Immunity & infection
Understanding of immune responses against newly emerging acute respiratory infection, Middle East respiratory Syndrome (MERS), is important for the development of efficient treatment strategies and preventive measures. Here, we investigated several immune parameters using peripheral blood samples obtained from 26 hospitalized patients with different disease severities in their acute and convalescent stage. In general, the immune responses increased with enhanced disease severity. At acute stage, higher levels of inflammatory cytokines and chemokines were detected in the severe patients compared to mild cases. The increased percentages of CD8+ T cells were also detected to express the activation markers in severely ill patients. Moreover, when PBMCs were stimulated with overlapping peptides spanning whole virus structural proteins, distinctively high frequencies of MERS-CoV-specific CD8+ T cells were observed at acute stage of severe infection, while CD4+ T cell responses were not clearly detected at this stage. At the convalescent stage, antigen-specific cells were clearly identified in both T cells subsets, with the higher frequencies in severe diseases. Similar frequencies of CD8+ T cells directed against E, M, and N proteins as well as S protein. However, in CD4+ T cell subset, more cells responded to E, M, N proteins compared with S protein. Our findings highlight the potential contribution of human CD8+ T cell response to the pathogenesis of MERS-CoV induced respiratory disease. They also provide basic information for MERS-CoV vaccine design.