In the experimental study, porcine TTSuV2 genome were identified in the serum of a conventional pig used as the source material of porcine TTSuV2 for inoculation into gnotobiotic porcine. TTSuV has been elucidated that it was readily transmitted to young gnotobiotic swine that had negative results for TTSuV genome , serial passage of liver tissue homogenate which was extracted twice with chloroform so as to remove infectivity of any extraneous enveloped viruses  obtained from the pig with positive result for porcine TTSuV2 and negative result for porcine TTSuV1 and PCV2 by using nPCR and conventional PCR. In pigs euthanized at 1, 3, 7, 10, 14, 17, 21 and 24 days post inoculation. The previous investigations have found a higher positive rate of porcine TTSuV in analyzed reproductive apparatus samples , indicating its importance in public hygienics and vertical transmission. Considering its transmission routine [30, 46–48], specific pathogen-free pregnant primiparous sows were subjected to produce porcine TTSuVs negative specific pathogen-free piglets.
The present study evaluated the histopathological lesions of inoculation infection of the porcine Circoviridae family DNA virus torque tero sus virus (TTSuV) in main parenchmatous organs containing heart, lung, kidney, digestive system and immune system tonsil, spleen and lymph nodes on account of the viral tropism to lymphoid cells [45, 49]. The results presented here specific histopathological lesions were conduced by porcine TTSuV2 infection alone in analyzed organs and tissues, there existed subtle pathologic changes in the tissues containing 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, necrosis or degeneration and focal gliosis of lymphocytes in the paracortical zone after inoculation with the porcine TTSuV2-containing tissue homogenate; these changes were not detected in uninoculated control pigs or pigs injected with tissue homogenate devoid of porcine TTSuV2 genome. Although TTSuV seems to be non-pathologic virus for the domestic pig , those results indicated it can induce a certain degree of lesions for some organs of pigs, and the present study was similar to the histopathological lesions via parenteral inoculation of g1-TTSuV-positive tissue homogenates into TTSUuV-negative gnotobiotes , so it is necessary to compare the different histopathological lesions caused by porcine TTSuVs between single-infection and co-infection. Through the investigation, we found that the main severely microscopic lesions happened at the respiratory system, urinary system and cardiovascular system, however, there existed only minimal injury in the digestive system and immune system, those results indicated no marked histopathological changes happened in those parenchymatous organs, especially the digestive system and immune system when the specific pathogen-free piglets were infected with porcine TTSuV2, hence we can think it was so poor pathological agent for domestic pigs at least.
To date, it has been found that it is common for an individual to coinfect with different genogroups of TTSuV  and the role of porcine TTSuV in co-infection with other pathogens has been investigated and demonstrated porcine TTSuV2 is frequently related to PCV2 associated diseases (PCVAD) while compared to porcine TTSuV1 in Spain . In the swine industry, TTSuV is thought to be one of the agents that aggravate clinical manifestation of porcine circovirus-associated disease (PCVAD), a newly emerging, economically devastating disease. However, a researcher verified there were no statically considerable differences in TTSuV viral load between the two genotypes in serum obtained from porcine circovirus-2-negative pigs and PCVAD-affected pigs with real-time quantitative polymerase chain reaction assay, which indicated that TTSuV might not be an etiology of aggravation in PCVAD, and TTSuV genogroup 2 could readily give rise to viremia even in the PCV-2-negative pigs . Other reports indicated thatTTSuV1 viral infection facilitated PCVAD . Interestingly, positive stillborn piglets were always positive with the same genotype as their mothers, but sequencing analysis showed nucleotide diversity of TTSuV genomes from the sows and in stillborns . It was hypothesized that stillborns may be infected with several strains of TTSuV, even from the semen, by the transpla cental route . Higher rate of PCV2 DNA in semen (47% of tested samples) and followed by TTSuV2 (11.7%) has been investigated in spite of presenting with a low viral load and all tested semen samples were negative for TTSuV1 . Other investigations published a higher prevalence of TTSuV1 and TTSuV2 in pig semen (55% and 32%, respectively), with no interference on semen quality .
Viral persistence and sporadic infection may be a risk factor for dissemination of PCV2 or TTSuV to negative sows, potentially resulting in reproductive failures. This irregular pattern of infection also paid attention to the fact that boars which tested negative on the first collection may be positive in subsequent ejaculates. A periodic monitoring for PCV2 or TTSuV2 must be established in boar community. PCV2 and TTSuV2 presence in semen samples of younger animals may indicate a recent infection or may even be related to management or measures of stress. Morphology and sperm motility analysis did not indicate significant diversities between PCV2 positive and negative boars. All semen samples tested presented motility superior to 80%, which could allow their use for processing, dilution and artificial insemination. No manifestation of reproductive failure was associated with this co-infection. These findings raised the problem of the importance of these viral infections in the pathology of reproductive failures . Although TTSuV2 was detected in almost 50% of the sows studied, the association with PCV2 co-infection and reproductive failure was statistically insignificant difference .
Moreover, in both species, genotype 2 is more prevalent than genotype 1. In domestic pig, TTSuV2 infections have been shown to be more common in pigs affected by postweaning multisystemic wasting syndrome (PMWS), a porcine circovirus type 2 (PCV2) disease, than non-PMWS affected pigs [18, 49]. Due to its ubiquitous nature in both domestic pig and wild boar, it is likely that TTSuV has adapted to both species and is circulating within these species with similar prevalence . On account of lack in a culture system or an animal model to support the viral multiplication, the infection and replication mechanisms and the pathogenicity of TTSuV are still unknown. Some reports have indicated that several different genotypes of TTSuV are considered responsible for human diseases . However, TTSuV has been indicated to be a commensal in normal conditions which should benefit for the host, this is an intriguing aspect hitherto unexplored with TTSuV . In 2006, a surprising finding was found some marked differences in prevalence of TTSuV genotype 2 were induced by age, that is to say that younger animals were more often infected than adults and sub-adults, it would be interesting to compare such dynamics in wild boar with that in domestic pig since the same agents apparently infect both species, prevalence of both TTSuV genotypes was higher in females than males, although only important for genotype 2. In addition, there lack in comparison patterns with domestic pigs or other species that suffer from TTSuV infection .
Up to now, to our knowledge, the only available method for detection of TTSuV is focused on nucleic acid detection, such as nested polymerase chain reaction (nPCR) , quantitative PCR (qPCR) , and enzyme-linked immunosorbent assay (ELISA) based on ORF1 of porcine TTSuV2 has presently been investigated but still not has been applied clinically . To date, no tissue culture system and little information for detection method of pathology has been available for the propagation of the virus. Further study of TTSuV pathology is required to answer those lesions of single infection of porcine TTSuV or co-infection with other agents, and diverse technologies are required for defining the role of TTSuV in clinics and public health. The pathogenesis of porcine TTSuV infection and its link with specific diseases are as yet undetermined. This result maybe be considered as important descriptive for the histological lesions caused by infection with porcine TTSuV type 2. In this study, it, to some extent, was lack of scientific by using liver homogenate containing porcine TTSuV2 genome to inoculate the specific pathogen-free piglets, because it was difficult to rule out others non-enveloped viral genomes contamination, despite non-infecting agents were isolated via marc145 and vero cells to purify the homogenate in our previous study, so we propose the primary task of researchers is to seek a new cell culture system to separate and isolate porcine torque teno sus virus.