Multisystem Inflammatory Syndrome in Children and Long COVID: The SARS-CoV-2 Viral Superantigen Hypothesis Frontiers | Multisystem Inflammatory Syndrome in Children and Long COVID: The SARS-CoV-2 Viral Superantigen Hypothesis (frontiersin.org) HHV-6A infection induces expression of HERV-K18-encoded superantigen Albert K. Taia, Janos Lukab, Dharam Ablashi, Brigitte T. Huber published online 08 June 2009. Abstract Background 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 treatment. Objectives Since the herpesvirus EBV induces HERV-K18 expression in human B cells, it was of interest to determine if other herpesviruses would have similar HERV-K18 transactivation properties. Human herpesvirus (HHV)-6A, a neurotropic virus associated with multiple sclerosis, was a logical candidate for these studies....