MERS-CoV Infection Elicits Long-lasting Specific Antibody, T and B Cell Immune Responses in Recovered Individuals

Background The Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic zoonotic betacoronavirus and a global public health concern. Better undersetting of the immune responses to MERS-CoV is needed to characterize the correlates of protection and durability of the immunity and to aid in developing preventative and therapeutic interventions. Although MERS-CoV-specific circulating antibodies could persist for several years post-recovery, their waning raises concerns about their durability and role in protection. Nonetheless, memory B and T cells could provide long-lasting protective immunity despite the serum antibodies levels. Methods Serological and flow cytometric analysis of MERS-CoV-specific immune responses were performed on samples collected from a cohort of recovered individuals who required intensive care unit (ICU) admission as well as hospital or home isolation several years after infection to characterize the longevity and quality of humoral and cellular immune responses. Results Our data showed that MERS-CoV infection could elicit robust long-lasting virus-specific binding and neutralizing antibodies as well as T- and B-cell responses up to 6.9 years postinfection regardless of disease severity or need for ICU admission. Apart from the persistent high antibody titers, this response was characterized by B-cell subsets with antibody-independent functions as demonstrated by their ability to produce tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-6, and interferon gamma (IFN-gamma) cytokines in response to antigen stimulation. Furthermore, virus-specific activation of memory CD8(+) and CD4(+) T cell subsets from MERS-recovered patients resulted in secretion of high levels of TNF-alpha, IL-17, and IFN-gamma. Conclusions MERS-CoV infection could elicit robust long-lasting virus-specific humoral and cellular responses. Significant gaps exist in understanding the longevity of the immune responses to Middle East respiratory syndrome coronavirus (MERS-CoV). In this study, we characterized the immune responses in MERS survivors and found detectable and persistent MERS-CoV-specific humoral and cellular memory responses for up to 6.9 years.