Search

The arbitrary-primed PCR (AP-PCR) technique was employed with the twin goals of identifying genetic polymorphisms within the Indian isolates and to identify differentially expressed gene sequences. The parasite isolates from Indian Kala-azar patients could be differentiated from Leishmania donovani isolates from distinct geographic regions. Moreover, differences within the Indian isolates could also be identified. A majority (17/19) of the Indian isolates gave identical AP-PCR pattern, while two isolates gave consistently divergent pattern. The distinctive AP-PCR fragments obtained with Indian isolates were used as probes in Northern blot analysis. Three such fragments were found to represent transcribed sequences that were differentially expressed in the two stages of the parasite. These sequences led to cloning and characterization of Leishmania Centrin gene and a novel gene termed A-1 that is over-expressed in amastigote stage of the parasite. The study demonstrates the utility of random genome sampling methods in genomic fingerprinting and in identifying differentially transcribed sequences that could potentially contribute to parasite virulence.

Development of simple, economical and non-invasive tests for the early diagnosis of visceral leishmaniasis (VL) or kala-azar (KA) remains a challenge, and serological studies based on antigen prepared from the amastigote stage of Leishmania donovani, the stage that causes infection, are lacking. In the present study, circulating antibodies to total antigen isolated from the promastigote and amastigote stages of the parasite, as well as to recombinant K39 (rK39) antigen, are measured by enzyme-linked immunosorbent assay (ELISA) and the results compared with a polymerase chain reaction (PCR) test for KA diagnosis. In 116 samples of KA examined, the amastigote antigen gave significantly higher mean absorbance values in ELISA than did the promastigote antigen. The sensitivity for KA detection was significantly higher using the amastigote antigen (94%) than the promastigote antigen (90.5%). Analysis in 91 controls showed that specificity was higher with amastigote antigen (92.3%) than with promastigote antigen (86.8-89.0%). Reliability of ELISA diagnosis with amastigote antigen was only marginally lower than that with rK39 ELISA or with the PCR test. Easy availability and low cost of indigenous amastigote antigen, together with the simplicity of ELISA compared with PCR, make ELISA based on amastigote antigen a promising choice for the diagnosis of KA.

Development of simple, economical and non-invasive tests for the early diagnosis of visceral leishmaniasis (VL) or kala-azar (KA) remains a challenge, and serological studies based on antigen prepared from the amastigote stage of Leishmania donovani, the stage that causes infection, are lacking. In the present study, circulating antibodies to total antigen isolated from the promastigote and amastigote stages of the parasite, as well as to recombinant K39 (rK39) antigen, are measured by enzyme-linked immunosorbent assay (ELISA) and the results compared with a polymerase chain reaction (PCR) test for KA diagnosis. In 116 samples of KA examined, the amastigote antigen gave significantly higher mean absorbance values in ELISA than did the promastigote antigen. The sensitivity for KA detection was significantly higher using the amastigote antigen (94%) than the promastigote antigen (90.5%). Analysis in 91 controls showed that specificity was higher with amastigote antigen (92.3%) than with promastigote antigen (86.8-89.0%). Reliability of ELISA diagnosis with amastigote antigen was only marginally lower than that with rK39 ELISA or with the PCR test. Easy availability and low cost of indigenous amastigote antigen, together with the simplicity of ELISA compared with PCR, make ELISA based on amastigote antigen a promising choice for the diagnosis of KA.

Leishmania donovani, a protozoan parasite, causes visceral disease in humans. To identify genes that control growth, we have isolated for the first time in the order Kinetoplastida a gene encoding for centrin from L. donovani. Centrin is a calcium-binding cytoskeletal protein essential for centrosome duplication or segregation. Protein sequence similarity and immunoreactivity confirmed that Leishmania centrin is a homolog of human centrin 2. Immunofluorescence analysis localized the protein in the basal body. Calcium binding analysis revealed that its C-terminal Ca(2+) binding domain binds 16-fold more calcium than the N-terminal domain. Electrophoretic mobility shift of centrin treated with EGTA and abrogation of the shift in its mutants lacking a Ca(2+) binding site suggest that Ca(2+) binding to these regions may have a role in the protein conformation. The levels of centrin mRNA and protein were high during the exponential growth of the parasite in culture and declined to a low level in the stationary phase. Expression of N-terminal-deleted centrin in the parasite significantly reduces its growth rate, and it was found that significantly more cells are arrested in the G(2)/M stage than in control cells. These studies indicate that centrin may have a functional role in Leishmania growth.

We have developed a PCR assay that is capable of amplifying kinetoplast DNA (kDNA) of Leishmania donovani in a species-specific manner among Old World leishmanias. With Indian strains and isolates of L. donovani the assay was sensitive enough to detect kDNA in an amount equivalent to a single parasite or less. The extreme sensitivity of the assay was reflected in its ability to detect parasite DNA from small volumes of peripheral blood of patients with kala-azar (KA) and from skin lesions from patients with post-KA dermal leishmaniasis (PKDL). A total of 107 clinical leishmaniasis samples were analyzed. Of these 102 (95.3%) were positive by PCR. The test provided a diagnosis of KA with 96% sensitivity using patient whole-blood samples instead of bone marrow or spleen aspirates that are obtained by invasive procedures. The assay was also successful in the diagnosis of 45 of 48 PKDL cases (93.8%). Cross-reactions with pathogens prevalent in the area of endemicity, viz., Mycobacterium tuberculosis, Mycobacterium leprae, and Plasmodium spp., could be ruled out. Eighty-one control samples, including dermal scrapings from healthy portions of skin from patients with PKDL were all negative. Two of twenty controls from the area of endemicity were found positive by PCR assay; however, there was a good possibility that these two were asymptomatic carriers since they were serologically positive for KA. Thus, this PCR assay represents a tool for the diagnosis of KA and PKDL in Indian patients in a noninvasive manner, with simultaneous species identification of parasites in clinical samples.

When infected with Leishmania donovani, patients develop specific antibodies that constitute the basis of serodiagnosis. Using immunoblot analysis, we examined the antibody response to antigens of L. donovani in 35 kala-azar (KA) patients and 67 controls. Sera from KA patients recognised numerous antigens with molecular weights ranging from 14-110 kDa. Antigens of 40 kDa, 55 kDa, 65 kDa, 70 kDa and 82 kDa were recognised most frequently. All KA patients produce an antibody response to one or more of these antigens. The majority (83%) of KA cases recognised at least four of these five parasite antigens. The 70 kDa antigen showed the greatest sensitivity for Indian KA, and produced a positive reaction in 94% of patients. This antigen gave 10% false-positive reactions in controls comprising patients with related diseases (i.e. tuberculosis, leprosy and malaria) and in healthy controls. Data indicated that the 70 kDa antigen may include a member of the heat shock protein 70 family. Studies with four clinical isolates of L. donovani showed that the 70 kDa component was expressed in all the strains examined. Immunoblot assay (Western blotting) provided a sensitive diagnostic test for KA patients, and identified the 70 kDa parasite antigen that is promising as a potential target antigen for the development of less complex serodiagnostic assays for KA.

During a 15 months period, 97 patients with AMI were monitored continuously at hospital discharge for one hour. The VPCs or no VPC noted during this period of continuous monitoring were correlated with subsequent cardiac events during one year follow up. Patients with complicated VPCs had a significantly higher incidence of cardiac deaths and non-fatal re-infarctions during one year follow up (54.5%) as compared to patients with no VPCs (6.5%) (p less than .001). Patients with higher grades of VPCs had more complicated course (30.3% to 66.7% for Lown Grade II to IV) as compared to 6.5% and 20.8% for grade Lown O and I. Though, the results of this 1 hour continuous monitoring at hospital discharge are not as sensitive as with ambulatory Holter monitoring as is evident from this study where complicated VPCs were detected in 11.4% patients vs. 33% with Holter monitoring, it could be a useful tool in institutions where the facility of Holter monitoring does not exist.

Roots and shoots of corn seedlings (Zea mays L. var. Dixie 18) germinated in trifluralin (alpha,alpha,alpha-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) solutions are characterized by radial enlargement of the cortical cells and by multinucleate cells in the meristematic regions. Trifluralin inhibits elongation of Avena coleoptile sections at concentrations of 0.1 mum to 10 mum. Synthesis of DNA, RNA, and protein is suppressed in the root tips while no significant effect is noticeable in the shoots of corn germinated in trifluralin. A (32)P time-course study of 48, 72, and 96 hours utilizing phenol extraction and MAK column separation of corn root and shoot nucleic acids showed suppression of (32)P incorporation in the treated roots; however, the 72 and 96 hour treated shoots incorporated a much greater amount than the control with most of the increased incorporation found in the sRNA and DNA fractions. The increased activity in the DNA may be due to a high G-C type DNA. No selective suppression or enhancement of any particular RNA species was noticed in the treated plants.