Presence of interferon and antibodies to BK virus in amniotic fluid of normal pregnant women.

Paired samples of maternal sera, umbilical cord sera and amniotic fluids were tested for antibodies to BK virus (BKV) and for interferon content. It was found that two out of 14 pregnant women were antibody negative, the latter were estimated to be susceptible to BKV primary infection. In contrast, there was no foetal case among those which were at risk of foetal infection with BKV as judged from the presence of BKV antibody in maternal sera and interferon in the placentas. It might be hypothesized that BKV may be transmitted to the foetus only in the case of BKV primary infection of antibody-negative pregnant women with undetectable amount of interferon (IFN) in the placenta.