With one exception, cats did not become provirus positive at any time point tested. The one cat (JCR2) that was found to be positive belonged to the group challenged with the highest of the three doses of FeLV (100 000 FFU). Proviral DNA was detected from week 2 p.i. on with a peak at week 3 (3.33 copies/cell) (Fig. 1) . Similarly, viral RNA was consistently detected only in samples of the provirus-positive cat (JCR2) until week 12 and additionally at week 18 once more. The highest viral RNA load measured was at week 2 p.i. (Ct-value of 22.95, Fig. 1 ). Viral RNA was not detectable in pooled plasma samples (5 samples each pool) of any of the provirus-negative cats at week 0, 10, and 20 p.i. In addition, samples from week 2, 3, and 4 were tested individually, as the viral RNA peak usually occurs in this time period; the results were negative, too.