Comparison of respiratory syncytial virus humoral immunity and response to infection in young and elderly adults.

Little information about immunity to respiratory syncytial virus (RSV) and disease pathogenesis in elderly persons exists. Humoral immunity to RSV was assessed in 41 young, 56 healthy elderly, and 49 frail elderly adults by measuring baseline RSV specific IgG by enzyme immunoassay (EIA) and microneutralization assay (MNA) in serum. A comparison of the immune response of 11 young and 28 elderly persons with natural RSV infection was also performed. Despite significant differences in age and functional status, no decreases in RSV antibody levels by either EIA or MNA were noted in the elderly compared with the young. Mean baseline MNA titers expressed as log2 were 10.5 +/- 1.1 for the young, 10.5 +/- 1.5 for the healthy elderly, and 10.9 +/- 1.6 for the frail elderly. The frail elderly who attend a daycare had the highest RSV titers to F by EIA at 16.6 +/- 2.0, compared with 15.4 +/- 1.4 and 15.1 +/- 1.4 in the healthy elderly and young, respectively. This finding may reflect recent infection due to their communal setting or increased production of non-neutralizing antibody. The immune response of older persons to RSV infection was as vigorous as the younger subjects, with 79% having a >/=fourfold rise in MNA titers compared to 64% in the young. These data suggest that the severe clinical manifestations of RSV in the elderly are not due to a significant defect in humoral immunity. Copyright 1999 Wiley-Liss, Inc.