Expression and characterization of a recombinant kinesin antigen from an old Indian strain (DD8) of Leishmania donovani and comparing it with a commercially available antigen from a newly isolated (KE16) strain of L. donovani.

Recently we had prepared a recombinant antigen (Ld-rKE16) from a newly isolated Indian strain of Leishmania donovani (MHOM/IN/KE16/1998) with high sensitivity and specificity and the same has been commercialized. While comparing the sequence data of kinesin gene of this (KE16) strain and its expressed protein with another commercially available recombinant antigen (Lc-rK39) from kinesin gene of L. chagasi we found significant genetic and amino acid variations. This prompted us to undertake the present study to unravel whether the kinesin gene and its expressed protein from another old but Indian isolate of L. donovani (MHOM/IN/DD8/1968) had any genetic and amino acid heterogeneity. Sequencing of the kinesin gene revealed that the kinesin gene of DD8 strain is 3016bp long and has immunodominant region consisting of 4.8 tandem repeats, 117 base pairs each. Further blast analysis of the immunodominant regions of 5 strains of L. donovani revealed that it has only 79% homology with L. chagasi, and 80% homology with L. infantum; while it had 82% homology with Sudan strain of L. donovani, 82% with another (Morena) strain of Indian L. donovani but highest homology of 83% with L. donovani KE16 strain of India. We also evaluated the diagnostic potential of the recombinant DD8 antigen (Ld-rDD8) and compared the results with that of Ld-rKE16. The study revealed that Ld-rKDD8 antigen was less sensitive and specific as compared to rKE16 antigen for the diagnosis of visceral and post-kala-azar dermal leishmaniasis. This was probably due to prolong in vitro culture maintenance of the DD8 strain.