Increased viral load and prevalence of Torque teno sus virus 2 (TTSuV2) in pigs experimentally infected with classical swine fever virus (CSFV).

Torque teno sus viruses (TTSuVs) are considered non-pathogenic viruses, although lately they have been linked to porcine circovirus diseases, mainly with post weaning multisystemic wasting syndrome (PMWS). These associations point out a possible pathogenic role of TTSuVs or, alternatively, that TTSuV replication is up-regulated under disease conditions. In order to further explore the association of TTSuVs with disease occurrence, TTSuVs prevalence and viral load were assessed before and after an experimental infection with a highly pathogenic classical swine fever (CSF) virus (CSFV) isolate. Serum samples from 56 animals were analyzed by means of a real time quantitative PCR (qPCR) for TTSuV1 and TTSuV2 before and after (between 6 and 13 days post-inoculation) the CSFV challenge. Based on the post-infection clinical evolution and immune response against CSFV, the animals were divided into two groups: group I, with protecting immunity against CSFV and no clinical signs at the day of necropsy, and group II, with no detectable immune response against CSFV and moderate to severe clinical signs. TTSuVs qPCR results indicated that TTSuV2 and not TTSuV1 load in serum increased significantly after challenge with CSFV in the group of pigs with clinical signs, specifically in those with a moderate course of the disease. Therefore, this study emphasizes the different behaviour of both TTSuVs, as already found in the PMWS background, and further supports the association of TTSuV2 with disease occurrence.

Exploratory study of Torque teno sus viruses in pulmonary inflammatory lesions in pigs.

The pathogenic role of Torque teno sus viruses 1 (TTSuV1) and 2 (TTSuV2), and their capacity to induce lesions are controversial. TTSuVs have been linked to porcine circovirus diseases (PCVDs) and described as cause of mild respiratory lesions in gnotobiotic pigs; moreover, an increased TTSuV prevalence has been found in porcine respiratory disease complex (PRDC) affected pigs. In the present study, TTSuV1 and TTSuV2 loads and their prevalence were evaluated in formalin-fixed, paraffin-embedded (FFPE) lung samples displaying different types of inflammatory lesions. Such measurements were made by means of a real time quantitative PCR technique to detect these viruses. The technique was optimised for its use on FFPE tissues comparing results with frozen lung tissues. Selection criteria included negativity against porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), Aujeszky's disease virus (ADV) and swine influenza virus (SIV). Results from the present study demonstrated that both TTSuVs were present in lung. However, TTSuV2 had higher viral load and prevalence in all the studied groups when compared to TTSuV1. TTSuV2 mean load was also higher in lungs with viral background (interstitial pneumonia and broncho-interstitial pneumonia) when compared to normal lungs or to those with bacterial background (catarrhal-purulent bronchopneumonia, fibrinous pleuritis and fibrinous-necrotizing pleuropneumonia). This result suggests a possible role of TTSuV2 in the pathogenic mechanism of inflammatory lesions of lungs compatible with viral infection.

Lack of effect of piglet vaccination against Porcine circovirus type 2 (PCV2) on serum viral loads of Torque teno sus virus 2 (TTSuV2).

Anelloviruses are small, non-enveloped viruses with circular single stranded DNA, which infect a number of animal species as well as humans. In pigs, two distinct Torque teno sus virus (TTSuV) species have been described so far, being one of them linked to disease occurrence. Specifically, TTSuV2 loads in serum have been found increased in pigs suffering from postweaning multisystemic wasting syndrome (PMWS). Since this pathological condition is able to be controlled by means of porcine circovirus type 2 (PCV2) vaccination, it was hypothesized the possibility that such vaccination would have an impact on TTSuV2 prevalence and loads. A total of 150 pigs were divided in two study groups. Half of them received a PCV2 commercial vaccine, while the other half remained as non-vaccinated controls. PCV2 infection was monitored at 3-4, 8, 12, 16 and 21 weeks of age by means of an standard PCR, while TTSuV2 loads were determined at 8, 16 and 21 weeks of age by a quantitative PCR. No obvious PMWS clinical signs were observed among studied animals, although PCV2 infection was confirmed in both groups of pigs. Almost all pigs got TTSuV2 infection throughout the study period, independently of the PCV2 vaccination status of animals. Moreover, TTSuV2 load did not show significant differences between different pig groups at each sampling time, but mean viral load increased with age. Taking into account that previous results suggest that TTSuV2 load in serum is increased in the background of PMWS, the present study suggests that this is not the case in a PCV2 subclinical infection scenario. Therefore, vaccination of PCV2 subclinically infected pigs did not modify the outcome of TTSuV2 infection.

Torque teno sus virus 1 and 2 viral loads in postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) affected pigs.

Torque teno viruses (TTV) are small, non-enveloped viruses with a circular single-stranded DNA genome, which are considered non-pathogenic. However, TTVs have been eventually linked to human diseases. TTVs infecting pigs, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2), have been recently associated to porcine circovirus diseases (PCVD). To get more insights into such potential disease association, the aim of this study was to quantify TTSuV1 and TTSuV2 viral loads in serum of pigs affected by two PCVDs, postweaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS). Such study was carried out by means of a newly developed real-time quantitative PCR (qPCR) method. Both TTSuVs were highly prevalent among studied pigs. TTSuV2 viral loads were significantly higher in PMWS affected animals, further supporting the previously suggested association between TTSuV2 and PMWS. On the contrary, TTSuV1 prevalence and loads were not related with the studied PCVDs.

Dynamics of Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2) DNA loads in serum of healthy and postweaning multisystemic wasting syndrome (PMWS) affected pigs.

Torque teno viruses (TTVs) are vertebrate infecting, small viruses with circular single stranded DNA, classified in the Anelloviridae family. In pigs, two different TTV species have been described so far, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2). TTSuVs have lately been linked to postweaning multisystemic wasting syndrome (PMWS). In the present study, TTSuV1 and TTSuV2 prevalence and DNA loads in longitudinally collected serum samples of healthy and PMWS affected pigs from Spanish conventional, multi-site farms were analyzed. Serum samples were taken at 1, 3, 7, 11 and around 15 weeks of age (age of PMWS outbreak) and viral DNA loads determined by quantitative PCR. For both TTSuV species, percentage of viremic pigs increased progressively over time, with the highest prevalence in animals of about 15 weeks of age. TTSuV1 and TTSuV2 viral DNA loads in healthy and TTSuV1 loads in PMWS affected animals increased until 11 weeks of age declining afterwards. On the contrary, TTSuV2 DNA loads in PMWS affected pigs increased throughout the sampling period. It seems that TTSuV species differ in the in vivo infection dynamics in PMWS affected animals.

Age-related tissue distribution of swine Torque teno sus virus 1 and 2.

Torque teno viruses (TTVs) are small, non-enveloped viruses with a circular single-stranded DNA genome, belonging to the family Anelloviridae. In swine, two genetically distinct species have been identified, Torque teno sus virus 1 (TTSuV1) and 2 (TTSuV2). The aim of the present work was to study the tissue distribution of TTSuV1 and TTSuV2 in pigs of different ages, including foetuses at the second and last thirds of gestation, and animals at 5 days and 5, 15 and 24 weeks of age. Investigated tissues included brain, lung, mediastinal and mesenteric lymph nodes, heart, liver, spleen, kidney and bone marrow. Viral DNA from tissue extractions were tested by a comparative PCR for the presence of TTSuVs. Overall, TTSuV1 and TTSuV2 species were found in all tissues tested, with variations depending on age, and following similar infection dynamics in all tissues, increasing progressively in prevalence and virus load over time. The highest prevalence was found at 5 weeks of age and maintained afterwards, and the highest loads of virus in the different tissues were seen in the oldest animals (15 and 24 weeks of age). No animals were negative to TTV, including foetuses. In conclusion, the present study indicated that swine TTSuV1 and TTSuV2 can be found virtually in all body tissues of the pig. Both swine TTV species were present in high levels in almost all older animals, while viral negative tissues were only found in 5-week-old and 5-day-old pigs, and foetuses.

Torque teno sus virus (TTV) detection in aborted and slaughterhouse collected foetuses.

The aim of this study was to estimate the presence of Torque teno sus virus (TTV) species in pig foetuses in order to assess the possible relationship between swine TTV infection and abortion in swine. A total of 98 abortion cases and foetuses collected from 55 pregnant sows at slaughterhouse were analysed by PCR for the presence of Torque teno sus virus 1 (TTV1) and Torque teno sus virus 2 (TTV2). All foetuses were necropsied and relevant tissues were collected, pooled, and submitted to DNA extraction. The overall prevalence of swine TTV1 and TTV2 in aborted foetuses (n = 98) was 17.0% and 29.6%, respectively. For slaughterhouse collected foetuses (n = 55), 10.9% were TTV1 PCR positive and 40.0% were positive for TTV2. There were no statistically significant differences when comparing prevalence of swine TTVs by type of sample (aborted versus slaughterhouse collected foetuses) or by gestation stage. The present work represents the first description of swine TTV infection in pig foetuses at different stages of gestation. Results obtained confirm that vertical transmission is an important route of TTVs dissemination. In addition, data obtained suggest that swine TTVs should not be considered as infectious agents responsible for abortion occurrence.