Biology subjects

de Jonge, M. I.

Publications and source records attributed to de Jonge, M. I..

6 recordsLinked to original sources

bioRxiv2025

Immune responses to human pathogens exposed to simulated Mars conditions

The identification of health risks associated with long-term crewed missions to Mars is critical for mission planning and crew safety. Human-associated pathogens can be part of the microbiome and are likely to be transported during these missions. This study examines the immunological responses of human immune cells stimulated with non-fastidious bacterial species that cause opportunistic infections, i.e. Klebsiella pneumoniae and Serratia marcescens, after exposure to simulated Martian conditions, including UV radiation, desiccation and atmospheric pressure. We observed that exposure of the bacteria to these conditions altered cytokine secretion, reactive oxygen species (ROS) production, and phagocytic activity in human peripheral blood mononuclear cells (PBMCs). Specifically, exposure to desiccation reduced cytokines and ROS production, indicating impaired innate immune recognition and stimulation. Notably, the altered immune response was partially restored when desiccated bacteria were regrown in standard media. Flow cytometry revealed decreased bacterial size and complexity of both species post-exposure. These findings indicate that Martian conditions induce bacterial morphological and physiological changes, which could impair immune recognition and response. Expanding these studies to in vivo models and a broader range of potentially pathogenic microorganisms is essential to estimate infection risks during Mars missions, which is vital for developing strategies to mitigate infection risks and maintain astronaut health during long-term space travel. ImportanceSince Yuri Gagarins 1961 flight, human space exploration has expanded, unintentionally transporting microorganisms, including pathogens, into space environments. Our previous studies demonstrated that opportunistic pathogens like Klebsiella pneumoniae and Serratia marcescens can survive simulated Mars conditions. With upcoming Mars missions, it is crucial to understand how such conditions influence these pathogens and their interaction with the human immune system. This research evaluates immune responses to bacteria pathogens exposed to Martian stressors such as UV radiation and desiccation, revealing significant changes of the immune responses to the exposed bacteria. These findings provide essential insights into the health risks that astronauts may face if infected with Mars-adapted pathogens. Understanding these interactions will help to develop preventive strategies and therapeutic measures, ensuring the safety and health of crew members during long-term missions. Ultimately, this work contributes to the broader objective of safe human exploration and colonization of Mars.

immunology↗

bioRxiv2024

The capsule and genetic background, rather than specific loci, strongly influence pneumococcal growth kinetics

Bacterial growth characteristics intrinsic to each strain can impact and influence gene expression, antibiotic susceptibility, and disease pathogenesis. However, little is known about specific genomic variations that influence these bacterial growth features. Here, we investigate the impact of Streptococcus pneumoniae genetics on its in vitro growth features to shed light on genes that may be important targets in the development of vaccines and therapeutics. We use statistical models to estimate growth features and demonstrate that they varied significantly across capsular serotypes and lineages, were strongly correlated with phylogeny, and showed high heritability, highlighting a strong genetic basis. Despite this, genome-wide association studies revealed no specific genomic loci statistically associated with the growth features independently of the genetic background, including those in the locus responsible for capsular polysaccharide synthesis. Our findings suggest that the serotype and lineage, as well as a combination of genomic loci, influence intrinsic pneumococcal growth kinetics, which may have implications for pneumococcal disease pathogenesis.

microbiology↗

bioRxiv2022

Tryptophan-like side chain holding aptamers inhibit respiratory syncytial virus infection of lung epithelial cells

Respiratory syncytial virus (RSV) is a leading cause of serious and even fatal acute lower respiratory tract infections in infants and in the elderly. Potent RSV neutralization has been achieved by antibodies that selectively bind the prefusion form of the viral fusion (F) protein. We hypothesised that similar potent neutralization could be achieved using F protein targeting aptamers. Aptamers have yet to reach their translational potential for therapeutics or diagnostics due to their short half-life and limited range of target-aptamer interactions; these shortcomings can, however, be ameliorated by application of amino acid-like side chain holding nucleotides. In this study, a stabilized version of the prefusion RSV F protein was targeted by aptamer selection using an oligonucleotide library holding a tryptophan-like side chain. This process resulted in aptamers that bound the F protein with high affinity and differentiated between pre- and postfusion conformation. Identified aptamers inhibited viral infection of lung epithelial cells. Moreover, introduction of modified nucleotides extended aptamer half-lives. Our results suggest that targeting aptamers to the surface of viruses could yield effective drug candidates, which could keep up with the pace of the continuously evolving pathogens.

molecular biology↗

bioRxiv2020

Berberine and obatoclax inhibit SARS-CoV-2 replication in primary human nasal epithelial cells in vitro

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as a new human pathogen in late 2019 and has infected an estimated 10% of the global population in less than a year. There is a clear need for effective antiviral drugs to complement current preventive measures including vaccines. In this study, we demonstrate that berberine and obatoclax, two broad-spectrum antiviral compounds, are effective against multiple isolates of SARS-CoV-2. Berberine, a plant-derived alkaloid, inhibited SARS-CoV-2 at low micromolar concentrations and obatoclax, originally developed as an anti-apoptotic protein antagonist, was effective at sub-micromolar concentrations. Time-of-addition studies indicated that berberine acts on the late stage of the viral life cycle. In agreement, berberine mildly affected viral RNA synthesis, but strongly reduced infectious viral titers, leading to an increase in the particle-to-pfu ratio. In contrast, obatoclax acted at the early stage of the infection, in line with its activity to neutralize the acidic environment in endosomes. We assessed infection of primary human nasal epithelial cells cultured on an air-liquid interface and found that SARS-CoV-2 infection induced and repressed expression of a specific set of cytokines and chemokines. Moreover, both obatoclax and berberine inhibited SARS-CoV-2 replication in these primary target cells. We propose berberine and obatoclax as potential antiviral drugs against SARS-CoV-2 that could be considered for further efficacy testing.

microbiology↗

bioRxiv2018

Bacterial Zombies And Ghosts: Production Of Inactivated Gram-Positive And Gram-Negative Species With Preserved Cellular Morphology And Cytoplasmic Content

There are many approaches available to inactivate bacteria, each with a different efficacy, impact on cell integrity, and potential for application in high-throughput. The aim of this study was to compare these approaches and develop a standardized protocol for generation of intact Gram-positive as well as on Gram-negative \"bacterial zombies\", i.e. cells that are metabolically dead with retained cellular integrity. Here, we introduce the term \"bacterial zombies\" in addition to \"bacterial ghosts\" to differentiate inactivated bacteria with preserved cellular integrity from those with perforated membranes, where DNA and cytoplasmic contents have been released. This differentiation of inactivated bacteria is important if the cell content is the subject of study, or if cell contents in the media may cause unwanted effects in downstream applications. We inactivated eight different bacterial species by treatment with beta-propiolactone, ethanol, formalin, sodium hydroxide, and pasteurization. Inactivation efficacy was determined by culturing, and cell wall integrity assessed by quantifying released DNA and visualization by scanning electron microscopy. Based on these results, we discuss the choice of bacterial inactivation methods, and conclude that beta-propiolactone and ethanol are the most promising approaches for standardized generation of bacterial zombies.\n\nIMPORTANCEFor applications such as vaccination or analyses that are sensitive to bacterial growth, inactivated bacteria are preferred because they simplify the analyses and the interpretation of results. This study compared various bacterial inactivation treatments that maintain cell integrity and may be used in high-throughput. Our results demonstrated that beta-propiolactone and 70% ethanol were the best techniques to achieve these goals.

microbiology↗

bioRxiv2017

The contribution of genetic variation of Streptococcus pneumoniae to the clinical manifestation of invasive pneumococcal disease

BackgroundDifferent clinical manifestations of invasive pneumococcal disease (IPD) have thus far mainly been explained by patient characteristics. Here we studied the contribution of pneumococcal genetic variation to IPD phenotype.\n\nMethodsThe index cohort consisted of 349 patients admitted to two Dutch hospitals between 2000-2011 with pneumococcal bacteraemia. We performed genome-wide association studies to identify pneumococcal lineages, genes and allelic variants associated with 23 clinical IPD phenotypes. The identified associations were validated in a nationwide (n=482) and a post-pneumococcal vaccination cohort (n=121). The contribution of confirmed pneumococcal genotypes to the clinical IPD phenotype, relative to known clinical predictors, was tested by regression analysis.\n\nFindingsThe presence of pneumococcal gene slaA was a nationwide confirmed independent predictor of meningitis (OR=10.5, p=0.001), as was sequence cluster 9 (OR=3.68, p=0.057). A set of 4 pneumococcal genes co-located on a prophage was a confirmed independent predictor of 30-day mortality (OR=3.4, p=0.003). We could detect the pneumococcal variants of concern in these patients blood samples by molecular amplification. In the post-vaccination cohort where the distribution of both patient characteristics and pneumococcal serotypes had changed, the relative importance of the prophage was no longer supported.\n\nInterpretationKnowledge of pneumococcal genotypic variants improved our clinical risk assessment for detrimental manifestations of IPD. This provides us with novel opportunities to target, anticipate or avert the pathogenic effects that are related to particular pneumococcal variants. Therefore, future diagnostics should facilitate prompt appreciation of pathogen diversity in clinical sepsis management. Ongoing surveillance is warranted to monitor the clinical value of information on pathogen variants in dynamic microbial and susceptible host populations.\n\nFundingNone.

microbiology↗