ALTERED ANTIBODY-RESPONSE TO INFLUENZA H1N1 VACCINE IN HEALTHY ELDERLY PEOPLE AS DETERMINED BY HI, ELISA, AND NEUTRALIZATION ASSAY

To determine the influence of ageing per se as well as of priming hist ories on the antibody response to influenza vaccination, haemagglutina tion inhibition (HI), ELISA IgG, IgA, IgM and neutralizing antibody ti tres were studied in 43 healthy young subjects (mean age 23 years) and 55 healthy elderly people (mean age 79 years). The HI and ELISA IgG r esponses to the A/Guizhou/54/89 strain (H3N2) for which both the young and the elderly had similar priming histories were equal. By contrast , the Hi and IgG responses to A/Taiwan/1/86 (H1N1), where the priming histories were different, were lower in the elderly (P < 0.05). influe nza-specific IgA responses in the elderly tended to be higher for all vaccine strains. Influenza-specific postvaccination IgM titres were si milar or tended to be higher in the elderly. A subgroup of elderly sub jects (18%) who did not express HI activity to the A/Taiwan/1/86 (H1N1 ) vaccine strain, reacted in the HI assay with the closely related A/S ingapore/6/86 (H1N1) strain. These elderly people, however, produced I gG antibodies which neutralized A/Taiwan/1/86 virus in vitro. It is co ncluded that the elderly are capable of mounting antibody responses si milar to those observed in the young. moreover, the observed age-relat ed differences in antibody responses to H1N1 strains are probably not due to ageing of the immune system itself, but are determined by diffe rences in priming histories. (C) 1998 Wiley-Liss, Inc.