Characterization of PTV-12, a newly described porcine teschovirus serotype: in vivo infection and cross-protection studies.

Porcine teschoviruses (PTVs) constitute 1 of the 31 genera within the Picornaviridae family, comprising at least 13 genetic types (PTV-1 to PTV-13), of which only 11 (PTV-1 to PTV-11) have been recognized as serotypes to date. Specific for swine and wild boars, most PTVs are usually non-pathogenic, but some viral variants cause severe disorders in the central nervous system (Teschen disease) or milder signs (Talfan disease), as well as reproductive, digestive and respiratory disorders and skin lesions. Previous studies revealed a high diversity of teschoviruses circulating in Spanish pig populations. Phylogenetic analysis performed with these sequences and others available in GenBank disclosed 13 clusters, 11 of which corresponded to the known PTV serotypes, and 1 of 2 additional groups is represented by isolate CC25, whose full-length genomic sequence has been obtained. This group is new to science, and was putatively named PTV-12. Here, a complete characterization of this isolate is presented, including the experimental infection of minipigs to assess tissue tropism and possible pathogenicity in vivo in the host species. In addition, using this experimental animal model, we investigated whether a pre-existing infection with this PTV-12 isolate could confer cross-protection against infection with a heterotypic PTV-1 virulent strain. Based on phylogenetic analysis and serological data, we propose CC25 as the prototype strain of a new teschovirus serotype, PTV-12.

Teschoviruses and sapeloviruses in faecal samples from wild boar in Spain.

Teschovirus and Sapelovirus are two genera of the Picornaviridae family, comprising highly variable and heterogeneous enteric viruses, commonly found in faecal samples from domestic pigs. Although both of them are also known to infect wild boar, studies on their presence in these wild suids are scarce. The present study aimed at determining the presence of porcine teschovirus (PTV) and sapelovirus (PSV) in free-living wild boar populations, as well as to study their relationships with similar viruses present in pigs. Fresh faecal samples (n=63) from wild boar were collected in Doñana Biological Reserve (SW Spain) during 2007 and 2011, and analysed using multiplex RT-PCR for the simultaneous detection and differentiation of PTV and PSV. A total of 32 samples (50.8%) presented positive PTV bands, while PSV amplicons were detected in 4 samples (6.4%). All PSV-positive samples were also positive for PTV, which indicated co-infection with both viruses. Virus isolation was successful from 6 samples, 4 of which were identified as PTV by RT-PCR, and three of these were further characterized by sequencing of the VP1 capsid protein. The remaining two isolates were negative for PTV or PSV. Genetic characterization of PSV-positive faecal samples, using the VP4 protein coding gene, was successful in 4 stool samples. Close phylogenetic relationship was found among wild boar and domestic pig strains in both PTV and PSV. More studies are needed to ascertain the epizootiological significance of these findings.

Analyzing the genetic diversity of teschoviruses in Spanish pig populations using complete VP1 sequences.

Porcine teschoviruses (PTVs) have been previously shown to be the most abundant cytopathic viruses found in swine feces. In the present study, the diversity of PTVs was studied, using PTV isolates collected between 2004 and 2009 in a wide territory in Spain. In order to characterize genetically the isolates, phylogeny reconstructions were made using maximum likelihood and Bayesian inference methods, based on the 1D (VP1) gene, and including sequences available in public databases. The phylogenetic trees obtained indicated that PTVs present 12 main lineages, 11 corresponding to the PTV serotypes described to date, and one lineage distinct from the rest. The geographic distribution of the different lineages does not seem to be strongly associated to particular territories, and co-circulation of multiple lineages was found in the same geographic areas. Nevertheless, some spatial structuring of the viral populations studied is indicated by the differences found between Spanish samples with respect to other European countries. A coalescent-based approach indicated that mutation may have been the main factor in originating the genetic diversity observed in the VP1 gene region. This study revealed a high diversity of teschoviruses circulating in the pig populations studied, and showed that molecular analysis of the complete VP1 protein is a suitable method for the identification of members of the porcine teschovirus group. However, further analyses are needed to clarify the geographical structuring of the different PTV populations.