Human herpesvirus 6A active infection in patients with autoimmune Hashimoto's thyroiditis

Hypothyroidism due to Hashimoto's thyroiditis (HT) is the commonest autoimmune endocrine illness in which antibodies against thyroid organ result in inflammation. The disease has a complex etiology that involves genetic and environmental influences. Viral infections may be involved in triggering of the disease as their molecular mimicry enhance autoimmune responses. Human herpesvirus-6 (HHV-6) is recognized for its contribution to some autoimmune diseases.

In the current study, the prevalence of HHV-6 active infection in patients with HT and with non-autoimmune thyroid disorders were compared with patients with euthyroidism. In addition, a correlation between presence of HHV-6 infections and HT was investigated.

A total of 151 patients with clinically and laboratory confirmed HT, 59 patients with non-autoimmune thyroid disorders, and 32 patients with normal thyroid function were included in the study. For further confirmation of HT disease, all the precipitants were tested for anti-thyroid peroxidase (TPO), and anti-thyroglobulin (TG) antibodies. For detection of both HHV-6 types A and B, nested PCR and restriction enzyme digestion were used. HHV-6 DNA positive samples were further investigated by DNA sequencing analysis.

HHV-6A DNA was found in serum sample of 57 out of 151 patients (38%) with HT, which was significantly more often than in patients with non-autoimmune thyroid disorders (p=0.001). However, HHV-6 DNA was not detected in serum samples of euthyroid subjects.

The results support a possible role for active HHV-6A infection, demonstrated by the presence of HHV-6 DNA in sera, in the development of HT.