Cloning, expression and antigenicity of the L. donovani reductase.
The protozoan parasite Leishmania undergoes a morphological and biochemical transformation from the promastigote to the amastigote form during its life cycle, which is reflected in the expression of stage-specific proteins. One of these proteins shows homology to a superfamily of reductase proteins. We have cloned the reductase gene from L donovani and have shown that it differs in only one nucleotide from the L. major homologue, resulting in one amino acid change. A cytosine (C) to guanine (G) transposition in the coding sequence leads to a nonconserved substitution of asparagine (N) for lysine (K). Only 2 of 22 plasma samples from patients with visceral leishmaniasis were found to have detectable anti-reductase antibodies and peripheral blood mononuclear cells (PBMC) from one of three individuals previously infected with visceral leishmaniasis proliferated in the presence of recombinant reductase protein. Interestingly, 6 of 10 PBMC isolated from Danish controls proliferated in the presence of the reductase protein. Intracellular IFNgamma was found in a significant percentage of cells in all the tested PBMC cultures from Danes, whereas IL4 was only found in a small proportion of cells, or not at all. The results indicate the presence of cross-reacting CD45R0 memory T-cells in individuals not exposed to Leishmania. Several previous studies have shown that T-cells from nonexposed individuals often respond to crude Leishmania antigen preparations. The present study suggests that this reactivity is partly caused by T-cells recognising L. donovani reductase.
Jensen
A T
AT
Centre for Medical Parasitology, Institute for Medical Microbiology and Immunology, University of Copenhagen, Denmark. parasite@biobase.dk
Kemp
K
K
Theander
T G
TG
Handman
E
E
D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics; D001483:Base Sequence; D016022:Case-Control Studies; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D016054:DNA, Protozoan / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D017125:Genes, Protozoan; D006801:Humans; D066298:In Vitro Techniques; D007893:Leishmania donovani / Q000201:enzymology* / Q000235:genetics* / Q000276:immunology; D018320:Leishmania major / Q000201:enzymology / Q000235:genetics; D007898:Leishmaniasis, Visceral / Q000276:immunology; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics* / Q000276:immunology; D013045:Species Specificity
D000953:Antigens, Protozoan; D017931:DNA Primers; D016054:DNA, Protozoan; D010088:Oxidoreductases