Estimating the time of HTLV-I infection following mother-to-child transmission in a breast-feeding population in Jamaica

Mother-to-child transmission of human T-cell lymphotropic virus type I (HTL V-I) is primarily due to prolonged breast-feeding (>6 months) in the postna tal period. Most infant infections are not identifiable until 12 to 18 mont hs 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 r eaction (PCR). IgA and IgG reactivity was assessed in periodic serum sample s from 16 HTLV-l-seropositive children while IgM reactivity was assessed in 9 of the 16 children. Approximately three to five samples were tested for each child. IgG reactivity was observed in 100% of children at 24 months of age and 73% of children at 6-12 months of age; however, this could represe nt maternal and not infant antibody. Both IgA and IgM reactivity were insen sitive indicators of infection, with only 50% of children showing reactivit y at 24 months of age. PCR testing was performed in biospecimens obtained f rom 11 of these children. An estimated median time of infection of 11.9 mon ths was determined by PCR, which was similar to the median time to infectio n 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 wh ole virus Western blot. (C) 1999 Wiley-Liss, Inc.