Respiratory syncytial infection is an acute viral disease characterized by phenomena of intoxication and moderate lesion predominantly lower divisions Respiratory with the frequent development of bronchitis, bronchiolitis and pneumonia.
A characteristic feature of this virus is its ability to determine syncytium formation or cells in tissue culture. Replicates in tissue culture HeLa, HEp-2 and human embryonic kidney. In the external environment is unstable at a temperature of 55 ° C is inactivated for 5 min.
A study of the pathogenesis of this disease is difficult. The clinical course of the disease, both natural and experimental infection among adults, does not reflect the essence of the process of developing among children, as adults disease often occurs as an acute respiratory illness. It is believed that the PC-infection is the leading pathology of the lower respiratory tract and the most characteristic - a heavy defeat bronchioles.
Inflammatory changes develop in the initial period of the mucous membrane of the nose and throat in adults, defeat these departments may be limited to the process. Among children (under the age of usually affects) bronchioles and lung parenchyma with the presence of necrosis of the tracheobronchial epithelium and necrotic obstructive bronchiolitis, leads to plugging of the bronchi lumps of mucus. Spasm leads to the formation of atelectasis and emphysema, which contributes to the emergence of viral and bacterial pneumonias.
Infection occurs through airborne droplets. The virus reproduces itself in the epithelial cells of the mucous membrane of the upper and lower respiratory tract. SIgA becomes important . Immunity lasts no more than 1 year. Repeated diseases are common, especially among children, even with the presence of antibodies in the serum. This is possibly due to the existence of several serotypes of the virus. PC-virus possesses immunosuppressive properties, resulting in depression of cellular and humoral immunity reactions. This explains the high incidence of secondary bacterial infections. When PC-infection develops immunopathological reactions associated with the formation of infectious immune complexes. PC-infection is often the main cause of severe nosocomial pneumonia in the wards for infants and young children. The severity of diseases caused by PC-virus, is reduced with time. Vaccine prophylaxis is not applicable.
Virulence.
The virulence of the RS virus is running in following way (mechanism):
The virus attaches to cell via F fusion and G attachment glycoproteins. Then, it penetrates the membrane of the cell and adds RNA into cell. The next step is a replication itself using cellular machinery. Viral RNA then covers into just synthesized RSV particles and then releases. In addition the host cell may die after the process. And the last step is the final stage when virus keeps on infection other healthy cells and develops the disease.
Virulence factors of this virus are:
-RSV virions contain two noteworthy envelope glycoproteins, F and G
-hmpv and hpiv have 2 envelope proteins, F and HN
-F protein is in charge of combination of the viral envelope with the plasma layer of the cell and is therefor discriminating for infection section
-cells tainted with these infections can combine w neighboring cells because of interpretation of the F and HN or G proteins on the contaminated cell surface. This cell-cell combination brings about syncytia development, which is the way RSV got its name
-HN and G are the receptor tying proteins
-the cell surface receptor for hmpv and hpivs is sialic corrosive found on the bodily fluid delivering epithelial cells lining the respiratory tract
-RSV ties to the Gags and to nucleolin which is a protein found on numerous cells sorts and found in cell surface and core
-the essential tissues focused in the lungs are the aviation route epithelial cells, despite the fact that RSV can contaminate dendritic cells in the lung. (Kahn et al., 2001)
Bibliography
Gonzalez, A. (2010). Global burden of acute lower respiratory
infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis. The Lancet, 375(9725), pp.1545-1555.
Kahn, J., Roberts, A., Weibel, C., Buonocore, L. and Rose, J. (2001). Replication-Competent or Attenuated, Nonpropagating Vesicular Stomatitis Viruses Expressing Respiratory Syncytial Virus (RSV) Antigens Protect Mice against RSV Challenge. Journal of Virology, 75(22), pp.11079-11087.
Mdtx.com, (2009). MDT-637. [online] Available at: http://mdtx.com/pipeline/proprietary-products/mdt-637/ [Accessed 21 Nov. 2014].
Surya,, W. (2013). Structural and Functional Aspects of Viroporins in Human Respiratory Viruses: Respiratory Syncytial Virus and Coronaviruses. [online] CDN. Available at: http://cdn.intechopen.com/pdfs-wm/42381.pdf [Accessed 21 Nov. 2014].
