The aim of this study was to investigate the possibility of using monocytes/macrophages as mediators in human herpesvirus-6 (HHV-6) infection of thyroid gland tissues in autoimmune thyroiditis (AIT). Seventy-three AIT patients were enrolled in this study. The control group consisted of 80 blood donors. Monocyte/macrophage isolation for AIT patient samples was performed by adherence. HHV-6 was detected in peripheral blood mononuclear cell (PBMC) DNA samples using nested polymerase chain reaction (nPCR). Gene expression of HHV-6 active infection marker (U79/80) and chemokine receptors (U12, U51) in patient monocyte/macrophage samples and blood donor PBMC samples was detected using reverse-transcription PCR. HHV-6 viral load was detected by using quantitative-PCR technique. The HHV-6 genomic sequence was found significantly more frequently among AIT patient than control group samples. Markers of active infection were found in 8 AIT patient monocyte/macrophage samples (11%) and in none of control group PBMC samples. HHV-6 U51 mRNA expression was detected only in AIT patient samples (2/24 previously positive for HHV-6). Since HHV-6 genomic sequences were found significantly more frequently in AIT patient samples and active infection markers were found in patient monocytes/macrophages, our results suggest that monocytes/macrophages may be used by HHV-6 as mediators for thyroid gland infection.
Viral infections have been frequently cited as important environmental factors implicated in autoimmune thyroiditis (AIT) development, although no specific virus has yet been conclusively associated with the disease. Some evidence implicates human herpesvirus-6 (HHV-6) in this disease. The aim of this study was to investigate the role of the HHV-6 U83 gene expression in autoimmune thyroiditis development. Fifty-one patients with AIT following thyroidectomy and a control group of 30 autopsied subjects without thyroid pathologies for comparing virology results and 30 healthy blood donors for comparing serology results were enrolled in this study. HHV-6 U83 gene expression was determined using nested PCR with complementary DNA as the template acquired from thyroid gland extracted RNA. Plasma samples of AIT patients and blood donors were tested for IL-2, IL-4, IL-10, sTNF-RII and IL-1beta levels by ELISA. Virology results were compared with pro- and anti-inflammatory cytokine levels to determine possible interaction of HHV-6 with host immune response. HHV-6 U83 gene expression was found only in 24% (12/49) of AIT patient thyroid gland tissue samples and in none of the control group individuals, showing possible involvement of this gene in AIT development. However, no interaction between HHV-6 and changes in cytokine levels was found.
Human herpesvirus-6 (HHV-6) is a ubiquitous betaherpesvirus with immunomodulating properties that have been suggested to play an important role in the development of several autoimmune disorders. Although the primary targets for HHV-6 replication, both in vitro and in vivo, are CD4+ and CD8+ T lymphocytes, some studies have reported the presence of HHV-6 sequences in different solid organs, including in the thyroid gland, showing possible involvement of this herpesvirus in development of autoimmune thyroid disease. The aim of this study was to determine loads of HHV-6 in thyroid gland tissue in comparison to those in peripheral blood of patients with autoimmune thyroiditis. Seven patients [women mean age 45 (28-65)] with histologically confirmed autoimmune thyroiditis were enrolled in this study. Fluorescence-activated cell sorting was used to distinguish and sort lymphocyte populations from peripheral blood mononuclear cells of patients. HHV-6 load was determined by real-time PCR for peripheral blood and thyroid gland tissue samples. Additionally, all results from molecular analyses were compared with histological results obtained by light microscopy. Viral load was detected only in one (46 viral copies/ 1×106cells) blood sample; others were under the detection limit of the used kit. However, in all HHV-6 positive tissue samples viral load was detected in the range of 132-1620 viral copies/106 cells. Substantial HHV-6 load in lymphocyte subpopulations was detected in two of seven patients. HHV-6 load was detected in NK and CD95+ cells of two patients. The obtained results show that thyroid gland cells (tyrocytes) act as target cells for HHV-6.