Persistence and differentiation of HTLV-I-transformed immature T-cells in HTLV-I carrier rabbits

Two T-cell lines with immature phenotypes, CD4⁻8⁻ and CD4⁺8⁺, were found among HTLV-I-transformed T-cell lines obtained during experiments using a rabbit model of adult T-cell leukemia. Persistence and differentiation of these clones in vivo were examined by retrospectively analysing a series of cell lines from individual animals and by adoptive transfer of these cells into syngeneic hosts. The double negative cell line did not differentiate and remained double negative in adoptive transfer into neonates and in long-term in vitro culture, while the double positive cell line differentiated both in vivo and in vitro into CD8⁺ cell, as if the fate of this cell line had been predetermined. Cells of the same clone as this double positive cell line persisted for more than one year in the peripheral blood of the animal. Long-term persistence was not observed for five cell lines of CD4 single positive phenotype, which were obtained from another carrier rabbit. These results suggested that HTLV-I-transformed immature T-cells persist in neonatally infected carriers, continuously giving rise to mature T-cells harboring HTLV-I.