Dynamics of neutralizing antibodies against enterovirus D68 in adults during the COVID-19 pandemic

BACKGROUND: Enterovirus D68 (EV-D68) causes acute respiratory illnesses and has also implicated in acute flaccid myelitis. Neutralizing antibodies (NtAbs) represent key components of the adaptative immunity. However, the dynamics of EV-D68 NtAbs in adults remain poorly characterized. We evaluated EV-D68 NtAb levels in retail workers in Canada during the COVID-19 pandemic. METHODS: NtAbs were measured in paired serum samples (N=194), from retail workers (≥ 18 years) enrolled in a prospective SARS-CoV-2 cohort at the Centre Hospitalier Universitaire de Québec-Université Laval, in Quebec City. Samples collected 48 weeks apart, between June 2021 to October 2022, were tested by microneutralization assays. RESULTS: EV-D68 NtAb seroprevalence was high (>85%). Over the 48-weeks follow-up, the vast majority of patients (97%) had stable or reduced titers with a statistically significant overall reduction in geometric mean titer (GMT), p<0.001. Furthermore, a small subset of participants 6/194 (3%) showed a marked increase of titers (≥4-fold) with the GMT rising from 21 (10-57) at the first visit to 593 (57-7241) at follow-up visit. CONCLUSIONS: Neutralizing antibody titers declined in most participants over 48 weeks. However, six individuals had significantly increased NtAb titers during the study period, which is consistent with potential ongoing EV-D68 or other enterovirus circulation in Quebec following sequential non-pharmaceutical interventions lift. This is in line with documented EV-D68 resurgence in the United States at the same period. Our work complements pediatric data on EV-D68 immunity and highlights the serological surveillance importance in adults.