Possible involvement of human herpesvirus-6 U12 and U51 gene coded proteins in the development of autoimmunity – an immunological investigation

HHV-6 has frequently been detected in autoimmune thyroiditis tissues, possibly implicating the infection in the initiation of autoimmunity. We investigated the role of two virally encoded chemokine receptor homologues (U12 and U51) as autoimmunity triggers by using potentially immunogenic peptides designed from viral protein amino acid sequences. Blood plasma from 64 autoimmune thyroiditis patients was analyzed in this study. Prior to this study thyroid tissues from these patients were analyzed for HHV-6 presence, and all were demonstrated to harbor HHV-6 genomic sequences. U12 and U51 protein amino acid sequences were aligned with human CCR1, 3 and 5 using the T-Coffee software. Alignment was combined with linear epitope prediction algorithms to design 20 mer peptides. Acquired viral peptides and recombinant human CCR1, 3 and 5 were conjugated to magnetic beads. Blood plasma and the conjugated beads were used in Suspension Multiplex Immunological Assay for the detection of human chemokine receptor and viral peptide specific IgG and IgM antibodies and the evaluation of peptide specific antibody cross-reactivity. Antibodies specific for several viral peptides were found in patient plasma samples. Peptides with highest MFI values were selected for cross-reactivity assessment. Overall MFI values for peptide specific IgM antibodies were significantly higher compared to IgG antibodies. Interestingly, patient plasma contained antibodies for two of the human chemokine receptors - CCR1 and 5. Again, MFI values for receptor specific IgM antibodies were much higher. Eluted peptide specific antibodies were not able to bind human chemokine receptors – no cross-reactivity was observed. HHV-6 peptide specific antibodies were found in patient’s samples, with higher signals for IgM antibodies, indicating HHV-6 reactivation and active infection. Even though, no cross reactivity between HHV-6 peptide specific antibodies and human recombinant CCR1, 3 and 5 was found, further investigation of potential conformational epitopes is necessary.