Torque teno virus infection in the pig and its potential role as a model of human infection

Torque teno viruses (TTVs), of the genus Anellovirus, are single-stranded circular DNA viruses that infect many vertebrate species. Although viruses of this type have quite a stable genome, they exhibit low nucleotide homology. Torque teno virus infection has not been consistently linked to specific diseases, although there is epidemiological evidence of an association with disease in humans. The recent recognition of naturally occurring TTV infection in swine and its epidemiological resemblance to human TTV raises the possibility of using the pig as a model to study human TTV infection. Such an approach will require the development of novel investigative tools to study the epidemiology, transmission, immune responses and potential pathogenesis of TTV infection. The present review summarises research on animal TTV infection, focussing in particular on TTV infection in the pig, and considers how a porcine experimental infection model might assist in the study of human TTV infection.