Epstein–Barr virus (EBV) is an oncogenic virus that is closely associated with several malignant and lymphoproliferative diseases. Studies have shown that the typical characteristic of EBV-associated diseases is aberrant methylation of viral DNA and the host genome. EBV gene methylation helps EBV escape from immune monitoring and persist in host cells. EBV controls viral gene promoter methylation by hijacking host epigenetic machinery to regulate the expression of viral genes. EBV proteins also interact with host epigenetic regulatory factors to mediate the methylation of the host’s important tumour suppressor gene promoters, thereby participating in the occurrence of tumorigenesis. Since epigenetic modifications, including DNA methylation, are reversible in nature, drugs that target DNA methylation can be developed for epigenetic therapy against EBV-associated tumours. Various methylation modes in the host and EBV genomes may also be of diagnostic and prognostic value. This review summarizes the regulatory roles of DNA methylation on the promotor of EBV gene and host genome in EBV-associated diseases, proposes the application prospect of DNA methylation in early clinical diagnosis and treatment, and provides insight into methylation-based strategies against EBV-associated diseases. Key points: • Methylation of both the host and EBV genomes plays an important role in EBV-associateddiseases. • The functions of methylation of the host and EBV genomes in the occurrence and development of EBV-associated diseases are diverse. • Methylation may be a therapeutic target or biomarker in EBV-associated diseases.

Epstein-Barr virus (EBV) is very common, with the infection rate in adults over 90% worldwide. Infectious mononucleosis (IM) is caused by primary infection with EBV. Most IM patients are generally considered to have a favorable prognosis, but a few patients will also develop complications. Children with severe symptoms will require hospitalization. However, the disease burden of children hospitalized with IM in China has been rarely described. In this study, we included the Face sheets of discharge medical records from 27 member children's hospitals of Futang Research Center of Pediatric Development from Jan 1st, 2016 to Dec 31st, 2020, and medical information such as gender, age, region, time of admission, length of stay and expenditure were extracted. There were 24,120 IM cases, which accounted for 0.42% (24,120/5,693,262) of all hospitalized cases during this period. The ratio of male to female was 1.48:1. Hospitalization for IM in the 4–6 ​years age group was the highest among inpatients of all age groups. Case numbers increased year by year between 2016 and 2020, and the monthly hospitalization was generally high from Jul to Sep but reduced from Jan to Feb per year. Bronchitis/pneumonia and hepatic dysfunction were two common complications in hospitalized IM patients. The median length of stay was 8 days, and the median cost of hospitalization was 970.59 US dollars. This study will help understand the epidemiological characteristics and disease burden of hospitalized children with IM in China.

Background: Congenital TORCH (Toxoplasma gondii (T.gondii), rubella virus (RV), cytomegalovirus (CMV), and herpes simplex virus (HSV)) infections are associated with a variety of adverse prenatal and neonatal events, including miscarriage, malformations and developmental abnormalities, and they remain an issue that cannot be neglected in China. However, the current research focuses more on the general screening of TORCH in women of childbearing age, and the medical information of children hospitalized due to congenital and perinatal TORCH infections has not been described in detail. This study summarized and analyzed the epidemiological characteristics, clinical manifestations, length of stay (LOS), and the disease burden of hospitalized children diagnosed with congenital TORCH infections in 27 children’s hospitals in China.Methodology: Based on the face sheet of discharge medical records (FSMRs) of hospitalized children in 27 tertiary children’s hospitals collected in the Futang Research Center of Pediatric Development and aggregated into FUTang Update medical REcords (FUTURE), we summarized and analyzed the epidemiological characteristics, clinical manifestations, LOS, the disease burden (in US dollars, USD) and potential risk factors for hospitalized children diagnosed with congenital toxoplasmosis, congenital rubella syndrome, congenital cytomegalovirus infection, and congenital HSV in 27 children’s hospitals in China from 2015 to 2020.Results: One hundred seventy-three patients aged 0–<1 year were hospitalized for congenital TORCH infections. Among infections with TORCH, hospitalization with congenital toxoplasmosis was the least common, with only five cases were reported (2.89%), while the LOS was the highest. The proportion of patients with congenital rubella syndrome (CRS) was 15.61%, and 86% of children hospitalized with CRS had cardiovascular malformations, and the economic burden was the highest. Congenital CMV infection cases accounted for the largest proportion (76.30%). Overall, 5.20% of patients were infected with HSV, and the expense of hospitalization for congenital HSV infection was relatively low.Conclusion: In the present study, the hospitalization proportion due to congenital TORCH infection was extremely low (17.56 per 100,000 neonates), indicating that China’s congenital TORCH infection prevention and control policies remain effective. The lowest proportion of patients was hospitalized with congenital toxoplasmosis, while the LOS was the longest. The economic burden of CRS was heavy, and infants are recommended be vaccinated against RV in a timely manner. Congenital CMV infections accounted for the largest proportion of patients, suggesting that the disease burden of congenital CMV infection cannot be ignored, and the prevention of congenital CMV infection during pregnancy is still an important issue that needs to pay attention. The expense of hospitalization for congenital HSV infection was relatively low, while the disease burden increases significantly when patients develop complications. These data illustrate the importance of improving screening for congenital TORCH infections in the early diagnosis and treatment of neonatal patients.

Epstein-Barr virus (EBV) infection is extremely common worldwide, with approximately 90% of adults testing positive for EBV antibodies. Human are susceptible to EBV infection, and primary EBV infection typically occurs early in life. EBV infection can cause infectious mononucleosis (IM) as well as some severe non-neoplastic diseases, such as chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which can have a heavy disease burden. After primary EBV infection, individuals develop robust EBV-specific T cell immune responses, with EBV-specific CD8⁺ and part of CD4⁺ T cells functioning as cytotoxic T cells, defending against virus. Different proteins expressed during EBV's lytic replication and latent proliferation can cause varying degrees of cellular immune responses. Strong T cell immunity plays a key role in controlling infection by decreasing viral load and eliminating infected cells. However, the virus persists as latent infection in EBV healthy carriers even with robust T cell immune response. When reactivated, it undergoes lytic replication and then transmits virions to a new host. Currently, the relationship between the pathogenesis of lymphoproliferative diseases and the adaptive immune system is still not fully clarified and needs to be explored in the future. Investigating the T cell immune responses evoked by EBV and utilizing this knowledge to design promising prophylactic vaccines are urgent issues for future research due to the importance of T cell immunity.