No abstract

Porcine teschovirus (PTV) is an OIE-listed pathogen with 13 known PTV serotypes. Heterologous PTV serotypes frequently co-circulate and co-infect with another swine pathogen, causing various symptoms in all age groups, thus highlighting the need for a pan-PTV diagnostic tool. Here, a recombinant protein composed of a highly conserved “RNNQIPQDF” epitope on the GH loop of VP1, predicted in silico, and a tandem repeat of this epitope carrying the pan DR (PADRE) and Toxin B epitopes was constructed to serve as a PTV detection tool. This recombinant GST-PADRE-(RNNQIPQDF)n-Toxin B protein was used as an immunogen, which effectively raised non-neutralizing or undetectable neutralizing antibodies against PTV in mice. The raised antiserum was reactive against all the PTV serotypes (PTV–1–7) tested, but not against members of the closely related genera Sapelovirus and Cardiovirus, and the unrelated virus controls. This potential pan-PTV diagnostic reagent may be used to differentiate naturally infected animals from vaccinated animals that have antibodies against a subunit vaccine that does not contain this epitope or to screen for PTV before further subtyping. To our knowledge, this is the first report that utilized in silico PTV epitope prediction to find a reagent broadly reactive to various PTV serotypes.

Viral vectors serve as promising tools for the development of novel multivalent or multipathogen vaccines. Poliovirus (of the family Picornaviridae) vectors offer the advantages of small genome size, ease of manipulation, inherent stability in the intestinal tract, and induction of potent mucosal immunity through oral administration. Porcine teschovirus (PTV), also belonging to Picornaviridae, generally causes asymptomatic infections in pigs. PTV’s wide tissue tropism suggests that it can act as a potential vector for vaccine development; however, no infectious PTV cDNA clone has been reported yet. In this study, infectious PTV cDNA was cloned and recombinant porcine teschovirus (rPTV) was constructed with a unique XhoI site introduced into 2A, as well as substitution of the G–H loop sequence “RNNQIPQDF” of VP1 by an 8-histidine marker which helps to differentiate it from the parental PTV. Subsequently, the coding sequence of a small fluorescent protein, iLOV, was incorporated into the XhoI site to rescue the recombinant rPTV-iLOV virus, allowing for direct visualization of the viral infection. These rescued viruses were replication-competent and antigenically identical to the parental virus, but showed attenuation due to an impaired self-cleaving function caused by the insertion of iLOV into the 2A protease site, as assessed by a double reporter expressing system. This rescued recombinant virus shows potential for the development of attenuated vaccines with few safety concerns and may serve as an important tool to visually study virus–cell interactions.