Reo Viruses:

Respiratory Enteric Orphan (REO) viruses infect human respiratory system and intestinal tracts; they don�t manifest any symptoms that is why ,they are called orphan viruses i.e. they are in search of a disease.� But now it is known that they do cause diseases such as infantile Diarrhea and Colorado tick fever and others.� There are more than 150 species; they infect animals and plants as well. They include Rotavirus.

Aqua Reo virus; http://www.colgate.edu/

One more diagram of Reovirus depicting various structural features; http://www.microbiologybytes.com/

Genus:	Outer capsid:	Core:	Non-structural:
Reoviruses:	σ-1, σ-3, μ-1c, λ-2	λ-1, λ-3, σ-2, μ-2	μ-NS, σ-NS
Orbiviruses:	VP2, VP5, VP7	VP3; VP1,VP4,VP6 (transcriptase complex)	NS1, NS2, NS3
Rotaviruses:	VP4, VP7	VP2, VP6, VP1, VP3	NSP1, NSP2, NSP3, NSP4, NSP5, NSP5A

����������� Microbiology bytes ; http://www.microbiologybytes.com/

General features:

All have isometric shape, naked, 70 to 85 nm thick, and made up of two concentric capsid layers.

• Genomic RNA exists as double stranded structures, ten different segments; each coding for a specific protein.

• Replicating enzymes are found within the core of the viruses.

• At the vertices, it has sigma 1HA proteins for cell recognition.� On the inner surface of the inner coat, nonstructural proteins are found which are associated with ds RNA genomes, which are ten in number.

Viral Proteins:

Gene/protein	Mol.wt (KD)	Function
Lambda-1	155	Inner capsid (core protein)
Lambda-2	140	Inner core-Guanyl transferase
Lambda-3	140	Replicase
Micron 1C	80	Outer capsid protein
Micron 2	72-80	Inner core
Micron NS1	80	Nonstructural protein
Micron NS2	36	Nonstructural protein
Sigma 1	42	Spike, 1HA
Sigma 2	38	Inner capsid protein
Sigma 3	34	Outer capsid protein

Replication:

Entry is gained through the spike protein binding to cellular receptors, and endocytosis leads to endosomes.�

� Inside endosomes outer capsid digested to release inner core, which now becomes active.

This figure shows the infection and reproductive cycle of the virus;

Development of Oncolytic Reovirus for Cancer Therapy; Ergin Sahin; http://file.scirp.org/

There are 10-(11?) dsRNA genomes, each code one or more proteins,

� The RNA dependent RNA polymerase or what is called RNA Replicase start replicating to produce only positive sense RNA from all the ten segments, as each transcript represents one protein.�

� What is not clear, but speculated, whether or not the ds RNA fully formed RNAs or one of them especially (+) strand is incomplete, at the time of infection.

� Aftermath of infection and activation, the incomplete plus strands of RNA are completed and the same are released into cytoplasm.� The released (+) RNAs have cap structure at 5� end with out a poly (A) tail.

� The negative RNA strands also have pppG-Pu-Py sequences at the 5� end.� The plus sense RNAs, as they are synthesized, they come out of the pores found at vertices.�� It is through the pores in the capsid, all the required NTPs and other components for replication enter. Even the RNA strands synthesized inside the viral capsid move out.

� Synthesis and the release of (+) RNAs continue.� The (+) RNA transcripts in cytoplasm act as mRNAs and they associate with ribosomes and translate.

� As sufficient number of the inner capsid proteins and replicating enzymes are produced, they get assembled into provirus particles with all ten different species of (+) RNAs.�

� Within these core particles, plus RNAs are transcribed or say replicated to generate (-) RNAs.� Pro- viral particles continue to produce more (+) RNAs and more proteins and more (-) RNAs.�

� As process goes on, many pro-viral cores with ds RNAs get encapsulated with second coat proteins to produce new viral particles.�

Many of the mechanisms are not well understood (or I haven�t got the material to know about it?).