| Torque teno sus virus (TTSuV), is a non-enveloped, single-stranded (ssDNA), circular DNA virus, which infects domestic swine and wild boar, and newly classified into the genus Iotatorquevirus of Anelloviridae family. A molecular study to detect positive evidence and phylogenic relationship of porcine TTSuV genogroups infection in244sera of pigs from21subordinate prefectures and/or cities of Sichuan was subjected to perform by means of nPCR. Besides, the molecular evolution of TTSuV genogroups was studied by using a272bp overlapping sequences for genogroup1,225bp overlapping sequences for genogroup2and a130bp overlapping sequences among two gengroups of the untranslated region of the viral genome. Both TTSuV genogroup genomes were found in pig sera from these different regions of our study.There exists no information about histopathological lesions caused by infection with porcine TTSuV2. Porcine liver tissue homogenate with1ml of6.91×107genomic copies viral loads of porcine TTSuV2that had positive result for torque teno sus virus type2and negative result for torque teno sus virus type1and porcine pseudorabies virus type1and2were used to inoculate specific pathogen-free piglets by intramuscular route and humanely killed at3,7,10,14,17,21and24days post inoculation (dpi), the control pigs were injected intramuscularly with1ml of sterile DMEM and humanely killed the end of the study for histopathological examination routinely processed, respectively.Taking account of sera samples,203out of244pigs (83.20%) were infected with one or other genogroup, while44out of244animals (18.03%) were co-infected with both genogroups. Moreover, TTSuV2(186out of244,76.23%) was significantly more prevalent than TTSuV1(61out of244,25%). The non-coding region of swine TTSuV genome sequenced showed its adequacy as a molecular marker in swine TTSuV. Phylogenetic analysis showed that both genogroup1and2could be divided into two subtypes, subtype b of TTSuV1and two subtypes of TTSuV2are mainly prevalent in Sichuan Province. All porcine TTSuV2inoculated piglets were clinic asymptomatic but developed myocardial fibroklasts and endocardium, interstitial pneumonia, membranous glomerular nephropathy, and modest inflammatory cells infiltration in portal areas in the liver, foci of hemorrhage in some pancreas islet, a tiny amount red blood cells in venule of muscularis mucosae and outer longitudinal muscle, rarely red blood cells in the microvasculation and infiltration of inflammatory cells (lymphocytes and eosinophils) of tonsil and hilar lymph nodes, infiltration of inflammatory lymphocytes and necrosis or degeneration and focal gliosis of lymphocytes in the paracortical zone after inoculation with porcine TTSuV2-containing tissue homogenate. Analysis of these presentations revealed that infection was associated with characteristic pathologic changes in specific pathogen-free piglets inoculated with porcine TTSuV2. Those results indicated no markedly histopathological changes happened in those parenchymatous organs, especially the digestive system and immune system when the specific pathogen-free pigs were infected with porcine TTSuV2, hence, to some extent, it was not remarkable pathological agent for domestic pigs at least. So, porcine TTSuV2could be an unrecognized pathogenic viral infectious etiology of swine. This study indicated a directly related description of lesions responsible for TTSuV2infection in swine.This study presents the detailed geographical and pathological evidence of TTSuV infection in China. The study would play a experimental biological foundation to understand the morphology structure, genetic variance, genic function and pathogenicity of torque tero sus virus. |
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