Natural infection with HHV-6 has been suggested to play a role in the pathogenesis of Hashimoto’s thyroiditis (Caselli 2012) and type 1 diabetes (Ericsson 2017). Inherited chromosomally integrated HHV-6 (iciHHV-6) can reactivate (Endo 2014), induce humoral and cellular immune responses, and modulate host-immune responses (Peddu 2019). For these reasons, a team led by Tetsushi Yoshikawa of Fujita Health University sought to determine if iciHHV-6 might be more prevalent among people with chronic autoimmune diseases.
The team examined 846 samples from patients with chronic autoimmune diseases: primarily, rheumatoid arthritis (243), lupus (159), polymyositis/dermatomyositis (104) and systemic sclerosis (44). HHV-6 copy numbers were measured by quantitative PCR. A threshold of 1.6 x 106 copies/mL was used to distinguish between active infection and iciHHV-6.
No HHV-6 DNA was detected in any of the pooled samples, indicating that there were no patients positive for iciHHV-6. Thus, present studies do not suggest a correlation between iciHHV-6 and CTDs. This result was consistent with other studies (Gravel 2015).
On the other hand, no study thus far has been large enough to make statistically robust statements about whether iciHHV-6 affects the risk of autoimmune diseases.
Finally, while the study was conducted to determine whether iciHHV-6 might increase the risk of several major autoimmune diseases, the fact that no cases of iciHHV-6 were found in a group of 846 raises the question of whether iciHHV-6 might decrease the risk of these autoimmune diseases.
Full text: Kawamura 2020