The coding domains of simple retrovirus genomes direct the synthesis of virion proteins. Complex retroviral genomes generate in addition to virion proteins regulatory transacting proteins that are translated from multiple spliced messenger RNAs and fulfill important functions in the virus life cycle. All human retroviruses have such complex genomes.

The transacting proteins of these pathogens are attractive targets for therapeutic intervention because they are viral specific, are essential for efficient virus replication and may be mediators of viral pathogenicity. In summarizing the current knowledge on the regulatory transacting proteins of human retroviruses this volume makes an important contribution toward the control of virus disease.