Comparative analysis of host responses related to immunosuppression between measles patients and vaccine recipients with live attenuated measles vaccines

Measles virus infection induces a profound immunosuppression. We analyzed i n a time-dependent manner peripheral bloods of one to two-year-old children immunized with live attenuated measles vaccines, compared with age-matched measles patients, for immunosuppression. In contrast to transient severe l ymphopenia with measles patients, primarily due to extensive apoptosis of a broad spectrum of uninfected lymphocytes, neither apoptosis nor lymphopeni a occurred with measles vaccine recipients. Increase in number and activati on of NK cells, which might compensate for the lymphopenia in measles patie nts, were not found with the vaccinees. While cell surface expression of ap optosis-related molecules such as TNF-related apoptosis-inducing ligand (TR AIL), TRAIL-receptors, CD95(Fas) and Fas-ligand, and plasma interferon-gamm a were increased for measles patients, they remained unchanged after vaccin ation. Plasma interleukin (IL)-18, which is responsible for inducing apopto sis in several infectious diseases, was increased predominantly with measle s patients, whereas the increase remained marginal with the vaccinees. IL-1 0 was elevated transiently in both measles patients and vaccinees. Decrease in plasma IL-12, which is often correlated with T cell suppression, was no t found for both cases. Serum IgM and IgG antibodies to measles virus were induced at lower titers in the vaccinees than measles patients. These resul ts indicate that in contrast to wild-type measles virus, live measles vacci nes hardly provoked host cytokine responses that lead to apoptotic cytolysi s of uninfected lymphocytes, lymphopenia and immunosuppression, and thereby induced weaker immune responses to the virus.