HHV-6 Infection and Chemokine RANTES Signaling Pathway Disturbance in Patients with Autoimmune Thyroiditis

Abstract

The aim of this study was to investigate the role of human herpesvirus-6 (HHV-6) in autoimmune thyroiditis (AIT) development. We examined the possible involvement of HHV-6 gene expression encoding immunomodulating proteins U12 and U51 in AIT development and their role in the modulation of chemokine signaling. One hundred patients with autoimmune thyroiditis following thyroidectomy were enrolled in this study. Nested polymerase chain reaction (nPCR) was used to detect the HHV-6 sequence in DNA samples. Reverse transcription PCR (RT-PCR) with three different HHV-6 gene targets (U79/80, U51 and U12) was to detect active infection markers. HHV-6 load was identified using a commercial real-time PCR kit. Immunohistochemistry was performed to investigate the expression of the HHV-6 antigen and RANTES (Regulated upon Activation, Normal T Cell Expressed and Secreted) in thyroid gland tissue. Different commercial immunosorbent assay kits were used for the detection of RANTES, IFNγ, IL-6, and TNFα levels in the AIT patient group and controls. We detected 98% presence of the HHV-6 genomic sequence in AIT patients’ thyroid gland tissues. Markers of active HHV-6 infection (HHV-6 U79/80, U12 and/or U51 mRNA) were predominant in AIT patients’ thyroid tissue samples in comparison with the control group (56% vs. 6%). Evidence from immunofluorescence microscopy showed that HHV-6 can persist in thyrocytes and can interact with RANTES. Visual confirmation of the intense immunofluorescence signal of RANTES detected in thyroid tissues could indicate high expression of this chemokine in the thyroid gland. On the other hand, immunosorbent assays showed very low RANTES levels in AIT patients’ peripheral plasma. These results indicate that RANTES level in AIT patients could be influenced by HHV-6 activation, which in turn may aid AIT development.

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

“…Such spread combined with immunomodulating properties of HHV-6 ensures its lifelong persistence within the host. In previous studies we also showed dominance of HHV-6 activity in thyroid tissue and the absence of it in peripheral blood ( 7 , 16 ). Since U12 and U51 can be expressed on infected cell’s surface, these proteins could be more frequently exposed to the immune system, than for example, major capsid protein, as virus remains in solid tissues during the cell-to-cell spread.…”

“…Results from our own and other studies led us to believe that the chemokine receptors encoded by HHV-6 (U12 and U51) could be involved in the development of AIT. Firstly, we have observed that the chemokine receptors are expressed in the thyroid gland tissues of AIT patients and that the levels of chemokine RANTES, which can be bound and downregulated by the viral chemokine receptors ( 15 ), are significantly decreased in AIT patients plasma samples ( 16 ). Secondly, U12 and U51 can be expressed on infected cell surfaces and they possess structural and functional similarities with human chemokine receptors ( 15 ).…”

“…Additionally, it has been shown in vitro that HHV-6 encoded GPCRs could interact with cytokine signaling pathways by downregulating RANTES ( 15 ). A recent study we published demonstrates a relatively high frequency of HHV-6 U12 and U51 mRNA presence in AIT patients' thyroid gland tissue samples, as well as significantly lower RANTES levels in peripheral blood in comparison to blood donors ( 16 ).…”

Immunological Investigations of HHV-6 U12 and U51 Encoded Proteins Involvement in Autoimmune Thyroiditis Development

“…In our latest manuscript, we show high frequency of HHV-6 U12 and/or U51 genes' mRNA presence in thyroid gland tissues acquired from AIT patients [16]. Proteins encoded by these genes are structurally similar to cellular G protein-coupled receptors like human CCR1, CCR3 and CCR5 [10,12].…”

Viral G Protein–Coupled Receptors: Attractive Targets for Herpesvirus-Associated Diseases

“…U51 is a positive regulator of HHV-6A replication that might be related to cell-cell spread and may induce leukocyte migration in response to chemokine gradients (Zhen et al, 2005;Catusse et al, 2008). Recently, the presence of HHV-6, and vGPCRs U12 and U51 mRNA, was detected in thyroid gland tissues of patients with autoimmune thyroiditis (AIT) (Sultanova et al, 2020). Moreover, CCL5 levels in blood plasma were lowered in patients with AIT in which U12 and U51 gene expression was detected, indicating a potential role for these vGPCRs in influencing CCL5 signaling in AIT.…”