Low concentrations of suramin can reduce in vitro infection of human cord blood lymphocytes with HTLV-I during long-term culture.

n vitro infection of human cord blood lymphocytes (CBL) with human T-cell leukemia/lymphoma virus type I (HTLV-I) was found to be reduced by suramin treatment at a concentration ranging from 10-100 micrograms/ml. At higher concentrations (500 micrograms/ml) suramin was toxic to the cells and even resulted in an increased percentage of cells positive for the p19 viral core protein. Suramin treatment at the onset of the CBL coculture with a lethally irradiated HTLV-I donor cell line (MT-2) reduced virus transmission, evaluated as number of p19+ cells, and the consequent amount of integrated provirus in the host genome. The amount of viral RNA transcripts was not reduced in CBL cocultures. On the other hand, suramin affected HTLV-I replication in infected MT-2 cells, when used at a concentration of 50 micrograms/ml, and this might contribute to the reduced infectivity of suramin-treated MT-2 cells. In addition to its antiviral effects, suramin exerted a modest positive regulation on the natural killing activity of CBL and their early proliferative response in mixed lymphocyte/tumor cell culture.