TF and infection: To investigate the effect of IFN-α on cell-free and cell-to-cell infection of TF and CC viruses, we used clinical strains isolated from a patient CH077 [3,40]; strain CH077_TF is the infectious molecular clone (IMC) of the TF virus from this patient, while strain CH077_CC is the IMC isolated from this patient during the chronic phase of infection (after 6 months postinfection) [6].