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Influenza: antibodies to influenza A and B blood virus
Last reviewed: 05.07.2025
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The causative agents of influenza belong to the family of orthomyxoviruses, the genus Influenzavirus, which includes two types of influenza viruses: A and B. Influenza viruses contain RNA and an outer membrane in which two antigens (hemagglutinin and neuramidinase) are located, capable of changing their properties, especially in the influenza virus type A. To diagnose the disease, the immunofluorescence method (direct and indirect) is used, which allows detecting the influenza virus in discharge from the upper respiratory tract or nasal swabs (sensitivity - 58-100%, specificity - 88-100%), as well as detection of NP-antigen (nucleoprotein protein associated with RNA) or M-protein (the main protein of the viral particle) of the influenza virus by the ELISA method (sensitivity - 40-100%, specificity - 52-100%).
To detect antibodies to influenza viruses, RSK or ELISA are used. With RSK, the study is carried out at the onset of the disease (1-2 days) and after 5-7 days; an increase in the antibody titer of at least 4 times when examining paired sera is considered diagnostic.
The ELISA method is characterized by greater sensitivity (according to various authors, from 39% to 100%) and very high specificity. As with the RSC, for the diagnostic use of ELISA, it is necessary to compare the antibody content in serum samples obtained from patients at the beginning and end of the disease.
Determination of the content of antibodies to influenza A and B viruses is used to diagnose acute respiratory viral infections, assess the intensity of post-vaccination immunity, and diagnose influenza A and B.
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