HHV-6 has long been researched as one of the infectious agents involved in autoimmunity development in various autoimmune conditions. It has been linked to the development of several autoimmune diseases – scleroderma, multiple sclerosis, and most importantly in the case of the reported results – autoimmune thyroiditis. As other herpesviruses, HHV-6 possesses several strategies for immunomodulation. HHV-6 encodes two viral chemokine receptors U12 and U51, which are structurally similar to cellular G protein-coupled receptors (GPCR). HHV-6 U12/51 can bind several chemokine, including RANTES, much like human GPCRs (CCR1, CCR3 and CCR5) and can be expressed on the surface of epithelial and some peripheral blood mononuclear cells, suggesting that these viral proteins are potentially immunogenic and could exacerbate autoimmune processes in the thyroid or even trigger an autoimmune response against host GPCRs. Therefore, the aim of this study was to detect HHV-6 GPCR and CCR1 and CCR5 specific antibodies in autoimmune thyroiditis (AIT) patients and evaluate the possibility of antibody cross-reactivity.
Blood plasma from 79 AIT patients harboring HHV-6 in their thyroid was analyzed in this study. HHV-6 U12 and U51 amino acid sequences were analyzed – aligned with human homologs and linear epitopes were predicted using Bepipred Linear Epitope Prediction and Kolaskar & Tongaonkar algorithm prior to this study. Based on previous immunological investigations 10 peptides were selected for this study – 6 from the sequence of U12, 4 from U51. Beads were conjugated with viral chemokine receptor - U12 and U51 linear epitopes and whole proteins, and human homologs – CCR1 and 5. Blood plasma and beads conjugated with HHV-6 U12, U51 antigens, CCR1 and 5 recombinant proteins were used in Suspension Multiplex Immunological Assay (SMIA) for the detection of specific IgG and IgM antibodies. Patient results were compared with results from 43 blood donors. The evaluation of antibody cross-reactivity was done by preabsorbing the plasma samples with the antigens prior to SMIA.
Both IgG and IgM antibodies against CCR1 and CCR5 and U12, U51 were found in AIT patients. All patients harbored antibodies against viral antigens – against both linear and conformational epitopes. Additionally patient samples harbored linear epitope specific IgG antibodies more frequently than blood donor samples (79/79 vs 18/43 for IgG) and at higher MFI values for most HHV-6 peptides (Fig. 2). No significant differences between AIT patients and blood donors could be observed when recombinant proteins were used for antibody detection (Fig. 3). CCR antibodies were less prevalent – CCR1 IgG antibodies were found in 24/79 patient samples, whereas CCR5 in 39/79 samples. Weak correlation in antibody MFI signals could be observed between HHV-6 U51 and CCR5, and U12 and CCR5 antibodies. Preabsorption assay with HHV-6 U12/U51 showed a notable decrease of signals of CCR1 and CCR5 SMIA reactions.
Presence of viral protein antibodies in all patients further provides proof to the link of HHV-6 and AIT, with linear epitopes showing clear immune response differences between AIT patients and blood donors. The preabsorption assay results combined with the detected CCR antibodies possibly point to a new HHV-6 mediated autoimmunity exacerbation mechanism. Further studies involving more AIT patients are on the way to test eluted HHV-6 U12, U51 antibody ability to bind human chemokine receptors.
|Period||10 Jun 2022 → 13 Jun 2022|
|Event title||13th International Congress on Autoimmunity|
|Degree of Recognition||International|