Mothers of children with Down syndrome have higher herpes simplex virus type 2 (HSV-2) antibody levels.

The antibody response to herpes simplex virus (HSV) was studied in 53 mothers of children with Down syndrome (Ds) and compared with that in 154 controls, using sera sampled during pregnancy or at delivery. Conventional analysis of HSV complement fixing antibodies showed the same frequency of positivity for the two groups (70%). When the levels of IgG antibodies to an HSV-1 and an HSV-2 antigen preparation were determined by an enzyme-linked immunosorbent assay (ELISA) technique, it was found that the Ds and control mothers had similar levels of IgG antibodies to HSV-1, whereas the level of IgG antibodies to HSV-2 was significantly (P less than 0.001) higher in Ds mothers. The ratio of HSV-2 to HSV-1 ELISA IgG was calculated for each mother and the distribution of these ratios also differed significantly between the control and Ds mothers. The differences found were not due to differences in age distribution in the control and Ds groups. For comparison a third procedure, measurement of thymidine kinase blocking antibody (TK ab), was used. With this procedure the mothers were divided into groups estimated to be positive for HSV-1, HSV-2, or both. Statistical analyses showed a good correlation between the type found in TK ab analyses and the ratio found in the ELISA HSV test. The results clearly demonstrated an overrepresentation of HSV-2 antibody positivity among Ds mothers, though not of sufficient magnitude to imply that HSV-2 can be the major cause of Ds. It is discussed whether HSV-2 might be related to the recently increased birthrate of children with Ds among young mothers in Sweden or to localized geographical clustering of Ds births, or whether the increased HSV-2 antibody positivity merely indicates that factors following the same epidemiological pattern are involved in the aetiology of Ds.