3'-orf and sor genes of human immunodeficiency virus: in vitro transcription-translation and immunoreactive domains.

An in vitro transcription and translation procedure was designed to translate multiple open reading frames from cloned DNAs. For human immunodeficiency virus (HIV) cloned DNA carrying three open reading frames (sor, tat, and 3'-orf), the approach yielded three authentic polypeptides. Clearly, the internal initiation codons can be used for reinitiation of translation of the downstream open reading frames. However, the downstream open reading frames were translated with relatively lower translational efficiencies. In general, the translational efficiency of RNAs depended significantly on their structures. The in vitro approach was utilized further to map the immunoreactive domains of the 3'-orf and sor gene products of HIV. Deletion clones were constructed with deletions within the open reading frames. Translation products of these clones reacted differentially with anti-3'-orf and anti-sor rabbit immune sera and human sera from individuals with acquired immunodeficiency syndrome and related disorders. Apparently, recombinant 3'-orf and sor polypeptides used to immunize rabbits express many more immunogenic epitopes and/or different set of epitopes than is the case for the native proteins in humans infected with HIV. Immunoreactivity and immunogenicity of these gene products were significantly dependent on their structure and/or conformation.