Lymphocyte subset analyses in healthy adults vaccinated with yellow fever 17DD virus

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% (SE ± 4%) to 61.15% (SE ± 4.2%), CD4⁺ T cells from 22.4% (SE ± 3.6%) to 39.17% (SE ± 2%) with 43% of these cells corresponding to CD4⁺CD45RO⁺ T cells, CD8⁺ T cells from 15.2% (SE ± 2.9%) to 27% (SE ± 3%) with 70% corresponding to CD8⁺CD45RO⁺ T cells in first-time vaccinees. In re-vaccinees, the CD3⁺ T cells increased from 50.7% (SE ± 3%) to 80% (SE ± 2.3%), CD4⁺ T cells from 24.9% (SE ± 1.4%) to 40% (SE ± 3%) presenting a percentage of 95% CD4⁺CD45RO⁺ T cells, CD8⁺ T cells from 19.7% (SE ± 1.8%) to 25% (SE ± 2%). Among CD8⁺CD38⁺ T cells there could be observed an increase from 15 to 41.6% in first-time vaccinees and 20.7 to 62.6% 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.

Keywords
yellow fever - vaccine - flow cytometry - neutralizing antibodies - lymphocyte subsets