IFNA1 and HIV-1 infection: Based on our findings and previous insights, we can consider the following scenario (Fig 8B): since cell-to-cell infection (Rcc) dominantly contributes to HIV-1 infection compared to cell-free infection (Rcf), our findings suggest that the resistance of TF viruses against the IFN-α-mediated antiviral effect [5,6,8] is due to the resistance to inhibition of cell-to-cell infection by IFN-α.