Aged mice produce reduced serum titers of class switched antibody and reduced neutralization titers following de novo γHV68 infection. Serum titers of γHV68-specific IgM (A) and IgG (B) were measured by ELISA in young (3 months old, closed symbols) and aged (19-24 months old, open symbols) C57BL/6 mice at 15, 30, and 60 days post infection. (C) The virus neutralization activity of sera at 34, 45, and 60 days post infection was determined as described in the Materials and Methods. Each symbol represents data obtained from an individual mouse and bars indicate the medians calculated from the data shown. Statistical significance was determined using the Mann-Whitney test.**; P ≤ 0.01. *; P ≤ 0.05.