The plant mannose-binding lectin NTL preserves cord blood haematopoietic stem/progenitor cells in long-term culture and enhances theirex vivoexpansion

Tarin stimulates granulocyte growth in bone marrow cell cultures and minimizes immunosuppression by cyclo-phosphamide in mice

Chemotherapeutic drugs, such as cyclophosphamide, cause severe immunosuppression and patients become susceptible to infections. Based on this, the immunomodulatory potential of tarin, a lectin from Colocasia esculenta, was evaluated in bone marrow cell cultures and in cyclophosphamide-immunosuppressed mice. Tarin promoted maintenance of hematopoietic progenitors and repopulation of Gr1 cells in vitro which was supported by in vivo results. In immunosuppressed mice, tarin increased bone marrow cell numbers and altered cell profile distribution by enhancing the frequency of Gr1+ progenitors, including Ly6-CintLy6-Glo, and anticipating their proliferation/differentiation in mature cells, especially Ly6-CloLy6-Ghi. Bone marrow cells harvested from tarin-treated immunosuppressed mice proliferated in response to GM-CSF or G-CSF in vitro and, the low numbers of bone marrow cells in the G0 phase, combined with a high number cells undergoing apoptosis confirmed that tarin promoted a faster and intense proliferation/differentiation, even in the presence of CY-induced toxicity. As a result, tarin minimized leukopenia in immunosuppressed mice promoting a faster recovery of peripheral leucocytes and protected erythroid bone marrow cells from CY-cytotoxicity in a dose-dependent manner. Data suggest that tarin could be considered a potential adjuvant to decrease leukopenia and possibly ameliorate anemia, if carefully evaluated in human cancer cell lineages and in clinical trials.

Narcissus tazetta lectin shows strong inhibitory effects against respiratory syncytial virus, influenza A (H1N1, H3N2, H5N1) and B viruses

A mannose-binding lectin (Narcissus tazetta lectin [NTL]) with potent antiviral activity was isolated and purified from the bulbs of the Chinese daffodil Narcissus tazetta var. chinensis, using ion exchange chromatography on diethylaminoethyl (DEAE)-cellulose, affinity chromatography on mannose-agarose and fast protein liquid chromatography (FPLC)-gel filtration on Superose 12. The purified lectin was shown to have an apparent molecular mass of 26 kDa by gel filtration and 13 kDa by SDS-PAGE, indicating that it is probably a dimer with two identical subunits. The cDNA-derived amino acid sequence of NTL as determined by molecular cloning also reveals that NTL protein contains a mature polypeptide consisting of 105 amino acids and a C-terminal peptide extension. Three-dimensional modelling study demonstrated that the NTL primary polypeptide contains three subdomains, each with a conserved mannose-binding site. It shows a high homology of about 60%–80% similarity with the existing monocot mannose-binding lectins. NTL could significantly inhibit plaque formation by the human respiratory syncytial virus (RSV) with an IC₅₀ of 2.30 µg/ml and exhibit strong antiviral properties against influenza A (H1N1, H3N2, H5N1) and influenza B viruses with IC₅₀ values ranging from 0.20 µg/ml to 1.33 µg/ml in a dose-dependent manner. It is worth noting that the modes of antiviral action of NTL against RSV and influenza A virus are significantly different. NTL is effective in the inhibition of RSV during the whole viral infection cycle, but the antiviral activity of NTL is mainly expressed at the early stage of the viral cycle of influenza A (H1N1) virus. NTL with a high selective index (SI=CC₅₀/IC₅₀≥141) resulting from its potent antiviral activity and low cytotoxicity demonstrates a potential for biotechnological development as an antiviral agent.

In vitro protection of umbilical cord blood-derived primitive hematopoietic stem progenitor cell pool by mannose-specific lectins via antioxidant mechanisms

BACKGROUND

Earlier we reported that an oral administration of two mannose-specific dietary lectins, banana lectin (BL) and garlic lectin (GL), led to an enhancement of hematopoietic stem and progenitor cell (HSPC) pool in mice.

STUDY DESIGN AND METHODS

Cord blood-derived CD34+ HSPCs were incubated with BL, GL, Dolichos lectin (DL), or artocarpin lectin (AL) for various time periods in a serum- and growth factor-free medium and were subjected to various functional assays. Reactive oxygen species (ROS) levels were detected by using DCHFDA method. Cell fractionation was carried out using lectin-coupled paramagnetic beads.

RESULTS

CD34+ cells incubated with the lectins for 10 days gave rise to a significantly higher number of colonies compared to the controls, indicating that all four lectins possessed the capacity to protect HSPCs in vitro. Comparative analyses showed that the protective ability of BL and GL was better than AL and DL and, therefore, further experiments were carried out with them. The output of long-term culture-initiating cell (LTC-IC) and extended LTC-IC assays indicated that both BL and GL protected primitive stem cells up to 30 days. The cells incubated with BL or GL showed a substantial reduction in the ROS levels, indicating that these lectins protect the HSPCs via antioxidant mechanisms. The mononuclear cell fraction isolated by lectin-coupled beads got enriched for primitive HSPCs, as reflected in the output of phenotypic and functional assays.

CONCLUSION

The data show that both BL and GL protect the primitive HSPCs in vitro and may also serve as cost-effective HSPC enrichment tools.