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Viremia and neutralizing antibody response in infants with exanthem subitum
1Department of Pediatrics, Fujita Gakuen Health University School of Medicine, Toyoake, Japan.
Abstract:
Mononuclear cell-associated viremia caused by human herpesvirus type 6 was detected in 39 (66%) of 59 blood samples from 38 children with exanthem subitum between day 0 and day 7 of the disease. The rate of virus isolation from mononuclear cells was 100% (26/26) on days 0 to 2 (just before appearance of skin rash), 82% (9/11) on day 3, 20% (2/10) on day 4, 7% (2/12) on days 5 to 7, and 0% (0/37) on day 8 and thereafter. The cell-free virus was detected in blood in 10 (21%) of 47 blood samples during the same period. The antibody activity to the virus, evaluated by a newly developed neutralization assay, was first detected on day 3 of the disease with a positive rate of 18% (2/11). It became 60% (6/10) on day 4, 75% (9/12) on days 5 to 7, and 100% on day 8 and thereafter. Thus the disappearance of the virus from blood was associated with the induction of specific immunity to the virus.
Insights
Human herpesvirus type 6 (HHV-6) viremia is common in children with exanthem subitum. Virus detection in mononuclear cells declines as antibody immunity develops, indicating viral clearance.
Area of Science:
- Virology
- Immunology
- Pediatrics
Background:
- Human herpesvirus type 6 (HHV-6) is a significant cause of exanthem subitum (roseola infantum) in young children.
- Understanding the dynamics of HHV-6 viremia and the host immune response is crucial for managing this common childhood illness.
Purpose of the Study:
- To investigate the kinetics of HHV-6 viremia in mononuclear cells and cell-free blood during exanthem subitum.
- To evaluate the development of the antibody response to HHV-6 using a novel neutralization assay.
Main Methods:
- Blood samples from children with exanthem subitum were analyzed for HHV-6 DNA in mononuclear cells and cell-free plasma.
- Virus isolation attempts were performed on mononuclear cells at different disease stages.
- A newly developed neutralization assay was used to detect and quantify HHV-6 specific antibodies.
Main Results:
- Mononuclear cell-associated HHV-6 viremia was detected in 66% of samples from children with exanthem subitum.
- High rates of virus isolation from mononuclear cells were observed early in the disease (days 0-3), declining significantly by day 4.
- Antibody activity against HHV-6 emerged by day 3 and reached 100% positivity by day 8, coinciding with viral clearance.
Conclusions:
- HHV-6 viremia, particularly within mononuclear cells, is a hallmark of the acute phase of exanthem subitum.
- The development of specific anti-HHV-6 antibody immunity is closely associated with the disappearance of the virus from the bloodstream.
- These findings elucidate the viral kinetics and immune response during HHV-6 infection in children.