Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Wed, 05 Dec 2018 06:59:40 Journal of General Virology (2002), 83, 1721–1728. Printed in Great Britain ................................................................................................................................................................................................................................................................................... Open reading frame sequence of an Asian enterovirus 73 strain reveals that the prototype from California is recombinant Helene Norder, Lotte Bjerregaard and Lars O. Magnius Department of Virology, Swedish Institute for Infectious Disease Control, S-171 82 Solna, Sweden Phylogenetic analysis within the VP1 region now enables molecular typing of enteroviruses consistent with neutralization results. Three untypable isolates, 2776/82, 57/99 and 22/00, from Korea, North India and Bangladesh, respectively, showed within this region 980–990% amino acid identities. These were less than 77 % to the previous enterovirus prototypes, but 915–925% to CA55-1988, the recently identified enterovirus 73 (EV73) prototype from California. All three strains were, however, most similar to CA64-4454, an EV73 prime strain, to which they shared 965–985 % identity. Seven compared EV73 strains formed two clusters in the VP1 dendrogram, one cluster with strains from South and East Asia and CA64-4454, and the other with strains from Oman and California including the prototype. When sequencing the complete open reading frame of 2776/82, its non-structural region was found to be divergent from all human enterovirus B (HEV-B) strains, including CA55-1988, indicating that one or other strain was recombinant. Boot scanning of the genomes showed a recombination point within the P2 region. Therefore, part of this was sequenced for 57/99 and 22/00 and was found similar to 2776/82, while CA55-1988 was similar to coxsackievirus B3, demonstrating that CA55-1988 was the recombinant. Since all strains of EV73 isolated so far outside California originate from Asia, where it has a broad geographical distribution, it seems that EV73 may have been introduced to California from Asia. Further analysis of EV73 strains will reveal if the recombination occurred in the USA or in Asia and will help to elucidate the origin of this virus. Introduction Enteroviruses form one genus of the Picornaviridae family of small non-enveloped plus-sense RNA viruses. The genome, 7500 nucleotides in length, has a single open reading frame (ORF), with three main genomic regions designated P1–P3 flanked by untranslated 5- and 3-extremities. The P1 region encodes the capsid proteins VP1–VP4, while the P2 and P3 regions encode seven nonstructural proteins with the same functions in different types (involvement in the viral RNA replication and processing of viral proteins). The 5-noncoding region contains the initiation site for synthesis of the genomic RNA and the internal ribosomal entry site enabling cap- independent translation, while the 3-noncoding region is Author for correspondence : Lars Magnius. Fax 46 8 32 83 30. e-mail lars.magniussmi.ki.se The sequences of strains 2776/82, 57/99 and 22/00 have been deposited in GenBank, accession numbers AF504533–AF504537. involved in the initiation and synthesis of the complementary RNA strand. The junction between the P1 region, and the P2 and P3 regions, may be the site for recombination events, which do not change the serotype or affect important virus functions. Such recombinants between wild-type and vaccine strains of polioviruses, as well as between different enterovirus types belonging to the same species, have been described (Furione et al., 1993; Santti et al., 1999 ; Guillot et al., 2000). The Enterovirus genus comprises 65 types, which are assigned to four genomic groups or species designated human enterovirus (HEV-A through D), based on degree of similarity within the VP2 region (Po  yry et al., 1994, 1996 ; Dahllund et al., 1995 ; Pulli et al., 1995 ; Huttunen et al., 1996 ; Oberste et al., 1999a). Coxsackie A virus 2–8, 10, 12, 14 and 16 and enterovirus (EV) 71 belong to HEV-A. All echo- and coxsackie B (CB) viruses, coxsackie A9 virus, EV69 and EV73 form HEV- B. Coxsackie A virus 1, 11, 13, 15, 17–22 and 24 form group HEV-C. Poliovirus 1–3 also cluster within HEV-C, although 0001-8222  2002 SGM BHCB