Study of Antibodies to Influenza Neuraminidase N2.

Humoral immunity to influenza neuraminidase (NA) was evaluated among different groups of people including patients with acute influenza infection and healthy people in different age groups using an enzyme linked lectin assay (ELLA). The amino acid composition of NA of seasonal influenza viruses A/Victoria/361/2011(H3N2) and A/Hong Kong/4801/2014(H3N2) differed by 2%, while cross-reacting neuraminidase-inhibiting (NI) antibodies to them in the same serum samples were detected in 10% of cases. Middle-aged patients born from 1977 to 2000 had a high level of hemagglutination-inhibiting (HI) antibodies to A/Hong Kong/4801/2014(H3N2), but almost no NI antibodies, which may indicate that in the case of a change in the hemagglutinin (HA) subtype, this age group will be susceptible to influenza A/H3N2 viruses.

Study of Neuraminidase-Inhibiting Antibodies in Clinical Trials of Live Influenza Vaccines.

Background: Currently, the immunogenicity of influenza vaccines is assessed by detecting an increase of hemagglutination inhibition (HI) antibodies. As neuraminidase (NA)-based immunity may be significant in protecting against influenza infection, detection of neuraminidase inhibiting (NI) antibodies may improve the assessment of the immunogenicity of influenza vaccines.

Methods: We investigated the immune response to NA in people after immunization with live influenza vaccines (LAIVs).

Amino Acid Substitutions N123D and N149D in Hemagglutinin Molecule Enhance Immunigenicity of Live Attenuated Influenza H7N9 Vaccine Strain in Experiment.

We compared three cold-adapted live attenuated influenza vaccine strains prepared by reverse genetics methods on the basis of master donor virus A/Leningrad/134/17/57 and influenza H7N9 strains A/Anhui/1/2013 and A/Shanghai/1/2013. Two strains based on A/Anhui/1/2013 differed by amino acid positions 123 and 149 in HA1 (123N/149N; 123D/149D). All strains efficiently replicated in developing chicken embryos; A/Shanghai/1/2013-based strain and A/Anhui/1/2013-123N/149N variant were characterized by reduced replication in MDCK cells.

Safety, immunogenicity and protection of A(H3N2) live attenuated influenza vaccines containing wild-type nucleoprotein in a ferret model.

Live attenuated influenza vaccines (LAIVs) are promising tools for the induction of broad protection from influenza due to their ability to stimulate cross-reactive T cells against influenza pathogens. One of the major targets for cytotoxic T-cell immunity is viral nucleoprotein (NP), which is relatively conserved among antigenically distant influenza viruses. Nevertheless, a diversity of epitope composition has been found in the NP protein of different lineages of influenza A viruses.

Anti-neuraminidase antibodies against pandemic A/H1N1 influenza viruses in healthy and influenza-infected individuals.

The main objective of the study was to evaluate neuraminidase inhibiting (NI) antibodies against A/H1N1pdm09 influenza viruses in the community as a whole and after infection. We evaluated NI serum antibodies against A/California/07/09(H1N1)pdm and A/South Africa/3626/2013(H1N1)pdm in 134 blood donors of different ages using enzyme-linked lectin assay and in 15 paired sera from convalescents with laboratory confirmed influenza. The neuraminidase (NA) proteins of both A/H1N1pdm09 viruses had minimal genetic divergence, but demonstrated different enzymatic and antigenic properties.