Evidence for mother-to-child transmission of human T lymphotropic virus type II.

Serologic analysis of the children of 2 married human T lymphotropic virus type II (HTLV-II)-infected prostitutes demonstrated antibodies to HTLV-II in an 8-year-old boy whose only recognizable risk for HTLV-II infection was breast-feeding during his first 4 years of life. Limited sequence analysis of isolates infecting the mother and child demonstrated 100% identical sequences in the long terminal repeat (LTR65-297; 236 bp), pol4762-4919 (157 bp), and env5523-6003 (480 bp) regions (both isolates were subtype a), suggesting mother-to-child transmission. In contrast, isolates obtained from 2 other prostitutes from the same geographic region had sequences different from those of the first woman and her child, and the second and third women were infected with HTLV-II subtype b. Although vertical transmission of HTLV-II in this 8-year-old child cannot be conclusively ascertained, the probability is overwhelming that infection occurred through breast-feeding for an extended period of time.