The nucleotide sequence of the small (S) RNA segment of Akabane (AKA) virus has been determined. The S RNA of AKA virus is 858 nucleotides long, and contains two overlapping open reading frames (ORFs) encoding the nucleocapsid (N) and nonstructural (NSs) proteins consistent with other bunyaviruses. Comparisons with the Aino virus S RNA sequence indicate that there is 73.5% homology in nucleotide sequence. However, the sequence homology of the 5' non-coding region of genomic RNA between these two viruses is only 55%. The N ORFs from 20 Japanese and two Australian isolates of AKA virus were sequenced, and analysed by phylogenic analysis. AKA virus has evolved in multiple lineages. Twenty-three isolates were grouped into three major clusters, and the cluster which includes recent isolates was subdivided into two branches. Phylogenic analysis of the AKA N protein gene gives a greater insight into bunyavirus evolution.
(Associate Director for Research, Department of Virology)
