Additional work is needed to further define and increase the sensitivity of the MVOA, including the examination of whether supplementation of the sustained activation provided by the graft versus host disease with pre- (in vitro) or post-xenograft (in vivo) anti-CD3/CD28 activating antibody and/or latency reversing agents, or elimination of CD8+ T cells pre- or post-xenograft, will increase the yield of virus. The gene discussed is CD28; the disease is graft versus host disease.