Junichi Kawada

ABSTRACT Background Cytomegalovirus (CMV) infection in pediatric liver transplant recipients is a major concern. Ganciclovir (GCV) and valganciclovir (VGCV) are the first‐line treatment agents; however, neutropenia is a common adverse effect. Nucleoside diphosphate‐linked moiety X‐type motif 15 (NUDT15) variants are linked to thiopurine‐induced myelosuppression; however, their associations with GCV/VGCV‐induced cytotoxicity remain unclear. We aimed to examine the association between loss‐of‐function variants of the NUDT15 genotype and drug‐related adverse reactions in pediatric transplant recipients, specifically liver transplant recipients, treated with GCV/VGCV. Methods We retrospectively analyzed data from pediatric liver transplant recipients treated with GCV/VGCV for CMV disease or infection between 2012 and 2022. Patients were genotyped for NUDT15 R139C, R139H, and V18I variants, and hematological outcomes were compared between the normal and variant groups. Results Of 40 patients, 10 (25%) harbored NUDT15 variants. The incidence rate of neutropenia (60% vs. 7%; p < 0.01) and percentage decrease in neutrophil count (−65.1% vs. −45.9%; p = 0.02) were significantly higher in the variant group than in the normal group. No significant differences were observed in the incidence of leukopenia, anemia, thrombocytopenia, hepatic toxicity, or renal toxicity. Conclusion NUDT15 variants were associated with an increased risk of neutropenia in pediatric liver transplant recipients receiving GCV/VGCV treatment. Genetic screening before treatment initiation may help optimize antiviral therapy, minimize hematological toxicity, and improve patient management. Further studies are needed to refine the treatment strategies.image

Background: Recent studies have reported the possible link between adeno-associated virus 2 (AAV2) and severe pediatric acute hepatitis. It has been suggested that aberrant AAV2 replication initiated by coinfection with “helper viruses” such as human adenovirus and human herpesvirus-6B (HHV-6B) may induce abnormal immune responses. Encephalitis/encephalopathy is a severe complication of primary HHV-6B infection, but the underlying mechanisms remain unclear. This study analyzed the association between AAV2 coinfection and neurologic complications of primary HHV-6B infection in children. Methods: Preserved serum samples obtained from 36 patients with HHV-6B-associated encephalitis/encephalopathy, 39 with febrile seizure, and 83 without neurologic complications were retrospectively analyzed. Primary HHV-6B infection was confirmed if HHV-6B DNA was detected and the HHV-6B antibody was negative in serum. AAV2 and HHV-6 DNA loads were quantitated using real-time PCR. Results: AAV2 was detected in 4 (11%) and 3 (8%) patients in the encephalitis/encephalopathy and febrile seizure groups, respectively. In contrast, AAV2 was undetectable in 83 patients without neurologic complications. AAV2 detection frequency was significantly higher in the encephalitis/encephalopathy and febrile seizure groups compared with the no neurologic complications group (P = 0.01 and P = 0.03, respectively). Among 4 patients with HHV-6B-associated encephalitis/encephalopathy, AAV2 DNA was detected in the cerebrospinal fluid of 2 patients. Serum HHV-6B DNA load was not significantly different among patients who were AAV2 positive or AAV negative and with or without neurologic complications. Conclusions: These findings suggest that coinfection of AAV2 and HHV-6B is associated with neurologic complications such as encephalitis/encephalopathy and febrile seizure in children.

Epstein-Barr virus (EBV) infects over 90% of humans and is associated with both hematological and epithelial malignancies. Here, we analyzed 990 EBV genomes (319 newly sequenced and 671 from public databases) from patients with various diseases to comprehensively characterize genomic variations, including single nucleotide variations (SNVs) and structural variations (SVs). While most SNVs were a result of conservative evolution and reflected the geographical origins of the viral genomes, we identified several convergent SNV hotspots within the central homology domain of EBNA3B, the transactivation domain of EBNA2, and the second transmembrane domain of LMP1. These convergent SNVs appear to fine-tune viral protein functionality and immunogenicity. SVs, particularly large deletions, were frequently observed in chronic active EBV disease (28%), EBV-positive diffuse large B-cell lymphoma (48%), extranodal NK/T-cell lymphoma (41%), and Burkitt lymphoma (25%), but were less common in infectious mononucleosis (11%), post-transplant lymphoproliferative disorder (7%), and epithelial malignancies (5%). In hematological malignancies, deletions often targeted viral microRNA clusters, potentially promoting viral reactivation and lymphomagenesis. Non-deletion SVs, such as inversions, were also prevalent, with several inversions disrupting the C promoter to suppress latent gene expression, thereby maintaining viral dormancy. Furthermore, recurrent EBNA3B deletions suggested that this viral transcription factor functions as a tumor suppressor. EBNA3B knockout experiments in vitro revealed downregulation of human tumor suppressors, including PTEN and RB1, which could explain the enhanced lymphomagenesis observed in EBNA3B-deficient lymphoblastoid cell line xenografts. Our findings highlight both disease-specific and general contributions of EBV genomic alterations to human cancers, particularly in hematological malignancies.

ABSTRACT The recent clinical features of Epstein‐Barr virus (EBV) and cytomegalovirus (CMV) infections in young children in developed countries remain unclear. This study investigated the clinical features of EBV and CMV infections and the latest seroepidemiology in Japan. Seroprevalence was analyzed 303 stored serum samples using commercial Enzyme Immunosorbent Assay kits, and viral infections were investigated in a cohort of febrile children under 5 years of age. After maternal antibody levels declined, the seroprevalences of EBV and CMV gradually increased by adolescence to 42.9% and 57.1%, respectively. Among 2,732 febrile children, serum EBV and CMV DNAs were detected in 1.76% and 1.24%, respectively. Of 25 primary EBV–infected patients, 15 (60.0%) had infectious mononucleosis (IM) with significantly higher IM frequency, WBC, atypical lymphocyte ratios, AST, ALT, LDH, and EBV DNA load compared to EBV–reactivated patients. No CMV DNA–positive patients had IM. Among primary EBV–infected patients, those with IM were older and had more atypical lymphocytes and higher EBV DNA load than those without IM. The age of primary EBV infection appears to have decreased compared to reports from Western countries in the 1990s. Even among children under 5 years of age, 60.0% of those with primary EBV infection developed IM.