Development and durability of measles antigen-specific lymphoproliferativeresponse after MMR vaccination

The correlates of long-term protection from measles infection are poorly un derstood. We followed the development of measles-specific antibody and lymp hoproliferative (LP) responses in 60 children for 6 months after MMR vaccin ation. Prevaccine plaque reduction neutralization antibody (PRN Ab) values were low (mean +/- SEM 9.9 +/- 1.1). Ninety-three percent (56/60) had excel lent PRN values at 6 months (PRN 1816 +/- 207). Prevaccine LP activity was also low (stimulation index (SI)= 1.4 +/- 0.1) but increased rapidly (SI 10 .7 +/- 4.5 at 2-3 weeks; p < 0.05). However, only 61% (37/60) of the childr en had both significant cellular and antibody responses (SI greater than or equal to 3 and PRN greater than or equal to 120. Ab(hi)CMI(hi)). One child had a strong LP response (SI = 6.7) despite little antibody production (PR N = 19 at 6 months: Ab(lo)CMI(hi)). We also conducted a cross-sectional stu dy in a separate group of 87 children 5-13 years after MMR vaccination. PRN values greater than or equal to 120 were present in most children at 5-8 ( n = 28) and 9-13 years (n = 59) after vaccination (PRN 550 +/- 120 and 360 +/- 60, respectively) but a significant minority had either undetected or ' subprotective' values (29 and 34%, respectively). LP responses (SI greater than or equal to 3) were detectable in 19/28 (66%) and 36/59 (56%) of the c hildren 5-8 and 9-13 years after vaccination (SI 11.4 +/- 2.4 and 7.75 +/- 1.9, respectively). Almost two thirds (18/28) of the children in the cross- sectional study with low or absent antibody titers (PRN 41 +/- 6) had stron g LP responses to measles antigens (SI 6.8 +/- 1.3). These data suggest tha t LP responses may be better sustained than antibody titers in some childre n. The susceptibility of Ab(lo)CMI(hi) children to infection and the value of the early LP response for predicting the durability of immunity remain t o be determined. (C) 2000 Elsevier Science Ltd. All rights reserved.