GENERATION OF DIVERSITY IN THE HIERARCHY OF T-CELL EPITOPE RESPONSES FOLLOWING DIFFERENT ROUTES OF IMMUNIZATION WITH SIMIAN IMMUNODEFICIENCY VIRUS PROTEIN

Objectives: To examine whether the route of immunization determines the hierarchy of T-cell epitope proliferative responses in macaques. Design: Macaques were immunized with a recombinant simian immunodeficiency virus (SIV) p27 core protein by the intramuscular, male and female genital or rectal route, each of which was augmented by oral immunization, and by the novel targeted lymph-node immunization route. Overlapping peptides were used to identify the proliferative T-cell epitopes and to determine their hierarchy in the circulation, spleen and lymph nodes. Methods: T-cell epitope mapping of the proliferative responses was studied in short-term cell lines. Dendritic cells and macrophages were enriched by metrizamide gradient and adherence to plastic, respectively. Results: Intramuscular immunization elicited in the circulating T cells a hierarchy of T-cell epitopes within four peptides in the following descending order of frequency: peptides 121-140 (57.9%), 41-60 (28.9%), 61-80 (18.9%) and 101-120 (5.4%). The hierarchy of these four T-cell epitope responses differed significantly with each of the five routes of immunization, when circulating (P<0.001), splenic (P<0.02-<0.001) or iliac lymph-node cells (P<0.001) were analysed. The effect of antigen-presenting cells was then investigated and enriched dendritic cells were more effective than macrophages in processing and presenting the p27 antigen and the immunodominant (121-140) and 61-80 T-cell epitopes. Conclusions: The route of immunization may determine the hierarchy of T-cell epitopes in the lymph nodes draining the mucosa in the circulating and splenic lymphocytes. The diversity of T-cell epitopes may affect the control of HIV at different anatomical sites, the administration route of the vaccine, and selection of polypeptides or recombinant antigens for immunization.