[Quantitation of HTLV-I proviral copies of infected cells in pregnant HTLV-I carriers and its correlation with vertical infection].

Using colony formation in poly-L-lysine chamber slides and the polymerase chain reaction (PCR), we quantitated the number of human T lymphotropic virus type-I (HTLV-I) infected cells and proviral copies in peripheral blood lymphocytes from 25 pregnant HTLV-I carriers. The number of HTLV-I proviral copies in 0.25 microgram of DNA ranged from 2.8 to 9,176, with approximately 1-40 HTLV-I proviral copies per infected cell. The number of HTLV-I proviral copies was correlated with the number of infected cells in PBL. The HTLV-I antibody level was not correlated with the number of HTLV-I proviral copies per infected cell. By comparing the HTLV-I antigen positivity rate in another 31 HTLV-I carriers who were fed breast milk, we found that the risk of vertical infection might be high at more than 9.4 copies per infected cell. Multiple proviral copies may therefore exist in 1 HTLV-I infected cell and the number of HTLV-I proviral copies per infected cell is an important factor in vertical infection.