To determine whether porcine genogroup 1 torque teno virus (g1-TTV) can infect and cause disease in gnotobiotic swine. 20 conventional baby pigs and 46 gnotobiotic baby pigs. Porcine g1-TTV was transmitted from conventional swine to gnotobiotic pigs via pooled leukocyte-rich plasmas (n=18) that had positive results for g1-TTV DNA. Bone marrow-liver homogenates that had positive results for torque teno virus (TTV) were used in 4 serial passages in gnotobiotic pigs (2 pigs/passage). A pathogenesis experiment was conducted with in vivo passages of g1-TTV in various groups of gnotobiotic pigs. All g1-TTV inoculated pigs had no clinical signs but developed interstitial pneumonia, transient thymic atrophy, membranous glomerulonephropathy, and modest lymphocytic to histiocytic infiltrates in the liver after inoculation with the TTV-containing tissue homogenate; these changes were not detected in uninoculated control pigs or pigs injected with tissue homogenate devoid of TTV DNAs. In situ hybridization was used to identify g1-TTV DNAs in bone marrow mononuclear cells. Analysis of these data revealed that porcine g1-TTV was readily transmitted to TTV-naïve swine and that infection was associated with characteristic pathologic changes in gnotobiotic pigs inoculated with g1-TTV. Thus, g1-TTV could be an unrecognized pathogenic viral infectious agent of swine. This indicated a directly associated induction of lesions attributable to TTV infection in swine for a virus of the genus Anellovirus.
