IL-17 and γδ T-lymphocytes play a critical role in innate immunity against Nocardia asteroides GUH-2

Nocardiosis in a Patient with Nephrotic Syndrome Treated with Glucocorticoids and Tacrolimus

Nephrotic syndrome (NS) predisposes patients to immunocompromised hosts owing to the loss of immunoglobulins, immunosuppressant use, and edema complications. In addition, aging impairs the immune system; thus, elderly individuals with NS are vulnerable to infection. Nocardiosis is not a common disease; however, once infected, it can disseminate hematogenously, causing serious health problems. An 88-year-old woman with amyloid light chain amyloidosis-induced NS was treated with prednisolone and tacrolimus and developed nocardiosis and invasive aspergillosis. Protecting the skin and wounds from direct exposure to nocardia is important. Physicians should consider the safe dose and treatment period of immunosuppressants in elderly patients with NS.

Molecular, cellular and neurological consequences of infection by the neglected human pathogen Nocardia

Background

Nocardia is a facultative intracellular pathogen that infects the lungs and brains of immunocompromised patients with consequences that can be fatal. The incidence of such infections is rising, immunocompetent individuals are also being infected, and there is a need to learn more about this neglected bacterial pathogen and the interaction with its human host.

Results

We have applied dual RNA-seq to assess the global transcriptome changes that occur simultaneously in Nocardia farcinica (N. farcinica) and infected human epithelial alveolar host cells, and have tested a series of mutants in this in vitro system to identify candidate determinants of virulence. Using a mouse model, we revealed the profiles of inflammation-related factors in the lung after intranasal infection and confirmed that nbtB and nbtS are key virulence genes for Nocardia infection in vivo. Regarding the host response to infection, we found that the expression of many histones was dysregulated during the infection of lung cells, indicating that epigenetic modification might play a crucial role in the host during Nocardia infection. In our mouse model, Nocardia infection led to neurological symptoms and we found that 15 of 22 Nocardia clinical strains tested could cause obvious PD-like symptoms. Further experiments indicated that Nocardia infection could activate microglia and drive M1 microglial polarization, promote iNOS and CXCL-10 production, and cause neuroinflammation in the substantia nigra, all of which may be involved in causing PD-like symptoms. Importantly, the deletion of nbtS in N. farcinica completely attenuated the neurological symptoms.

Conclusions

Our data contribute to an in-depth understanding of the characteristics of both the host and Nocardia during infection and provide valuable clues for future studies of this neglected human pathogen, especially those addressing the underlying causes of infection-related neurological symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01452-7.

Interleukin-17A Expression Correlated with the Prognosis of Chronic Rhinosinusitis with Nasal Polyps and the Anti-Interleukin-17A Effect in a Murine Nasal Polyps Model

OBJECTIVE

To investigate the expression of interleukin-17A (IL-17A) in patients with chronic rhinosinusitis with nasal polyps (CRSwNP) and to analyze its effect on prognosis and to explore the role and mechanism of anti-IL-17A effect in vivo by establishing a murine nasal polyps (NP) model.

METHODS

Patients with CRSwNP who underwent endoscopic sinus surgery and matched control subjects were collected. We investigated IL-17A expression in human NP tissues using immunohistochemistry and analyzed their clinical features, including Lund-Mackay computed tomography scoring (LMCS) before surgery, Lund-Kennedy endoscopic scoring (LKES) before surgery (LKES B), LKES 6 months after surgery (LKES A), and reduction of LKES (LKES R). Then, after establishing the murine NP model to detect the expression and correlation of IL-17A and matrix metalloproteinase-9 (MMP-9) in nasal tissue, we studied nasal lavage fluid and serum by PCR and enzyme-linked immunosorbent assay in vivo. Anti-IL-17A treatment was administered in the murine NP model to confirm the function of IL-17A during the pathogenic processes.

RESULTS

IL-17A expression was upregulated in NP tissues from patients with CRSwNP compared with control subjects (p < 0.001). The number of IL-17A+ cells was significantly negatively correlated with LKES R in patients with CRSwNP (p < 0.01). However, there was no significant correlation between IL-17A and LMCS or LKES B (all p < 0.05). Further, IL-17A and MMP-9 were more abundant in nasal mucosa of the murine NP model compared with that of control mice (all p < 0.05), and severe polypoid lesions were apparently observed in murine NP models. Anti-IL-17A treatment downregulated the mRNA and protein expression of MMP-9 in nasal mucosa and reduced the number of polypoid lesions in the murine NP model (all p < 0.05).

CONCLUSION

Our results suggest that IL-17A plays a crucial role and may affect the prognosis of CRSwNP. Anti-IL-17A treatment may reduce the formation of polypoid lesions through inhibition of MMP-9 expression.

The Heparin-Binding Hemagglutinin of Nocardia cyriacigeorgica GUH-2 Stimulates Inflammatory Cytokine Secretion Through Activation of Nuclear Factor κB and Mitogen-Activated Protein Kinase Pathways via TLR4

Heparin-binding hemagglutinin (HBHA) from mycobacteria is involved in the dissemination of infection and the activation of the host immune response. However, the interaction of Nocardia cyriacigeorgica HBHA with the host cells remains unknown. In the present study, we describe N. cyriacigeorgica HBHA interactions with epithelial cells and organ colonization. We then investigate the mechanisms by which HBHA induces the production of inflammatory cytokines in macrophages. Immunofluorescent microscopy showed that HBHA adhered to A549 cells and HeLa cells and that the C-terminal fragment, which contains a Pro-Ala-Lys–rich domain, was responsible for adhesion. The deletion of the hbha gene in N. cyriacigeorgica mutant strains impaired adhesion to A549 cells and HeLa cells. In addition, the HBHA protein activated the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) signaling pathways and promoted the production of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-10 in macrophages. HBHA-mediated TNF-α production was dependent on the activation of the c-Jun N-terminal kinase (JNK) signal pathways, and the IL-6 and IL-10 production was dependent on the activation of extracellular regulated kinase (ERK) 1/2, MAPK p38 (p38), JNK, and nuclear NF-κB signaling pathways. Additionally, the HBHA-mediated activation of innate immunity was dependent on Toll-like receptor 4 (TLR4). Taken together, these results indicate that N. cyriacigeorgica HBHA not only adheres to epithelial cells and may be involved in organ colonization, but also plays a critical role in the modulation of innate immunity through the MAPK and NF-κB signaling pathways via TLR4.

Nocardia otitidiscaviarum meningitis in a diffuse large B-cell lymphoma patient with CD4-positive lymphocytopenia and persistent oligoclonal CD8-positive lymphocytes in the peripheral blood

Nocardiosis, sometimes presenting with multiple granulomatous lesions, is a rare opportunistic infection occurring in immunocompromised patients. However, its immunological features remain largely unaddressed. We investigated the immunological characteristics of human nocardiosis and examined the component cells of the granulomatous lesions. A 66-year-old man with diffuse large B-cell lymphoma presented with fever and multiple nodules in the lung during chemotherapy. The blood culture formed white colonies, but their characterization was difficult by routine microbiological laboratory methods. Matrix-assisted laser desorption ionization-time of flight mass spectrometry identified the colonies as Nocardia otitidiscaviarum. Meanwhile, the patient suddenly experienced an epileptic seizure without a brain abscess. His cerebrospinal fluid (CSF) showed neutrophilic pleocytosis (108/mm³). The conventional agar culturing failed to isolate colonies, but culturing with brain-heart infusion agar generated colonies. These colonies were completely concordant with those from the blood, as confirmed by 16S rRNA gene sequencing. Therefore, the patient had developed meningitis through sepsis induced by N. otitidiscaviarum. His CD4-positive T-lymphocyte counts were low, and oligoclonal CD8-positive αβ T-lymphocytes were present in the blood prior to the first and after three cycles of chemotherapy. He had bone marrow granulomatous lesions comprising lymphoma and CD8-positive αβ T-cells. Treatment with sulfamethoxazole/trimethoprim relieved all of his symptoms. The combined analysis by microbiological and molecular methods determined the cause of his epileptic seizure. His immunological characteristics, including low CD4-positive or CD8-positive αβ T-lymphocytes, may have contributed to the unusual clinical presentations by N. otitidiscaviarum, which rarely involves the central nervous system.

Experimental Granulomatous Pulmonary Nocardiosis in BALB/C Mice

Pulmonary nocardiosis is a granulomatous disease with high mortality that affects both immunosuppressed and immunocompetent patients. The mechanisms leading to the establishment and progression of the infection are currently unknown. An animal model to study these mechanisms is sorely needed. We report the first in vivo model of granulomatous pulmonary nocardiosis that closely resembles human pathology. BALB/c mice infected intranasally with two different doses of GFP-expressing Nocardia brasiliensis ATCC700358 (NbGFP), develop weight loss and pulmonary granulomas. Mice infected with 10⁹ CFUs progressed towards death within a week while mice infected with 10⁸ CFUs died after five to six months. Histological examination of the lungs revealed that both the higher and lower doses of NbGFP induced granulomas with NbGFP clearly identifiable at the center of the lesions. Mice exposed to 10⁸ CFUs and subsequently to 10⁹ CFUs were not protected against disease severity but had less granulomas suggesting some degree of protection. Attempts to identify a cellular target for the infection were unsuccessful but we found that bacterial microcolonies in the suspension used to infect mice were responsible for the establishment of the disease. Small microcolonies of NbGFP, incompatible with nocardial doubling times starting from unicellular organisms, were identified in the lung as early as six hours after infection. Mice infected with highly purified unicellular preparations of NbGFP did not develop granulomas despite showing weight loss. Finally, intranasal delivery of nocardial microcolonies was enough for mice to develop granulomas with minimal weight loss. Taken together these results show that Nocardia brasiliensis microcolonies are both necessary and sufficient for the development of granulomatous pulmonary nocardiosis in mice.

The IL-17A/IL-17RA axis in pulmonary defence and immunopathology

The interleukin (IL)-17A/IL-17 receptor A (IL-17RA) axis is emerging as a key player in host defence. Several studies have demonstrated that IL-17A-mediated responses play a critical role in both acute and chronic inflammation induced by infectious agents, environmental stimuli and genetic diseases in the airways. In this regard, it is becoming evident that IL-17A/IL-17RA signalling may have a protective and beneficial impact on health, but that it can also result in detrimental outcomes. On one hand, the IL-17A/IL-17RA axis can contribute to the elimination of noxious stimuli and to the resolution of acute inflammatory processes; on the other hand, it can exacerbate immunopathological responses, contributing to the development and progression of chronic respiratory illnesses. In addition, cellular and molecular signatures underlying IL-17A/IL-17RA signalling have been increasingly identified, although further studies are needed to clarify such complex responses. Here, we discuss the latest discoveries on the role of the IL-17A/IL-17RA axis in driving host pulmonary defence and immunopathology.

γδ T cells exhibit multifunctional and protective memory in intestinal tissues

The study of T cell memory and the target of vaccine design have focused on memory subsumed by T cells bearing the αβ T cell receptor. Alternatively, γδ T cells are thought to provide rapid immunity, particularly at mucosal borders. Here, we have shown that a distinct subset of mucosal γδ T cells mounts an immune response to oral Listeria monocytogenes (Lm) infection and leads to the development of multifunctional memory T cells capable of simultaneously producing interferon-γ and interleukin-17A in the murine intestinal mucosa. Challenge infection with oral Lm, but not oral Salmonella or intravenous Lm, induced rapid expansion of memory γδ T cells, suggesting contextual specificity to the priming pathogen. Importantly, memory γδ T cells were able to provide enhanced protection against infection. These findings illustrate that γδ T cells play a role with hallmarks of adaptive immunity in the intestinal mucosa.

Characteristics of IL-17 induction by Schistosoma japonicum infection in C57BL/6 mouse liver

Schistosomiasis japonica is a severe tropical disease caused by the parasitic worm Schistosoma japonicum. Among the most serious pathological effects of S. japonicum infection are hepatic lesions (cirrhosis and fibrosis) and portal hypertension. Interleukin-17 (IL-17) is a pro-inflammatory cytokine involved in the pathogenesis of many inflammatory and infectious conditions, including schistosomiasis. We infected C57BL/6 mice with S. japonicum and isolated lymphocytes from the liver to identify cell subsets with high IL-17 expression and release using flow cytometry and ELISA. Expression and release of IL-17 was significantly higher in hepatic lymphocytes from infected mice compared with control mice in response to both non-specific stimulation with anti-CD3 monoclonal antibody plus/anti-CD28 monoclonal antibody and PMA plus ionomycin. We then compared IL-17 expression in three hepatic T-cell subsets, T helper, natural killer T and γδT cells, to determine the major source of IL-17 during infection. Interleukin-17 was induced in all three subsets by PMA + ionomycin, but γδT lymphocytes exhibited the largest increase in expression. We then established a mouse model to further investigate the role of IL-17 in granulomatous and fibrosing inflammation against parasite eggs. Reducing IL-17 activity using anti-IL-17A antibodies decreased infiltration of inflammatory cells and collagen deposition in the livers of infected C57BL/6 mice. The serum levels of soluble egg antigen (IL)-specific IgGs were enhanced by anti-IL-17A monoclonal antibody blockade, suggesting that IL-17 normally serves to suppress this humoral response. These findings suggest that γδT cells are the most IL-17-producing cells and that IL-17 contributes to granulomatous inflammatory and fibrosing reactions in S. japonicum-infected C57BL/6 mouse liver.