Abstract
BACKGROUND: Enterovirus D68 (EV-D68) causes worldwide outbreaks of human respiratory illness with spacio-temporally related outbreaks of acute flaccid myelitis (AFM), a polio-like illness. Numerous seroepidemiology studies show that nearly all humans older than 2 years have EV-D68-neutralizing antibodies in their serum, even in serum collected prior to large outbreaks. However, little else is known about the human antibody response to this virus. We sought to isolate human monoclonal antibodies (mAbs) from B cells in peripheral blood mononuclear cells (PBMCs) of immune subjects, induced by natural infection, to understand human humoral immunity to EV-D68. METHODS: We obtained PBMCs from donors with known infection during the largest ever recorded outbreak, which occurred in the United States in 2014. We used EV-D68 virus isolates from this outbreak in an indirect ELISA to screen immortalized PBMCs for antigen-specificity, then fused them with myeloma cells to create hybridomas. RESULTS: To date, we have isolated > 60 naturally occurring anti-EV-D68 human mAbs from the B cells of subjects with documented infection. These mAbs exhibit diverse binding affinities when compared across different clades of recent EV-D68 isolates. Many mAbs neutralize EV-D68 quite potently in vitro, with [ng/mL] half maximal effective concentrations. Some mAbs neutralize diverse clades of EV-D68, whereas others are highly clade-specific. Binding of antibodies to at least three, but likely more, major antigenic sites on the virus leads to neutralization. CONCLUSION: We observed a qualitative difference among antibodies isolated from patients who had natural infection. These differences could contribute to certain individuals being susceptible to respiratory disease and AFM. Our studies of humoral immunity are especially important for a disease with nearly universal apparent seroprotection, in which the virus somehow persistently causes outbreaks across the world. Furthermore, no licensed vaccines or treatments exist for EV-D68. Given the ability of human intravenous immune globulin to protect mice from AFM, these mAbs are being tested for therapeutic benefit in vivo, and may have promise in the prevention and/or treatment of EV-D68-related diseases. DISCLOSURES: All authors: No reported disclosures.