Humoral and cell-mediated immune responses of foxes (Vulpes vulpes) after experimental primary and secondary oral vaccination using SAG2 and V-RG vaccines.

Humoral and cell-mediated immune responses of 36 captive foxes to two oral vaccines against rabies currently used for foxes in Europe were studied. The Street Alabama Dufferin (SAD) mutant Gif (SAG2) vaccine has been selected by double mutation from the SAD virus. The vaccinia recombinant virus (V-RG) expresses the rabies glycoprotein. Both vaccines induce similar humoral and cell-mediated responses after primary and secondary oral administration. We observed a typical anamnestic response, although of a limited duration, after the booster vaccination. Therefore, our results suggested that two successive oral vaccination campaigns should not significantly improve the immunisation of foxes. Lymphocyte in vitro proliferative response to the SAD antigen highlighted the presence in blood of a T-cell specific memory 6 months after vaccination. The synthesis of several vulpine cytokines was detected in peripheral blood mononuclear cells (PBMC) stimulated by SAD antigen via reverse transcription polymerase chain amplification. The data showed a concomitant expression of interleukin (IL)-4 and interferon-gamma in PBMC of vaccinated foxes. No change was detected in the level of IL-2, IL-10 and IL-12 synthesis, whereas the pro-inflammatory cytokine tumour necrosis factor-alpha seemed involved in the activation of naive T lymphocytes.