Longevity of seropositivity and neutralizing antibodies in recovered MERS patients: a 5-year follow-up study

OBJECTIVES: We aimed to assess the longevity of spike-specific antibody responses and neutralizing activity in the plasma of recovered Middle East respiratory syndrome (MERS) patients. METHODS: We traced the antibody responses and neutralizing activity against MERS coronavirus (MERS-CoV) in peripheral blood samples collected from 70 recovered MERS patients for 5 years after the 2015 MERS outbreak in South Korea. We also measured the half-life of neutralizing antibody titres in the longitudinal specimens. RESULTS: The seropositivity rate persisted for up to 4 years (50.7–56.1%), especially in MERS patients who suffered from severe pneumonia, and then decreased (35.9%) in the fifth year. Although the spike-specific antibody responses decreased gradually, the neutralizing antibody titres decreased more rapidly (half-life: 20 months) in 19 participants without showing negative seroconversion during the study period. Only five (26.3%) participants had neutralizing antibody titres greater than 1/1000 of PRNT(50), and a high neutralizing antibody titre over 1/5000 was not detected in the participants at five years after infection. DISCUSSION: The seropositivity rate of the recovered MERS patients persisted up to 4 years after infection and significantly dropped in the fifth year, whereas the neutralizing antibody titres against MERS-CoV decreased more rapidly and were significantly reduced at 4 years after infection.