Search Results (169)

Objectives: COVID-19, caused by the SARS-CoV-2 virus, has infected over 777 million individuals and led to approximately 7 million deaths worldwide. Despite significant efforts to develop effective therapies, treatment remains largely supportive, especially for severe complications like acute respiratory distress syndrome (ARDS). Numerous compounds from diverse pharmacological classes are currently undergoing preclinical and clinical evaluation, targeting both the virus and the host immune response. Methods: Despite the large number of articles published and after a preliminary attempt was published, we discarded the option of a systematic review. Instead, we have done a description of therapies with these results and a tentative mechanism of action. Results: Preliminary studies and early-phase clinical trials have demonstrated the potential of Mesenchymal Stem Cells (MSCs) in mitigating severe lung damage in COVID-19 patients. Previous research has shown MSCs to be effective in treating various pulmonary conditions, including acute lung injury, idiopathic pulmonary fibrosis, ARDS, asthma, chronic obstructive pulmonary disease, and lung cancer. Their ability to reduce inflammation and promote tissue repair supports their potential role in managing COVID-19-related complications. This review demonstrates the utility of MSCs in the acute phase of COVID-19 and postulates the etiopathogenic role of mitochondria in Long-COVID. Even more, their combination with other therapies is also analyzed. Conclusions: While the therapeutic application of MSCs in COVID-19 is still in early stages, emerging evidence suggests promising outcomes. As research advances, MSCs may become an integral part of treatment strategies for severe COVID-19, particularly in addressing immune-related lung injury and promoting recovery. However, a full pathogenic mechanism may explain or unify the complexity of signs and symptoms of Long COVID and Post-Acute Sequelae (PASC). Full article

The broad-spectrum insect growth regulator (IGR) and insecticide 2-((1-(4-Phenoxyphenoxy)propan-2-yl)oxy)pyridine (MPEP; also known as pyriproxyfen) is increasingly being used to address public health programs for vector control, initiated by the spread of Zika virus in 2015–2016. While considered relatively safe for humans under normal conditions, limited toxicology data are available. Current studies were undertaken to address the data gap regarding potential immunotoxicity of MPEP, with particular emphasis on host resistance to viral infection. Hsd:Harlan Sprague Dawley SD^® rats were treated for 28 days by oral gavage with doses of 0, 62.5, 125, 250 or 500 mg/kg/day of MPEP in corn oil. There was a dose-dependent increase in liver weights which is consistent with the liver playing a dominant role in MPEP metabolism. However, no histological correlates were observed. Following treatment, rats were subjected to a battery of immune tests as well as an established rat model of influenza virus infection to provide a comprehensive assessment of immune function and host resistance. While several of the immune tests showed minor exposure-related changes, evidenced by negative dose–response trends, most did not show significant differences in any of the MPEP treatment groups relative to vehicle control. Most notable was a negative trend in pulmonary mononuclear cell phagocytosis with increases in dose of MPEP. There was also a positive trend in early humoral immune response (5 days after immunization) to keyhole limpet hemocyanin (KLH) as evidenced by increased serum anti-KLH IgM antibodies which was followed later (14 days following immunization) by decreasing trends in anti-KLH IgM and IgG antibody levels. However, MPEP treatment had no effect on the ability of rats to clear the influenza virus nor the T-dependent IgM and IgG antibody response to the virus. The lack of effects of MPEP on host resistance to influenza suggests the immune effects were minimal and unlikely to present a hazard with respect to susceptibility to respiratory viral infection. Full article

Macrophages are a principal pulmonary source of type I and III interferons (IFNs), initiating and coordinating the early antiviral response to respiratory viral infections. Yet the contribution of macrophage-derived IFNs to host defense during human metapneumovirus (HMPV) infection remains poorly defined. Here, we use human primary monocyte-derived macrophages (MDMs) and THP-1-derived macrophages to analyze the IFN responses induced by HMPV compared to its closely related human pneumovirus, respiratory syncytial virus (RSV). We show that HMPV induced a robust response of type I and type III IFNs and ISGs, whereas RSV elicited only a modest, delayed IFN response despite strong IRF activation; instead, RSV preferentially activates NF-κB and exhibits a pronounced proinflammatory cytokine output. Our results highlight the role of macrophages as key modulators of the IFN and proinflammatory responses during HMPV and RSV infection. Full article

Acute pneumonia is frequently accompanied by immune suppression, particularly affecting T-cell subsets, such as CD4⁺, CD4⁺CD25⁺, and CD4⁺CD25⁺FoxP3⁺, which are critical for immune regulation. This study evaluates the immunomodulatory potential of a novel fluorinated piperazine-based aminophosphonate, complexed with β-cyclodextrin ((o-Fph)PPhβCD), comparing it with the clinically approved agent Polyoxidonium (PO) in a rat model of oleic acid-induced acute pneumonia. Flow cytometric analysis revealed that (o-Fph)PPhβCD significantly restored CD4⁺ and CD4⁺CD25⁺ T-cell levels and induced a sustained reduction in regulatory CD4⁺CD25⁺FoxP3⁺ cells, suggesting enhanced effector immune activity. While PO provided early immunorestorative effects, (o-Fph)PPhβCD exerted a more prolonged response, which was particularly evident by day 14. Structural confirmation of the inclusion complex was achieved through IR and NMR spectroscopy. These findings highlight (o-Fph)PPhβCD as a promising immunotherapeutic candidate that is capable of rebalancing immune cell populations and supporting host defense mechanisms during acute pulmonary inflammation. Full article

Pulmonary arterial hypertension (PAH) is an irreversible disease characterized by vascular and systemic inflammation, ultimately leading to right ventricular failure. There is a great need for adjunctive therapies to extend survival for PAH patients. The gut microbiome influences the host immune system and is a potential novel target for PAH treatment. We review the emerging preclinical and clinical evidence which strongly suggests that there is gut dysbiosis in PAH and that alterations in the gut microbiome may either initiate or facilitate the progression of PAH by modifying systemic immune responses. We also outline approaches to modify the intestinal microbiome and delineate some practical challenges that may impact efforts to translate preclinical microbiome findings to PAH patients. Finally, we briefly describe studies that demonstrate contributions of infections to PAH pathogenesis. We hope that this review will propel further investigations into the mechanisms by which gut dysbiosis impacts PAH and/or right ventricular function, approaches to modify the gut microbiome, and the impact of infections on PAH development or progression. Full article

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a severe pulmonary disease with high mortality, particularly in low-income countries. Early diagnosis and timely treatment, including both intensive and maintenance phases, are critical for controlling the disease and preventing its transmission. In Brazil, where TB incidence remains high, thousands of new cases are reported annually. Transmission occurs primarily through airborne droplets expelled by infected individuals. The immune response involves various cell types, such as lymphocytes and macrophages, which form granulomas to limit the spread of the bacillus. Upon entering the lungs, Mtb is phagocytosed by immune cells, where it evades destruction by blocking phagolysosome formation and inhibiting phagosome acidification. In response, the immune system forms granulomas that contain the infection, although these can become reactivated if immune function deteriorates. Mtb also interferes with host cellular organelles, particularly the endoplasmic reticulum (ER) and mitochondria, inducing cellular stress and apoptosis, which aids in its survival. Key Mtb-secreted proteins, such as BAG2 and CdhM, modulate autophagy and apoptosis pathways, influencing pathogen survival within immune cells. A deeper understanding of these molecular mechanisms, particularly the role of ER stress and its impact on immune responses, is essential for developing novel therapeutic strategies for TB prevention and treatment. Full article

Influenza A virus (IAV) infection causes considerable morbidity and mortality worldwide, and the secondary bacterial infection further exacerbates the severity and fatality of the initial viral infection. Mitophagy plays an important role in host resistance to pathogen infection and immune response, while its role on pulmonary epithelial cells with viral and bacterial co-infection remains unclear. The present study reveals that the secondary Staphylococcus aureus infection significantly increased the viral and bacterial loads in human lung epithelial cells (A549) during the initial H1N1 infection. Meanwhile, the secondary S. aureus infection triggered more intense mitophagy in A549 cells by activating the PINK1/Parkin signaling pathway. Notably, mitophagy could contribute to the proliferation of pathogens in A549 cells via the inhibition of cell apoptosis. Furthermore, based on an influenza A viral and secondary bacterial infected mouse model, we showed that activation of mitophagy was conducive to the proliferation of virus and bacteria in the lungs, aggravated the inflammatory damage and severe pneumonia at the same time, and eventually decreased the survival rate. The results elucidated the effect and the related molecular mechanism of mitophagy in pulmonary epithelial cells following IAV and secondary S. aureus infection for the first time, which will provide valuable information for the pathogenesis of virus/bacteria interaction and new ideas for the treatment of severe pneumonia. Full article

Background/Objective: Neutrophils are essential for vaccine-mediated protection against pneumococcal infection and impairment in their antibacterial function contributes to reduced vaccine efficacy during aging. However, the signaling pathways that control the neutrophil responses in vaccinated hosts are not fully understood. The extracellular adenosine pathway is a known regulator of neutrophils in naïve hosts. The aim of this study was to test the role of this pathway in the function of neutrophils and their protection against infection upon vaccination as a function of the host’s age. Methods: To test the role of adenosine in the antimicrobial activity of neutrophils against antibody-opsonized pneumococci, we used bone marrow-derived neutrophils isolated from wild-type or specific-adenosine-receptors knock-out mice. To measure the effect of adenosine receptor signaling in vivo, we treated vaccinated mice with agonists or antagonists that were specific to the different adenosine receptors prior to pulmonary challenge with pneumococci and assessed the bacterial burden and clinical score post-infection. Results: We found that signaling via the adenosine 2B (A2BR) receptor but not the A2A or A1 receptors diminished the intracellular pneumococcal killing following antibody-mediated uptake in young hosts. In vivo, the agonism of the A2BR receptor significantly worsened the pneumococcal infection outcomes in young, vaccinated mice. In contrast, A2BR signaling had no effect on the intracellular bacterial killing by neutrophils from aged mice. Further, in vivo A2BR inhibition had no effect on the pneumococcal disease progression in aged, vaccinated mice. Conclusions: A2BR signaling reduced pneumococcal vaccine-mediated protection by impairing the antimicrobial activity of neutrophils against antibody-opsonized bacteria in young hosts. However, inhibiting this pathway was not sufficient to boost responses in aged hosts. Full article

Background: Nontuberculous mycobacterial pulmonary disease (NTM-PD) is an increasingly prevalent chronic infection, where the host immune status plays a crucial role in disease susceptibility and progression. The complex pulmonary microenvironment, characterized by diverse microbial communities and host immune interactions, exhibits distinct features that may be fundamentally altered by the patient’s underlying immune state. Methods: A total of 111 sputum specimens and 64 bronchoalveolar lavage fluid (BALF) specimens were collected from 143 patients diagnosed with NTM-PD under different immune states. Metagenomic sequencing was performed on these specimens to characterize and compare the pulmonary microenvironmental features among NTM-PD patients with a distinct immune status through comprehensive bioinformatic analyses. Results: The immunosuppressed group exhibited a lower α-diversity in sputum specimens (p < 0.05). Principal Coordinates Analysis (PCoA) of β-diversity for sputum and BALF specimens revealed significant differences between the groups (p < 0.05). Linear discriminant analysis Effect Size (LEfSe) analysis identified species enriched in the immunosuppressed group. A co-occurrence network analysis indicated that the immunosuppressed group had more structured and actively connected networks compared to the control group. The Mantel test confirmed that the abundance of these species enriched was associated with clinical immune–inflammation-related indicators in patients. Conclusions: Our study reveals the pulmonary microenvironment in immunosuppressed patients with NTM-PD. Further work is required to explore the two-way relationship between micro-organisms and immune and inflammatory responses, with the influence on patient outcomes. Full article

Lung manifestations of chronic obstructive pulmonary disease (COPD) are often exacerbated by influenza A virus infections; however, the underlying mechanisms remain largely unknown, and hence therapeutic options are limited. Using a physiologically relevant human lung airway-on-a-chip (Airway Chip) microfluidic culture model lined with human airway epithelium from COPD or healthy donors interfaced with pulmonary microvascular endothelium, we observed that Airway Chips lined with COPD epithelium exhibit an increased sensitivity to influenza virus infection, as is observed clinically in COPD patients. Differentiated COPD airway epithelial cells display increased inflammatory cytokine production, barrier function loss, and mucus accumulation upon virus infection. Transcriptomic analysis revealed gene expression profiles characterized by upregulation of serine proteases that may facilitate viral entry and downregulation of interferon-related genes associated with antiviral immune responses. Importantly, treatment of influenza virus-infected COPD epithelium with a protease inhibitor, nafamostat, ameliorated the disease phenotype, as evidenced by dampened viral replication, reduced mucus accumulation, and improved tissue barrier integrity. These findings suggest that targeting host serine proteases may represent a promising therapeutic avenue against influenza-afflicted COPD exacerbations. Full article

Background/Objectives: The viral pandemic caused by the SARS-CoV-2 virus has affected millions of people. However, it was noticed that high mortality was often a result of bacterial co-infections. One of the main pathogens responsible for secondary infections in patients with viral respiratory tract infections, including COVID-19, is Staphylococcus aureus. In recent years, the number of infections caused by drug-resistant strains of S. aureus has been growing rapidly, often exceeding the number of infections caused by antibiotic-sensitive strains. In addition, biofilm-related infections are more difficult to treat due to the lower sensitivity of biofilm structure to antibiotics. Bacteriophages are seen as alternative treatment of bacterial infections. Therefore, in our work, we have analyzed the efficacy of three Kayviruses against S. aureus strains isolated from COVID-19 patients. Methods: We analyzed the ability of tested phages to remove S. aureus biofilm both from polystyrene plates as well as from the surface of pulmonary epithelial cells. Results: We have observed that tested Kayviruses had a broad host range. Furthermore, phages were able to effectively reduce biofilm biomass and number of viable cells in pure culture. During our research, none of the tested phages was shown to have a negative effect on cell viability and were able to inhibit the negative effect S. aureus had on cell condition. Conclusions: Our results show tested phages were effective in reducing the biofilm of S. aureus strains isolated from COVID-19 patients, had no adverse effect on lung epithelial cell viability. Therefore, it should be recognized that the properties of three studied Kayviruses give them an advantage in the selection of phages for treatment of staphylococcal infections. Full article

Background/Objectives: Mycobacterium abscessus (MAB) is a highly resilient pathogen that causes difficult-to-treat pulmonary infections, particularly in individuals with cystic fibrosis (CF) and other underlying conditions. Its ability to form robust biofilms within the CF lung environment is a major factor contributing to its resistance to antibiotics and evasion of the host immune response, making conventional treatments largely ineffective. These biofilms, encased in an extracellular matrix, enhance drug tolerance and facilitate metabolic adaptations in hypoxic conditions, driving the bacteria into a persistent, non-replicative state that further exacerbates antimicrobial resistance. Treatment options remain limited, with multidrug regimens showing low success rates, highlighting the urgent need for more effective therapeutic strategies. Methods: In this study, we employed artificial sputum media to simulate the CF lung environment and conducted high-throughput screening of 24,000 compounds from diverse chemical libraries to identify inhibitors of MAB biofilm formation, using the Crystal Violet (CV) assay. Results: The screen established 17 hits with ≥30% biofilm inhibitory activity in mycobacteria. Six of these compounds inhibited MAB biofilm formation by over 60%, disrupted established biofilms by ≥40%, and significantly impaired bacterial viability within the biofilms, as confirmed by reduced CFU counts. In conformational assays, select compounds showed potent inhibitory activity in biofilms formed by clinical isolates of both MAB and Mycobacterium avium subsp. hominissuis (MAH). Key compounds, including ethacridine, phenothiazine, and fluorene derivatives, demonstrated potent activity against pre- and post-biofilm conditions, enhanced antibiotic efficacy, and reduced intracellular bacterial loads in macrophages. Conclusions: This study results underscore the potential of these compounds to target biofilm-associated resistance mechanisms, making them valuable candidates for use as adjuncts to existing therapies. These findings also emphasize the need for further investigations, including the initiation of a medicinal chemistry campaign to leverage structure–activity relationship studies and optimize the biological activity of these underexplored class of compounds against nontuberculous mycobacterial (NTM) strains. Full article

Background: For investigating the host response in Acinetobacter baumannii associated pneumonia, we analyzed the host genetic sequences obtained from metagenomic next-generation sequencing (mNGS). Methods: The samples for mNGS were bronchoalveolar lavage fluid (BALF) collected from the lungs of patients infected with A. baumannii and from patients without bacterial infections. BALF samples from patients with pneumonia were collected from the lungs of patients infected with A. baumannii with New Delhi metallo-β-lactamase (NDM, before treatment), A. baumannii with NDM (post-treatment), A. baumannii without resistant genes, and those without bacterial infection. Partek was used for investigating enriched functions and pathways related to the pulmonary host response to pneumonia caused by A. baumannii with NDM infection and A. baumannii without antimicrobial-resistant genes. The STRING was employed for identifying protein interaction pathways related to the pulmonary host response to pneumonia caused by A. baumannii without antimicrobial-resistant genes. Results: In pulmonary host response to pneumonia caused by A. baumannii with NDM, five immune system-related pathways and five pathways related to signal transduction were identified. No significant differences were observed in the immune system and signal transduction pathways in the pulmonary host response to pneumonia caused by A. baumannii without antimicrobial-resistant genes. However, significant differences were noted in the phagosome, ferroptosis, and regulation of the actin cytoskeleton in cellular processes. Conclusions: mNGS provides information not only on pathogen gene expression but also on host gene expression. In this study, we found that pneumonia with A. baumannii carrying the NDM resistance gene triggers stronger immune responses in the lung, while pneumonia with A. baumannii lacking antimicrobial resistance genes is more linked to iron-related pathways. Full article

PANoptosis is a newly identified programmed cell death pathway that integrates characteristics of apoptosis, pyroptosis, and necroptosis. It plays a dual role in the host immune response to bacterial infections. On one hand, PANoptosis acts as a protective mechanism by inducing the death of infected cells to eliminate pathogens and releasing pro-inflammatory cytokines to amplify the immune response. On the other hand, bacteria can exploit PANoptosis to evade host immune defenses. This dual nature underscores the potential of PANoptosis as a target for developing novel therapies against bacterial infections. This review summarizes the molecular mechanisms of PANoptosis, along with the crosstalk and integration of different cell death pathways in response to various bacterial pathogens. We also discuss the dual roles of PANoptosis in bacterial infectious diseases, including sepsis, pulmonary infections, and intestinal infections. Elucidating the molecular mechanisms underlying PANoptosis and how bacteria manipulate this pathway offers critical insights into host–pathogen interactions. These insights provide a foundation for designing targeted antibacterial strategies, modulating inflammation, and advancing precision medicine to improve clinical outcomes. Full article

Multidrug-resistant tuberculosis (MDR-TB) poses a significant global health threat, especially when it involves the central nervous system (CNS). Tuberculous meningitis (TBM), a severe manifestation of TB, is linked to high mortality rates and long-term neurological complications, further exacerbated by drug resistance and immune evasion mechanisms employed by Mycobacterium tuberculosis (Mtb). Although pulmonary TB remains the primary focus of research, MDR-TBM introduces unique challenges in diagnosis, treatment, and patient outcomes. The effectiveness of current treatments is frequently compromised by poor CNS penetration of anti-TB drugs and the necessity for prolonged therapy, which often involves considerable toxicity. This review explores the potential of cytokine-based adjunct immunotherapies for MDR-TBM, addressing the challenges of balancing pro-inflammatory and anti-inflammatory signals within the CNS. A central focus is the prospective role of glutathione, not only in reducing oxidative stress but also in enhancing host immune defenses against Mtb’s immune evasion strategies. Furthermore, the development of vaccines aimed at upregulating glutathione synthesis in macrophages represents a promising strategy to bolster the immune response and improve treatment outcomes. By integrating glutathione and innovative vaccine approaches into MDR-TBM management, this review proposes a comprehensive strategy that targets Mtb directly while supporting immune modulation, with the potential to enhance patient outcomes and reduce treatment related adverse effects. We underscore the urgent need for further research into adjunctive therapies and immunomodulatory strategies to more effectively combat MDR-TBM. Full article