HHV-6 and CIHHV-6 may cause AIDS and Chronic Fatigue Syndrome by activating HERVK-18 which acts as a superantigen capable of bring down the whole immune system.
More information on HERVK-18 here.
HHV-6A infection induces expression of HERV-K18-encoded superantigen
"The human endogenous retrovirus K-18 (HERV-K18) encodes a superantigen that causes deregulation of the immune system. This provirus is transcriptionally silent, but can be induced by Epstein–Barr virus (EBV) infection and IFN-α treatmen" --Albert K. Taia, Janos Lukab, Dharam Ablashic, Brigitte T. Huber
http://www.journalofclinicalvirology.com/article/S1386-6532%2809%2900194-2/abstract
Brigitte Huber on HERVK-18
changed August 22, 2009