The present invention relates to a synthetic immunogen represented by the general formula 1, useful for generating long lasting protective immunity against various intracellular pathogens which are the causative agents of tuberculosis, leishmaniasis, AIDS, trypanosomiasis, malaria and also allergy, cancer and a process for the preparation thereof. The developed immunogen is able to circumvent HLA restriction in humans and livestock. The invention further relates to a vaccine comprising the said immunogen for generating enduring protective immunity against various diseases. The said vaccine is targeted against intracellular pathogens, more particularly the pathogen M. tuberculosis in this case. In the present invention, promiscuous peptides of M. tuberculosis are conjugated to TLR ligands especially Pam2Cys to target them mainly to dendritic cells and therefore elicit long-lasting protective immunity. wherein, X1=a promiscuous CD4 T helper epitope selected from SEQ ID No. 1 to 98 OR nil X2=a promiscuous CD8 T cytotoxic epitope selected from SEQ ID No. 99 to 103 OR nil when X1=nil X2=SEQ ID No. 99 to 103 and when X2=nil X1=SEQ ID No. 1 to 98 Y=Lysine and S=Serine.
