Biology subjects

Thaler, M.

Publications and source records attributed to Thaler, M..

6 recordsLinked to original sources

bioRxiv2025

Extracellular vesicles as indicators of environmental stress response in Lactiplantibacillus plantarum: a multi-platform study

Extracellular vesicles (EVs) are key mediators of bacterial communication and adaptation to environmental stress. Their size, cargo, and surface charge are influenced by several factors, including environmental conditions, bacterial physiology, and isolation methods, and are highly strain-specific. Herein, we investigated how exposure to bile, a physiological component of the gut environment, affects the production and properties of EVs released by the probiotic strain Lactiplantibacillus plantarum NCIMB 8826. Through ultracentrifugation followed by size-exclusion chromatography (SEC), we isolated highly purified L. plantarum EVs (LpEVs) and characterized them according to the Minimal Information for Studies of Extracellular Vesicles guidelines. SEC purification significantly reduced the contents of contaminating proteins and peptidoglycans, improving the compositional purity of the isolated EVs. Compared with the parent bacteria, purified LpEVs exhibited distinct surface lipid profiles and zeta potential as well as remarkable stability across varying pH levels, elevated NaCl concentrations, and increasing detergent challenges. Under bile stress, the bacteria released larger LpEVs enriched in bile metabolism-related proteins, suggesting vesicle-mediated adaptation. Fourier-transform infrared spectroscopy further revealed bile-induced molecular alterations in LpEVs that differed from those in the parent bacteria. These findings highlight bacterial EVs as dynamic environmental communicators that respond to stress and may modulate host-microbe interactions before detectable changes occur in the bacterial cells.

microbiology↗

bioRxiv2022

SARS-CoV-2-specific CD4+ and CD8+ T cell responses can originate from cross-reactive CMV-specific T cells

Detection of SARS-coronavirus-2 (SARS-CoV-2) specific CD4+ and CD8+ T cells in SARS-CoV-2-unexposed donors has been explained by the presence of T cells primed by other coronaviruses. However, based on the relative high frequency and prevalence of cross-reactive T cells, we hypothesized CMV may induce these cross-reactive T cells. Stimulation of pre-pandemic cryo-preserved PBMCs with SARS-CoV-2 peptides revealed that frequencies of SARS-CoV-2-specific T cells were higher in CMV-seropositive donors. Characterization of these T cells demonstrated that membrane-specific CD4+ and spike-specific CD8+ T cells originate from cross-reactive CMV-specific T cells. Spike-specific CD8+ T cells recognize SARS-CoV-2 spike peptide FVSNGTHWF (FVS) and dissimilar CMV pp65 peptide IPSINVHHY (IPS) presented by HLA-B*35:01. These dual IPS/FVS-reactive CD8+ T cells were found in multiple donors as well as severe COVID-19 patients and shared a common T cell receptor (TCR), illustrating that IPS/FVS-cross-reactivity is caused by a public TCR. In conclusion, CMV-specific T cells cross-react with SARS-CoV-2, despite low sequence homology between the two viruses, and may contribute to the pre-existing immunity against SARS-CoV-2.

immunology↗

bioRxiv2022

Honokiol inhibits SARS-CoV-2 replication in cell culture

SARS-CoV-2 emerged in 2019 and since its global spread has caused the death of over 6 million people. There are currently few antiviral options for treatment of COVID-19. Repurposing of known drugs can be a fast route to obtain molecules that inhibit viral infection and/or modulate pathogenic host responses. Honokiol is a small molecule from Magnolia trees, for which several biological effects have been reported,, including anticancer and anti-inflammatory activity. Honokiol has also been shown to inhibit several viruses in cell culture. In this study, we show that honokiol protected Vero E6 cells from SARS-CoV-2-mediated cytopathic effect with an EC50 of 7.8 {micro}M. In viral load reduction assays we observed that honokiol decreased viral RNA copies as well as viral infectious progeny titers. The compound also inhibited SARS-CoV-2 replication in the more relevant A549 cells, expressing ACE2 and TMPRSS2. A time-of-addition assay showed that honokiol inhibited virus replication even when added post infection, suggesting it acts at a post-entry step of the replication cycle. Honokiol was also effective against more recent variants of SARS-CoV-2, including omicron and it inhibited other human coronaviruses as well. Our study suggests that honokiol is an interesting molecule to evaluate in animal studies and clinical trials to investigate its effect on virus replication and pathogenic (inflammatory) host responses.

microbiology↗

bioRxiv2021

Impact of human airway epithelial cellular composition on SARS-CoV-2 infection biology

Infection biology and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19), are incompletely understood. Here, we assessed the impact of airway epithelial cellular composition on infection in air-liquid interface (ALI) cultures of differentiated primary human tracheal (PTEC) and bronchial epithelial cells (PBEC). We first compared SARS-CoV-2 infection kinetics, related antiviral and inflammatory responses, and viral entry factors in PTEC and PBEC. Next, the contribution of differentiation time was investigated by differentiating ALI-PTEC/PBEC for 3-5 weeks and comparing dynamics of viral replication/spread, cellular composition and epithelial responses. We observed a gradual increase in viral load with prolonged culture duration. Ciliated and goblet cells were predominantly infected in both PTEC and PBEC. Immunofluorescence analysis and RT-qPCR showed that compared to other cell types mainly ciliated and goblet cell numbers were affected by increased culture duration. An increased proportion of these two target cell types was associated with increased viral load. Furthermore, modulation of cellular composition using IL-13 and the Notch signaling inhibitor DAPT, underlined the importance of both ciliated and goblet cells for infection. DAPT treatment resulted in a lower viral load and a relative increase in ciliated cells at the expense of goblet cells, compared to IL-13 treated cultures in which both cell types were present and viral load was higher. In conclusion, our results identify cellular composition as a contributing factor to airway epithelial susceptibility to SARS-CoV-2. IMPORTANCEIn this study, we determined an effect of culture duration and airway cellular composition of ALI-PBEC and ALI-PTEC cultures on SARS-CoV-2 infection. We found that SARS-CoV-2 infection was increased with prolonged cell culture time and the total percentage and proportion of ciliated and goblet cells played an important role in infection level, suggesting that airway epithelial differentiation/maturation levels may in part determine susceptibility of SARS-CoV-2 infection. The development of effective therapies either targeting virus replication or pathogenesis against SARS-CoV-2 requires robust cell culture-based infection models to test small molecules and biologicals. Therefore, it is important to identify factors that are essential for reliably modeling SARS-CoV-2-airway epithelial cell interactions. This study sheds light on virus-airway epithelial cell interactions and adds to the complexity of SARS-CoV-2 cell tropism in the airways. In addition, the effect of IL-13 on viral infection hints at a causal connection between SARS-CoV-2 infection and (allergic) asthma.

cell biology↗

bioRxiv2020

Suramin inhibits SARS-CoV-2 infection in cell culture by interfering with early steps of the replication cycle

The SARS-CoV-2 pandemic that originated from Wuhan, China, in December 2019 has impacted public health, society and economy and the daily lives of billions of people in an unprecedented manner. There are currently no specific registered antiviral drugs to treat or prevent SARS-CoV-2 infections. Therefore, drug repurposing would be the fastest route to provide at least a temporary solution while better, more specific drugs are being developed. Here we demonstrate that the antiparasitic drug suramin inhibits SARS-CoV-2 replication, protecting Vero E6 cells with an EC50 of [~]20 {micro}M, which is well below the maximum attainable level in human serum. Suramin also decreased the viral load by 2-3 logs when Vero E6 cells or cells of a human lung epithelial cell line (Calu-3) were treated. Time of addition and plaque reduction assays showed that suramin acts on early steps of the replication cycle, possibly preventing entry of the virus. In a primary human airway epithelial cell culture model, suramin also inhibited the progression of infection. The results of our preclinical study warrant further investigation and suggest it is worth evaluating whether suramin provides any benefit for COVID-19 patients, which obviously requires well-designed, properly controlled randomized clinical trials.

microbiology↗

bioRxiv2020

A regulatory network of a piRNA and lncRNA initiates responder and trailer piRNA formation during embryonic development of (i)Aedes(/i) mosquitoes

PIWI-interacting (pi)RNAs are small silencing RNAs that are crucial for the defense against transposable elements in germline tissues of animals. In Aedes aegypti mosquitoes, the piRNA pathway also contributes to gene regulation in somatic tissues, illustrating additional roles for piRNAs and PIWI proteins besides transposon repression. Here, we identify a highly abundant endogenous piRNA (propiR1) that associates with both Piwi4 and Piwi5. PropiR1-mediated target silencing requires base pairing in the seed region with supplemental base pairing at the piRNA 3 end. Yet, propiR1 represses a limited set of targets, among which the lncRNA AAEL027353 (lnc027353). Slicing of lnc027353 initiates production of responder and trailer piRNAs from the cleavage fragment. Expression of propiR1 commences early during embryonic development and mediates degradation of maternally provided lnc027353. Both propiR1 and its lncRNA target are conserved in the closely related Aedes albopictus mosquito, underscoring the importance of this regulatory network for mosquito development.

molecular biology↗