Detection of influenza A virus homo‐ and heterosubtype‐specific memory B‐cells using a novel protein microarray‐based analysis tool

The emergence of the A(H1N1) 2009 pandemic influenza virus was initially seen as a major world‐wide health concern since a low degree of immunity to this virus strain was anticipated. However, age‐specific infection attack rates and age‐specific differences in seroresponse indicate that pre‐existing immunity may have played a significant role in protection especially in older age groups. This study describes the use of a protein microarray as a multiplex analysis tool for detection of influenza virus H1 strain‐specific memory B‐cells before and after infection with A(H1N1)pdm09. The discrimination was based on detection of specific antibodies in culture supernatants from polyclonally stimulated B‐cells against recombinant influenza virus HA1 proteins representing influenza virus subtypes H1 through H9. The protein microarray proved sensitive and specific for antibody detection in culture supernatants of B‐cells, and with the potential to deduce a person's history of infection with particular influenza virus variants, including A(H1N1)pdm09. Blood samples obtained from different age groups prior to the pandemic in 2009 partly showed the presence of B‐cells producing antibodies binding to the closely related A(H1N1) 1918 pandemic influenza virus, and of which the magnitude increased with age. These cross‐reactive antibodies were produced by single memory B‐cells present in these donors, and either bind to epitopes on HA1 which are shared within different H1 strains (homosubtypic response) or shared between different subtypes (heterosubtypic response). J. Med. Virol. 85:899–909, 2013. © 2013 Wiley Periodicals, Inc.