Human respiratory syncytial virus
A Microbial Biorealm page on the genus Human respiratory syncytial virus
Classification
Higher order taxa
Viruses; ssRNA viruses; ssRNA negative-strand viruses; Mononegavirales; Paramyxoviridae; Pneumovirinae; Pneumovirus
Species
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NCBI: Taxonomy |
Genus species
Description and significance
Human Respiratory Syncytial Virus was first isolated in 1956 from a laboratory chimpanzee with a respiratory illness and was later discovered to be of human origin. RSV consists of two antigenic subtypes, A and B. Subtype B is characterized as the asymptomatic strains that of which the majority of individuals experiences. The more severeillnesses and which usually predominate during outbreaks are associated with subtype A strains. RSV was determined to be the leading cause of lower respiratory tract infections particularly in young infants. The severity of the disease is very diverse ranging from mild cold symptoms to severe and life-threatening. It's the leading cause of pneumonia and bronchiolitis in infants. It may cause mortality or morbidity in the elderly as well as immunodeficient individuals. It is the most common pathogen leading to hospitalization in young children up to the age of 5. Approximately two thirds of infants are infected with RSV within their first year and 90% have been infected by the age of 2.
Genome Structure
The genome of RSV was completely sequenced in 1997. It is a linear single stranded negative-sense RNA consisting of 15,191 base pairs. The genome is found in the helical nucleocapsid. The genome encodes for 11 proteins including structural and non-structural. The virion of the RSV is enveloped with a lipid bilayer, which is obtained from the host’s plasma membrane. It contains three surface glycoproteins, the attachment protein G, fusion protein F, and the small hydrophobic SH protein, which are separated from each other and can be seen as “spikes” that project out of the virion. The glycoproteins can be measured to be about 11-20nm in size, while the virion appears to be about 150-300nm in diameter. The major function of the F protein is to direct viral penetration by the fusion between the virion and the host plasma membrane. The F protein is also able to mediate fusion with other neighboring cells forming syncytia, when it is expressed on the cell surface. The glycoprotein, G, is a type II transmembrane glycoprotein and is the major RSV attachment protein. It contains a single hydrophobic region which serves as a signal peptide and also as a membrane anchor. The small hydrophobic SH protein is a short integral membrane protein whose function is unknown. However, it is suggested that the SH protein enhances the function of the attachment protein and or fusion protein. Another RSV protein is the matrix protein M, located in the inner layer of the lipid bilayer, and is found to play a role in the formation of virus-like particles. These four proteins are used to form the viral envelop. The non-structural proteins are NS1 and NS2, these proteins enhance viral growth but are not essential. The virion consists of a nucleocapsid which is contained in the lipid bilayer. The nucleocapsid has a symmetrical helix shape and is measured to be about 12-15nm in diameter. There are four nucleocapsid proteins inside the virion which carry out the replication and transcription of the RSV genome, the nucleocapsid protein N, the phosphoprotein P, the antitermination factor M2-1, and the large polymerase subunit L. The RSV nucleocapsid N protein binds to genomic and antigenomic RNA and forms an RNAse-resistant nucleocapsid. This provides protection of the viral RNA from the toll-like receptors and RNA recognition helicases that initiate immune responses. In order for the N protein to encapsidate minigenome RNAs the help of the P protein is required. The P protein acts as a chaperonin for the N protein, without it the N protein would be incapable to binding to minigenome RNA. The L protein is responsible for all enzymatic activity and the M2-1 protein is a transcription antitermination factor which is crucial for viral viability. Proteins M2-1 and M2-1 are both play important roles in balancing transcription and RNA replication.
Cell structure and metabolism
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Ecology
Habitat; symbiosis; contributions to the environment.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Current Research
Enter summarries of the most rescent research here--at least three required
References
Edited by student of Emily Lilly at University of Massachusetts Dartmouth.
