Abstract: Anti-lentivirus vaccines and immunotherapeutics and methods for preparing and using same are disclosed. The vaccines and immunotherapeutics are produced using non-immunosuppressive lentivirus trans-activator of transcription (Tat) proteins. An associated in vitro ultra-sensitive macrophage Tat bioassay is disclosed for assessing the immunosuppressive qualities of the lentivirus Tat preparations of the present invention. Additionally, a related long-term T4 cell propagation system for characterizing lentivirus Tat is also disclosed. The present invention has additional utility in the treatment and prevention of AIDS.