The present invention relates to non toxic, immunogenic viral Tat DNA sequences comprising wherein the Tat Sequence is rendered non toxic and immunogenic by insertion of T-Helper Epitope into the Cysteine-rich domain, or Basic domain or Core domain of said Tat DNA sequence, optionally along with insertion of a synthetic Intron between C-terminal region and Exon II region of the Tat DNA Sequence. The present invention also relates to elongation factor promoter constructs and process thereof. Also the present invention relates to a process of obtaining the non toxic and immunogenic Tat DNA sequence and vaccine and a method thereof.
