A Maternal Risk Factor for Mother‐to‐Child HTLV‐I Transmission: Viral Antigen‐producing Capacities in Culture of Peripheral Blood and Breast Milk Cells

We examined the relationship between productivity of HTLV‐I antigen‐positive cells in cultured peripheral blood mononuclear cells (PBMC) and breast milk mononuclear cells (BMMC) and the incidence of mother‐to‐child transmission of HTLV‐I. Among 61 cases of HTLV‐I carrier mothers, 17 cases were revealed to produce large numbers of HTLV‐I antigen‐positive cells (high HTLV‐I antigen‐producing mothers) whose positive rate was 9.6% in PBMC and 10.2% in BMMC, while the remaining 44 cases produced small numbers of HTLV‐I antigen‐positive cells (low HTLV‐I antigen‐producing mothers) whose positive rate was 0.3% In PBMC and 0.5% in BMMC. The HTLV‐I transmission rate among children born to the high HTLV‐I antigen‐producing mothers was 37.5% (6/16 children from 11 mothers), while that of the low HTLV‐I antigen‐producing mothers was 3.2% (1/31 children from 20 mothers). The transmission rate of HTLV‐I was significantly different between high and low HTLV‐I antigen‐producing mothers (P<0.05). However, there was no positive relationship between anti‐HTLV‐I antibody titers and productivity of HTLV‐I antigen‐positive cells (P=0.11). These results suggested that mother‐to‐child transmission of HTLV‐I might be influenced by a maternally determined factor to produce HTLV‐I antigen‐positive cells in PBMC and BMMC of HTLV‐I carrier mothers.