On the basis of the results of a collaborative study the Expert Committee on Biological Standardisation of the World Health Organisation has issued an international standard (IS) serum for parvovirus B19 IgG antibody (NIBSC 93/724). In this study this IS was used to calibrate an in-house standard serum for reporting the results of parvovirus B19 IgG testing in IU/ml. The IgG titre distribution in 939 pregnant women was determined. These samples were sent to the laboratory for determining the immune status to parvovirus B19 following contact with parvovirus B19 infected individuals or for detecting acute infection in patients with symptoms suggestive of parvovirus B19 infection.
The serological and virological course of parvovirus B19 infection was followed in 14 women who suffered symptomatic or subclinical acute infection during pregnancy. Serial serum samples from the patients were tested for IgG and IgM antibodies and the levels of parvovirus B19 DNA were monitored using a semi-quantitative PCR assay. In addition, the outcome of the pregnancies was documented by clinical information and by testing cord blood for parvovirus B19 specific antibodies as well as for parvovirus B19 DNA by PCR. Levels of IgG antibodies rose steadily within 2 months of infection and in some cases began to decline at the end of pregnancy. IgM antibodies were usually detected for at least 2 months and persisted for as long as 9 months in one case. Viral DNA was detectable for at least 8 weeks following infection and semi-quantitative analysis revealed a gradual reduction in virus load during the viraemic phase of infection. There were no apparent differences in the course of antibody development and duration of viraemia in symptomatic versus subclinical infections.
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