Due to high genome plasticity, the evolutionary fate and geographical history of picornaviruses is hard to follow. Here, we determined the complete coding sequences of eight human parechoviruses (HPeV) of types 1, 5 and 6 directly from clinical samples from Brazil. The capsid genes of these strains were not remarkably different from European, North American and Japanese HPeV. Full genome analysis revealed frequent intertypic recombination in the nonstructural genome region. In addition, evidence of recombination between viruses of the same type in the capsid-encoding genome region among HPeV1 and HPeV4 was obtained. Bayesian phylogenetic analysis indicated that strains without evidence of recombination with each other in any genome region were separated by no more than 35 years of circulation. Interestingly, in the 3C gene, all Brazilian parechoviruses grouped together regardless of serotype. The most recent common ancestor of these strains dated back 108 years, suggesting long-term endemicity of this particular P3 genome lineage in South America. Our results support the idea that picornavirus replicative genes acquire capsid proteins introduced by new strains. Under certain epidemiological conditions, replicative genes may be maintained in circumscript geographical regions.
INTRODUCTIONHuman parechoviruses (HPeV) are small non-enveloped viruses that define a genus of the family Picornaviridae. Their positive-sense RNA genome encodes a single polyprotein that is cleaved into three structural proteins, VP0, VP3 and VP1 (defining the P1 genome region), and seven non-structural proteins, 2A-2C (P2) and 3A-3D (P3). The first two HPeV serotypes were isolated in the 1950s and designated echovirus 22 and 23. In the 1990s, parechoviruses were reclassified into a new genus based on their distinct genome organization (Hyypiä et al., 1992). High prevalence of HPeV was not truly appreciated until the last few years. Recently, HPeVs were shown to be highly diverse, with up to 14 provisionally assigned types (AlSunaidi et al., 2007;Benschop et al., 2008a; Drexler et al., 2009;Ito et al., 2004; Kim Pham et al., 2010;Li et al., 2009;Watanabe et al., 2007). HPeV also proved highly prevalent in the human population, with seropositivity rates reaching 88 % at the age of 2 years (Joki-Korpela & Hyypiä, 1998;Takao et al., 2001), and an important cause of meningitis and sepsis-like disease of newborns (Baumgarte et al., 2008; 3These authors contributed equally to this work.The GenBank/EMBL/DDBJ accession numbers for the sequences reported in this paper are HQ696570-HQ696577. Wolthers et al., 2008). In general, recent reports showed that epidemiological and clinical features of HPeV are similar to the most common picornavirus genus, Enterovirus. HPeV genetic and evolutionary properties also resemble those of enteroviruses. They feature both high mutation rate (Faria et al., 2009) and frequent natural recombination (Benschop et al., 2008bCalvert et al., 2010;Williams et al., 2009;Zoll et al., 2009). Unfortunately, analyses of re...