Heterosubtype neutralizing responses to influenza A (H5N1) viruses are mediated by antibodies to virus haemagglutinin.
BACKGROUND
It is increasingly clear that influenza A infection induces cross-subtype neutralizing antibodies that may potentially confer protection against zoonotic infections. It is unclear whether this is mediated by antibodies to the neuraminidase (NA) or haemagglutinin (HA). We use pseudoviral particles (H5pp) coated with H5 haemagglutinin but not N1 neuraminidase to address this question. In this study, we investigate whether cross-neutralizing antibodies in persons unexposed to H5N1 is reactive to the H5 haemagglutinin.


RESULTS
We measured H5-neutralization antibody titers pre- and post-vaccination using the H5N1 micro-neutralization test (MN) and H5pp tests in subjects given seasonal vaccines and in selected sera from European elderly volunteers in a H5N1 vaccine trial who had detectable pre-vaccination H5N1 MN antibody titers. We found detectable (titer > or = 20) H5N1 neutralizing antibodies in a minority of pre-seasonal vaccine sera and evidence of a serological response to H5N1 in others after seasonal influenza vaccination. There was excellent correlation in the antibody titers between the H5N1 MN and H5pp tests. Similar correlations were found between MN and H5pp in the pre-vaccine sera from the cohort of H5N1 vaccine trial recipients.


CONCLUSIONS
Heterosubtype neutralizing antibody to H5N1 in healthy volunteers unexposed to H5N1 is mediated by cross-reaction to the H5 haemagglutinin.
Garcia
Jean-Michel
JM
HKU-Pasteur Research Centre, Hong Kong Special Administrative Region, China. jmgarcia@hku.hk
Pepin
Stephanie
S
Lagarde
Nadège
N
Ma
Edward S K
ES
Vogel
Frederick R
FR
Chan
Kwok H
KH
Chiu
Susan S S
SS
Peiris
J S M
JS
D000368:Aged; D000818:Animals; D000914:Antibodies, Viral / Q000737:chemistry; D002460:Cell Line; D002648:Child; D004285:Dogs; D005060:Europe; D006388:Hemagglutinins / Q000737:chemistry*; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology; D007251:Influenza, Human / Q000097:blood / Q000276:immunology* / Q000821:virology*; D008875:Middle Aged; D009439:Neuraminidase / Q000378:metabolism; D009500:Neutralization Tests
D000914:Antibodies, Viral; D006388:Hemagglutinins; D007252:Influenza Vaccines; D009439:Neuraminidase