Innate effectors against Zika virus

• Applicant: Professor Dr. Janis-Alexander Müller
• Subject Area: Virology ; Immunology ; Cell Biology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 445272774

Over the last 12 years, Zika virus (ZIKV) re-emerged and caused several outbreaks in the Americas. Infection with the virus can cause neurological complications such as the Guillain-Barrée syndrome and have teratogenic effects during pregnancy. This mosquito-borne virus is shed into various body fluids such as plasma, saliva, amniotic fluid, breast milk, semen, and vaginal fluid and horizontal transmissions i.e. via sexual intercourse have occasionally been recorded.We are interested in how body fluids influence viral infection and transmission and found that semen and saliva contain extracellular vesicles (EVs) that potently inhibit ZIKV infection. The major goal of this study is to purify these EVs, characterize them in terms of numbers, size, charge, morphology and composition and to elucidate their antiviral mechanism.Several flaviviruses use the strategy of viral apoptotic mimicry to attach to and enter target cells by exposing phosphatidylserine (PS) on their membrane that interacts with apoptosis-sensing PS-receptors. Interestingly, EVs from semen are rich in PS and we found that they inhibit infection by Dengue, West Nile and Zika viruses. This raises the possibility that PS-containing EVs inhibit flavivirus infection by competing for PS-receptor binding. We will therefore analyze their PS exposure and determine how they interfere with ZIKV infection. Moreover, we will isolate EVs from other body fluids naturally containing high amounts of ZIKV and analyze their PS-composition and antiviral potential against ZIKV and other viruses employing viral apoptotic mimicry. Finally, we will adopt this antiviral strategy and test whether artificial PS-liposomes can prevent ZIKV transmission or spread in vivo.Aside from lipids, some EVs also contain antivirally active host proteins. For example, sialophorin (SPN, CD43) is a transmembrane protein that is incorporated into EVs and has been shown to restrict infection by the human immunodeficiency virus (HIV). In preparative experiments for this proposal, we found that ZIKV replication is drastically reduced in cells overexpressing SPN. Therefore, we will analyze the relevance of SPN-mediated ZIKV restriction in primary target cells and investigate whether body fluids harbor SPN-containing EVs that could modify recipient cells to restrict virus replication. We will determine the subcellular localization of SPN and identify crucial domains and/or post-translational modifications that are required to fulfil its antiviral effect. Finally, we will elucidate the mechanism of restriction and analyze whether ZIKV evolved strategies of evasion.Deciphering the lipid- and protein-mediated activities of EVs from body fluids will provide important insights into how the human body combats viral infections, may identify entirely novel branches of innate immunity and possibly translate into strategies that help to limit viral transmission and spread.

• DFG Programme: Research Grants