AURA VIRUS IS A NEW-WORLD REPRESENTATIVE OF SINDBIS-LIKE VIRUSES

Aura virus is an alphavirus present in Brazil and Argentina that is se rologically related to Sindbis virus (present throughout the Old World ) and to Western equine encephalitis (WEE) virus (present in the Ameri cas). We have previously shown that WEE is a recombinant virus whose g lycoproteins and part of whose 3' nontranslated region (NTR) are deriv ed from a Sindbis-like virus, but the remainder of whose genome is der ived from Eastern equine encephalitis (EEE) virus. We show here that A ura virus is a Sindbis-like virus that shares considerable organizatio nal and sequence identity with Sindbis virus. Certain nucleotide seque nce elements present in Aura RNA that are believed to function as prom oters are almost identical to their Sindbis counterparts, repeated ele ments in the 3' nontranslated region are shared with Sindbis virus, an d important antigenic epitopes are conserved between the two viruses. Despite their close relationship, the two viruses have diverged signif icantly, sharing 73% amino acid sequence identity in the nonstructural proteins and 62% identity in the structural proteins. This is about t he same as the identities between EEE and Venezuelan equine encephalit is virus, whose promoter elements, 3' NTRs, and antigenic epitopes hav e diverged more radically, such that these two viruses are considered to belong to different subgroups. Importantly, the glycoproteins of WE E are more closely related to those of Sindbis than to those of Aura v irus. From this we propose that an ancestral Sindbis-like virus presen t in the Americas (probably South America) diverged 1000-2000 years ag o into a lineage that gave rise to Aura virus and a lineage that gave rise to Sindbis virus and to the Sindbis-like parent of WEE. At some t ime after this divergence, a Sindbis-like virus belonging to the latte r lineage was transferred to the Old World where it gave rise to Sindb is viruses distributed throughout the Old World, and in a separate eve nt a Sindbis-like virus belonging to the same lineage underwent recomb ination with EEE to give rise to WEE. (C) 1995 Academic Press, Inc.