- Immunization with a modified vaccinia virus expressing simian immunodeficiency virus (SIV) Gag-Pol primes for an anamnestic Gag-specific cytotoxic T-lymphocyte response and is associated with reduction of viremia after SIV challenge. Seth, A., Ourmanov, I., Schmitz, J.E., Kuroda, M.J., Lifton, M.A., Nickerson, C.E., Wyatt, L., Carroll, M., Moss, B., Venzon, D., Letvin, N.L., Hirsch, V.M. J. Virol. (2000)