Specific NK Cell subsets Associated with HHV-6 Infection in Hashimoto’s Thyroiditis

In All, Endocrine Conditions, Thyroid Disease by Kristin Loomis

Human herpesvirus-6 (HHV-6) has been associated with multiple autoimmune diseases, including Sjogren’s syndrome, multiple sclerosis, and systemic lupus erythematosus. A recent study led by Rizzo and Caselli from the University of Ferrara has found a possible link to another autoinflammatory process, Hashimoto’s Thyroiditis (HT). They found that HHV-6 infection correlated with higher levels of a particular type of NK cell associated with a potent release of cytokines.

The Italian group analyzed fine needle thyroid aspirates (FNAs) and blood from 8 HT patients and 8 controls. HHV-6 was found in 8/8 (100%) HT FNAs compared to only 2/8 (25%) control FNAs. Furthermore, the viral load in HT specimens was higher than in controls (mean 1.2 x 104 copies/ug DNA vs. mean 3.9 x 102 copies/ug DNA, respectively). Similarly, viral load was higher (mean 1.8 x 104 copies/ug DNA) and detected more often (8/8 HT specimens) in PBMCs than in controls, where the mean viral load was 3.7 x 102 copies/ug DNA in 3/8 (37%) samples.

The researchers also measured the antibody response and the percentages of natural killer (NK) cells. An antibody response directed against the HHV-6 U94/Rep protein was not only found to be more prevalent in HT patients than in controls (8/8 vs. 6/8), but the titer was also significantly higher in HT patients than in control subjects (1:1624 vs 1:543, p<0.01). In addition, a higher percentage and activation status of CD3-CD56bright NK cells were found in samples from HT patients compared to controls.

The authors believe that these results demonstrate a possible relationship between HHV-6 and the development of Hashimoto’s Thyroiditis. They point out that since CD3-CD56bright NK cells have the ability to produce abundant cytokines following activation, these NK cells might play an important role in disease activity and viral infection.

For more information, read the full paper.