ABSTRACT
In this study the kinetics of humoral and cellular immune responses in first-time vaccinees and re-vaccinees with the yellow fever 17DD vaccine virus was analyzed. Flow cytometric analyses were used to determine percentual values of T and B cells in parallel to the yellow fever neutralizing antibody production. All lymphocyte subsets analyzed were augmented around the 30th post vaccination day, both for first-time vaccinees and re-vaccinees. CD3+ T cells increased from 30.8 percent (SE ± 4 percent) to 61.15 percent (SE ± 4.2 percent), CD4+ T cells from 22.4 percent (SE ± 3.6 percent) to 39.17 percent (SE ± 2 percent) with 43 percent of these cells corresponding to CD4+CD45RO+ T cells, CD8+ T cells from 15.2 percent (SE ± 2.9 percent) to 27 percent (SE ± 3 percent) with 70 percent corresponding to CD8+CD45RO+ T cells in first-time vaccinees. In re-vaccinees, the CD3+ T cells increased from 50.7 percent (SE ± 3 percent) to 80 percent (SE ± 2.3 percent), CD4+ T cells from 24.9 percent (SE ± 1.4 percent) to 40 percent (SE ± 3 percent) presenting a percentage of 95 percent CD4+CD45RO+ T cells, CD8+ T cells from 19.7 percent (SE ± 1.8 percent) to 25 percent (SE ± 2 percent). Among CD8+CD38+ T cells there could be observed an increase from 15 to 41.6 percent in first-time vaccinees and 20.7 to 62.6 percent in re-vaccinees. Regarding neutralizing antibodies, the re-vaccinees presented high titers even before re-vaccination. The levels of neutralizing antibodies of first-time vaccinees were similar to those presented by re-vaccinees at day 30 after vaccination, indicating the success of primary vaccination. Our data provide a basis for further studies on immunological behavior of the YF 17DD vaccine.