Junichi Kawada

ABSTRACT Human herpesvirus 6B (HHV‐6B) encephalitis is a rare but severe complication of hematopoietic cell transplantation. This study investigated the pathogenesis of HHV‐6B encephalitis by comparing plasma proteomic profiles of four pediatric patients with HHV‐6B encephalitis to three with asymptomatic HHV‐6B reactivation following umbilical cord blood transplantation (UCBT). Plasma proteomic profiling was conducted using liquid chromatography‐mass spectrometry. Overall, 260 proteins were identified and quantified in plasma samples. At the onset of HHV‐6B encephalitis and asymptomatic reactivation, 20 and 24 proteins, respectively, were significantly upregulated compared to their respective pre‐onset levels. Of these, 11 proteins were uniquely upregulated in HHV‐6B encephalitis. S100‐A9 and S100‐A8 were the most and second‐most upregulated proteins in HHV‐6B encephalitis, respectively. Elevated plasma S100A8/A9 heterodimer levels were confirmed via enzyme‐linked immunosorbent assay in three of the four patients with HHV‐6B encephalitis. Pathway analysis identified neutrophil degranulation as the most enriched category among upregulated proteins in HHV‐6B encephalitis. Additionally, proteins related to the protein‐lipid complex remodeling pathway were more prominently upregulated in HHV‐6B encephalitis than in asymptomatic reactivation. Proteomic analysis revealed distinct plasma protein profiles between HHV‐6B encephalitis and asymptomatic HHV‐6B reactivation in pediatric UCBT recipients. The inflammatory response mediated by S100A8/A9 proteins may play a critical role in the pathogenesis of HHV‐6B encephalitis. These findings indicate that proteomic analysis may provide novel insights into the host response to HHV‐6B reactivation and the subsequent development of HHV‐6B encephalitis.

ABSTRACT Background and Aims Interactions between the lung microbiome and pulmonary epithelium plays a pivotal role in shaping immunity in the lung. Idiopathic pulmonary fibrosis (IPF) is the most common interstitial lung disease (ILD). Some patients with IPF develop episodic acute exacerbations often associated with microbial dysbiosis in the lungs. This study aimed to investigate etiologic agents as well as the lung microbiome in patients with ILDs and sarcoidosis. Methods This study analyzed 31 patients divided into the IPF (IPF‐stable, n = 12), acute exacerbation of ILDs (AE‐ILDs, n = 6), and sarcoidosis (n = 13) groups. Bronchoalveolar lavage fluid (BALF) samples were analyzed by RNA‐based metagenomic next‐generation sequencing (NGS) on an Illumina platform. Results In total, 87 pathogens were detected using metagenomic NGS at the genus level. Prevotella, Streptococcus, and Veillonella dominated the BALF microbial communities, and sequence reads of these bacteria were abundant, especially in the sarcoidosis group. Conversely, only a small number of bacterial reads were detected in the AE‐ILDs group, and the overall proportion of microbial composition differed from that of the other groups. No significant difference was found in community diversity (α‐diversity) among the groups, whereas the structural similarity of the microflora (β‐diversity) differed significantly between the AE‐ILDs and sarcoidosis groups. Conclusions Bacterial sequence reads in BALF were smaller in both the IPF‐stable and AE‐ILD groups than in the sarcoidosis group. Dysbiosis in the lung microbiome has been observed in patients with AE‐ILD and may be related to the progression of inflammation.