Serum titers of γHV68-specific antibody are maintained in latently infected mice with age, but serum neutralization activity wanes. The titers of virus-specific IgG were measured in the serum of latently-infected young (1-3 months p.i.) and aged (18-22 months p.i.) by ELISA (Panel A). Neutralization activity (measured in the same sera samples as A) were determined using an in vitro neutralization assay (Panel B). As a control, antibody titers (C) and neutralization activity (D) were measured in serum taken from mice (young and aged, as above) previously infected with influenza virus ×31. Symbols represent serum antibody titers and neutralization activities measured for individual mice. Bars indicate the medians calculated from the data shown. Significance was assessed using the Mann-Whitney rank test (two-tailed, 95% confidence). Ns; not significant.