Nipah Virus Matrix Protein Influences Fusogenicity and Is Essential for Particle Infectivity and Stability

Abstract

Nipah virus (NiV) causes fatal encephalitic infections in humans. To characterize the role of the matrix (M) protein in the viral life cycle, we generated a reverse genetics system based on NiV strain Malaysia. Using an enhanced green fluorescent protein (eGFP)-expressing M protein-deleted NiV, we observed a slightly increased cell-cell fusion, slow replication kinetics, and significantly reduced peak titers compared to the parental virus. While increased amounts of viral proteins were found in the supernatant of cells infected with M-deleted NiV, the infectivity-to-particle ratio was more than 100-fold reduced, and the particles were less thermostable and of more irregular morphology. Taken together, our data demonstrate that the M protein is not absolutely required for the production of cell-free NiV but is necessary for proper assembly and release of stable infectious NiV particles. IMPORTANCEHenipaviruses cause a severe disease with high mortality in human patients. Therefore, these viruses can be studied only in biosafety level 4 (BSL-4) laboratories, making it more challenging to characterize their life cycle. Here we investigated the role of the Nipah virus matrix protein in virus-mediated cell-cell fusion and in the formation and release of newly produced particles. We found that even though low levels of infectious viruses are produced in the absence of the matrix protein, it is required for the release of highly infectious and stable particles. Fusogenicity of matrixless viruses was slightly enhanced, further demonstrating the critical role of this protein in different steps of Nipah virus spread.

Mutations in the Transmembrane Domain and Cytoplasmic Tail of Hendra Virus Fusion Protein Disrupt Virus-Like-Particle Assembly

“…This may potentially create an interesting dynamic for certain paramyxoviruses, including the henipaviruses, whose glycoproteins are independently capable of inducing particle release. Indeed, a matrixless Nipah virus was recovered by reverse genetics and is viable, albeit with severely defective infectivity and irregular particle morphology (52). Here we observed that the Hendra virus M protein, even expressed at a level below that required for budding function, could still assemble as a passenger in VLPs whose formation was driven by the F protein.…”

Morbillivirus and henipavirus attachment protein cytoplasmic domains differently affect protein expression, fusion support and particle assembly

“…The M-protein-mediated incorporation of NiV G is also much less efficient than that of the F protein (Landowski et al, 2014), further supporting our findings. In addition, infectious NiV particles are released into the culture supernatant even when the entire M ORF is deleted (Dietzel et al, 2016), demonstrating that the role of the henipavirus M protein in virus assembly is less prominent than for other paramyxoviruses. This implies a greater contribution of the henipavirus glycoproteins to the budding process, suggesting a fundamentally different process of henipavirus assembly compared with other members of this virus family.…”

Species-specific and individual differences in Nipah virus replication in porcine and human airway epithelial cells

“…All experiments with live NiV were performed under biosafety level 4 (BSL-4) conditions at the Institute of Virology, Philipps University Marburg. The NiV Malaysia strain used in this study was described previously (Diederich et al, 2012;Dietzel et al, 2015;Moll et al, 2004).…”