[Presence of antibodies to human herpesvirus type 6 and 7 in Hungarian children].

Prevalence of antibodies to variants HHV-6A and B as well as HHV-7, the time of primary infections are not know in Hungarian children. Therefore, antibodies to these viruses were studied in 21 healthy children aged between 6 and 18 months. Lymphoid cultures were infected with standard virus strains for indirect immunofluorescence. IgM, IgG and high avidity IgG after 8M urea treatment were quantified in serial dilutions of sera. It was established that, three of 13 boys had low level (1:20) IgG or IgM antibodies to HHV-6A, but all girls were negative. With exception of one girl and one boy, all had antibodies to HHV-6B in different titres (1:20 to 1:640 by immunofluorescence), in 9 cases only IgM, in further 4 cases only low avidity IgG were detected. Children studied gradually acquired symptom-free HHV-6B infection between age of 8 and 18 months. Antibodies to HHV-7 were found in 3 boys and one girl before their age of 12 months, but the majority were infected after that age. Approximately three quarters of children acquired either HHV-6B or HHV-7 before age of 18 months. More than half of the children were infected with HHV-6B prior to HHV-7. Antibody level to HHV-6B was slightly higher in boys, while that to HHV-7 was higher in girls. In Hungary, childhood infection with HHV-6A seems to be a very rare event. Epidemiology of HHV-6B primary infection is similar to that of industrial countries, while that of HHV-7 resembles data of developing world: onset of antibodies occurs 1 or 2 years earlier than in the industrial nations.