Staphylococcus aureus Lung Infection Results in Down-Regulation of Surfactant Protein-A Mainly Caused by Pro-Inflammatory Macrophages

A review of chemical signaling mechanisms underlying quorum sensing and its inhibition in Staphylococcus aureus

Staphylococcus aureus is a significant bacterium responsible for multiple infections and is a primary cause of fatalities among patients in hospital environments. The advent of pathogenic bacteria such as methicillin-resistant S. aureus revealed the shortcomings of employing antibiotics to treat bacterial infectious diseases. Quorum sensing enhances S. aureus's survivability through signaling processes. Targeting the key components of quorum sensing has drawn much interest nowadays as a promising strategy for combating infections caused by bacteria. Concentrating on the accessory gene regulator quorum-sensing mechanism is the most commonly suggested anti-virulence approach for S.aureus. Quorum quenching is a common strategy for controlling illnesses triggered by microorganisms since it reduces the pathogenicity of bacteria and improves bacterial biofilm susceptibility to antibiotics, thus providing an intriguing prospect for drug discovery. Quorum sensing inhibition reduces selective stresses and constrains the emergence of antibiotic resistance while limiting bacterial pathogenicity. This review examines the quorum sensing mechanisms involved in S. aureus, quorum sensing targets and gene regulation, environmental factors affecting quorum sensing, quorum sensing inhibition, natural products as quorum sensing inhibitory agents and novel therapeutical strategies to target quorum sensing in S. aureus as drug developing technique to augment conventional antibiotic approaches.

Organ-on-chip models for infectious disease research

Research on microbial pathogens has traditionally relied on animal and cell culture models to mimic infection processes in the host. Over recent years, developments in microfluidics and bioengineering have led to organ-on-chip (OoC) technologies. These microfluidic systems create conditions that are more physiologically relevant and can be considered humanized in vitro models. Here we review various OoC models and how they have been applied for infectious disease research. We outline the properties that make them valuable tools in microbiology, such as dynamic microenvironments, vascularization, near-physiological tissue constitutions and partial integration of functional immune cells, as well as their limitations. Finally, we discuss the prospects for OoCs and their potential role in future infectious disease research.

Use of 2D minilungs from human embryonic stem cells to study the interaction of Cryptococcus neoformans with the respiratory tract

Organoids can meet the needs between the use of cell culture and in vivo work, bringing together aspects of multicellular tissues, providing a more similar in vitro system for the study of various components, including host-interactions with pathogens and drug response. Organoids are structures that resemble organs in vivo, originating from pluripotent stem cells (PSCs) or adult stem cells (ASCs). There is great interest in deepening the understanding of the use of this technology to produce information about fungal infections and their treatments. This work aims the use 2D human lung organoid derived from human embryonic stem cells (hESCs), to investigate Cryptococcus neoformans-host interactions. C. neoformans is an opportunistic fungus acquired by inhalation that causes systemic mycosis mainly in immunocompromised individuals. Our work highlights the suitability of human minilungs for the study of C. neoformans infection (adhesion, invasion and replication), the interaction with the surfactant and induction of the host's alveolar pro-inflammatory response.

In vitro modelling of bacterial pneumonia: a comparative analysis of widely applied complex cell culture models

Bacterial pneumonia greatly contributes to the disease burden and mortality of lower respiratory tract infections among all age groups and risk profiles. Therefore, laboratory modelling of bacterial pneumonia remains important for elucidating the complex host-pathogen interactions and to determine drug efficacy and toxicity. In vitro cell culture enables for the creation of high-throughput, specific disease models in a tightly controlled environment. Advanced human cell culture models specifically, can bridge the research gap between the classical two-dimensional cell models and animal models. This review provides an overview of the current status of the development of complex cellular in vitro models to study bacterial pneumonia infections, with a focus on air-liquid interface models, spheroid, organoid, and lung-on-a-chip models. For the wide scale, comparative literature search, we selected six clinically highly relevant bacteria (Pseudomonas aeruginosa, Mycoplasma pneumoniae, Haemophilus influenzae, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Staphylococcus aureus). We reviewed the cell lines that are commonly used, as well as trends and discrepancies in the methodology, ranging from cell infection parameters to assay read-outs. We also highlighted the importance of model validation and data transparency in guiding the research field towards more complex infection models.

Surrogate infection model predicts optimal alveolar macrophage number for clearance of Aspergillus fumigatus infections

The immune system has to fight off hundreds of microbial invaders every day, such as the human-pathogenic fungus Aspergillus fumigatus. The fungal conidia can reach the lower respiratory tract, swell and form hyphae within six hours causing life-threatening invasive aspergillosis. Invading pathogens are continuously recognized and eliminated by alveolar macrophages (AM). Their number plays an essential role, but remains controversial with measurements varying by a factor greater than ten for the human lung. We here investigate the impact of the AM number on the clearance of A. fumigatus conidia in humans and mice using analytical and numerical modeling approaches. A three-dimensional to-scale hybrid agent-based model (hABM) of the human and murine alveolus allowed us to simulate millions of virtual infection scenarios, and to gain quantitative insights into the infection dynamics for varying AM numbers and infection doses. Since hABM simulations are computationally expensive, we derived and trained an analytical surrogate infection model on the large dataset of numerical simulations. This enables reducing the number of hABM simulations while still providing (i) accurate and immediate predictions on infection progression, (ii) quantitative hypotheses on the infection dynamics under healthy and immunocompromised conditions, and (iii) optimal AM numbers for combating A. fumigatus infections in humans and mice.

Correlation Analysis of Staphylococcus aureus Drug Resistance and Virulence Factors with Blood Cell Counts and Coagulation Indexes

OBJECTIVE

The influence of different Staphylococcus aureus variants on blood cells and coagulation system was evaluated by investigating the carrying status of drug resistance genes and virulence genes of methicillin-resistantStaphylococcus aureus (MRSA) and methicillin-sensitiveStaphylococcus aureus (MSSA).

METHODS

A total of 105 blood culture-derivedStaphylococcus aureus strains were collected. The carrying status of drug resistance genes mecA and three virulence genes tst, pvl, and sasX was analyzed by polymerase chain reaction (PCR). The changes in routine blood routine counts and coagulation indexes of patients infected with different strains were analyzed.

RESULTS

The results showed that the positive rate of mecA was consistent with that of MRSA. Virulence genes tst and sasX were detected only in MRSA. Compared with MSSA, patients infected with MRSA or MSSA patients infected with virulence factor, leukocyte count and neutrophil count in peripheral blood were significantly increased, and the platelet count decreased to a higher degree. Part thromboplastin time increased, D-dimer increased, but fibrinogen content decreased more. The changes of erythrocyte and hemoglobin had no significant correlation with whether Staphylococcus aureus carried virulence genes.

CONCLUSION

The detection rate of MRSA in patients with positive Staphylococcus aureus in blood culture had exceeded 20%. The detected MRSA bacteria carried three virulence genes, tst, pvl, and sasX, which were more likely than MSSA. MRSA, which carries two virulence genes, is more likely to cause clotting disorders.

Silica nanoparticle exposure inhibits surfactant protein A and B in A549 cells through ROS-mediated JNK/c-Jun signaling pathway

Exposure to silica nanoparticles (SiNPs) is related to the dysregulation of pulmonary surfactant that maintains lung stability and function. Nevertheless, there are limited studies concerning the interaction and influence between SiNPs and pulmonary surfactant, and the damage and mechanism are still unclear. Herein, we used A549 cells to develop an in vitro model, with which we investigated the effect of SiNPs exposure on the expression of pulmonary surfactant and the potential regulatory mechanism. The results showed that SiNPs were of cytotoxicity in regarding of reduced cell viability and promoted the production of excessive reactive oxygen species (ROS). Additionally, the JNK/c-Jun signaling pathway was activated, and the expression of surfactant protein A (SP-A) and surfactant protein B (SP-B) was decreased. After the cells being treated with N-acetyl-L-cysteine (NAC), we found that the ROS content was effectively downregulated, and the expression of proteins related to JNK and c-Jun signaling pathways was suppressed. In contrast, the expression of SP-A and SP-B was enhanced. Furthermore, we treated the cells with JNK inhibitor and c-Jun-siRNA and found that the expression of protein related to JNK and c-Jun signaling pathways, as well as SP-A and SP-B, changed in line with that of NAC treatment. These findings suggest that SiNPs exposure can upregulate ROS and activate the JNK/c-Jun signaling pathway in A549 cells, thereby inhibiting the expression of SP-A and SP-B proteins.

Women in the European Virus Bioinformatics Center

Viruses are the cause of a considerable burden to human, animal and plant health, while on the other hand playing an important role in regulating entire ecosystems. The power of new sequencing technologies combined with new tools for processing "Big Data" offers unprecedented opportunities to answer fundamental questions in virology. Virologists have an urgent need for virus-specific bioinformatics tools. These developments have led to the formation of the European Virus Bioinformatics Center, a network of experts in virology and bioinformatics who are joining forces to enable extensive exchange and collaboration between these research areas. The EVBC strives to provide talented researchers with a supportive environment free of gender bias, but the gender gap in science, especially in math-intensive fields such as computer science, persists. To bring more talented women into research and keep them there, we need to highlight role models to spark their interest, and we need to ensure that female scientists are not kept at lower levels but are given the opportunity to lead the field. Here we showcase the work of the EVBC and highlight the achievements of some outstanding women experts in virology and viral bioinformatics.

Review of LINC00707: A Novel LncRNA and Promising Biomarker for Human Diseases

Long noncoding RNAs (lncRNAs) are a major type of noncoding RNA greater than 200 nucleotides in length involved in important regulatory processes. Abnormal expression of certain lncRNAs contributes to the pathogenesis of multiple diseases, including cancers. The lncRNA LINC00707 is located on chromosome 10p14 and is abnormally expressed in numerous disease types, and particularly in several types of cancer. High LINC00707 levels mediate a series of biological functions, including cell proliferation, apoptosis, metastasis, invasion, cell cycle arrest, inflammation, and even osteogenic differentiation. In this review, we discuss the main functions and underlying mechanisms of LINC00707 in different diseases and describe promising applications of LINC00707 in clinical settings.

Organoids as host models for infection biology - a review of methods

Infectious diseases are a major threat worldwide. With the alarming rise of antimicrobial resistance and emergence of new potential pathogens, a better understanding of the infection process is urgently needed. Over the last century, the development of in vitro and in vivo models has led to remarkable contributions to the current knowledge in the field of infection biology. However, applying recent advances in organoid culture technology to research infectious diseases is now taking the field to a higher level of complexity. Here, we describe the current methods available for the study of infectious diseases using organoid cultures.

Serum SP-A and KL-6 levels can predict the improvement and deterioration of patients with interstitial pneumonia with autoimmune features

BACKGROUND

Some patients with interstitial pneumonia with autoimmune features (IPAF) showed a progressive course despite therapy. This study aimed to evaluate whether serial changes in the serum levels of surfactant protein-A (SP-A) and Krebs von den Lungen-6 (KL-6) can predict disease progression.

METHODS

Sixty-four patients with IPAF and 41 patients with non-fibrotic lung disease (non-FLD) were examined. Based on long-term changes in lung function, 36 IPAF patients who were followed up for more than 3 months were divided into a progressive group (n = 9), an improvement group (n = 13), and a stable group (n = 14). Serum KL-6 and SP-A levels were measured. The sensitivity, specificity, cut-off value, and area under the curve (AUC) value for each of the indices were determined using receiver operating characteristic (ROC) curve analysis. The expression differences in these biomarkers and their correlation with disease severity were analyzed.

RESULTS

Compared with non-FLD patients, serum SP-A and KL-6 levels in IPAF patients were increased significantly [SP-A: (p < 0.001); KL-6: (p < 0.001)] and negatively correlated with DLCO (SP-A: r_S = - 0.323, p = 0.018; KL-6: r_S = - 0.348, p = 0.0011). In patients with progressive disease, the posttreatment serum SP-A and KL-6 levels were increased significantly compared with pretreatment levels [SP-A: (p = 0.021); KL-6: (p = 0.008)]. In patients showing improvement, the levels were decreased significantly [SP-A (p = 0.007) and KL-6 (p = 0.002)]. Changes in serum biomarkers (Delta SP-A and Delta KL-6) were significantly negatively correlated with changes in lung function (Delta FVC, Delta DLCO and Delta FEV1) (r_S = 0.482, p < 0.05). A significant positive correlation was found between Delta SP-A and Delta KL-6 (r_S = 0.482, p < 0.001).

CONCLUSIONS

Serum SP-A and KL-6 offer high sensitivity and specificity for the diagnosis of IPAF. The decrease in serum SP-A and/or KL-6 levels in patients with IPAF is related to the improvement in pulmonary function. SP-A and KL-6 may be important biomarkers for predicting disease progression in patients with IPAF.

Hybrid Agent-Based Modeling of Aspergillus fumigatus Infection to Quantitatively Investigate the Role of Pores of Kohn in Human Alveoli

The healthy state of an organism is constantly threatened by external cues. Due to the daily inhalation of hundreds of particles and pathogens, the immune system needs to constantly accomplish the task of pathogen clearance in order to maintain this healthy state. However, infection dynamics are highly influenced by the peculiar anatomy of the human lung. Lung alveoli that are packed in alveolar sacs are interconnected by so called Pores of Kohn. Mainly due to the lack of in vivo methods, the role of Pores of Kohn in the mammalian lung is still under debate and partly contradicting hypotheses remain to be investigated. Although it was shown by electron microscopy that Pores of Kohn may serve as passageways for immune cells, their impact on the infection dynamics in the lung is still unknown under in vivo conditions. In the present study, we apply a hybrid agent-based infection model to quantitatively compare three different scenarios and discuss the importance of Pores of Kohn during infections of Aspergillus fumigatus. A. fumigatus is an airborne opportunistic fungus with rising incidences causing severe infections in immunocompromised patients that are associated with high mortality rates. Our hybrid agent-based model incorporates immune cell dynamics of alveolar macrophages – the resident phagocytes in the lung – as well as molecular dynamics of diffusing chemokines that attract alveolar macrophages to the site of infection. Consequently, this model allows a quantitative comparison of three different scenarios and to study the importance of Pores of Kohn. This enables us to demonstrate how passaging of alveolar macrophages and chemokine diffusion affect A. fumigatus infection dynamics. We show that Pores of Kohn alter important infection clearance mechanisms, such as the spatial distribution of macrophages and the effect of chemokine signaling. However, despite these differences, a lack of passageways for alveolar macrophages does impede infection clearance only to a minor extend. Furthermore, we quantify the importance of recruited macrophages in comparison to resident macrophages.

Recent progress on surfactant protein A: cellular function in lung and kidney disease development

Pulmonary surfactant is a heterogeneous active surface complex made up of lipids and proteins. The major glycoprotein in surfactant is surfactant protein A (SP-A), which is released into the alveolar lumen from cytoplasmic lamellar bodies in type II alveolar epithelial cells. SP-A is involved in phospholipid absorption. SP-A together with other surfactant proteins and phospholipids prevent alveolar collapse during respiration by decreasing the surface tension of the air-liquid interface. Additionally, SP-A interacts with pathogens to prevent their propagation and regulate host immune responses. Studies in human and animal models have shown that deficiencies or mutations in surfactant components result in various lung or kidney pathologies, suggesting a role for SP-A in the development of lung and kidney diseases. In this mini-review, we discuss the current understanding of SP-A functions, recent findings of its dysfunction in specific lung and kidney pathologies, and how SP-A has been used as a biomarker to detect the outcome of lung diseases.