Non-enveloped, spherical, about 32-34 nm in diameter. The RNA genome is enclosed within a capsid that is composed of 60 capsid proteins, assembled into a T=1 icosahedral particle.
Monopartite, linear, ssRNA(+) genome of 7.2 kb. The 5' end is capped and the 3' terminus is polyadenylated. Their is no VPg at the 5'-terminus of the genome. The genome consists of three partially overlapping ORFs.
The virion RNA is infectious and serves as both the genome and viral messenger RNA. ORF 1 encodes the nonstructural proteins, it is not clear wether this polyprotein is cleaved or not; ORF 2 encodes the capsid protein; ORF 3 encodes a small immunogenic protein. ORF2 is translated by leaky scanning from the bicistronic ORF3-2 subgenomic RNA.
- Attachement of the virus to host receptors mediates internalization into the host cell by clathrin-mediated endocytosis.
- RNA genome is released into the cytoplasm.
- The positive-sense genomic ssRNA is translated into a processed ORF1 polyprotein to yield the mature non-structural proteins involved in RNA transcription.
- Replication takes place in cytoplasmic viral factories. A dsRNA genome is synthesized from the genomic ssRNA(+).
- The dsRNA genome is transcribed/replicated thereby providing viral mRNAs/new ssRNA(+) genomes.
- Expression of two other messenger RNAs, a 3.7 kb subgenomic one and a 2.0 kb coterminal one.
- Virus assembly and release.