Expression of interleukin-2 (IL-2) receptor alpha and CD45RO antigen on T-lymphocytes cultured with measles virus antigens, compared with humoral immunity in measles vaccinees.

In response to two types of measles virus (MV) antigens, a vaccine strain CAM and a wild strain isolated in 1994, the expression of IL-2 receptor alpha (CD25)(+)CD45RO(+)CD4(+) T-lymphocytes (T-cell activation) was analyzed by flow cytometry. In 75 healthy subjects with measles hemagglutination inhibition tests > or =1:16, the percentage of T-cell activation was significantly increased compared with that in seronegative individuals (p) < 0.05). Moreover, the T-cell expression was not significantly different among the vaccinated (n = 38), the naturally infected (n = 28) and the subclinically infected (exposed with wild type without history of measles infection and HI titers > or =1:16) (n = 10) groups. T-cell activation stimulated with MV antigens and HI antibody titers persisted for almost 30 years in the vaccinated group. These results suggest that cell-mediated immunity persists for long periods after vaccination and does not be influenced by antigenic drift.