Hypersensitivity pneumonitis: A fibrosing alveolitis produced by inhalation of diverse antigens

Masks of hypersensitivity pneumonitis in children

Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is the most common interstitial lung disease in children, but remains rarely recognized in the pediatric population. Early recognition of triggering factors and a high index of suspicion of HP could lead to timely diagnosis and individualized treatment. This study aimed to present four clinical cases of HP reported between 2012 and 2022 in Lithuania to improve the suspicion of the disease in children.

Recurrent episodes of febrile dyspnoea: hypersensitivity pneumonitis caused by a household ultrasonic humidifier

Hypersensitivity pneumonitis is an immune-mediated interstitial lung disease that presents with respiratory symptoms, with or without systemic symptoms, following exposure to an identified or unidentified external factor. It can be caused by extrinsic factors including household items such as ultrasonic humidifiers.We present an intriguing case of a previously healthy 50-year-old man who displayed recurrent episodes of progressive dyspnoea and fever after repeated exposure to his household ultrasonic humidifier. He was treated with corticosteroids, followed by the removal of the humidifier, resulting in total recovery and absence of recurrence of further episodes.The clinical presentation of hypersensitivity pneumonitis can be dramatic, and the differential diagnosis is broad. The correct diagnosis is achieved by combining clinical, radiological and histopathological patterns. The key to finding the aetiology lies in a thorough history, with an important role for household investigations to identify the external factor.

The controversial effect of smoking and nicotine in SARS-CoV-2 infection

The effects of nicotine and cigarette smoke in many diseases, notably COVID-19 infection, are being debated more frequently. The current basic data for COVID-19 is increasing and indicating the higher risk of COVID-19 infections in smokers due to the overexpression of corresponding host receptors to viral entry. However, current multi-national epidemiological reports indicate a lower incidence of COVID-19 disease in smokers. Current data indicates that smokers are more susceptible to some diseases and more protective of some other. Interestingly, nicotine is also reported to play a dual role, being both inflammatory and anti-inflammatory. In the present study, we tried to investigate the effect of pure nicotine on various cells involved in COVID-19 infection. We followed an organ-based systematic approach to decipher the effect of nicotine in damaged organs corresponding to COVID-19 pathogenesis (12 related diseases). Considering that the effects of nicotine and cigarette smoke are different from each other, it is necessary to be careful in generalizing the effects of nicotine and cigarette to each other in the conducted researches. The generalization and the undifferentiation of nicotine from smoke is a significant bias. Moreover, different doses of nicotine stimulate different effects (dose-dependent response). In addition to further assessing the role of nicotine in COVID-19 infection and any other cases, a clever assessment of underlying diseases should also be considered to achieve a guideline for health providers and a personalized approach to treatment.

Timber-colonizing gram-negative bacteria as potential causative agents of respiratory diseases in woodworkers

Occurrence

Gram-negative bacteria occur commonly in the inner tissues of stored coniferous and deciduous timber, showing a marked variation in numbers. The greatest maximal numbers are found in the sapwood of coniferous timber. The common constituents of the Gram-negative biota are potentially pathogenic species of Enterobacteriaceae family of the genera Rahnella, Pantoea, Enterobacter, and Klebsiella. The air of wood-processing facilities is polluted with the wood-borne Gram-negative bacteria and produced by them endotoxin, as demonstrated worldwide by numerous studies.

Effects

There are three potential pathways of the pathogenic impact of wood-borne Gram-negative bacteria on exposed woodworkers: allergic, immunotoxic, and infectious. Allergic impact has been underestimated for a long time with relation to Gram-negative bacteria. Hopefully, the recent demonstration of the first documented case of hypersensitivity pneumonitis (HP) in woodworkers caused by Pantoea agglomerans which developed in extremely large quantities in birch sapwood, would speed up finding of new wood-related cases of HP caused by Gram-negative bacteria. The second pathway is associated with endotoxin, exerting strong immunotoxic (excessively immunostimulative) action. It has been demonstrated that endotoxin is released into wood dust in the form of nano-sized microvesicles, by peeling off the outer membrane of bacteria. Endotoxin microvesicles are easily inhaled by humans together with dust because of small dimensions and aerodynamic shape. Afterwards, they cause a nonspecific activation of lung macrophages, which release numerous inflammatory mediators causing an inflammatory lung reaction, chest tightness, fever, gas exchange disorders, and bronchospasm, without radiographic changes. The resulting disease is known as “Organic Dust Toxic Syndrome” or “toxic pneumonitis.” The potential third pathway of pathogenic impact is infection. The suspected species is Klebsiella pneumoniae that may occur commonly in wood dust; however, until now this pathway has not been confirmed.

Conclusion

Summarizing, Gram-negative bacteria-inhabiting timber should be considered, besides filamentous fungi and actinobacteria, as important risk factors of occupational disease in woodworkers that could be either HP with allergenic background or toxic pneumonitis elicited by endotoxin.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-021-01829-1.

A Review of Systemic Minocycline Side Effects and Topical Minocycline as a Safer Alternative for Treating Acne and Rosacea

Resistance of Cutibacterium acnes to topical antibiotics historically used to treat acne (topical erythromycin and clindamycin and, more recently, topical azithromycin and clarithromycin) has been steadily increasing and new topical antibiotics are needed. Minocycline is a semisynthetic tetracycline-derived antibiotic currently used systemically to treat a wide range of infections caused by Gram-negative and Gram-positive bacteria. In addition to its antibiotic activity, minocycline possesses anti-inflammatory properties, such as the downregulation of proinflammatory cytokine production, suppression of neutrophil chemotaxis, activation of superoxide dismutase, and inhibition of phagocytosis, among others. These characteristics make minocycline a valuable agent for treatment of dermatological diseases such as acne vulgaris and papulopustular rosacea. However, more frequent or serious adverse effects have been observed upon the systemic administration of minocycline than with other tetracyclines. Examples of serious adverse effects include hypersensitivity syndrome reaction, drug-induced lupus, idiopathic intracranial hypertension, and other autoimmune syndromes that may cause death. Here, we review adverse effects and drug–drug interactions observed with oral administration of minocycline and contrast this with topical minocycline formulations recently approved or under development for effectively treating dermatological disorders with fewer adverse effects and less drug interaction.

The association between fungi exposure and hypersensitivity pneumonitis: a systematic review

A systematic review of published studies focused on the association between hypersensitivity pneumonitis (HP) and fungi exposure was conducted on PubMed, following PRISMA guidelines for systematic reviews. A total of 14 studies met the inclusion criteria but only 6 of these studies were eligible, as the remaining 8 represented case reports that were separately included for further discussion. HP is an interstitial lung disease (ILD) characterized by a hypersensitization response to inhalable antigens and represents 1.5% to 12% of all ILD in the European population. Several fungi species that populate the indoor environment have been associated with the incidence of HP upon cumulative exposure, with Penicillium spp and Aspergillus spp being the fungi species most frequently associated with the onset of disease. Although some studies have shown that avoiding exposure to causative HP fungi tends to improve patients’ symptoms, other studies were unable to identify the source of sensitization. More microbial exposure studies are needed to properly estimate the risk of HP development in the built environment.

IL-17A-Secreting Memory γδ T Cells Play a Pivotal Role in Sensitization and Development of Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) typically presents with interstitial inflammation and granulomas induced by an aberrant immune response to inhaled Ags in sensitized individuals. Although IL-17A is involved in the development of HP, the cellular sources of IL-17A and the mechanisms by which IL-17A contributes to granuloma formation remain unclear. Recent studies report that γδ T cells produce IL-17A and exhibit memory properties in various diseases. Therefore, we focused on IL-17A-secreting memory γδ T cells in the sensitization phase and aimed to elucidate the mechanisms by which IL-17A contributes to granuloma formation in HP. We induced a mouse model of HP using pigeon dropping extract (PDE) in wild-type and IL-17A knockout (IL-17A^-/-) mice. IL-17A^-/- mice exhibited reduced granulomatous areas, attenuated aggregation of CD11b⁺ alveolar macrophages, and reduced levels of CCL2, CCL4, and CCL5 in the bronchoalveolar lavage fluid. Among IL-17A⁺ cells, more γδ T cells than CD4⁺ cells were detected after intranasal PDE administration. Interestingly, the expansion of IL-17A-secreting Vγ4⁺ or Vγ1^-Vγ4^- cells of convalescent mice was enhanced in response to the sensitizing Ag. Additionally, coculture of macrophages with PDE and Vγ4⁺ cells purified from PDE-exposed convalescent mice produced significantly more IL-17A than coculture with Vγ4⁺ cells from naive mice. Our findings demonstrate that in the sensitization phase of HP, IL-17A-secreting memory γδ T cells play a pivotal role. Furthermore, we characterized the IL-17A/CCL2, CCL4, CCL5/CD11b⁺ alveolar macrophage axis, which underlies granuloma formation in HP. These findings may lead to new clinical examinations or therapeutic targets for HP.

Therapeutic Effect of Neuraminidase-1-Selective Inhibition in Mouse Models of Bleomycin-Induced Pulmonary Inflammation and Fibrosis

Pulmonary fibrosis remains a serious biomedical problem with no cure and an urgent need for better therapies. Neuraminidases (NEUs), including NEU1, have been recently implicated in the mechanism of pulmonary fibrosis by us and others. We now have tested the ability of a broad-spectrum neuraminidase inhibitor, 2,3-dehydro-2-deoxy-N-acetylneuraminic acid (DANA), to modulate the in vivo response to acute intratracheal bleomycin challenge as an experimental model of pulmonary fibrosis. A marked alleviation of bleomycin-induced body weight loss and notable declines in accumulation of pulmonary lymphocytes and collagen deposition were observed. Real-time polymerase chain reaction analyses of human and mouse lung tissues and primary human lung fibroblast cultures were also performed. A predominant expression and pronounced elevation in the levels of NEU1 mRNA were observed in patients with idiopathic pulmonary fibrosis and bleomycin-challenged mice compared with their corresponding controls, whereas NEU2, NEU3, and NEU4 were expressed at far lower levels. The levels of mRNA for the NEU1 chaperone, protective protein/cathepsin A (PPCA), were also elevated by bleomycin. Western blotting analyses demonstrated bleomycin-induced elevations in protein expression of both NEU1 and PPCA in mouse lungs. Two known selective NEU1 inhibitors, C9-pentyl-amide-DANA (C9-BA-DANA) and C5-hexanamido-C9-acetamido-DANA, dramatically reduced bleomycin-induced loss of body weight, accumulation of pulmonary lymphocytes, and deposition of collagen. Importantly, C9-BA-DANA was therapeutic in the chronic bleomycin exposure model with no toxic effects observed within the experimental timeframe. Moreover, in the acute bleomycin model, C9-BA-DANA attenuated NEU1-mediated desialylation and shedding of the mucin-1 ectodomain. These data indicate that NEU1-selective inhibition offers a potential therapeutic intervention for pulmonary fibrotic diseases. SIGNIFICANCE STATEMENT: Neuraminidase-1-selective therapeutic targeting in the acute and chronic bleomycin models of pulmonary fibrosis reverses pulmonary collagen deposition, accumulation of lymphocytes in the lungs, and the disease-associated loss of body weight-all without observable toxic effects. Such therapy is as efficacious as nonspecific inhibition of all neuraminidases in these models, thus indicating the central role of neuraminidase-1 as well as offering a potential innovative, specifically targeted, and safe approach to treating human patients with a severe malady: pulmonary fibrosis.

Usefulness of bronchoalveolar lavage in a French pediatric cohort with hypersensitivity pneumonitis

BACKGROUND

Hypersensitivity pneumonitis (HP) is a rare interstitial lung disease in children, and very little data are available on the frequency, diagnosis, and outcomes of HP. In a pediatric cohort with HP, the characteristics of the CD4/CD8 lymphocyte ratio are often described as nonspecific.

METHODS

We used the National French Database (RespiRare) to collect data from the last decade on HP. The diagnosis of HP was defined by the presence of a relevant exposure, clinical symptoms, and compatible lung imaging radiology and was usually defined by positive precipitins antibodies.

RESULTS

A total of 16 children with a mean age of 10 years (4-13) presented with HP. All children presented with dyspnea on exertion. Diffuse ground-glass opacity was present in all computed tomography (CT) scans. Research guided by a questionnaire and precipitins antibodies against the corresponding antigens showed that patients were positive for contact with birds with or without fungi. Bronchoalveolar lavage (BAL) was performed in 12 children. The total cell counts were elevated in BAL fluid, with a mean value of 36% lymphocytes. The CD4/CD8 lymphocyte ratio was below one for all children.

CONCLUSION

BAL in our pediatric cohort with HP had the same characteristics as that of adults with HP. An HP diagnosis must be considered when dyspnea on exertion and diffuse ground-glass opacity are observed. Carrying out BAL and serological tests can help diagnose and avoid lung biopsy.