Inactivated trivalent seasonal influenza vaccine induces limited cross-reactive neutralizing antibody responses against 2009 pandemic and 1934 PR8 H1N1 strains.
BACKGROUND
In June 2009, we conducted a prospective study in Singapore on 51 individuals to determine their serologic responses before and following receipt of the 2009 Southern Hemisphere seasonal influenza vaccine.


METHODS
Paired serum samples were obtained before and 3-4 weeks after vaccination. Virus microneutralization assays were performed to quantify antibodies against A/Brisbane/59/2007 vaccine, pandemic H1N1-2009 and A/Puerto Rico/08/34 H1N1 strains.


RESULTS
Post-vaccination, 43%, 12% and 24% of subjects displayed a 4-fold or greater rise in neutralizing antibody titers against the three strains, respectively. There was a positive correlation among individuals who showed increased titers to both pandemic H1N1-2009 and A/Puerto Rico/08/34 (p<0.001). However, this correlation was not observed for A/Brisbane/59/2007 with either strain. The relative conservation and accessibility of predicted B-cell epitopes may explain the limited cross-reactivity of the antibodies directed against common H1N1 epitopes.


CONCLUSIONS
These results suggest that seasonal influenza vaccination confers a certain degree of cross-protection to other H1N1 strains. The correlation in cross-reactive antibody titers to A/Puerto Rico/08/34 and pandemic H1N1-2009 implies that previous exposure to pre-1957 H1N1 strains may confer some protection against the 2009 pandemic strain.
Lee
Vernon J
VJ
Biodefence Center, Singapore Armed Forces, 701 Transit Road #04-01, Singapore 778910, Singapore. vernonljm@hotmail.com
Tay
Joshua K
JK
Chen
Mark I C
MI
Phoon
M C
MC
Xie
M L
ML
Wu
Y
Y
Lee
Cynthia X X
CX
Yap
Jonathan
J
Sakharkar
K R
KR
Sakharkar
M K
MK
Lin
Raymond T
RT
Cui
Lin
L
Kelly
Paul M
PM
Leo
Yee Sin
YS
Tan
Yee Joo
YJ
Chow
Vincent T K
VT
D000328:Adult; D057134:Antibodies, Neutralizing / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D056738:Cross Protection; D003429:Cross Reactions; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009500:Neutralization Tests; D011446:Prospective Studies; D015164:Vaccines, Inactivated / Q000276:immunology; D055815:Young Adult
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D018985:Epitopes, B-Lymphocyte; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated