Abstract
Three variants of herpes simplex virus type 1 strain 17 were isolated. One variant had a deletion of 2.5 X 10(6) Mr in IRL/UL and 0.8 X 10(6) Mr in TRL such that sequences were deleted from both long repeats. The deletion in UL removed the 20K and 22K open reading frames. The second variant had a deletion of 3.5 X 10(6) Mr in IRL/UL which again removed the 20K and 22K open reading frames. The third variant had a similar deletion in UL, but in this case the deleted sequences were replaced by sequences from the left end of UL, such that the long repeat was extended by 3 X 10(6) Mr and the overall genome size by 2 X 10(6) Mr. All three variants grew almost normally in vitro. The analysis of 11 isolates with extensive variation in the long repeats outside the 'a' sequence is also reported.