A tortoise-infecting picornavirus expands the host range of the family Picornaviridae.

While picornaviruses can cause diseases in many mammals, little is known of their host range for replication in non-mammalian vertebrates. Here, a picornavirus in liver and kidney tissues from diseased Sulawesi tortoises (Indotestudo forsteni) was genetically characterized. Tortoise rafivirus A (ToRaV-A, KJ415177) represents a potential new genus in the family Picornaviridae, for which we propose the name "Rafivirus". Our finding confirms the susceptibility of reptiles to picornaviruses.

Sequencing and phylogenetic analysis identifies candidate members of a new picornavirus genus in terrestrial tortoise species.

Near-complete genome sequences of seven picornavirus (PV) strains isolated from different terrestrial tortoise species were determined and characterized. The genome organization of the strains proved to be similar and displayed a typical PV layout, and the polyprotein-encoding regions showed low similarity to those of other PVs. The predicted regions of the tortoise PV genomes were related to the corresponding genome parts of viruses belonging to distinct genera, implying modular evolution of these novel viruses. Our results suggest that these tortoise PVs belong to a prototype species in a separate proposed genus in the family Picornaviridae, tentatively called Topivirus (Tortoise picornavirus).

Iridovirus-like viruses in erythrocytes of lacertids from Portugal.

Icosahedral nucleo-cytoplasmic large DNA viruses (NCLDV)-like viruses, which forminclusions in the erythrocyte cytoplasm of reptiles, were previously presented as candidates for a new genus of the Iridoviridae family. The present work describes the distribution of infected lizard hosts and ultrastructural characteristics of the viral inclusions of NCLDV-like viruses from Portugal and adjacent locations in Spain. Giemsa-stained blood smears of 235 Lacerta schreiberi from Portugal and Spain, 571 Lacerta monticola from the mountain Serra da Estrela (Portugal), 794 Podarcis hispanica from several localities in Portugal and Spain, and 25 Lacerta dugesii from Madeira Island, were studied. Infection in L. schreiberi was only found in mountain populations, up to 30% in Serra da Estrela and 9-11% elsewhere. It was absent in lizards from lowlands. Prevalence of infection among L. monticola in Serra da Estrela was 10%; infected lizards were found during March to July and October but not in August and September. Infection in P. hispanica was below 3.3%. Only one infected specimen of L. dugesii was identified by light microscopy. Ultrastructural examination of infected samples revealed that the inclusions are virus assembly sites of icosahedral cytoplasmic iridovirus-like virions. Virions from different host species have different ultrastructural features and probably represent different related viruses.

RNA viruses and the host microRNA machinery.

Gene silencing by small RNAs (sRNAs) occurs in all three domains of life. In recent years, our appreciation of the diverse functions of sRNAs has increased, and we have identified roles for these RNAs in cellular differentiation, fitness and pathogen defence. Interestingly, although plants, nematodes and arthropods use sRNAs to combat viral infections, chordates have replaced this defence strategy with one based exclusively on proteins. This limits chordate use of sRNAs to the silencing of genome-encoded transcripts and has resulted in viruses that do not perturb sRNA-related cellular processes. This evolutionary phenomenon provides an opportunity to exploit the pre-existing chordate sRNA pathways in order to generate a range of virus-based biological tools. Here, I discuss the relationship between sRNAs and RNA viruses, detail how microRNA expression can be harnessed to control RNA viruses and describe how RNA viruses can be designed to deliver sRNAs.

A neurotropic herpesvirus infecting the gastropod, abalone, shares ancestry with oyster herpesvirus and a herpesvirus associated with the amphioxus genome.

BACKGROUND: With the exception of the oyster herpesvirus OsHV-1, all herpesviruses characterized thus far infect only vertebrates. Some cause neurological disease in their hosts, while others replicate or become latent in neurological tissues. Recently a new herpesvirus causing ganglioneuritis in abalone, a gastropod, was discovered. Molecular analysis of new herpesviruses, such as this one and others, still to be discovered in invertebrates, will provide insight into the evolution of herpesviruses. RESULTS: We sequenced the genome of a neurotropic virus linked to a fatal ganglioneuritis devastating parts of a valuable wild abalone fishery in Australia. We show that the newly identified virus forms part of an ancient clade with its nearest relatives being a herpesvirus infecting bivalves (oyster) and, unexpectedly, one we identified, from published data, apparently integrated within the genome of amphioxus, an invertebrate chordate. Predicted protein sequences from the abalone virus genome have significant similarity to several herpesvirus proteins including the DNA packaging ATPase subunit of (putative) terminase and DNA polymerase. Conservation of amino acid sequences in the terminase across all herpesviruses and phylogenetic analysis using the DNA polymerase and terminase proteins demonstrate that the herpesviruses infecting the molluscs, oyster and abalone, are distantly related. The terminase and polymerase protein sequences from the putative amphioxus herpesvirus share more sequence similarity with those of the mollusc viruses than with sequences from any of the vertebrate herpesviruses analysed. CONCLUSIONS: A family of mollusc herpesviruses, Malacoherpesviridae, that was based on a single virus infecting oyster can now be further established by including a distantly related herpesvirus infecting abalone, which, like many vertebrate viruses is neurotropic. The genome of Branchiostoma floridae (amphioxus) provides evidence for the existence of a herpesvirus associated with this invertebrate chordate. The virus which likely infected amphioxus is, by molecular phylogenetic analysis, more closely related to the other 2 invertebrate viruses than to herpesviruses infecting vertebrates (ie chordates).

Genomic characterization of two novel reptilian papillomaviruses, Chelonia mydas papillomavirus 1 and Caretta caretta papillomavirus 1.

In this paper we describe the characterization of the genomes of two sea turtle papillomaviruses, Chelonia mydas PV (CmPV-1) and Caretta caretta PV (CcPV-1). The isolation and sequencing of the first non-avian reptilian PVs extend the evolutionary history of PVs to include all amniotes. PVs have now been described in mammals, birds and non-avian reptiles. The chelonian PVs form a distinct clade most closely related to the avian PVs. Unlike the avian PVs, both chelonian PVs have canonical E6 and E7 ORFs, indicating that these genes were present in the common ancestor to mammalian and non-mammalian amniote PVs. Rates of evolution among the non-mammalian PVs were generally slower than those estimated for mammalian PVs, perhaps due to lower metabolic rates among the ectothermic reptiles.