[Source: PLoS ONE, full page: (LINK). Abstract, edited.]

Research Article

Heterosubtypic Antiviral Activity of Hemagglutinin-Specific Antibodies Induced by Intranasal Immunization with Inactivated Influenza Viruses in Mice

Mieko Muramatsu, Reiko Yoshida, Hiroko Miyamoto, Daisuke Tomabechi, Masahiro Kajihara, Junki Maruyama, Takashi Kimura, Rashid Manzoor, Kimihito Ito, Ayato Takada


Influenza A virus subtypes are classified on the basis of the antigenicity of their envelope glycoproteins, hemagglutinin (HA; H1?H17) and neuraminidase. Since HA-specific neutralizing antibodies are predominantly specific for a single HA subtype, the contribution of antibodies to the heterosubtypic immunity is not fully understood. In this study, mice were immunized intranasally or subcutaneously with viruses having the H1, H3, H5, H7, H9, or H13 HA subtype, and cross-reactivities of induced IgG and IgA antibodies to recombinant HAs of the H1?H16 subtypes were analyzed. We found that both subcutaneous and intranasal immunizations induced antibody responses to multiple HAs of different subtypes, whereas IgA was not detected remarkably in mice immunized subcutaneously. Using serum, nasal wash, and trachea-lung wash samples of H9 virus-immunized mice, neutralizing activities of cross-reactive antibodies were then evaluated by plaque-reduction assays. As expected, no heterosubtypic neutralizing activity was detected by a standard neutralization test in which viruses were mixed with antibodies prior to inoculation into cultured cells. Interestingly, however, a remarkable reduction of plaque formation and extracellular release of the H12 virus, which was bound by the H9-induced cross-reactive antibodies, was observed when infected cells were subsequently cultured with the samples containing HA-specific cross-reactive IgA. This heterosubtypic plaque reduction was interfered when the samples were pretreated with anti-mouse IgA polyclonal serum. These results suggest that the majority of HA-specific cross-reactive IgG and IgA antibodies produced by immunization do not block cellular entry of viruses, but cross-reactive IgA may have the potential to inhibit viral egress from infected cells and thus to play a role in heterosubtypic immunity against influenza A viruses.

Citation: Muramatsu M, Yoshida R, Miyamoto H, Tomabechi D, Kajihara M, et al. (2013) Heterosubtypic Antiviral Activity of Hemagglutinin-Specific Antibodies Induced by Intranasal Immunization with Inactivated Influenza Viruses in Mice. PLoS ONE 8(8): e71534. doi:10.1371/journal.pone.0071534

Editor: Gary P. Kobinger, Public Health Agency of Canada, Canada

Received: April 12, 2013; Accepted: June 28, 2013; Published: August 16, 2013

Copyright: ? 2013 Muramatsu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was funded by the Japan Initiative for the Global Research Network on Infectious Diseases (J-GRID) (http://www.crnid.riken.jp/jgrid/en/), the Global COE Program (http://www.jsps.go.jp/english/index.html), the Japan Science and Technology Agency Basic Research Programs (http://www.jst.go.jp/EN/), and the Ministry of Education, Culture, Sports, Science and Technology (http://www.mext.go.jp/english/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.