Immunoblotting identifies an antigen recognized by anti gp63 in the immune complexes of Indian kala-azar patient sera

In SDS-PAGE the immune complexes (IC) of kala-azar patient sera showed intense bands at 55 kDa and 20 kDa corresponding to heavy and light chains of immunoglobulins. In immunoblot experiment, kala-azar and normal IC after treatment with patient sera showed multiple bands of which the band at 55 kDa was most prominent in kala-azar IC. It is known that in kala-azar sera antihuman IgG is present, so the heavy band at 55 kDa region may be due to higher amount of IgG and/or other antigen(s) present at that region. Immunoblot experiments of kala-azar IC with anti gp63 also developed a major band at 55 kDa. It suggests that the antigen (55 kDa) and gp63 have common antigenic epitope (s). Normal IC did not react with anti gp63 indicating absence of this antigen in normal IC. Antigenic similarity between the IC antigen (55 kDa) and gp63 indicated that the former antigen may have been processed from gp63. In summary, identification of a parasite antigen (55 kDa) in IC of kala-azar patients sera may be useful in developing a serodiagnostic assay for visceral leishmaniasis.

Purification of two azoreductases from Escherichia coli K12

Two azoreductases (I and II) were purified to homogeneity from extracts of E. coli K12. Azoreductase I was a dimer of two identical subunits of molecular weight 28000 whereas azoreductase II was a monomer of 12,000 molecular weight. Both NADH and NADPH functioned as electron donors for the azoreductases. Azoreductase I and II used Ponceau SX, Tartrazine, Amaranth and Orange II as substrates. Ponceau SX was the best substrate for both the enzymes. However, azoreductase II utilized tartrazine, amaranth and orange II less efficiently than azoreductase I.

Experimental visceral leishmaniasis: role of trans-aconitic acid in combined chemotherapy

We previously reported the effectiveness of trans-aconitic acid (TAA) as an antileishmanial compound. Inhibitory effects of TAA along with other antileishmanial compounds on transformation and in vitro multiplication in macrophage cultures of Leishmania donovani have been assessed. The efficacy of TAA in combined chemotherapy of experimental visceral leishmaniasis has also been evaluated along with those of commonly used antileishmanial compounds such as sodium stibogluconate, pentamidine, and allopurinol. TAA (2 mM) inhibited transformation of L. donovani amastigotes to promastigotes by 95.2%, whereas in combination with pentamidine (5 micrograms/ml), allopurinol (10 micrograms/ml), and sodium stibogluconate (50 micrograms of Sb per ml), it inhibited transformation by about 100, 99, and 98.5%, respectively. Sodium stibogluconate (20 micrograms of Sb per ml), pentamidine (2 micrograms/ml), and allopurinol (5 micrograms/ml) suppressed the amastigote burden in peritoneal macrophage cultures from BALB/c mice by 32.6, 56.1, and 46.3%, respectively. When these three drugs were used along with TAA (5 mM), the parasite loads were reduced by 100, 100, and 88.1%, respectively. TAA (5 mM) alone suppressed the amastigote burden by 59.5%. In experimental visceral leishmaniasis in hamsters (1-month model), TAA at a dose of 200 mg/kg of body weight per day suppressed the spleen parasite load by 73.5%, and TAA in combination with sodium stibogluconate (50 mg of Sb per kg per day), pentamidine (8 mg/kg/day), and allopurinol (15 mg/kg/day) inhibited the spleen parasite load by 98, 98.9, and 97%, respectively. Individually, these three drugs inhibited the parasite load by 35, 20, and 22%, respectively. TAA (400 mg/kg/day) inhibited the spleen parasite load by 99.8%, but an inhibitory effect of approximately 100% was noted when TAA was supplemented with an antileishmanial drug. TAA was administered in experimental animals through oral, intraperitoneal, and intramuscular routes; the intramuscular route was most effective.

Purification and partial characterization of two azoreductases from Shigella dysenteriae type 1

Two azoreductases (I and II) were purified to homogeneity from extracts of Shigella dysenteriae (type 1). Azoreductase I was a dimer of identical subunits of M(r) 28,000, whereas azoreductase II was a monomer of 11,000 M(r). Both were flavoproteins, each containing 1 mol of FMN per mol enzyme. Both NADH and NADPH functioned as electron donors for the azoreductases. Azoreductase I used Ponceau SX, Tartrazine, Amaranth and Orange II as substrates. Azoreductase II utilized all the dyes except Amaranth.

Leishmania donovani: isolation of a concanavalin-A specific antigen and its evaluation for serodiagnosis of visceral leishmaniasis

A glycoconjugate antigen of 27-39 kDa was isolated from a cell-free extract of Leishmania donovani by affinity chromatography using a Concanavalin-A sepharose-4B column and eluted with 0.5 M alpha-methylmannoside. The antigen was recognized specifically by sera from kala-azar (visceral leishmaniasis) patients and did not react with sera from tuberculosis, leprosy or malaria patients. The antigen may therefore be useful in developing a serodiagnostic assay for visceral leishmaniasis.

Effect of bioamines on uptake of promastigotes of Leishmania donovani by hamster peritoneal macrophages

Epinephrine and norepinephrine inhibit attachment of Leishmania donovani promastigotes to cultured hamster peritoneal macrophages. The inhibition was significant at catecholamine concentrations of 10(-4) and 10(-5) M and occurred when they were added to the cell mixtures, or after pre-treatment of either macrophages or parasites. Inhibition of attachment after pre-treatment was less marked than when the catecholamines were added to parasite-cell mixtures. Similar results were obtained with dibutyryl cyclic AMP, cholera toxin, theophylline, and cadaverine which raise intracellular cyclic AMP (cAMP). Pretreatment of parasites or macrophages with the bioamines elevated the intracellular cAMP concentration. It is suggested that the inhibitory effect on the host-parasite interaction is mediated through cAMP.

Anemia in experimental visceral leishmaniasis in hamsters

Experimental infection of hamsters with Leishmania donovani caused visceral leishmaniasis in which hematological changes occurred. The infected hamsters were anemic and reticulocyte counts were high. No significant change in the serum erythropoietin level was noted. Red cell membrane Na(+)-K(+)-ATPase and acetylcholinesterase activities increased. Osmotic fragility of the erythrocytes from infected animals increased. The level of 2,3-diphosphoglycerate of the red cells increased with the degree of anemia.

Biochemical and immunological characterization of exometabolites from an Indian strain of Leishmania donovani promastigotes grown in a chemically defined medium

Exometabolites (EXOM) of an Indian strain of Leishmania donovani promastigotes isolated from a chemically defined medium by ultrafiltration consisted of proteins, glycoproteins, lipid and lipophosphopolysaccharide (LPPS). LPPS of Mr 40-28 kDa in SDS-PAGE could be labelled metabolically with [32P]-phosphate and recovered in the aqueous phase of hot-phenol-water extraction of EXOM (PE-Aq) along with a glycoprotein of Mr 150-130 kDa (GP150-130). These two molecules could be eluted from DE-52 column with 200 mM NaCl (D2). The 300 mM NaCl (D3) and 400 mM NaCl (D4) eluates from DE-52 column contained one unsaturated polar lipid component. The LPPS had Rf value of 0.65-0.75 in Thin Layer Chromatography (TLC) using saturated phenol water solvent system. EXOM revealed 15 bands in SDS-PAGE of which proteins of Mr 84, 66, 56, 50 and 29 kDa were prominent. When EXOM were fractionated through Con A-Sepharose column, the fraction eluted with alpha-methyl-D-mannoside (Con A-E) had seven bands as revealed by SDS-PAGE of which 25, 16, 13 and 12 kDa glycoproteins were prominent. The antigens present in EXOM can be classified as slower anodic migrating and faster anodic migrating antigens as revealed by immunoelectrophoresis (IEP). The slower anodic migrating antigens, LPPS and GP150-130 recovered in PE-Aq and D2 did not cross-react with kala-azar patients' sera but cross-reacted with homologous anti-promastigote sera. Two faster anodic migrating antigens which could be recovered in organic phase of hot phenol extraction of EXOM (PE-O) and eluted in D3 and D4 and Con A-E, cross-reacted with kala-azar patients' sera. The antigens of both the classes were sensitive to periodic acid oxidation.

Metacyclogenesis of Leishmania spp: species-specific in vitro transformation, complement resistance, and cell surface carbohydrate and protein profiles

Metacyclic (stationary) and logarithmic (log) forms of promastigotes of Leishmania donovani and Leishmania major were characterized in several ways. The highly active metacyclic forms were larger with more protein and less carbohydrate. The flagellum increased in length 2.4 times in L. major as compared to 1.8 times in L. donovani. Resistance to complement-mediated lysis by normal human serum of in vitro grown Leishmania promastigotes was related to the species, the growth phase in culture, and also the temperature. Metacyclic forms of both species had a much increased resistance to killing by normal serum at different temperatures. Differences in membrane-exposed carbohydrates were detected by fluorescein-conjugated lectins. Peanut agglutinin and Ulex agglutinin I differentiated log and stationary phase promastigotes of L. major. Higher amounts of acid phosphatase were demonstrated in the metacyclic phase. Differences in polypeptides were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two polypeptides of approximately 51 and 114 kDa were found exclusively in metacyclic promastigotes of both species, whereas 38- and 23-kDa polypeptides were lost or reduced during transformation from log to metacyclic phase promastigotes of L. donovani. In addition, a 75-kDa polypeptide was expressed only in metacyclic promastigotes of L. major.

Identification of immune complex antigens in sera of Indian kala-azar patients

Level of circulating immune complex (IC) in visceral leishmaniasis is much higher than that in control sera. In immunoblot experiment, treatment of kala-azar IC with patient sera showed at least 6 bands of which the band around 55 kDa region was most prominent. The band at 55 kDa is primarily due to the presence of an antigen recognized by its corresponding antibody present in the patient sera. This was confirmed by using radiolabelled antibody from kala-azar patient serum and antipromastigote serum. The heavy chain of IgG originating from IC is also present in the same region which was detected by its recognition with antihuman IgG. The IC gave a band at 55 kDa region with sea-urchin antitubulin. Kala-azar sera also reacted with purified rat brain tubulin. The present results suggest that a tubulin like protein is present at 55 kDa region along with the heavy chain of IgG.

A cloned kinetoplast DNA mini-circle fragment from a Leishmania spp. specific for post-kala-azar dermal leishmaniasis strains

DNA-DNA hybridization techniques have been found to be very useful in the classification and identification of Leishmania parasites. We report here the cloning of a mini-circle from Leishmania strain UR6 in a plasmid and subcloning of the mini-circle fragments in M13 mp9. Clone MLURk32, containing a 560 bp fragment of mini-circle, has been found to have unique specificity. Application of this specific probe in identifying different Leishmania isolates reveals that the probe reacted only with strains of post-kala-azar dermal leishmaniasis but not with strains or isolates of visceral leishmaniasis.

Role of Ca2+ ion on Leishmania-macrophage attachment

Leishmania donovani, the etiological agent for the disease visceral leishmaniasis, attach themselves to the macrophages for initiation of the disease. The attachment process has been found to be regulated by Ca2+ ions. Verapamil, a Ca(2+)-channel blocker inhibits Leishmania-macrophage attachment. The inhibitory effect is increased with time. Nifedipine, another Ca(2+)-channel blocker exhibits the same effect. The attachment process is stimulated by Ca(2+)-ionophore alone. The inhibitory effects of the calcium channel blockers are reversed by the ionophore.

Plasma membrane of Leishmania donovani

Plasma membrane of Leishmania donovani promastigotes was isolated by disrupting the cells in Dounce homogenizer and found to be having two fractions M1 and M2. Chemical analysis of the two membrane fractions revealed that M1 had less RNA content and high sterol-phospholipid molar ratio than M2. M1 was also rich in membrane marker enzymes, e.g., 5' nucleotidase and acid phosphatase. Glucose-6-phosphatase, the marker enzyme of endoplasmic reticulum was higher in M2 fraction. The electron micrograph also revealed the presence of plasma membrane vesicles in M1 fraction.

Evaluation of direct agglutination test (DAT) and ELISA for serodiagnosis of visceral leishmaniasis in India

The direct agglutination test (DAT) and the enzyme-linked immunosorbent assay (ELISA) were used for serodiagnosis of parasitologically confirmed Indian visceral leishmaniasis (VL) cases. All the sera of VL cases were positive by both the methods. DAT titres of VL cases were greater than or equal to 1:3,200, and ELISA values were greater than or equal to 0.55 1:400 dilution. In the control group, sera of widely prevalent diseases of India, such as leprosy, tuberculosis, malaria, and liver cirrhosis, were included. Both tests could discriminate between VL and other patients of the control group. The sera of post-kala-azar dermal leishmaniasis (PKDL) patients gave OD values of greater than 0:55 and had DAT titres of 1:1,600. Both tests are sensitive and specific for the diagnosis of VL cases. DAT, being simpler and more economical, will be suitable for diagnosis and epidemiological studies for VL under rural conditions of India.

Direct enzyme-linked immunosorbent assay: a simple immunoassay using Leishmania donovani promastigote for diagnosis of kala-azar

For immunodiagnosis of kala-azar enzyme-linked immunosorbent assay (ELISA) and immunofluorescence testing (IFAT) are commonly used. In IFAT, whole parasite antigen and in ELISA the soluble antigen have been used. Preparation of ELISA antigen has certain inherent difficulties. We have developed a simple, specific, and quantitative immunoassay, "direct ELISA" for diagnosis of kala-azar. Intact formalinized promastigote suspension has been used to combine with the antibodies of the patient sera. The colour developed in the supernatant by the enzyme conjugate combined on the parasite surface was measured with a spectrophotometer. The test was able to detect kala-azar-specific antibodies at very high serum dilution and could discriminate between kala-azar and the common diseases prevalent in Asia. The optical densities of the sera of different control groups were significantly low. The method has potential for use as a diagnostic tool in less well equipped laboratories.

Leishmania donovani: a chemically defined medium suitable for cultivation and cloning of promastigotes and transformation of amastigotes to to promastigotes

A chemically defined medium using commercially available alpha-MEM supplemented with hemin, HEPES, L-glutamine, D-glucose, folic acid, D-biotin and adenine supports the luxuriant growth and propagation of Leishmania donovani promastigotes. A peak parasite population of about 7.0 x 10(7)/ml at stationary phase and a population doubling time of 11.4 h for high-subpassage promastigotes were obtained. The medium was suitable for transformation of isolated amastigotes from infected hamster spleen. Promastigotes could be detected by culturing kala-azar patients' bone-marrow aspirate or spleen puncture material in this medium. Four out of six freshly transformed isolates gradually adapted and grew well in this medium. Macroscopic colonies appeared on agar plates prepared with the medium within 16-20 days after inoculation. The cloning efficiency was increased about five-fold by glycerol supplementation.

Effect of ureastibamine on Leishmania donovani amastigote

Ureastibamine, a pentavalent antimonial, reduced the parasitic load in the 60-day model of infection of L. donovani in hamsters. It also inhibited the in vivo multiplication of I donovani amastigotes in hamster peritoneal macrophages. No inhibition in either promastigote multiplication or amastigotes transformation was noted with filtrate obtained after incubation of the drugs for 72 h in the macrophage culture. Incubation of macrophages with ureastibamine revealed an impairment in the uptake of deoxyglucose. The effect of ureastibamine was compared with that of another pentavalent antimonial, sodium stibogluconate. It is suggested that impairment of macrophage membrane may contribute towards the adverse effect of these drugs against the intracellular parasite.

Targeting of urea stibamine encapsulated in liposomes to reticuloendothelial system for the treatment of experimental leishmaniasis

The antileishmanial antimonial drug urea stibamine was encapsulated in mannosylated and nonmannosylated liposomes and was tested against experimental leishmanial infection in hamsters. The study demonstrated that liposome encapsulation of urea stibamine enhanced its effectiveness, an effect which was greater when mannosylated liposomes were used.

Kinetoplastid flagellates: surface-reactive carbohydrates detected by fluorescein-conjugated lectins

Membrane-associated carbohydrate residues of 3 isolates of Leishmania derived from etiological agents of visceral leishmaniasis (VL), postkala-azar dermal leishmaniasis (PKDL), and cutaneous leishmaniasis (CL), as well as 2 other nonpathogenic insect gut kinetoplastid flagellates, Bodo sp. and Herpetomonas sp., were characterized with the aid of 8 fluorescein-conjugated lectins. Four lectins, concanavalin A, Dolichos biflorus, phytohemagglutinin P, Ricinus communis agglutinin, bound to all kinetoplastid flagellates at different concentrations. All Leishmania promastigotes showed reactions with Ulex agglutinin. Although these lectins were bound to all kinetoplastids, the site and intensity of binding was different. All skin-dwelling Leishmania parasites, viz., Leishmania donovani of PKDL and Leishmania tropica of CL showed unique selectivity toward peanut agglutinin (PNA), soybean agglutinin, and wheatgerm agglutinin (WGA). More interestingly, Herpetomonas showed positive fluorescence with PNA and WGA, whereas Bodo was negative. The results demonstrated that no lectin could distinguish between the pathogenic and nonpathogenic status of kinetoplastid flagellates. Moreover, the antigenic (carbohydrate) profiles of Herpetomonas corresponded more closely to those of L. tropica, whereas Bodo shared some common lectin receptors with L. donovani of VL.

An approach for immunodiagnosis of clinical cases of filariasis

In this communication an immunodiagnostic approach has been adopted for detection of antigen and antibody in amicrofilaeamic Mf(-) patients by countercurrent immuno electrophoresis (CCIE) and immunodiffusion (ID). Using Setaria cervi and Immune Complex (IC) antigens, out of fifteen clinical cases the number of positive patients in CCIE were twelve and ten respectively. Sixty percent of the Mf(-) cases were positive in antigen detection against both the homologous and heterologous antibody. In ID nine Mf(-) cases gave precipitin bands against S. cervi antigen while with IC antigens ten patients were positive. In similar experiments, it was found that out of fifteen Mf(-) cases nine and eleven patients were positive in antigen detection against microfilaraemic Mf(+) sera and S. cervi antibody respectively. All the Mf(+) cases were positive in both antibody and antigen detection. From the standpoint of immunodiagnosis the data were analysed by two-way analysis of variance study and a newly developed system using Binomial distribution. The sera from the control group were negative in all the immunodiagnostic tests.