Detection and Differentiation of Current Influenza B Viruses by the Microculture Enzyme-Linked Immunosorbent Assay Using Monoclonal Antibodies

To detect and differentiate current influenza B viruses of both evolutionary lineages, the sensitivity of a new variant of microcultural enzyme immunoassay (cell-ELISA) has been assessed using a panel of 16 monoclonal antibodies (mAbs) specific to hemagglutinin of influenza B viruses. Nasopharyngeal samples from patients with acute respiratory viral infections (ARVI) were analyzed. The cell-ELISA was tested for the detection of influenza B viruses in 192 PCR-positive clinical samples. The highest sensitivity in detection and differentiation of influenza B viruses of the Yamagata and Victoria evolutionary lineages was shown for 5B11 and 5B7 mAbs, respectively. The detection of Yamagata influenza B viruses with cell-ELISA in PCR-positive clinical samples obtained in 2018 showed a lower sensitivity (61.7%) compared to traditional methods, that is, isolation of viruses in cell culture with subsequent determination of their belonging to the evolutionary lineage in the hemagglutination inhibition test (HIT) using strain-specific immune sera of animals (95.0%). The sensitivity of cell-ELISA while detecting the more variable Victoria viruses depended on the pathogen circulation time. The level of virus identification in samples collected in 2016–2018 was comparable for cell-ELISA and the traditional method (71–80%). Some of the current viruses circulating in 2020‒2021 did not interact with immune sera obtained to the corresponding reference strains, which made it difficult to identify them by HIT. Thus, the viruses circulating at that time were identified using cell-ELISA with a higher frequency than by isolation and subsequent HIT (59.5 vs. 35.7%, p < 0.05). In addition to the identification of the evolutionary lineage, the use of mAb 9B5 in the cell-ELISA made it possible to detect deletion variants of the Victoria influenza B viruses circulating in Russia in 2018‒2022.