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.