Structure and antigenic properties
RSV is a classic representative of the genus Pneumovirus. Inside the polymorphic virion, which can be either spherical or filamentous, lies the genetic material—single-stranded helical negative-sense RNA.
Unlike many other paramyxoviruses, this pathogen completely lacks the surface enzymes hemagglutinin and neuraminidase. The outer lipoprotein envelope contains specific structural proteins that play a key role in the infectious process:
- Glycoprotein G—ensures adhesion, i.e., the binding of the virion to the receptors of a susceptible cell.
- Glycoprotein F (from English fusion)—is responsible for the fusion of the viral envelope with the cell membrane. It is this protein that triggers the formation of characteristic syncytia.
- SH protein (small hydrophobic)—functions as a transmembrane protein.
The antigenic structure allows the virus to be divided into two main serogroups: A and B.
Epidemiology and stability
The only source of infection in nature is an infected human. Transmission occurs via two main routes:
- Aerosol (classic airborne mechanism via coughing or sneezing).
- Contact-fomite (transmission via contaminated hands, household items, and linens).
The pathogen is highly contagious and accounts for 3 to 16% of all registered acute respiratory infections (ARIs). The virus circulates actively in the population: by the age of three, 75% of children already show protective virus-neutralizing antibodies (IgA).
Despite its high contagiousness, the virus is extremely unstable in the external environment. It is rapidly inactivated by standard physical and chemical factors.
Pathogenesis and clinical presentation
The portal of entry for the infection is the upper respiratory tract epithelium. Following the incubation period, the virus begins to actively replicate in epithelial cells, leading to their destruction.
The disease manifests as a typical ARI, but the infection tends to rapidly spread to the lower respiratory tract, causing tracheobronchitis or pneumonia. The pathological process is exacerbated by the formation of immune complexes, which trigger immunopathological reactions that enhance lung tissue damage. Concurrently, secondary immunodeficiency develops against the background of the infection.
The clinical course strongly depends on age. In older children and adults, RSV infection usually runs a mild course. However, for infants in their first six months of life, it poses a serious threat due to the high risk of respiratory failure.
Principles of microbiological diagnostics
To isolate the pathogen, nasopharyngeal secretions or lung tissue samples are sent to the laboratory. A strict rule of the pre-analytical phase: the test material must under no circumstances be frozen.
The core of diagnostics is the classic virological method—inoculation of cell cultures (e.g., continuous lines or primary monkey kidney cultures).
- Virus indication is carried out based on its specific cytopathic effect (CPE)—the formation of multinucleated giant cells (symplasts) and syncytia.
- Identification is performed using the neutralization test (NT), complement fixation test (CFT), or molecular genetic methods such as RT-PCR.
Briefly: answers to topical questions
What classic lower respiratory tract disease (besides pneumonia) is the hallmark of RSV infection in infants?
The classic lower respiratory tract disease characteristic of respiratory syncytial virus infection in infants is acute bronchiolitis. This inflammatory condition predominantly affects the small bronchi and bronchioles in young children (especially during the first year of life). RSV serves as the primary causative agent of this pathology, which is frequently a clinical manifestation of acute viral respiratory infection in this age group. In infants during their first months of life, the virus can also cause severe bronchitis.
What agents are used for specific passive immunoprophylaxis of RSV infection in premature infants and risk groups?
For specific passive immunoprophylaxis of respiratory syncytial virus infection in high-risk infants, the monoclonal antibody palivizumab (Synagis), which is specific to RSV, is used. The drug is administered intramuscularly during the seasonal peak of incidence. For patients with 5q spinal muscular atrophy, palivizumab is indicated during the first two years of life.
What rapid diagnostic methods are used for the direct detection of RSV antigens in nasopharyngeal swabs?
For the direct detection of respiratory syncytial virus antigens in nasopharyngeal mucosa swabs, the following rapid diagnostic methods are used:
- Immunochromatographic assay (ICA)—allows rapid identification of pathogen antigens for the timely initiation of etiotropic therapy.
- Immunofluorescence assay (IFA)—used in direct and indirect modifications to detect viral antigens directly within cells.
- Enzyme-linked immunosorbent assay (ELISA)—also used for antigen detection in the test material.
The optimal timeframe for performing rapid testing is the first two days from the onset of symptoms.
The functions of the glycoproteins are easy to remember by their initial letters: G — Readiness to attach (adhesion to receptors), F — Formation of syncytia (fusion of membranes).
Class and exam questions
Why is the virus called "syncytial"?
The virus got its name from its characteristic cytopathic effect. In cell culture, it causes the membranes of adjacent infected cells to fuse, forming giant multinucleated structures — symplasts and syncytia.
Does lasting immunity develop after overcoming the infection?
No, post-infection immunity is short-lived. Repeated episodes of the disease (reinfection) are possible, although they generally run a significantly milder course.
How does the virus attach to cells if it lacks hemagglutinin?
The function of attachment to susceptible target cell receptors in RSV is carried out by the specific surface glycoprotein G.
What else to study on this topic
- Molecular organization and replication of single-stranded negative-sense RNA
- Mechanism of immune complex formation in RSV infection
- Features of RSV cultivation in primary monkey kidney cultures
- Differential diagnosis of RSV and other members of the Paramyxoviridae family
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