Nucleotide sequence and variability of the inverted terminal repetitions of African swine fever virus DNA.

African Swine fever virus (ASFV) genome is a large (170-190 kb) double-stranded DNA molecule with structural features similar to those of Poxviruses. Prominent among those features are the presence of a hairpin loop structure at the end of the DNA molecule and terminal-inverted repeats (TIR). The TIRs have been previously demonstrated by electron microscopy and cross-hybridization of terminal restriction fragments. We have determined the sequence of both left and right DNA ends from the BA71V virus strain. The TIR is composed of 2134 bp and was identical at both genome ends. As much as 82% of the TIR sequence is made up of short (27-35 bp) sequences repeated within the TIR, in five different sets of repeats. The central portion of the TIR is occupied by a 34-bp sequence which is repeated in tandem 33 times. Length differences were found within TIRs of virus clones isolated from a single infected animal. The ASFV TIR resembles in structure the TIR of the related Poxviruses.