Reactivation of human herpesvirus 6 (HHV-6) infection in patients with connective tissue diseases.

Background: Little is known about the involvement of human herpesviruses 6 and 7 (HHV-6 and HHV-7) in autoimmune connective tissue diseases (ACTD).
Objective: To determine the prevalence of active infection with HHV-6 and HHV-7 in patients with ACTD.
Study Design: The presence and quantity of HHV-6 DNA was determined by quantitative real-time PCR in a cross-sectional study of serum, peripheral blood mononuclear cells, and tissues obtained from 58 ACTD patients and 38 healthy subjects (HS). Specific anti-HHV-6 antibody titer was also measured.
Results: HHV-6 serum viremia occurred in a significantly higher proportion of ACTD patients compared to HS [26/58 (44.8%) vs. 1/38 (2.6%), p=0.001] with the highest reactivation frequency [7/10 (70%)] observed in patients with scleroderma. Moreover, HHV-6 in serum was associated with ACTD activity (22/38 vs. 4/20, p<0.05). Higher titers of HHV-6 antibodies were found in ACTD patients than in HS, although HHV-6 seroprevalence among patients with ACTD and HS was similar. HHV-7 viremia was not detected in any patients or HS controls.
Conclusion: The frequent reactivation of HHV-6 in scleroderma and other ACTD, especially when active, suggests that HHV-6 may play a role in the pathogenesis of these diseases.