SUMMARYAn enzyme-linked immunosorbent assay was applied for determining separately IgM and IgG antibodies against tick-borne encephalitis virus. A micro-modification in microtitre plates proved to be at least as sensitive as the HI test. However, more precise information could be achieved by a macrotest using antigen coated polystyrene balls. False positive results in IgM antibody determinations could be caused by a rheumatoid factor. A high content of IgM antibodies in a serum could impair the determination of its IgG antibodies but not vice versa. Titres were expressed in comparison to a positive control serum.

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Fifty children with malignant diseases were vaccinated against hepatitis B. Twenty-nine children suffered from leukaemia or non-Hodgkin's lymphoma; 14 of these were on intensive chemotherapy (group I) and 15 were without intensive therapy (group II). The other 21 children had various forms of solid tumours, 14 of them were on intensive therapy (group III) and 7 were without intensive therapy (group IV). To evaluate the immune response, we determined antibody titres over a period of more than 14 weeks after the first vaccination. As 22 out of 50 patients had received passive immunisation together with either the first or the first and second vaccination, antibody titres at the 14th and 18th week (i.e. more than 10 weeks after passive immunisation) were used to evaluate the vaccination results. An antibody titre of greater than or equal to 10 mIU/ml was considered to be a positive response. All patients of group IV, but only 4 out of 14 in group III, 4 out of 15 in group II, and 0 out of 14 in group I produced antibody titres higher than 50 mIU/ml. In contrast to the full response in group IV, two-thirds of all other patients had no immune response (less than 10 mIU/ml). Based on our experience we recommend vaccinating patients suffering from solid tumours and receiving no intensive therapy (group IV) against hepatitis B and protecting all the other children with malignant diseases by passive immunisation, if necessary.

The protective capacities of IgM and IgG immunoglobulins from fractionated human or mouse sera were investigated in tests with tick-borne encephalitis virus. Mice were resistant to challenge with tick-borne encephalitis virus if previously inoculated with specific immunoglobulins but not nonspecific immunoglobulins. The protective ability of IgM, whether derived from mouse or human sera, was only about 1/40 of that of IgG preparations adjusted to the same haemagglutination inhibition or neutralising titres.

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