Extracellular vesicles from Zika virus‐infected cells display viral E protein that binds ZIKV‐neutralizing antibodies to prevent infection enhancement

Abstract

Mosquito‐borne flaviviruses including Zika virus (ZIKV) represent a public health problem in some parts of the world. Although ZIKV infection is predominantly asymptomatic or associated with mild symptoms, it can lead to neurological complications. ZIKV infection can also cause antibody‐dependent enhancement (ADE) of infection with similar viruses, warranting further studies of virion assembly and the function of envelope (E) protein‐specific antibodies. Although extracellular vesicles (EVs) from flavivirus‐infected cells have been reported to transmit infection, this interpretation is challenged by difficulties in separating EVs from flavivirions due to their similar biochemical composition and biophysical properties. In the present study, a rigorous EV‐virion separation method combining sequential ultracentrifugation and affinity capture was developed to study EVs from ZIKV‐infected cells. We find that these EVs do not transmit infection, but EVs display abundant E proteins which have an antigenic landscape similar to that of virions carrying E. ZIKV E‐coated EVs attenuate antibody‐dependent enhancement mediated by ZIKV E‐specific and DENV‐cross‐reactive antibodies in both cell culture and mouse models. We thus report an alternative route for Flavivirus E protein secretion. These results suggest that modulation of E protein release via virions and EVs may present a new approach to regulating flavivirus‐host interactions. image Flavivirus‐infected cells have been reported to secrete extracellular vesicles (EVs) that are able to transmit the infection. An optimized purification protocol shows that EVs derived from cells infected with Zika or dengue viruses do not mediate infection but display viral envelope (E) proteins. CD9‐affinity captured EVs from ZIKV‐infected cells contain viral RNA, but are not infectious in cell culture and in a mouse model. EVs derived from ZIKV‐ or DENV‐infected cells display viral E protein on the surface. Flavivirus E protein‐coated EVs attenuate antibody‐dependent enhancement mediated by both monoclonal antibodies and patient sera at subneutralizing concentration.