Investigation of the Involvement of HHV-6 Encoded Viral Chemokine Receptors in Autoimmune Thyroiditis Development

Human herpesvirus-6 (HHV-6) contains two genes (U12 and U51) that encode putative homologues of human G-protein-coupled receptors like CCR1, CCR3, and CCR5. It has been shown that these viral proteins can be expressed on the surface of epithelial and some peripheral blood mononuclear cells, suggesting that they could potentially induce autoimmunity. We aimed to investigate the possibility of HHV-6 encoded viral chemokine receptors (U12 and U51) involvement in autoimmune thyroiditis (AIT) development by detecting viral peptide specific antibodies in AIT patient samples. Seventy-nine AIT patients whose thyroid tissues were shown to be positive for HHV-6 and 32 blood donors were enrolled in this study. Twenty-eight synthetic peptides derived from HHV-6 U12 and U51 proteins’ amino acid sequences, as well as recombinant human CCR1, CCR3, and CCR5 proteins were used in suspension multiplex immunological assay to detect specific IgG and IgM antibodies. HHV-6 peptide specific IgG and IgM antibodies were found in patients’ samples. AIT patients' samples were found to be more frequently positive for peptide IgGs in comparison to control group’s samples. Even though peptide antibody cross-reactivity with human CCRs was not demonstrated, our results show a new immunogenic HHV-6 antigen—a possible new player in the HHV-6 induced autoimmunity exacerbation. IMPORTANCE The study of human herpesvirus-6 (HHV-6) involvement in autoimmunity development is very challenging, due to the complex nature of this virus. HHV-6 is a ubiquitous, lifelong persistent, and immunomodulating virus, which mainly spreads in solid tissues using cell-to-cell mechanics, and thus can escape from the host’s immune response. It has been implicated as an environmental factor in several autoimmune diseases. An association between HHV-6 and autoimmune thyroiditis has been demonstrated, yet clear mechanism of involvement remains to be elucidated, since the virus can be detected in nearly all autoimmune thyroiditis patient thyroid glands. Our results show new potentially immunogenic human herpesvirus-6 antigens—possible new players in the HHV-6 induced autoimmunity exacerbation, which could be subjects for further research. Together with previously published results, this study described possible mechanisms which may underlie the induction of autoimmune reactivities against thyroid tissues in AIT.