Detection and Pathogenesis of Torque Teno Sus Virus in Swine Lymphoid Tissues by in Situ Hybridization
Date Issued
2012
Date
2012
Author(s)
Lee, Yao
Abstract
Torque teno sus virus (TTSuV), belonging to Anelloviridae, is a non-enveloped DNA virus that has a circular, single-stranded, negative sense genome with high sequence diversity. TTSuV contains two major groups, Torque teno sus virus 1 (TTSuV1) and Torque teno sus virus 2 (TTSuV2), infecting pigs world-wide. The prevalence of TTSuV1 in Taiwan was 96.88% (465/480) (Shyu, 2010), while the prevalence of TTSuV2 in Taiwan was 56.25% (270/480) (Huang, 2010). As porcine parvovirus (PPV) and porcine reproductive and respiratory syndrome virus (PRRSV), TTSuV has been suggested as a co-factor with porcine circovirus type 2 (PCV2) infection belonging to porcine circovirus-associated diseases (PCVAD), including postweaning multisystemic wasting syndrome (PMWS). However, information regarding the cell tropism and pathogenesis of TTSuV is rather limited. In the present study, in situ hybridization (ISH) combined with tissue microarray (TMA) for the detection of TTSuVs in swine inguinal lymph nodes was established in order to identify the target cells. Subsequently, automatic positive pixel evaluation combined with statistical analysis was applied to investigate the association between TTSuV and other porcine viral factors including PCV2, PPV, and PRRSV which were related with PMWS or PCVAD. The histological results revealed that viral nucleic acid of TTSuV was mainly located in the mantle zone and interfollicular region of lymph nodes. In high magnification, the TTSuV-positive cells in ISH were lymphocytes and plasma cells. According to microscopic observation accompanied with Duncan’s multiple range test, lymphocyte proliferation was present in mild infections of TTSuV1 and TTSuV2, whereas lymphocyte depletion was present in moderate infection of PCV2. Granulomatous inflammation was noted among moderate to severe infections of TTSuV1, TTSuV2, and PCV2. Furthermore, the results of multiple regression analysis demonstrated that TTSuV1 had significant effect for B lymphocyte proliferation (P< 0.05), while TTSuV2 had significant effect for macrophage infiltration (P< 0.05). PCV2, on the other hand, had multiple significant effects for B lymphocyte depletion, T lymphocyte proliferation, and macrophage proliferation (P< 0.05). In addition, Pearson correlation analysis indicated that there was significantly positive correlation between the viral loads of TTSuV2 and PCV2 (r= 0.236, P< 0.05). Nevertheless, chi square tests showed that there was no relation between infections of TTSuV and PCV2 (P> 0.05). The results implied that the collaboration between the viral loads of TTSuV and PCV2 was discernible when in co-infection, though there was no significant relationship among TTSuV and PCV2 infection rates. Based on the present study, TTSuV was suspected to replicate in stimulated and activated lymphocytes, followed by infections of PCV2 and other pathogens that brought about further fluctuation of various immunocytes. Compared with ubiquitous distribution of TTSuV1, TTSuV2 was assumed to be more pathogenetic, and it might co-infect with PCV2 to cause granulomatous inflammation, which is suggested as a PMWS-like lesion. The results may support that TTSuV1 and TTSuV2 are common co-factors with PCV2 in PMWS or PCVAD, and that could contribute to some fluctuations in various populations of immune cells.
Subjects
TTSuV
PCV2
PMWS
PCVAD
ISH
TMA
Type
thesis
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