A Perspective on the Emergence of Sialic Acids as Potent Determinants Affecting Leishmania Biology

Leishmaniasis caused by Leishmania sp. has a wide range of manifestations from cutaneous to the deadly visceral form. They shuttle between the invertebrate and vertebrate hosts as promastigotes and amastigotes having adaptations for subverting host immune responses. Parasite-specific glycoconjugates have served as important determinants influencing parasite recognition, internalization, differentiation, multiplication, and virulence. Despite the steady progress in the field of parasite glycobiology, sialobiology has been a less traversed domain of research in leishmaniasis. The present paper focuses on identification, characterization, and differential distribution of sialoglycotope having the linkage-specific 9-O-acetylated sialic acid in promastigotes of different Leishmania sp. causing different clinical ramifications emphasizing possible role of these sialoglycotopes in infectivity, virulence, nitric oxide resistance, and host modulation in Leishmania spp. asserting them to be important molecules influencing parasite biology

Glycobiology of Leishmania donovani

Leishmania donovani, the causative organism of visceral leishmaniasis (VL) is one of the deadliest of the entire known Leishmania species. This protozoan parasite displays immense adaptability to survive under extremely harsh conditions. Cell surface glycoconjugates play a pivotal role in parasite virulence and infectivity. This review mainly highlights on the importance of these molecules and their reported roles with special emphasis on L. donovani sialobiology. The recently evolved information reported by our group regarding the identification and characterization of sialoglycans and their possible mode(s) of acquisition as also the detailed identification, characterization of anti-O-acetylated sialic acid (anti-OAcSA) antibodies and their emerging biological roles, notably as molecules that may aid in host defense against the pathogen has been vividly discussed in this review

SUBSTRATE TEMPERATURE DEPENDENT OPTICAL AND STRUCTURAL PROPERTIES OF VACUUM EVAPORATED CdTe THIN FILMS

Substrate temperature dependent optical and structural properties of Cadmium Telluride (CdTe) thin films were studied. Films were grown onto glass substrate by thermal evaporation method in high vacuum (10-6 Torr) with varying thickness (200 ~ 500 nm). All the films were characterized optically by UV-VIS-NIR spectrophotometer in photon wavelength range (300 nm ~ 2500 nm). The optical transmittance and reflectance were utilized to compute the absorption coefficient, refractive index and band gap energy of the films. The calculated band gap energy was found to increase (1.49eV ~ 1.55eV) with varying thickness and to decrease (1.56eV ~ 1.46eV) with varying substrate temperature. The X-ray diffraction (XRD) patterns exhibited the zinc-blende structure of CdTe films with (111) preferential orientation. The lattice parameters, grain size, average internal stress, micro strain, dislocation density in the films were calculated. The grain size was varied from 32nm to 52nm with variation of substrate temperature. Micro strain and dislocation density were also found to vary between 0.69×10-3 ~ 1.12×10-3 and 3.59×1010 cm-2 ~ 9.49×1010 cm-2 respectively

Down regulation of membrane-bound Neu3 constitutes a new potential marker for childhood acute lymphoblastic leukemia and induces apoptosis suppression of of neoplastic cells

Membrane-linked sialidase Neu3 is a key enzyme for the extralysosomal catabolism of gangliosides. In this respect, it regulates pivotal cell surface events, including trans-membrane signaling, and plays an essential role in carcinogenesis. In this report, we demonstrated that acute lymphoblastic leukemia (ALL), lymphoblasts (primary cells from patients and cell lines) are characterized by a marked down-regulation of Neu3 in terms of both gene expression (-30 to 40%) and enzymatic activity toward ganglioside GD1a (-25.6 to 30.6%), when compared with cells from healthy controls. Induced overexpression of Neu3 in the ALL-cell line, MOLT-4, led to a significant increase of ceramide (+66%) and to a parallel decrease of lactosylceramide (-55%). These events strongly guided lymphoblasts to apoptosis, as we assessed by the decrease in Bcl2/Bax ratio, the accumulation of Neu3 transfected cells in the sub G0-G1 phase of the cell cycle, the enhanced annexin-V positivity, the higher cleavage of procaspase-3. Therefore, the reduced expression of Neu3 in ALL could help lymphoblasts to survive, maintaining the cellular content of ceramide below a critical level. Interestingly, we found that Neu3 activity varied in relation to disease progression, increasing in clinical remission after chemotherapy, and decreasing again in patients that relapsed. In addition, a negative correlation was observed between Neu3 expression and the percentage of the ALL marker 9-OAcGD3 positive cells. Consequently, Neu3 could represent a new potent biomarker in childhood ALL, to assess the efficacy of therapeutic protocols and to rapidly identify an eventual relapse

Phenotypic Characterization of Escherichia Coli Isolated From Urine and Stool from Short Term and Long Term Catheterized Patients

Background: Uropathogenic strains of Escherichia coli possess a number of phenotypic characters which allow them to colonize the catheter and cause infection of the same and the chances of colonization by these micro-organisms increase with the duration of catheterization. Objectives: This study was carried out to understand the differences between the phenotypic characters between the strains of E.coli isolated from the urine and gut of short term catheterized (STC) and long term catheterized (LTC) patients. Materials and Methods: Urine from the catheter and stool sample was processed by standard methods. The following special tests like α-hemolysis, haemagglutination, cell surface hydrophobicity, serum bactericidal assay, biofilm formation and congo red binding assay were performed to detect the phenotypic characters of the isolated E.coli. Antibiotic susceptibility testing was performed by Kirby Bauer method as per the Clinical Laboratory Standards Institute. Results: Majority (93.75%, 75% and 81.25%) of the E.coli isolates from urine of LTC patients were positive for MRHA, cell surface hydrophobicity and resistant to serum killing respectively, while majority (93.75%) of the urine isolates from short term catheterization. On congo red agar, the majority (80% and 60%) of isolates producing rdar type of colony and biofilm respectively,were isolated from urine of long term catheterized patients. ESBL production was noted in 68.75% of the urine isolates from long term catheterized patients. Conclusion: Serum resistance and biofilm formation are significant assays in terms of differentiating between the short term and long term catheterization and by elucidating these mechanisms better, it may become easier to combat and prevent such infections

Differential expression of 9-O-acetylated sialoglycoconjugates on leukemic blasts: a potential tool for long-term monitoring of children with acute lymphoblastic leukemia

Earlier studies have demonstrated overexpression of 9-O-acetylated sialoglycoconjugates (9-O-AcSGs) on lymphoblasts, concomitant with high titers of anti-9-O-AcSG antibodies in childhood acute lymphoblastic leukemia (ALL). Our aim was to evaluate the correlation between expression of different 9-O-AcSGs during chemotherapeutic treatment. Accordingly, expression of 9-O-AcSGs on lymphoblasts of ALL patients (n = 70) were longitudinally monitored for 6 years (1997-2002), using Achatinin-H, a 9-O-acetylated sialic acid (9-O-AcSA) binding lectin with preferential affinity for 9-O-AcSGs with terminal 9-O-AcSAα2→6GalNAc. Western blot analysis of patients (n = 30) showed that 3 ALL-specific 9-O-AcSGs (90, 120 and 135 kDa) were induced at presentation; all these bands disappeared after treatment in patients (n = 22) who had disease-free survival. The 90 kDa band persisted in 8 patients who subsequently relapsed with reexpression of the 120 kDa band. FACS analysis revealed that at presentation (n = 70) 90.1 ± 5.0% cells expressed 9-O-AcSGs, which decreased progressively with chemotherapy, remained <5% during clinical remission and reappeared in relapse (80 ± 10%, n = 18). Early clearance of 9-O-AcSG+ cells, during 4-8 weeks of treatment showed a good correlation with low risk of relapse. Sensitivity of detection of 9-O-AcSG+ cells was 0.1%. Numbers of both high- and low-affinity binding sites were maximum at presentation, decreased with treatment and increased again in clinical relapse. We propose that close monitoring of 90 and 120 kDa 9-O-AcSGs may serve as a reliable index for long-term management of childhood ALL and merits therapeutic consideration

Chemical approaches to penicillin allergy - V. Nature of reaction between rabbit antigen (CRP-penicillin conjugate) and rabbit antipenicillin antibody

The availability of an electrophoretically homogeneous rabbit penicillin carrier receptor protein (CRP) and rabbit antipenicillin antibody afforded an idealin vitro system to calculate the thermodynamic parameters of the binding of14C benzyl penicillin CRP conjugate (antigen) to the purified rabbit antipenicillin antibody. The thermodynamic parameters of this antigen-antibody reaction has been studied by radio-active assay method by using millipore filter. Equilibrium constant (K) of this reaction has been found to be 2.853x109M-2 and corresponding free energy (ΔG) at 4°C and 37°C has been calculated to be -12.02 and -13.5 kcal/mole, enthalpy (ΔH) and entropy (ΔS) has been found to be 361 kcal/mole and +30 eu/mole respectively. Competitive binding studies of CRP-analogue conjugates with the divalent rabbit antibody has been carried out in the presence of14C-penicilloyl CRP. It was found that 7-deoxy penicillin-CRP complex and 6-amino penicilloyl CRP conjugate binds to the antibody with energies stronger than that with the14C-penicilloyl CRP. All the other analogue conjugates are much weaker in interfering with the binding of the penicilloyl CRP with the antibody. The conjugate of methicillin,o-nitro benzyl penicillin and ticarcillin with CRP do not materially interfere in the process

Exacerbation of ulcerative colitis due to Edwardsiella tarda infection

Infectious gastroenteritis can lead to exacerbations of inflammatory bowel disease (IBD) such as ulcerative colitis, which warrants appropriate and timely control with the initiation of specific antibacterial therapy. Herein, we discuss a patient who had presented with an exacerbation of ulcerative colitis due to an infectious gastroenteritis caused by Edwardsiella tarda and had responded to the appropriate antibacterial therapy. This study outlines the importance of a culture of stool samples in all cases of IBD with acute exacerbations

Antibodies against 9-O-acetylated sialoglycans: a potent marker to monitor clinical status in childhood acute lymphoblastic leukemia

Background: Although childhood acute lymphoblastic leukemia (ALL) is highly responsive to chemotherapy, reliable techniques are needed to determine treatment outcome and predict impending relapse. In ALL, the cell surface over expression of 9-O-acetylated sialoglycans (9-OAcSGs) on lymphoblasts and concomitant high antibody titers in patients' sera was reported. Objectives: The present study was aimed to evaluate whether anti-9-OAcSG titers can be harnessed to monitor the clinical outcome of ALL. Design and methods: Anti-9-OAcSGs were analyzed by ELISA in children receiving either UK ALL X (n = 69, Group I) in India or UK ALL 97 (n = 47, Group II) in UK along with age-matched normal healthy controls at different time points over a period of > 2 years. An attempt was also made to investigate subclass distribution of disease-specific IgG. Moreover, 17 patients having a higher sample size were longitudinally monitored. Results: Antibody levels were raised at disease presentation, decreased with remission induction, and importantly, reappeared with clinical relapse. Sera from patients with other hematological disorders and normal controls showed negligible levels of circulating anti-9-OAcSGs. In patients of both Groups I and II, the assay showed high sensitivity (98.92% and 96.77%) and specificity (92.1% and 95.91%), respectively. IgG subclass analyses during different phases of treatment revealed that 9-OAcSG-specific IgG1 could serve as a better prognostic marker in ALL. Conclusions: This study demonstrated the potential of this disease-specific antibody as an alternate marker in diagnosis and long-term assessment of ALL patients, suggesting its application in detection and prediction of impending relapse. Therefore, the expression of anti-9-OAcSGs, irrespective of their treatment protocol, may serve as an economical yet effective index for monitoring of childhood ALL

Flow-cytometric monitoring of disease-associated expression of 9-O-acetylated sialoglycoproteins in combination with known CD antigens, as an index for MRD in children with acute lymphoblastic leukaemia: a two-year longitudinal follow-up study

<p>Abstract</p> <p>Background</p> <p>Over expression of 9-<it>O-</it>acetylated sialoglycoproteins (Neu5,9Ac₂-GPs, abbreviated as <it>O</it>AcSGP) has been demonstrated as a disease-associated antigen on the lymphoblasts of childhood acute lymphoblastic leukaemia (ALL). Achatinin-H, a lectin, has selective affinity towards terminal 9-<it>O-</it>acetylated sialic acids-α2-6-<it>N</it>acetylated galactosamine. Exploring this affinity, enhanced expression of <it>O</it>AcSGP was observed, at the onset of disease, followed by its decrease with chemotherapy and reappearance with relapse. In spite of treatment, patients retain the diseased cells referred to as minimal residual disease (MRD) responsible for relapse. Our aim was to select a suitable template by using the differential expression of <it>O</it>AcSGP along with other known CD antigens to monitor MRD in peripheral blood (PB) and bone marrow (BM) of Indian patients with B- or T-ALL during treatment and correlate it with the disease status.</p> <p>Methods</p> <p>A two-year longitudinal follow-up study was done with 109 patients from the onset of the disease till the end of chemotherapy, treated under MCP841protocol. Paired samples of PB (n = 1667) and BM (n = 999) were monitored by flow cytometry. Three templates selected for this investigation were <it>O</it>AcSGP⁺CD10⁺CD19⁺or <it>O</it>AcSGP⁺CD34⁺CD19⁺for B-ALL and <it>O</it>AcSGP⁺CD7⁺CD3⁺for T-ALL.</p> <p>Results</p> <p>Using each template the level of MRD detection reached 0.01% for a patient in clinical remission (CR). 81.65% of the patients were in CR during these two years while the remaining relapsed. Failure in early clearance of lymphoblasts, as indicated by higher MRD, implied an elevated risk of relapse. Soaring MRD during the chemotherapeutic regimen predicted clinical relapse, at least a month before medical manifestation. Irrespective of B- or T-lineage ALL, the MRD in PB and BM correlated well.</p> <p>Conclusion</p> <p>A range of MRD values can be predicted for the patients in CR, irrespective of their lineage, being 0.03 ± 0.01% (PB) and 0.05 ± 0.015% (BM). These patients may not be stated as normal with respect to the presence of MRD. Hence, MRD study beyond two-years follow-up is necessary to investigate further reduction in MRD, thereby ensuring their disease-free survival. Therefore, we suggest use of these templates for MRD detection, during and post-chemotherapy for proper patient management strategies, thereby helping in personalizing the treatment.</p