Bacterial peptidoglycan binds to tubulin

Cell wall fraction of Mycobacterium indicus pranii shows potential Th1 adjuvant activity

Very few adjuvants inducing Th1 immune response have been developed and are under clinical investigation. Hence, there is the need to find an adjuvant that elicits strong Th1 immune response which should be safe when injected in the host along with vaccines. Mycobacterium indicus pranii (MIP), a non-pathogenic vaccine candidate, has shown strong immunomodulatory activity in leprosy/tuberculosis/cancer and in genital warts patients where its administration shifted the host immune response towards Th1 type. These findings prompted us to study the components of MIP in detail for their Th1 inducing property. Since mycobacterial cell wall is very rich in immunostimulatory components and is known to play important role in immune modulation, we investigated the activity of MIP cell wall using Ovalbumin antigen (OVA) as model antigen. 'Whole cell wall' (CW) and 'aqueous soluble cell wall fractions' (ACW) induced significant Th1 immune response while 'cell wall skeleton' (CWS) induced strong Th2 type of immune response. Finally, functional activity of fractions having Th1 inducing activity was evaluated in mouse model of melanoma. CW demonstrated significant anti-tumor activity similar to whole MIP. Anti-tumor activity of CW could be correlated with enhanced tumor antigen specific Th1 immune response observed in tumor draining lymph nodes.

Characterization of chickpea (Cicer arietinum L.) lectin for biological activity

Lectins are proteins that are subject of intense investigations. Information on lectin from chickpea (Cicer arietinum L.) with respect to its biological activities are very limited. In this study, we purified lectin from the seeds of chickpea employing DEAE-cellulose and SP-Sephadex ion exchange chromatography and identified its molecular subunit mass as 35 kDa. The free radical scavenging activity of lectin measured by the DPPH assay has IC₅₀ of 0.88 µg/mL. Lectin exerted antifungal activity against Candida krusei, Fusarium oxysporium oxysporium, Saccharomyces cerevisiae and Candida albicans, while antibacterial activity against E. coli, B. subtilis, S. marcescens and P. aeruginosa. The minimum inhibitory concentrations were 200, 240, 160 and 140 µg for C. krusei, F. oxysporium, S. cerevisiae and C. albicans respectively. Lectin was further examined for its antiproliferative potential against cancerous cell line. The cell viability assay indicated a high inhibition activity on Ishikawa, HepG2, MCF-7 and MDA-MB-231 with IC₅₀ value of 46.67, 44.20, 53.58 and 37.46 µg/mL respectively. These results can provide a background for future research into the benefits of chickpea lectin to pharmacological perspective.

Antimicrobial Activity of Cladonia verticillaris Lichen Preparations on Bacteria and Fungi of Medical Importance

Cladonia verticillaris lichen lectin (ClaveLL) was purified using a previously established protocol and then evaluated for its potential antimicrobial activity. Initially, the autochthonous lichen was submitted to extraction with sodium phosphate buffer pH 7.0, followed by filtration and centrifugation to obtain crude extract. A salt fractionation was performed with 30% ammonium sulfate. After centrifugation, the protein fraction was loaded onto molecular exclusion chromatography using Sephadex G-100 matrix to purify active lectin. ClaveLL showed antibacterial activity against Gram-positive (Bacillus subtilis, Staphylococcus aureus, and Enterococcus faecalis) and Gram-negative (Escherichia coli and Klebsiella pneumoniae) assayed strains, with greater inhibitory effect on growth of E. coli (MIC of 7.18 μg mL−1). The lowest minimum bactericidal concentration (MBC, 57.4 μg mL−1) was detected against E. faecalis. The antifungal assay performed with Trichophyton mentagrophytes, Microsporum gypseum, Trichophyton rubrum, Trichosporon cutaneum, and Trichosporon asahi evaluated crude extract, fraction, and ClaveLL preparations. ClaveLL was the most active against T. rubrum with an inhibition percentage of 35% compared to negative control (phosphate buffer). Extract and fraction showed better activity on growth inhibition of T. mentagrophytes (35%). The results indicate the potential of ClaveLL and other C. verticillaris preparations as antimicrobial agents useful for applications focusing on human health.

Antimicrobial lectin from Schinus terebinthifolius leaf

AIMS

Schinus terebinthifolius leaves are used for treating human diseases caused by micro-organisms. This work reports the isolation, characterization and antimicrobial activity of S. terebinthifolius leaf lectin (SteLL).

METHODS AND RESULTS

The isolation procedure involved protein extraction with 0.15 mol l(-1) NaCl, filtration through activated charcoal and chromatography of the filtrate on a chitin column. SteLL is a 14-kDa glycopeptide with haemagglutinating activity that is inhibited by N-acetyl-glucosamine, not affected by ions (Ca(2+) and Mg(2+)) and stable upon heating (30-100 °C) as well as over the pH 5.0-8.0. The antimicrobial effect of SteLL was evaluated by determining the minimal inhibitory (MIC), bactericide (MBC) and fungicide (MFC) concentrations. Lectin was active against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella enteritidis and Staphylococcus aureus. Highest bacteriostatic and bactericide effects were detected for Salm. enteritidis (MIC: 0.45 μg ml(-1)) and Staph. aureus (MBC: 7.18 μg ml(-1)), respectively. SteLL impaired the growth (MIC: 6.5 μg ml(-1)) and survival (MFC: 26 μg ml(-1)) of Candida albicans.

CONCLUSIONS

SteLL, a chitin-binding lectin, purified in milligram quantities, showed antimicrobial activity against medically important bacteria and fungi.

SIGNIFICANCE AND IMPACT OF THE STUDY

SteLL can be considered as a new biomaterial for potential antimicrobial applications.

Phage display against corneal epithelial cells produced bioactive peptides that inhibit Aspergillus adhesion to the corneas

Dissection of host-pathogen interactions is important for both understanding the pathogenesis of infectious diseases and developing therapeutics for the infectious diseases like various infectious keratitis. To enhance the knowledge about pathogenesis infectious keratitis, a random 12-mer peptide phage display library was screened against cultured human corneal epithelial cells (HCEC). Fourteen sequences were obtained and BLASTp analysis showed that most of their homologue counterparts in GenBank were for defined or putative proteins in various pathogens. Based on known or predicted functions of the homologue proteins, ten synthetic peptides (Pc-A to Pc-J) were measured for their affinity to bind cells and their potential efficacy to interfere with pathogen adhesion to the cells. Besides binding to HCEC, most of them also bound to human corneal stromal cells and umbilical endothelial cells to different extents. When added to HCEC culture, the peptides induced expression of MyD88 and IL-17 in HCEC, and the stimulated cell culture medium showed fungicidal potency to various extents. While peptides Pc-C and Pc-E inhibited Aspergillus fumigatus (A.f) adhesion to HCEC in a dose-dependent manner, the similar inhibition ability of peptides Pc-A and Pc-B required presence of their homologue ligand Alb1p on A.f. When utilized in an eyeball organ culture model and an in vivo A.f keratitis model established in mouse, Pc-C and Pc-E inhibited fungal adhesion to corneas, hence decreased corneal disruption caused by inflammatory infiltration. Affinity pull-down of HCEC membrane proteins with peptide Pc-C revealed several molecules as potential receptors for this peptide. In conclusion, besides proving that phage display-selected peptides could be utilized to interfere with adhesion of pathogens to host cells, hence could be exploited for managing infectious diseases including infectious keratitis, we also proposed that the phage display technique and the resultant peptides could be used to explore host-pathogen interactions at molecular levels.

Mycobacterium bovis BCG cell wall-specific differentially expressed genes identified by differential display and cDNA subtraction in human macrophages

We have analyzed the gene expression profile of monocytes in response to a highly purified cell wall fraction of Mycobacterium bovis BCG, a clinically approved adjuvant known as BCG cell wall skeleton (BCG-CWS). It is composed of mycolic acid, arabinogalactan, and peptidoglycan and confers Toll-like receptor 2 (TLR2)- and TLR4-dependent signaling that induces monocytes to differentiate into antigen-presenting cells (APCs). Here we report differential gene expression analysis with BCG-CWS-stimulated versus nonstimulated monocytes. BCG-CWS exerted massive induction of genes regulated by TLR signaling. Marked gene regulatory characteristics in BCG-CWS-stimulated cells compared to lipopolysaccharide (LPS)-stimulated cells follow. (i) Spliced mRNAs encoding soluble forms of TREM-1 and TREM-2 (recently discovered inflammatory-signal-amplifying receptors) were regulated by BCG-CWS, resulting in their differential expression. (ii) The genes for zinc-iron transporter protein (ZIP)-like family proteins HKE-1 and LIV-1 were induced exclusively by BCG-CWS. (iii) Interleukin-23 (IL-23), rather than IL-12p70, was induced by BCG-CWS, while interferon-inducible genes were induced only by LPS. By Northern and reverse transcription-PCR analyses, we confirmed the differential expression of more than 30 BCG-CWS regulatory genes, and their expression was compared with that of LPS and other known TLR ligands. A battery of genes responded rapidly and for a short time to LPS but for a long time to BCG-CWS. Structural analysis of the identified novel or hypothetical proteins revealed that some are potential candidates as signaling mediators or transcriptional regulators. Hence, BCG-CWS may profoundly modulate APC responses in a way distinct from that of LPS, leading to possible advantages for its adjuvant-active therapeutic potential.