Torque teno sus viruses (TTSV) are small non-enveloped viruses with circular, single-stranded DNA genome. TT viruses belong to the family Anelloviridae and may infect humans and different animal species. Two different virus species have been identified to date in pigs, Torque teno sus virus 1 (TTSV1) and Torque teno virus sus 2 (TTSV2), which belong to the genus Iotatorquevirus. TTSV are widely prevalent in the pig population but TTSV infection is not directly responsible for any disease. The genome of porcine TT virus contains three open reading frames. ORF1 is coding for nucleocapsid protein which potentially induces immune response of infected animals.
The goal of this work was to identify immunodominant peptides in the structure of ORF1 protein of TTSV1 and TTSV2 which could be used as antigens to detect TTSV1 and TTSV2 antibodies following natural infection in pigs. Translated ORF1 genes of both viruses were analyzed for prediction of linear B-cell epitopes. Peptides were synthesized and used as the antigens in indirect ELISA test. Selected and synthesized peptides covered more than 40% of the length of ORF1 proteins. The total of 307 pig serum samples was collected from 16 herds and different age categories of animals were examined. TTSV1 and TTSV2 specific IgG antibodies were detected in piglets at age of 4 weeks. After vanishing of these presumably maternally derived antibodies post-infection antibody titers started to increase significantly and peaked at week 20. Relatively high antibody titer persisted till the adulthood.