SPAIN - A study carried out by scientists of IRTA-CReSA and MSD Animal Health demonstrates for the first time that Torque teno sus virus (TTSuV) viremia can be controlled by a combined DNA and protein immunization during naturally occurring infection.
TTSuV infection in pigs is distributed worldwide, and is characterized by a persistent viremia. TTSuV are small, non-enveloped viruses with a circular single-stranded DNA genome, belonging to the family Anelloviridae.
Four species have been found to infect swine with high prevalence of TTSuV1a, TTSuV1b and TTSuVk2a species, while prevalence of TTSuVk2b is lower.
TTSuV persistently infect a high proportion of animals that are apparently healthy. Thus, infection by itself does not cause overt disease and therefore TTSuV by itself is not considered pathogenic.
However, it is believed that TTSuVs can influence the development of some diseases or even affect their outcome.
In the present study led by Dr Tuija Kekarainen, researcher from IRTA-CReSA, the impact of pig immunization against TTSuVk2a was evaluated by following the specific seroconversion and the viral load dynamics during natural infection.
Three-week old conventional pigs were primed with a combined DNA and protein immunization while another group served as unvaccinated control animals.
Immunization led to delayed onset of TTSuVk2a infection and at the end of the study when the animals were 15 weeks of age, a number of animals in the immunized group had cleared the TTSuVk2a viremia, which was not the case in the control group.
This study demonstrated for the first time that TTSuV viremia can be controlled by a combined DNA and protein immunization, especially apparent two weeks after the first DNA immunization, before seroconversion was observed. Further studies are needed to improve vaccine efficacy, to know the mechanism behind it, and to assess the impact for pig producers.
The real impact of TTSuV, if any, on the pig health is still under debate. Although TTSuVs are currently considered non-pathogenic, it is hard to believe that a viral infection characterized by high viral loads and virus persistence would not have any consequences to its host.
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