Characterization of bi-segmented and tri-segmented recombinant Pichinde virus particles.

Mammarenaviruses include several highly virulent pathogens (e.g., Lassa virus) capable of causing severe hemorrhagic fever diseases for which there are no approved vaccines and limited treatment options. Mammarenaviruses are enveloped, bi-segmented ambisense RNA viruses. There is limited knowledge about cellular proteins incorporated into progeny virion particles and their potential biological roles in viral infection. Pichinde virus (PICV) is a prototypic arenavirus used to characterize mammarenavirus replication and pathogenesis. We have developed a recombinant PICV with a tri-segmented RNA genome as a viral vector platform. Whether the tri-segmented virion differs from the wild-type bi-segmented one in viral particle morphology and protein composition has not been addressed. In this study, recombinant PICV (rPICV) virions with a bi-segmented (rP18bi) and a tri-segmented (rP18tri) genome were puri fied by density-gradient ultracentrifugation and analyzed by cryo-electron microscopy and mass spectrometry. Both virion types are pleomorphic with spherical morphology and have no significant difference in size despite rP18tri having denser particles. Both virion types also contain similar sets of cellular proteins. Among the highly enriched virion-associated cellular proteins are components of the endosomal sorting complex required for transport pathway and vesicle trafficking, such as ALIX, Tsg101, VPS, CHMP, and Ras-associated binding proteins, which have known functions in virus assembly and budding. Other enriched cellular proteins include peripheral and transmembrane proteins, chaperone proteins, and ribosomal proteins; their biological roles in viral infection warrant further analysis. Our study provides important insights into mammarenavirus particle formation and aids in the future development of viral vectors and antiviral discovery. [ABSTRACT FROM AUTHOR]