SLAMF1 and infection: We finally selected the canine mammary carcinoma cell line P114 (29) because (i) OPneon mediates a lytic infection (Fig. 1B, left panel), (ii) a wild-type CDV strain (A75/17; wtneon) that exclusively employs SLAM and N4 as receptors did not infect those cells (Fig. 1B, right panel), (iii) canine N4-expression is below the detection limit as monitored by immunofluorescence (IF) as well as reverse transcription polymerase chain reaction (RT-PCR) assays (Fig. 1C and D), and (iv) SLAM is known to be expressed exclusively by immune cells and not epithelial cells, such as P114 (30).