Role of the matrix protein during Nipah virus infection of polarized epithelial cells

• Applicant: Professorin Dr. Andrea Susanne Maisner
• Subject Area: Virology
• Term: from 2009 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 143013272

Nipah virus (NiV) is a highly pathogenic, BSL-4 classified paramyxovirus that causes severe respiratory and encephalitic diseases. The virus infects via the respiratory tract and overcomes the mucosal barrier to subsequently cause a generalized infection. In late infection phases, polarized epithelial cells are importantly involved in virus shedding from mucosal surfaces in the respiratory and urinary tract. Productive NiV replication in epithelia has thus significant implications for virus spread within epithelial tissues and for virus transmission from host-to-host.Due to the polarized nature of epithelia, viral proteins can be selectively expressed at either apical or basolateral cell surfaces. This can influence virus budding or lateral virus spread. Our studies in the last funding period revealed that the two NiV glycoproteins possess targeting signals that are responsible for transport to the basolateral cell surfaces of epithelia. This allows a rapid spread of infection from infected to uninfected cells by cell-to-cell fusion. Later, the glycoproteins also reach the apical cell surface. Here, they meet the matrix protein M, which turned out to be the key player in viral assembly. Since M accumulates almost exclusively at apical membranes, virus budding is targeted to the apical side of epithelial cells thereby contributing to efficient virus shedding from mucosal surfaces. Unclear is, how M is selectively targeted to the apical cell membrane to trigger polarized NiV release. In the next funding period, we therefore want to elucidate the molecular mechanisms underlying the M-mediated apical virus budding by making use of our recently established reverse genetics system. This allows us to generate recombinant NiV encoding fluorescently tagged or mutant M proteins to study M transport and M-driven assembly in the context of a virus infection. This will greatly increase the current knowledge which is mostly based on studies with expressed NiV-M in non-polarized cells. In the first part of the project, we will analyze the spatio-temporal distribution of fluorescently tagged M proteins in NiV-infected cells. Herewith, we want to define which cytoskeleton- and vesicle-based host cell trafficking pathways are involved in apical M transport. In the second part of the project, we want to generate recombinant viruses with mutated M genes to determine the functional importance of potential trafficking signals in the NiV-M for selective virus budding from apical surfaces.From the comprehensive infection studies in epithelial cells, we expect to get an improved molecular understanding of the spread of highly pathogenic NiV within epithelial tissues and its productive apical budding. Both, spread within and efficient shedding from epithelial surfaces are essential in-vivo for successful transmission of a NiV infection from host-to-host.

• DFG Programme: Research Grants