RESUMO
Mother-to-child transmission of human T-cell lymphotrophic virus type 1 (HTLV-I) is primarily due to prolonged breast-feeding (>6 months) in the post-natal period. Most infant infections are not identifiable until 12-18 months of age by available whole virus Western blot serologic tests because of their inability to distinguish passively transferred maternal antibody from infant antibody. We investigated two methods to assess more accurately the time of infant infection. In prospectively collected serial biospecimens, HTLV-I-specific immunoglobulin (Ig) isotypes of IgM and IgA were determined by Western blot and HTLV-I proviral DNA was detected by polymerase chain reaction (PCR). IgA and IgG reactivity was assessed in periodic serum samples from 16 HTLV-I-seropositive children while IgM reactivity was observed in 100 percent of children at 24 months of age and 73 percent of children at 6-12 months of age; however, this could represent maternal and not infant antibody. Both IgA and IgM reactivity were insensitive indicators of infection, with only 50 percent of children showing reactivity at 24 months of age. PCR testing was performed in biospecimens obtained from 11 of these children. An estimated median time of infection of 11.9 months was determined by PCR, which was similar to the median time to infection determined by whole virus Western blot (12.4 months; P=0.72). PCR Tests support a median time to infection that is similar to that estimated by whole virus Western blot. (AU)
