Viral infection is implicated as a cause of autoimmune diseases. Whereas its role in Hashimoto's thyroiditis (HT) remains undefined, recent studies suggested a link between human parvovirus B19 (B19) infection and HT. We tested such possibility by using B19 nonstructural protein 1 (NS1) transgenic C57BL/6 mice, which harbor nonpermissive genetic background (H-2 b). Mice were immunized with either thyroglobulin (Tg) or saline. No thyroiditis developed in saline-treated mice and Tg-immunized males regardless of the presence or absence of NS1. In contrast, thyroiditis was induced by Tg immunization in 25% of transgenic females, but not in wild-type females. However, the thyroiditis incidence in the former did not differ significantly from that of the latter. In addition, intrathyroidal T-cell receptor gene expression was not augmented in Tg-immunized transgenic females. Immunization with Tg led to a comparable increase in serum anti-Tg antibody levels in the wild-type and transgenic mice. Our results indicate that the introduction of B19 NS1 gene into C57BL/6 mice is insufficient to promote the development of autoimmune thyroiditis. Further studies are required, however, before concluding that B19 infection is not involved in HT induction.
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