Kihei Terada, Kimiko Hagihara, Yuhei Tanaka, Hideto Teranishi, Tomohiro Oishi, Ippei Miyata, Satoko Ogita, Naoki Ohno and Kazunobu Ouchi
Objective: This study measured cell-mediated immunity (CMI) and serum antibody levels against rubella to clarify antibody changes associated with CMI during 2 years after vaccination.
Methods: The study subjects were 64 college students in two groups: 38 subjects who (having exhibited hemagglutination-inhibition (HI) anti-rubella antibody titers of ≤ 1:16) had been vaccinated with a rubella vaccine 2 years previously (Group 1); and 26 subjects who (having exhibited HI titers ≥ 1:32) had not been vaccinated 2 years previously (Group 2). All students were tested for IgG antibody levels (by enzyme-linked immunosorbent assay) and CMI (by interferon-γ (IFN-γ release assay).
Results: The IgG antibody and IFN-γ values decreased significantly in Group 1 during the 2 years postvaccination, while antibody titers in Group 2 did not decrease over this interval. The proportion of Group-1 individuals with HI antibody titers ≤ 1:16 increased to 27/38 (71.1%) at two years following vaccination, compared with 6/26 (23.1%) in Group 2. No correlation of IgG antibody titers was observed in Group 1 between one month and two years after vaccination. However, a strong correlation (r=0.85, p<0.00001) was detected in Group 2 between two years ago and the present. The correlation of IFN-γ values in Group 1 between one month and two years after vaccination was 0.614 (p<0.00005). When the subjects were classified by CMI status, the numbers of individuals who were intermediate and negative for IgG antibody at two years after vaccination were 1 and 0 of 13 subjects, 3 and 1 of 9 subjects, and 3 and 2 of 16 subjects in Group 1, respectively, while the antibody-positive status was maintained in all subjects in Group 2.
Conclusion: The IgG antibody and IFN-γ values decreased in distinct ways during the 2 years of the study; the persistence of the seropositivity was associated with CMI status.