Multiple sclerosis (MS) is associated with Epstein-Barr virus (EBV) infection, but impaired immune suppression may be part of the disease pathogenesis. CD8+ T cells that are restricted by HLA-E exert an important immunoregulatory mechanism. To explore how EBV might interfere with immune regulation, we examined the expression of HLA-E and the frequency of CD8+ cells recognizing HLA-E, presenting either an EBV peptide from the BZLF1 protein or a signal sequence peptide from HLA-A2, in relapsing remitting (MS-RR), primary progressive (MS-PP) MS patients, and healthy controls (HC). Treatment with IFN-α or EBV increased HLA-E expression on CD4+ cells. However, only MS-PP had increased expression of HLA-E on resting CD4+ cells when compared with HC (p<0.005). CD8+ cells were divided into CD8bright and CD8dim cells by flow cytometry analyses. MS-RR had significantly fewer CD8dim cells than HC (p<0.003). Flow cytometry analyses were performed with HLA-E tetramers folded in the presence of the EBV or HLA-A2 peptide to identify HLA-E-interacting cells. MS-RR had increased frequency of CD8bright cells recognizing HLA-E/A2 (p = 0.006) and HLA-E/BZLF1 (p = 0.016). Conversely, MS-RR had fewer CD8dim cells that recognized HLA-E/BZLF1 (p = 0.001), but this could be attributed to the overall lower number of CD8dim cells in MS-RR. Whereas HLA-E/A2 was predominantly recognized by CD8dim cells, HLA-E/BZLF1 was predominantly recognized by CD8bright cells in MS-RR and MS-PP, but not in HC. As expected, HLA-E/A2 was also recognized by CD8-negative cells in a CD94-dependent manner, whereas HLA-E/BZLF1 was poorly recognized in all groups by CD8-negative cells. These data demonstrate that MS-RR patients have expanded their CD8bright cells recognizing HLA-E/BZLF1. Moreover, HLA-E/BZLF1 appears to be recognized by the immune system in a different manner than HLA-E/A2.
