Background: Currently, the immunogenicity of influenza vaccines is assessed by\ndetecting an increase of hemagglutination inhibition (HI) antibodies. As neuraminidase (NA)-based\nimmunity may be significant in protecting against influenza infection, detection of neuraminidase\ninhibiting (NI) antibodies may improve the assessment of the immunogenicity of influenza vaccines.\nMethods: We investigated the immune response to NA in people after immunization with live\ninfluenza vaccines (LAIVs). A number of A/H7NX or A/H6NX viruses were used to detect NI\nantibodies, using an enzyme-linked lectin assay (ELLA). Results: Seasonal LAIV immunization\nstimulated an increase in NI antibodies not only to homologous A/H1N1 influenza, but also to\nA/H1N1pdm09 and A/H5N1 influenza. After A/17/California/09/38 (H1N1) pdm09 LAIV vaccination,\nthere was no statistical relationship between post-vaccinated antibody seroconversion and two surface\nglycoproteins in serum samples obtained from the same individuals (p = 0.24). Vaccination with LAIV\nof H5N2, H2N2, H7N3, and H7N9 subtypes led to 7%â??29.6% NI antibody seroconversions in the\nabsence of HI antibody conversions. There was relatively low coordination of hemagglutinin (HA)\nand NA antibody responses (r = 0.24â??0.59). Conclusions: The previously noted autonomy for HI and\nNI immune responses was confirmed when assessing the immunogenicity of LAIVs. Combining the\ntraditional HI test with the detection of NI antibodies can provide a more complete assessment of\nLAIV immunogenicity.
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