Proliferation response to interleukin-2 and Jak/Stat activation of T cellsimmortalized by human T-cell lymphotropic virus type 1 is independent of open reading frame I expression

Human T-cell lymphotropic virus type 1 (HTLV-1), a complex retrovirus, enco des a hydrophobic 12-kD protein from pX open reading frame (ORF) I that loc alizes to cellular endomembranes and contains four minimal SH3 binding moti fs (PXXP), We have demonstrated the importance of ORF I expression in the e stablishment of infection and hypothesize that p12(I) has a role in T-cell activation. In this study, we tested interleukin-2 (IL-2) receptor expressi on, IL-2-mediated proliferation, and Jak/Stat activation in T-cell lines im mortalized with either wild-type or ORF I mutant clones of HTLV-1. All cell lines exhibited typical patterns of T-cell markers and maintained mutation fidelity. No significant differences between cell lines were observed in I L-2 receptor chain (alpha, beta, or gamma(c)) expression, in IL-2-mediated proliferation, or in IL-2-induced phosphorylated forms of Stat3, Stat5, Jak 1, or Jak3. The expression of ORF I is more likely to play a role in early HTLV-1 infection, such as in the activation of quiescent T cells in vivo.