A virus (FLUAV) pre-exposure resulted in slightly more pronounced pathology in the NT and lungs early on (3 dpc), and more notable changes in lungs compared to the gut microbiome dynamics. Similarities among aged GSH and the microbiome in critically ill COVID-19 patients, particularly in the lower respiratory tract, suggest that GSHs are a representative model to investigate microbial changes during SARS2 infection. The relationship between the residential microbiome and other confounding factors, such as SARS2 infection, in a widely used animal model, contributes to a better understanding of the complexities associated with the host responses during viral infections. Author SummaryThe SARS-CoV-2 pandemic led to millions of human losses, notably affecting the geriatric population, who are at greater risk of developing acute respiratory distress infection leading to prolonged hospitalization and death. However, the mechanism of age-related pathogenicity is not fully understood. Here, we utilized an aged Syrian hamster model resembling ~60-year-old humans to analyze the pathobiology, host response, and effects of SARS2 on the respiratory and intestinal microbiome. We identified specific microbial markers observed in severe COVID-19 patients within the lungs of aged hamsters infected with SARS-CoV-2. Prior influenza A virus (H1N1) exposure amplified these changes. Similarities among aged GSH and critically ill COVID-19 patients suggest that GSHs are a valuable model for investigating microbial changes during SARS2 infection. The relationship between the age, residential microbiome and viral pathogens contributes to a better understanding of the complexities associated with the host responses during viral infection while limiting potential environmental factors that may contribute to inter-individual variation.

microbiology↗

bioRxiv2021

Efficacy of GC-376 against SARS-CoV-2 virus infection in the K18 hACE2 transgenic mouse model

The COVID-19 pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is the defining global health emergency of this century. GC-376 is a Mpro inhibitor with antiviral activity against SARS-CoV-2 in vitro. Using the K18-hACE2 mouse model, the in vivo antiviral efficacy of GC-376 against SARS-CoV-2 was evaluated. GC-376 treatment was not toxic in K18-hACE2 mice and produced milder tissue lesions, reduced viral loads, fewer presence of viral antigen, and reduced inflammation in comparison to vehicle-treated controls, most notably in the brain in mice challenged with a low virus dose. Although GC-376 was not sufficient to improve neither clinical symptoms nor survival, it did show a positive effect against SARS-CoV-2 in vivo. This study supports the notion that the K18-hACE2 mouse model is suitable to study antiviral therapies against SARS-CoV-2, and GC-376 represents a promising lead candidate for further development to treat SARS-CoV-2 infection.

microbiology↗