Biology subjects

Pohl, M.

Publications and source records attributed to Pohl, M..

3 recordsLinked to original sources

bioRxiv2023

Salt-mediated inactivation of influenza A virus in 1-ul droplets exhibits exponential dependence on NaCl molality

Influenza A virus (IAV) spreads through exhaled aerosol particles and larger droplets. Estimating the stability of IAV is challenging and depends on factors such as the respiratory matrix and drying kinetics. Here, we combine kinetic experiments on millimeter-sized saline droplets with a biophysical aerosol model to quantify the impact of NaCl on IAV stability. We show that IAV inactivation is determined by NaCl concentration, which increases during water evaporation and then decreases again when efflorescence occurs. When drying in air with relative humidity RH = 30%, inactivation follows an inverted sigmoidal curve, with inactivation occurring most rapidly when the NaCl concentration exceeds 20 molal immediately prior to efflorescence. Efflorescence reduces the NaCl molality to saturated conditions, resulting in a significantly reduced inactivation rate. We demonstrate that the inactivation rate k depends exponentially on NaCl molality, and after the solution reaches equilibrium, the inactivation proceeds at a first-order rate. Introducing sucrose, an organic co-solute, attenuates IAV inactivation via two mechanisms, firstly by decreasing the NaCl molality during the drying phase, and secondly by a protective effect against the NaCl-induced inactivation. For both pure saline and sucrose-containing droplets, our biophysical model ResAM accurately simulates the inactivation when NaCl molality is used as the only inactivating factor. This study highlights the role of NaCl molality in IAV inactivation and provides a mechanistic basis for the observed inactivation rates. SYNOPSIS: This work quantifies the dependence of influenza A virus stability on salt molality in drying droplets and furthers the understanding of airborne virus transmission.SYNOPSIS: This work quantifies the dependence of influenza A virus stability on salt molality in drying droplets and furthers the understanding of airborne virus transmission.

microbiology↗

bioRxiv2023

Co-inhibition of topoisomerase 1 and BRD4-mediated pause release selectively kills pancreatic cancer via readthrough transcription

Pancreatic carcinoma is one of the most lethal cancers and the absence of efficient therapeutic strategies results in poor prognosis. Transcriptional dysregulation due to alterations in KRAS and MYC impacts initiation, development, and survival of this tumor type. Using patient-derived xenografts of pancreatic carcinoma driven by KRAS and MYC oncogenic transcription, we show that co-inhibition of Topoisomerase 1 (TOP1) and bromodomain containing protein 4 (BRD4) synergistically induce tumor regression through targeting promoter pause-release, a rate-limiting step in transcription elongation. By comparing the nascent transcriptome with the recruitment of elongation and termination factors along genes, we found that co-inhibition of TOP1 and BRD4, while globally impairing RNA production, disturbs recruitment of proteins involved in termination. Thus, RNA polymerases continue transcribing downstream of genes for hundreds of kilobases leading to readthrough transcription. This pervasive transcription also occurs during replication, perturbing replisome progression and leading to DNA damage. The synergistic effect of TOP1 and BRD4 inhibition is specific for cancer cells leaving normal cells unharmed, highlighting the sensitivity of the tumor to these transcriptional defects. This preclinical study provides a mechanistic understanding of the benefit of combining TOP1 and BRD4 inhibitors to treat pancreatic carcinomas addicted to oncogenic drivers of high transcription and replication. One Sentence SummaryTOP1 and BRD4 inhibitors synergize to selectively kill pancreatic cancer in vivo via readthrough transcription without emergence of drug resistance

cancer biology↗

bioRxiv2022

Inactivation of Influenza A virus by pH conditions encountered in expiratory aerosol particles results from localized conformational changes within Haemagglutinin and Matrix 1 proteins.

Multiple respiratory viruses including Influenza A virus (IAV) can be transmitted via expiratory aerosol particles, and aerosol pH was recently identified as a major factor influencing airborne virus infectivity. For indoor air, small exhaled aerosols undergo rapid acidification to pH [~]4. IAV is known to be sensitive to mildly acidic conditions encountered within host endosomes, however, it is unknown whether the same mechanisms could mediate viral inactivation within the more acidic aerosol micro-environment. Here, we identified that transient exposure to pH 4 caused IAV inactivation by a two-stage process, with an initial sharp decline in infectious titers that was mainly attributed to premature attainment of the post-fusion conformation of viral protein haemagglutinin (HA). Changes to HA were observed by hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) as early as 10 seconds post-exposure to acidic conditions. In addition, virion integrity was partially but irreversibly affected by acidic conditions. This was attributed to a progressive unfolding of the internal matrix protein 1 (M1), and aligned with a more gradual decline in viral infectivity with time. In contrast, no acid-mediated changes to the genome or lipid envelope were detected. Our HDX-MS data are in agreement with other more labor-intensive structural analysis techniques such as X-ray crystallography, highlighting the usefulness of whole-virus HDX-MS for multiplexed protein analyses, even within enveloped viruses such as IAV. Improved understanding of respiratory virus fate within exhaled aerosols constitutes a global public health priority, and information gained here could aid development of novel strategies to control the airborne persistence of seasonal and/or pandemic influenza in the future.

microbiology↗