#91: Human Antibodies Neutralize Enterovirus D68 and Protect Against Infection and Paralytic Disease

Abstract

Abstract Background Enterovirus D68 (EV-D68) causes worldwide outbreaks of human respiratory illness with spatiotemporally related outbreaks of acute flaccid myelitis (AFM). The major circulating clade of EV-D68 has changed since the largest ever recorded outbreak, which occurred in the United States in 2014. Numerous seroepidemiology studies show that essentially all adult humans have EV-D68-neutralizing antibodies in their serum, even in serum collected prior to large outbreaks. But some studies show a lack of neutralizing antibodies in pediatric populations. 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 further understand human humoral immunity to EV-D68. Methods We obtained PBMCs from donors with known infection during 2014. We used EV-D68 virus isolates from this outbreak as antigen in an indirect ELISA to screen immortalized PBMCs for antigen-specificity, then fused B cells with myeloma cells to create hybridomas. Results We isolated >60 naturally occurring anti-EV-D68 human mAbs. These mAbs exhibit diverse binding affinities when compared across clades of recent EV-D68 isolates. Many mAbs neutralize EV-D68 quite potently in vitro, with [ng/mL] half-maximal effective concentrations. Some mAbs like EV68-228 neutralize diverse clades, 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. When given as either prophylaxis before or treatment after EV-D68 inoculation, mAb EV68-228 protects mice from both respiratory and neurologic disease, whereas equivalent doses of polyclonal human immunoglobulin protect only partially. Conclusions We observed a qualitative difference among antibodies isolated from patients who had a history of natural infection. These differences could contribute to certain individuals being susceptible to respiratory disease and AFM. These 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. These mAbs have therapeutic benefit in vivo and show promise for the prevention and/or treatment of EV-D68-related diseases in humans. We are pursuing the use of mAb EV68-228 in humans with partners in industry and government agencies.