Respiratory syncytial virus (RS virus)
Last reviewed: 23.04.2024
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RS virus is one of the most frequent pathogens of ARI in children of the first 2-3 years of life. It was first isolated in 1956 from a chimpanzee suffering from acute respiratory disease, and in 1957 R. Chenok (and others) isolated similar strains from children with acute respiratory disease.
The virion is spherical in shape, its diameter varies in individual particles from 120 to 200 nm. The genome is represented by a single-stranded unfragmented negative RNA with a mass of about 5.6 MD; it obviously carries 10 genes encoding 10 virus-specific proteins, of which 7 are part of the virion, and the rest are non-structural. The RS virus differs from other paramyxoviruses in that it does not have haemagglutinin and neuraminidase and does not have hemolytic activity. The structure of the genome is as follows: 3'-lC-lB-NPM-lA-GF-22K-L-5 '. Proteins G and F are glycoproteins, which are part of the supercapsid and form surface spines. Protein G secures the virus on sensitive cells, and protein F provides a fusion of two types: a) fusion of the membrane of the virus with the cell membrane and its lysosomes; b) the fusion of the infected cell with the adjacent uninfected cells, as a result of which syncytium is formed - a symplast from cells connected by cytoplasmic processes ("mesh tissue"). This phenomenon also served as the basis for calling the virus "respiratory syncytial." Proteins N, P and L (a polymerase complex containing transcriptase) are part of the nucleocapsid. The proteins M and K are connected with the inner surface of the virion supercapsid. The functions of the remaining proteins are not yet known. According to antigenic properties, there are two serovariants of the virus. The virus multiplies well in cultures of many strains of transfected cells (HeLa, HEp-2, etc.) with the manifestation of a characteristic cytopathic effect, as well as the formation of plaques; It is not cultivated in chick embryos. The RS virus is very labile and easily destroyed by freezing and thawing, when treated with fat solvents, detergents, various disinfectants; when heated to 55 "C perished in 5-10 minutes.
[Symptoms of respiratory syncytial infection
The source of infection is a sick person. Infection occurs by airborne droplets. The incubation period is 3-5 days. The virus multiplies in the epithelial cells of the respiratory tract, the process quickly spreads to their lower divisions. Especially severe respiratory syncytial infection occurs in children of the first six months of life in the form of bronchitis, bronchiolitis, pneumonia. In 75% of children of the age of three, antibodies to the virus are detected.
Postinfectious immunity is persistent and prolonged, it is caused by the appearance of viral neutralizing antibodies, immune memory cells and secretory antibodies of the IgA class.
Diagnosis of respiratory syncytial infection
Laboratory diagnosis of respiratory syncytial infection is based on the rapid detection of viral antigens in the nasopharyngeal discharge (the lungs, trachea, and bronchial tubes are examined in the dead) using the immunofluorescence method, the isolation and identification of the virus and the determination of specific antibodies. To isolate the virus, the culture material is infected with the test material, its propagation is judged by the characteristic cytopathic effect; the virus is identified by the immunofluorescence method, RSK and neutralization reaction in the cell culture. The serological method (RSK, PH) in children of the first six months of life, which have maternal antibodies in a titer of up to 1: 320, is not sufficiently reliable. To diagnose the disease, it is better to use methods of detecting specific antigens with the help of RIF or IFM.