This study seeks to identify and test host protein biomarkers and RNA expression profiles in dried blood spot samples as novel diagnostic markers of congenital cytomegalovirus sequelae and to improve the understanding of the pathogenesis of the disease.

Background:

Human cytomegalovirus (CMV) is one of the most common causes of congenital viral infection, leading to a significant number of children with permanent disabilities. It is recognized as the major infectious cause of sensorineural hearing loss (SNHL) and neurodevelopmental abnormalities in infants. Its pathogenesis is largely unknown due to the complex interplay between viral, maternal, placental, and child factors. In Western Europe the incidence is estimated to 0.5-0.7% of all live births. In Denmark there are 240-480 children born every year with CMV infection, but the incidence has not been studied since 1979. Among the congenitally infected infants, approximately 10% are estimated to have symptoms at birth, ranging from mild, such as petechiae, to severe, such as microcephaly. Approximately half of these symptomatic children develop permanent long-term disabilities, such as hearing loss, cognitive and motor developmental delay. Asymptomatic children are also at risk for CMV-related disabilities, and 10-15% will develop SNHL. SNHL after congenital CMV infection may be present at birth or occur later in childhood and therefore, a significant part of these will not be detected in time for diagnosis and appropriate treatment, e.g., ganciclovir within the first 30 days of life. At present, there is no reliable virological marker to determine which infants will develop sequelae.

Method:

A nationwide retrospective case-control study of all neonates with congenital CMV infection in Denmark from 2010 through 2025. DBS samples will be obtained from the Danish Neonatal Screening Biobank, Statens Serum Institut. Proteomic analyses and RNA sequencing will be performed at the Department for Congenital Disorders, Statens Serum Institut. Cases will be randomly assigned to a "Discovery cohort" and compared to a control group of neonates matched on gestational age, sex, birthweight and age at DBS sample collection.

Perspectives:

New molecular-based diagnostic tools may contribute to improve early diagnosis and treatment of infants with congenital CMV infection and potentially prevent development of sequelae. Additionally, understanding of the pathogenesis at a molecular level of severe disease manifestations of the disease, could form the basis for development of novel interventions for better prevention and treatment.

Inclusion Criteria:

1. Children born between 1 January 2010 and 31 December 2025 with an available neonatal dried blood spot sample collected through the Danish National Newborn Screening Program.
2. Cases: children with verified congenital CMV infection, defined as a positive CMV PCR result on neonatal dried blood spot, blood, or urine collected within the neonatal period.
3. Controls: children without evidence of congenital CMV infection selected from the same newborn screening population and matched to cases on sex, gestational age, birthweight, and age at DBS sampling.

Exclusion Criteria:

1. DBS samples not approved for research use.
2. DBS samples with insufficient blood material for RNA expression profiling and/or proteomic analyses.
3. Samples with inadequate analytical quality for molecular or proteomic analyses.

The study population consists of children born in Denmark between January 1, 2010 and December 31, 2025 with available neonatal dried blood spot samples collected through the Danish National Newborn Screening Program. The study includes children with verified congenital cytomegalovirus (CMV) infection and matched controls without congenital CMV infection. Children with congenital CMV infection will be categorized according to the presence or absence of CMV-associated sequelae based on clinical follow-up data.