Chromosome profile ofLeishmania donovani: Interstrain and interspecific variations

Evolutionary comparison of prenylation pathway in kinetoplastid Leishmania and its sister Leptomonas

Background

Leptomonas is monogenetic kinetoplastid parasite of insects and is primitive in comparison to Leishmania. Comparative studies of these two kinetoplastid may share light on the evolutionary transition to dixenous parasitism in Leishmania. In order to adapt and survive within two hosts, Leishmania species must have acquired virulence factors in addition to mechanisms that mediate susceptibility/resistance to infection in the pathology associated with disease. Rab proteins are key mediators of vesicle transport and contribute greatly to the evolution of complexity of membrane transport system. In this study we used our whole genome sequence data of these two divergent kinetoplastids to analyze the orthologues/paralogues of Rab proteins.

Results

During change of lifestyle from monogenetic (Leptomonas) to digenetic (Leishmania), we found that the prenyl machinery remained unchanged. Geranylgeranyl transferase-I (GGTase-I) was absent in both Leishmania and its sister Leptomonas. Farnesyltransferase (FTase) and geranylgeranyl transferase-II (GGTase-II) were identified for protein prenylation. We predict that activity of the missing alpha-subunit (α-subunit) of GGTase-II in Leptomonas was probably contributed by the α-subunit of FTase, while beta-subunit (β-subunit) of GGTase-II was conserved and indicated functional conservation in the evolution of these two kinetoplastids. Therefore the β-subunit emerges as an excellent target for compounds inhibiting parasite activity in clinical cases of co-infections. We also confirmed that during the evolution to digenetic life style in Leishmania, the parasite acquired capabilities to evade drug action and maintain parasite virulence in the host with the incorporation of short-chain dehydrogenase/reductase (SDR/MDR) superfamily in Rab genes.

Conclusion

Our study based on whole genome sequences is the first to build comparative evolutionary analysis and identification of prenylation proteins in Leishmania and its sister Leptomonas. The information presented in our present work has importance for drug design targeted to kill L. donovani in humans but not affect the human form of the prenylation enzymes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-015-0538-3) contains supplementary material, which is available to authorized users.

Cloning, expression, and purification of a novel recombinant antigen from Leishmania donovani

Visceral leishmaniasis (VL) is a major health problem in the tropical and subtropical regions of the world. The conventional methods for diagnosis of Old World Visceral leishmaniasis are difficult, insensitive, and hazardous. There is no recombinant antigen from old world Leishmania species which can be commercially used for rapid diagnosis. There is an urgent need for a less invasive and accurate method. Here, we report a recombinant antigen from Indian Leishmania donovani for its diagnosis. The kinesin gene of a L. donovani clinical isolate (KE16) from India was PCR amplified for cloning and the immunodominant domain was expressed in Escherichia coli. This recombinant protein or Ld-rKE16 was evaluated for serodiagnosis of Indian kala-azar by ELISA. The recombinant antigen was found to be 100% sensitive and specific for Old World VL cases from India, Pakistan, China, and Turkey. The antigen showed no cross-reactivity with sera from other endemic diseases or healthy controls. The expressed Ld-rKE16 antigen is highly specific and sensitive for diagnosing visceral and post-kala-azar dermal leishmaniasis and is ready for commercialization.

Involvement ofLeishmania donovani major surface glycoprotein gp63 in promastigote multiplication

The major surface glycoprotein gp63 of the kinetoplastid protozoal parasite Leishmania is implicated as a ligand mediating uptake of the parasite into, and survival within, the host macrophage. By expressing gp63 antisense RNA from an episomal vector in L. donovani promastigotes, gp63-deficient transfectants were obtained. Reduction of the gp63 level resulted in increased generation times, altered cell morphology, accumulation of cells in the G2/M phase of the cell cycle, and increased numbers of binucleate cells with one or two kinetoplasts. Growth was stimulated, and the number of binucleate cells reduced, by addition to the culture of a bacterially expressed fusion protein containing the fibronectin-like SRYD motif and the zinc-binding (metalloprotease) domain of gp63. These observations support an additional role of gp63 in promastigote multiplication; the fibronectin-like properties of gp63 may be important in this process