HHV-6A in vitro infection of thyrocytes and T cells alters the expression of miRNA associated to autoimmune thyroiditis

Abstract

Background: Human herpesviruses have been hypothesized as environmental triggers in the development of autoimmune thyroid diseases (AITD), and in particular active human herpesvirus 6A (HHV-6A) infection was detected in thyrocytes of Hashimoto's thyroiditis (HT) patients, who also show specific anti-viral immune responses. On the other hand, AITD patients display modulation of specific miRNAs in thyroid tissue and blood. We wanted to ascertain whether HHV-6A infection might be correlated to the miRNA dysregulation observed in AITD.

Methods: Human thyroid and T-cell lines were infected in vitro with HHV-6A,-6B or -7, and analysed for miRNAs expression, either by microarray or by specific RT-PCR assays detecting miRNAs associated with AITD in vivo.

Results: HHV-6A infection, but not -6B or -7 infections, induced a decrease in miR-155_2 expression and an increase in miR-1238 expression in thyrocytes, as well as an increase in the expression levels of several autoimmunity-associated miRNAs in T lymphocytes, including miR-16_1, miR34a, miR-130a, miR-143_1, miR-202, miR-301b, miR-302c, miR-449b, miR-451_1, and miR-1238_2.

Conclusions: HHV-6A infection modulates miRNAs expression in the cell types involved in the development of AITD. Notably, our in vitro findings correlate with what observed in AITD patients, further supporting the association between HHV-6A infection and AITD development. Moreover, these effects are 6A-specific, emphasizing the differences between the two HHV-6 virus species, and suggesting diverse virus mechanisms of action and therapeutic approaches.

Keywords: Autoimmune thyroiditis; HHV-6; miRNA.

Fig. 1

Herpesvirus infection in human thyroid and T lymphoid cell lines. Nthy-ori3-1 (a) and Jurkat T cell lines (b) were infected with HHV-6A, −6B or −7 cell-free virus inocula (m.o.i. 10:1). Virus presence (DNA) and transcription (RNA) were evaluated respectively by qPCR and RT-qPCR performed on U42 virus genes at 1, 3 and 7 d.p.i., as already detailed [3]

Fig. 2

Herpesviruses-induced modulation of autoimmunity-related miRNAs in thyroid and T lymphoid cell lines. Nthy-ori3-1 and Jurkat T cells were uninfected (control) or infected with HHV-6A, HHV-6B or HHV-7 and analysed at 48 h.p.i. for miRNA expression by a microarray analysis evidencing 84 miRNAs associated to inflammation and autoimmunity. Results are expressed as fold-change compared to control values, and represent the mean value of triplicate samples. a miRNA expression in thyroid cells b miRNA expression in T lymphocytes

Fig. 3

Herpesviruses-induced modulation of AITD-related miRNAs in thyroid and T lymphoid cell lines. Nthy-ori3-1 and Jurkat T cells were uninfected (control) or infected with HHV-6A, HHV-6B or HHV-7 and analysed for expression of individual AITD-associated miRNAs at the indicated times post infection. Results are expressed as fold-change compared to control values, and represent the mean value of triplicate samples in two independent experiments. a miRNA expression in thyroid cells (*, p < 0.01; **, p < 0.001). b miRNA expression in T lymphocytes (*, p < 0.001; **, p < 0.0001)