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PLoS Pathog. 2019 Jan 3;15(1):e1007427. doi: 10.1371/journal.ppat.1007427. eCollection 2019 Jan.

IgA tetramerization improves target breadth but not peak potency of functionality of anti-influenza virus broadly neutralizing antibody.

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Department of Pathology, National Institute of Infectious Diseases, Shinjuku, Tokyo, Japan.
Influenza Virus Research Center, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan.
Division of Infectious Diseases Pathology, Department of Global Infectious Diseases, Tohoku Graduate School of Medicine, Sendai, Miyagi, Japan.
Nippi Research Institute of Biomatrix, Toride, Ibaraki, Japan.
Department of Life Science and Medical Bioscience, Waseda University, Shinjuku, Tokyo, Japan.
National Institute of Health Research and Development, Ministry of Health RI, Jakarta, Indonesia.


Mucosal immunoglobulins comprise mainly secretory IgA antibodies (SIgAs), which are the major contributor to pathogen-specific immune responses in mucosal tissues. These SIgAs are highly heterogeneous in terms of their quaternary structure. A recent report shows that the polymerization status of SIgA defines their functionality in the human upper respiratory mucosa. Higher order polymerization of SIgA (i.e., tetramers) leads to a marked increase in neutralizing activity against influenza viruses. However, the precise molecular mechanisms underlying the effects of SIgA polymerization remain elusive. Here, we developed a method for generating recombinant tetrameric monoclonal SIgAs. We then compared the anti-viral activities of these tetrameric SIgAs, which possessed variable regions identical to that of a broadly neutralizing anti-influenza antibody F045-092 against influenza A viruses, with that of monomeric IgG or IgA. The tetrameric SIgA showed anti-viral inhibitory activity superior to that of other forms only when the antibody exhibits low-affinity binding to the target. By contrast, SIgA tetramerization did not substantially modify anti-viral activity against targets with high-affinity binding. Taken together, the data suggest that tetramerization of SIgA improved target breadth, but not peak potency of antiviral functions of the broadly neutralizing anti-influenza antibody. This phenomenon presumably represents one of the mechanisms by which SIgAs present in human respiratory mucosa prevent infection by antigen-drifted influenza viruses. Understanding the mechanisms involved in cross neutralization of viruses by SIgAs might facilitate the development of vaccine strategies against viral infection of mucosal tissues.

Conflict of interest statement

National Institute of Infectious Diseases and Nippi, Inc. have filed patents regarding construction and use of tetrameric SIgA (application no. PCT/JP2015/070742). SS, TS, AA, YT, TU, KOG and HH are named as inventors on the application. YT, TU, and KOG are employees of Nippi, Inc.

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