Parvovirus B19 is a common human pathogen, which has been linked to autoimmune diseases recently. The aim of the study is to evaluate whether B19 is involved in adult Hashimoto's thyroiditis (HT).

Eighty-six thyroid tissues from the adult patients with a spectrum of thyroid disorders were examined for B19 DNA and capsid protein by nested PCR, in-situ hybridization and immunohistochemistry. The presence of viral DNA in HT epithelium was studied by laser-capture microdissection and sequencing of PCR products. The expressions of nuclear factor-κB (NF-κB) and interleukin-6 were investigated by immunohistochemistry.

B19 DNA was significantly present in HT tissues by both PCR (29/32, 90.6%) and in-situ hybridization (23/32, 71.9%, all p < 0.01) compared with normal thyroid tissue (7/16, 43.8%; 2/16, 12.5%). Laser-capture microdissection further confirmed this difference. B19 capsid protein in HT group was significantly higher than that in all the control groups (p < 0.01), and the expression of NF-κB and interleukin-6 in HT tissues was up-regulated. NF-κB was well co-localized with B19 protein in thyroid epithelia by double-labeling immunofluorescence and confocal microscopy.

The presence of B19 nuclear acid and viral protein was significantly common in HT tissues and it suggested a possible role of B19 in adult HT.