In enteric viral infections, such as those with rotavirus and norovirus, individual viral particles shed in stool are considered the optimal units of fecal-oral transmission. We reveal that rotaviruses and noroviruses are also shed in stool as viral clusters enclosed within vesicles that deliver a high inoculum to the receiving host. Cultured cells non-lytically release rotaviruses and noroviruses inside extracellular vesicles. In addition, stools of infected hosts contain norovirus and rotavirus within vesicles of exosomal or plasma membrane origin. These vesicles remain intact during fecal-oral transmission and thereby transport multiple viral particles collectively to the next host, enhancing both the MOI and disease severity. Vesicle-cloaked viruses are non-negligible populations in stool and have a disproportionately larger contribution to infectivity than free viruses. Our findings indicate that vesicle-cloaked viruses are highly virulent units of fecal-oral transmission and highlight a need for antivirals targeting vesicles and virus clustering.

The outstanding elastomeric properties of natural resilin, an insect protein, have motivated the engineering of resilin-like polypeptides (RLPs) as a potential material for cardiovascular tissue engineering. The RLPs, which incorporate biofunctional domains for cell-matrix interactions, are cross-linked into RLP–PEG hybrid hydrogels via a Michael-type addition of cysteine residues on the RLP with vinyl sulfones of an end-functionalized multi-arm star PEG. Oscillatory rheology indicated the useful mechanical properties of these materials. Assessments of cell viability via con-focal microscopy clearly show the successful encapsulation of human aortic adventitial fibroblasts in the three-dimensional matrices and the adoption of a spread morphology following 7 days of culture.

Poliovirus protein 2C contains a predicted N-terminal amphipathic helix that mediates association of the protein with the membranes of the viral RNA replication complex. A chimeric virus that contains sequences encoding the 18-residue core from the orthologous amphipathic helix from human rhinovirus type 14 (HRV14) was constructed. The chimeric virus exhibited defects in viral RNA replication and produced minute plaques on HeLa cell monolayers. Large plaque variants that contained mutations within the 2C-encoding region were generated upon subsequent passage. However, the majority of viruses that emerged with improved growth properties contained no changes in the region encoding 2C. Sequence analysis and reconstruction of genomes with individual mutations revealed changes in 3A or 2B sequences that compensated for the HRV14 amphipathic helix in the polio 2C-containing proteins, implying functional interactions among these proteins during the replication process. Direct binding between these viral proteins was confirmed by mammalian cell twohybrid analysis.Poliovirus (PV) RNA replication takes place in replication complexes that form de novo in cultured cells after virus infection. Synthesis of viral proteins induces extensive rearrangement of intracellular membrane structures that produce perinuclear foci of vesicle-associated viral proteins and RNA (reference 11 and references therein). These coalesce into large clusters of vesicles engaged in viral RNA synthesis, accompanied by the loss of preexisting Golgi stacks and endoplasmic reticulum (ER). All viral nonstructural proteins, derived from the P2 and P3 polyprotein regions of the single open reading frame in the viral genome, are found associated with the membranous replication complexes and have been implicated by genetic analysis as playing essential roles in the process of viral RNA replication. Proteins containing 2B, 2C, or 3A sequences manifest inherent membrane-binding properties. It is not known how the other viral proteins are recruited to and/or retained in the replication complexes. They may enter or induce formation of the complexes as larger precursor proteins prior to cleavage and maintain their associations via protein-protein or protein-RNA interactions, a hypothesis supported by the observation that complementation of defective proteins by expression of individual functional gene products does not occur readily in infected cells (32) and requires expression of whole P2 or P3 precursor proteins in vitro (16,35).The precise biochemical roles in viral RNA synthesis played by each of the nonstructural proteins are poorly defined (summarized in reference 21). From the P3 region, protein 3D catalyzes polynucleotide chain elongation as well as uridylylation of VPg (protein 3B) to form a primer for RNA chain initiation. Protein 3C is the protease responsible for the majority of polyprotein cleavages, both in cis and in trans. Protein 3CD, in addition to serving a proteinase function for generation of capsid proteins from P1 precursors, binds and sti...