MX1 and infection: It is noteworthy that it was previously shown that after transfection with a control plasmid harboring a canine Mx1 inactivated by five successive stop codons, the infection rate of RFP-positive/V5-positive cells was similar to that of RFP-negative/V5-negative cells, which shows that the expression of RFP per se does not alter the viral biological cycle of the studied cells [17].