The study of heterosubtypic neutralising antibody responses against H5N1 influenza viruses in human subjects using a comparative serology approach

The continuous rapid genetic and antigenic evolution of H5 subtype

influenza viruses has major implications for the sensitivity of serological

assays and can limit the efficacy of pre-pandemic human vaccines and the

ability to undertake effective sero-surveillance in susceptible populations.

A panel of serum samples collected from the Italian population between

1992 and 2007 and previously found to be positive for antibodies against

H5N1 as determined by SRH, were evaluated using pseudotype based

neutralisation assays in combination with haemagglutination-inhibition

assays using a clade 1 and a clade 2 H5N1 serological antigen. From

the results obtained it can be concluded that the pseudotype assay

measures cross-reactive antibody responses that are not picked up with

the HI assay. Both assays measure antibodies with different (functional)

specificities contributing to a comprehensive analysis of humoral

immunity to influenza viruses.