INTRODUCTION
THE RESPIRATORY EPITHELIUM ACTIVELY CONTRIBUTES TO DIFFERENCES IN CLINICAL DISEASE CHARACTERISTICS BETWEEN MYCOPLASMA PNEUMONIAE AND STREPTOCOCCUS PNEUMONIAE
Abstract
Background
Mycoplasma pneumoniae (Mp) and Streptococcus pneumoniae (Sp) are the most common bacteria to cause pneumonia in children. The clinical characteristics of Mp pneumonia are markedly different from Sp pneumonia. Respiratory epithelium plays an important role in the host response. We hypothesized that the differences in clinical infection characteristics could be explained by differences in the epithelial cell response to the two bacteria.
Methods
Primary human bronchial epithelial cells (pHBECs), derived from lung resection material, were cultured in air-liquid-interface to obtain 3D bronchial tissue cultures. 3D tissue cultures or epithelial cell lines A549, Calu-3 and Detroit 562, were stimulated with Mp and Sp. Cytokine and chemokine expression were determined at 6h or 24h using qPCR or ELISA. TLR signaling after bacterial stimulation was assessed using a pNifty2Luc reporter system.
Results
Sp induced a stronger pro-inflammatory response in pHBECs compared to Mp, with up to 10-fold higher levels of IL-6, IL-8, CCL2 and CCL20. This difference was present in epithelial cell lines derived from both upper and lower respiratory tract. In contrast to cytokine responses, Mp induced stronger TLR2-mediated signaling than Sp, indicating qualitatively different responses. Indeed Mp maintained expression of Th2-associated IL-33 and IL25R , whereas these markers were downregulated by Sp, both under homeostatic and Th2-promoting conditions.
Conclusions
The clinical disease characteristics induced by Mp and Sp already arise at the epithelial cell level and show quantitative and qualitative differences in the immune response to Mp and Sp. Additionally, Mp maintained Th2-associated cytokine production, which concurs with the known association of Mp infection with asthma. By directly comparing Mp and Sp we demonstrate that the respiratory epithelium is an active contributor to the different clinical disease characteristics of Mp and Sp pneumonia.
Clinical Trial Registration
No results from a controlled trial were used in this work.
GENOME-WIDE ASSOCIATION STUDY OF ALL-CAUSE PNEUMONIA AMONG NEPALESE CHILDREN.
Abstract
Background
Determining the host molecular genetic characteristics of childhood pneumonia may inform the development of new clinical interventions for the treatment and prevention of the disease. We performed a genome-wide association study to identify the genes associated with all-cause pneumonia.
Methods
DNA collected from healthy Nepalese children and Nepalese children admitted to Patan Hospital, Kathmandu with clinician diagnosed pneumonia were genotyped using Illumina Global Screening Arrays. Array data underwent QC and filtering before undergoing imputation using the HRC R1.1 2016 reference panel. Association analysis, by conducting a logistic regression using multidimensional scaling values, was performed using PLINK 1.9.
Results
Following filtering, 773 children with pneumonia (cases) and 2121 healthy community based children (controls) were analysed. A single variant within an intergenic region on chromosome 13 was strongly associated with all-cause pneumonia (p=1.1x10-10, MAF cases = 0.09 vs MAF controls = 0.04, OR 2.3, 95% CI 1.8-2.9). Two further variants, on chromosomes 2 (p=9.5x10-7, MAF cases = 0.005 vs MAF controls 0.029, OR 0.2, 95% CI 0.1-0.3) and 17 (p=2.8x10-7, MAF cases = 0.229 vs MAF controls = 0.3, OR 0.7, 95% CI 0.6-0.8) respectively, were associated with all-cause pneumonia.
Conclusions
We identified host genetic variants associated with all-cause pneumonia. Further studies confirming this association and its biological role in pneumonia are needed.
Clinical Trial Registration
ClinicalTrials.govN/A
THE ROLE OF BREAST MILK BACTERIAL COMMUNITIES AND THE METABOLOME IN SHAPING THE COMPOSITION OF THE INFANT GUT MICROBIOTA
Abstract
Background
Breastfeeding contributes to shaping of the infant gut microbiome through a variety of mechanisms. Breast milk contains a diverse population of skin bacteria and intestinal organisms that directly seed the infant gut, but also contains compounds such as human milk oligosaccharides, which can selectively shape the growth and function of beneficial microbes.
Methods
We used 16S rRNA gene sequencing to assess the microbiota composition in breast milk samples and rectovaginal swabs from 90 Gambian women, and the rectal swab samples from their infants at birth and at day 60 of life. After DNA extraction, 16S amplicon libraries were generated and sequenced. Taxonomic and functional analyses were then performed. Source tracking analysis was used to estimate the contribution of the breast milk microbiome to the infant gut microbiome. The breast milk samples also underwent metabolomic profiling using a multiplatform approach.
Results
Bacterial communities were distinct in breast milk, maternal rectovaginal swabs and infant rectal swabs, differing in both composition and diversity. Overall, a greater proportion of the infant gut microbiome was derived from the infant’s mother’s breast milk (39.9%) than the maternal rectovaginal (15.1%) microbiomes. Dynamic changes in breast milk composition were characterized over the first 60 days of lactation. Metabolites identified as altering in abundance over lactation included fucose, di- and triacylglycerols, and short chain fatty acids, known to be important for infant immunological, neurological, and gastrointestinal development, as well as being an important source of energy.
Conclusions
The results of this study indicate that bacteria in mother's breast milk seed the infant gut and that distinct metabolomic profiles in milk may contribute to the development of the infant microbiome, underscoring the importance of breastfeeding in the development of the infant gut microbiome.
Clinical Trial Registration
Not applicable
GROUP A STREPTOCOCCUS INFECTION ASSOCIATED WITH KIKUCHI DISEASE
Abstract
Title of Case(s)
Group A Streptococcus infection associated with Kikuchi disease
Background
Kikuchi disease, or idiopathic histiocytic necrotizing lymphadenitis, is an uncommon condition that presents with cervical lymphadenopathy and fever, frequently in young female patients of East Asian origin. The pathogenesis is thought to be an immune response of CD8 cytotoxic T-lymphocytes and histiocytes to infection, autoimmune disease, or malignancy. Several infectious triggers have been described. We describe patients with Kikuchi disease possibly triggered by recent streptococcal infection.
Case Presentation Summary
Between September 2018 and December 2019, during a period of increased streptococcal infection in the UK, three teenage female patients with European and South Asian ancestry were diagnosed with Kikuchi disease following cervical lymph node resection. Two of three patients had travelled to South Asia prior to onset of symptoms. All patients presented with prolonged fever and cervical lymphadenopathy. Two had associated sore throat and rash. All patients received antibiotics without resolution of symptoms. Bacterial studies (blood, urine and throat swab cultures) were negative. Viral serology (cytomegalovirus, Ebstein-Barr virus, hepatitis and HIV) were negative, and serology for brucella, bartonella, toxoplasma was negative. Tuberculosis screen was negative. All had normal immunoglobulin and complement levels. Autoimmune screen was negative. Bone marrow aspirate and trephine did not suggest malignancy. The only positive finding in all patients was raised antistreptolysin-O-titre suggestive of recent group A Streptococcus infection. Symptoms in all patients resolved following lymph node resection.
Learning Points/Discussion
Group A streptococcus infection may be an infectious trigger for Kikuchi disease in susceptible patients. Kikuchi disease often resolves with conservative management. There is association of autoimmune disease (systemic lupus erythematosus) and Kikuchi disease, though autoimmune markers for our patients were negative and their symptoms did not recur. This is the first case series describing group A streptococcal infection associated with Kikuchi disease.
LOCAL IMMUNE RESPONSES DURING LOWER RESPIRATORY TRACT INFECTIONS ARE SHAPED INDEPENDENTLY OF THE INFECTION-CAUSING PATHOGEN
Abstract
Background
Lower respiratory tract infections (LRTIs) in children can be caused by several pathogens. However, LRTI clinical outcome is not only the result of microbial factors but environmental factors and the local host immune response as well. However, what determinants are most important in shaping the local host immune response during LRTI is unknown. We asked if the infection-causing pathogen is the major driver of the local immune response during LRTI.
Methods
Within a LRTI-cohort we included children with fever >38.5°C, respiratory tract symptoms, no alternative infectious diagnosis and available induced sputum samples. LRTIs were attributed to specific pathogens using a pre-specified clinical algorithm based on microbiological and clinical data. We measured immune system-related proteins in induced sputum using Olink’s proteomics panel and used these proteomics measurements as input for unsupervised clustering analysis.
Results
Patients (n=37) who met inclusion criteria and had detectable protein levels of at least 20% of proteins in the panel were included. Hierarchical Clustering Analysis revealed three robust clusters of patients based on the proteomics data (Figure 1). A proteome signature consisting of 24 cytokines/chemokines was sufficient to separate LRTI patients into one of these three patient clusters (Figure 2). Patient clusters did not relate to specific pathogens as attributed by the clinical algorithm. Furthermore, patient age and levels of systemic inflammation (i.e. CRP) were not significantly different between patient clusters as well.
Conclusions
Our data suggest that the causative pathogen is not the major driver of the local immune response during LRTI. Other factors such as genetic predisposition and microbiome composition could play an important role. Further research should identify the mechanisms responsible for shaping imune responses during LRTI.
Clinical Trial Registration
Clinical trial registration: N/A