About RSV
How does the RSV multiply?
The RSV replication cycle begins with the fusion of the virus membrane and the membrane of the host cell. It lasts for 16-20 hours.
The virus uses HN, H and G proteins of the virion’s envelope to bind to the host cell through surface proteins or the sialic acid of glycolipids. The F protein allowes fusion of the envelope and the plasma membrane through changes in it’s conformation.
Once the virus and the host cell have joint together, RNA ( – ) with viral RNA polymerase and other components of the nucleocapsid, enter the host cell. In the cytoplasm, the genome is transcribed into an mRNA for each individual protein, this occurs with the aid of the M2 -1 protein that allowes to pass through regions between genes.
When the gene products and the M2 -1 are stored to a certain amount, the polymerase complex stops transcribing and begins to replicate RNA ( – ) forming complete RNA(+) templates, these new RNA will serve as templates to develop RNA ( – ) viruses . New RNA ( – ) joins proteins L and NP to form the nucleocapsid. Helped by protein N, viruses associate with M proteins of the plasma membranes that were modified by viral glycoprotein, resulting in mature virions. Mature virions leave the host cell traversing the plasma membrane by budding.
As the virus is released, cell membranes are destroyed, and protoplasmic masses containing disrupted cell nuclei are formed. These protoplasmic masses are multinucleated giant cells called syncytia, they are responsible for naming the RSV «syncytial «.
How is it?
The Respiratory syncytial virus belongs to the subfamily Pneumovirinae, genre Pneumovirus, part of the Paramyxiviridae family.
The name of this virus comes from it’s capacity of making syncytia, as a cytopathic efect, in cell cultures. Syncytia are protoplasmic masses that contain nuclei of destroyed cells, these syncytia are introduced in the host cell forming multinucleate cells.
Syncytial viruses fusionate with host cells. RSV merges with cells that belong to the respiratory tract.
Myxoviruses are a group of spherical viruses with an helical virion. RSV is part of this group, it’s an enveloped virus, with a single strand of unsegmented linear RNA. It forms a helix with a diameter between 100 and 300nm. The RNA replicates in the host cell’s cytoplasm
We have to keep in mind that myxoviruses have affinity towards mucoproteins (such as mucin), serum, and certain epithelia and erythrocyte receptors.
It’s genome has various genes that encode different proteins:
-F gene: encodes proteins that allow penetration of the RSV in the host cell, merging the viral envelope with the plasma membrane of the cell. When the host cells melt together, syncytia are formed. F protein is immunogenic
– G gene: makes glycoproteins (spicules) that allow attachment of the virus to the cell. The G protein is immunogenic
– M gene: located in the inner part of the cover, encodes matrix proteins. M proteins give shape and stability to the envelope
– N gene: results in nucleoproteins
– P gene: encodes for phosphoproteins, proteins that bind covalently to the phosphoric acid
– L gene: known as the “large gene” because it’s the largest gene in the genome. It’s responsible for encoding polymerases
– M2 gene: encodes proteins found in the envelope
– SH gene: encodes shorter sequences of hydrophobic amino acids, arranged in the lipid envelope
The envelope is a fragile double layer with SH, F and G proteins on the surface. While SH protein allowes a hydrophobic behavior, F and G proteins induce the synthesis of neutralizing antibodies in the host cells due to the antigenic activity.
RSV has a single serotype, it’s divided in two groups: A and B (infections by subgroup A tend to be worse). These subgroups differ according to the antigenicity of the surface of the G protein
To begin
We are Carol Monzó and Estefanía Gómez, 3rd grade biology students in the University of Valencia. We opened up this blog to talk about the Human respiratory syncytial virus (RSV), a very appropiated virus to talk about during the winter months. From time to time, we will upload information concerning this virus. We hope you will find it interesting.