Determination of serum neutralization antibodies against seasonal influenza A strain H3N2 and the emerging strains 2009 H1N1 and avian H5N1

Abstract

Background: Humoral virus neutralizing activity is crucial in preventing influenza virus infection. However, the influenza neutralizing activity in the general population remains unclear. Methods: In this study we performed a serological survey of 200 blood donors from Guangzhou, China. Using a microneutralization (MN) assay, neutralizing activities against influenza A 2009 H1N1, H3N2 and H5N1 were measured. Anti-haemagglutinin antibody was assayed by haemagglutination inhibition (HI) test. Also, antibodies against M1 and M2 matrix proteins were measured using an enzyme-linked immunosorbent assay (ELISA). Results: By MN assay, 86% of the individuals showed neutralizing activity against H3N2, 11% against 2009 H1N1, and none against H5N1. The positive rate for H3N2 increased as the age of individuals increased. Interestingly, males displayed a 4 times higher positive rate against 2009 H1N1 than females. The results of ELISA revealed that 97.5% of the individuals had positive M1 titres and 21% had positive M2 titres. Furthermore, anti-haemagglutinin antibody had a much higher correlation with the neutralization activity than anti-M1 and anti-M2 antibodies. Conclusions: Neutralizing activities against H5N1 and 2009 H1N1 were low in the general population. Therefore, public health agencies should design strategies for preventing potential H5N1 and 2009 H1N1 pandemics.

Keywords::

• Serological survey
• 2009 pandemic H1N1
• seasonal strain H3N2
• emerging strain H5N1
• neutralizing antibody

Acknowledgements

We thank Dr Jinsong Liu for providing the M1 and M2 recombinant proteins and Dr Rong Zhou for the valuable suggestions. This work was supported by the National Basic Research Program (973) (Grant No. 2009CB522300, 2010CB530100), the Chinese Academy of Sciences (Grant No. KSCX1-YW-10), the Science and Technology Program of Guangdong Province, China (Grant No. 2007B030501012), and the Science and Technology Program of Guangzhou, China (Grant No. 2007Z1-E0111).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.