Synthesis and in vitro anti-HCV activity of beta-D- and 1-2'-deoxy-2'-fluororibonucleosides

Based on the discovery of beta-D-2'-deoxy-2'-fluorocytidine as a potent anti-hepatitis C virus (HCV) agent, a series of beta-D- and L-2'-deoxy-2'-fluoroibonucleosides with modifications at 5 and/or 4 positions were synthesized and evaluated for their in vitro activity against HCV and bovine viral diarrhea virus (BVDV). The introduction of the 2'-fluoro group was achieved by either fluorination of 2,2'-anhydronucleosides with hydrogen fluoride-pyridine or potassium fluoride, or a fluorination of arabinonucleosides with DAST. Among the 27 analogues synthesized, only the 5-fluoro compounds, namely beta-D-2'-deoxy-2',5-difluorocytidine (5), had anti-HCV activity in the subgenomic HCV replicon cell line, and inhibitory activity against ribosomal RNA. As beta-D-N4-hydroxycytidine (NHC) had previously shown potent anti-HCV activity, the two functionalities of the N4-hydroxyl and the 2'-fluoro were combined into one molecule, yielding beta-D-2'-deoxy-2'-fluoro-N4-hydroxycytidine (12). However, this nucleoside showed neither anti-HCV activity nor toxicity. All the L-forms of the analogues were devoid of anti-HCV activity. None of the compounds showed anti-BVDV activity, suggesting that the BVDV system cannot reliably predict anti-HCV activity in vitro.     

Unusual olefin formation by PhSe-F trans-elimination

A new approach to the synthesis of 2',3'-didehydro-2',3-dideoxynucleosides was described in excellent yield through unusual olefin formation by PhSe-F trans-elimination.     

Molecular cloning and functional analysis of ESGP, an embryonic stem cell and germ cell specific protein

Several putative Oct-4 downstream genes from mouse embryonic stem （ES） cells have been identified using the suppression-subtractive hybridization method. In this study, one of the novel genes encoding an ES cell and germ cell specific protein （ESGP） was cloned by rapid amplification of cDNA ends. ESGP contains 801 bp encoding an 84 amino acid small protein and has no significant homology to any known genes. There is a signal peptide at the N-terminal of ESGP protein as predicted by SeqWeb （GCG） （SeqWeb version 2 ttp：//gcg.biosino.org：8080/）. The result of immunofluorescence assay suggested that ESGP might encode a secretory protein. The expression pattern of ESGP is consistent with the expression of Oct-4 during embryonic development. ESGP protein was detected in fertilized oocyte, from 3.5 day postcoital （dpc） blastocyst to 17.5 dpc embryo, and was only detected in testis and ovary tissues in adult. In vitro, ESGP was only expressed in pluripotent cell lines, such as embryonic stem cells, embryonic carcinoma cells and embryonic germ cells, but not in their differentiated progenies. Despite its specific expression, forced expression of ESGP is not indispensable for the effect of Oct-4 on ES cell self-renewal, and does not affect the differentiation to three germ layers.     

Efficacy of a DNA vaccine delivered in attenuated Salmonella typhimurium against Eimeria tenella infection in chickens

The efficacy of an oral DNA vaccine carrying the Eimeria tenella 5401 antigen gene delivered by attenuated Salmonella typhimurium was examined in an experimental challenge study. The DNA vaccine preparation was made by transforming the recombinant plasmid pcDNA3-5401 into the attenuated S. typhimurium strain (Dam(-) and PhoP(-)) (designated hereafter as ZJ111/pcDNA3-5401). The chickens were randomly divided into six groups, 50 per group. Group A were given PBS as control. Chickens in group B were fed with 10(8) colony forming units (CFU) of attenuated S. typhimurium carrying pcDNA3. Group C were immunised with 100 microg of the recombinant 5401 protein via intramuscular injection. Groups D to F orally received ZJ111/pcDNA3-5401 at doses of 10(7), 10(8) and 10(9)CFU per chicken, respectively. All immunisations were boosted 2 weeks later. The immunised chickens were challenged with 6x10(4) homologous sporulated oocysts 14 days after the second immunisation. No significant differences in body weight were detected between the groups before immunisation and at week 4 after the booster immunisation. The ZJ111/pcDNA3-5401 was eventually eliminated from the spleen and liver on week 6 post-immunisation. The plasmid pcDNA3-5401 was stably maintained in over 80% of the attenuated S. typhimurium population after 100 generations of growth in antibiotic-free media. Oral immunisation of chickens with ZJ111/pcDNA3-5401 elicited specific humoral responses and stimulated proliferation of peripheral blood lymphocytes. The lymphocyte proliferation response was significantly higher in all vaccinated groups than in the control chickens. Antibody response was significantly lower in group C than in groups immunised with strain ZJ111/pcDNA3-5401. Vaccination with the strain ZJ111/pcDNA3-5401 at 10(8) (group E) and 10(9) (group F) CFU per chicken provided 55.0 and 57.5% protection against E. tenella challenge, respectively. These results have important implications for the development of DNA vaccines against avian coccidiosis by bacteria-vectored oral delivery system.     

Analysis of binding sites in human C-reactive protein for Fc{gamma}RI, Fc{gamma}RIIA, and C1q by site-directed mutagenesis

Human C-reactive protein (CRP) is a classical, acute phase serum protein synthesized by the liver in response to infection, inflammation, or trauma. CRP binds to microbial antigens and damaged cells, opsonizes particles for phagocytosis and regulates the inflammatory response by the induction of cytokine synthesis. These activities of CRP depend on its ability to activate complement and to bind to Fcgamma receptors (FcgammaR). The goal of this study was to elucidate amino acid residues important for the interaction of CRP with human FcgammaRI (CD64) and FcgammaRIIa (CD32). Several mutations of the CRP structure were studied based on the published crystal structure of CRP. Mutant and wild-type recombinant CRP molecules were expressed in the baculovirus system and their interactions with FcgammaR and C1q were determined. A previous study by our laboratory identified an amino acid position, Leu(176), critical for CRP binding to FcgammaRI and work by others (Agrawal, A., Shrive, A. K., Greenhough, T. J., and Volanakis, J. E. (2001) J. Immunol. 166, 3998-4004) determined several residues important for C1q binding. The amino acid residues important to CRP binding to FcgammaRIIa were previously unknown. This study newly identifies residues Thr(173) and Asn(186) as important for the binding of CRP to FcgammaRIIa and FcgammaRI. Lys(114), like Leu(176), was implicated in binding to FcgammaRI, but not FcgammaRIIa. Single mutations at amino acid positions Lys(114), Asp(169), Thr(173), Tyr(175), and Leu(176) affected C1q binding to CRP. These results further identify amino acids involved in the binding sites on CRP for FcgammaRI, FcgammaRIIa, and C1q and indicate that these sites are overlapping.     

Cdc42 induces activation loop phosphorylation and membrane targeting of mixed lineage kinase 3

Mixed lineage kinase 3 (MLK3) functions as a mitogen-activated protein kinase kinase kinase to activate multiple mitogen-activated protein kinase pathways. Our current studies demonstrate that lack of MLK3 blocks signaling of activated Cdc42 to c-Jun N-terminal kinase, giving strong support for the idea that Cdc42 is a physiological activator of MLK3. We show herein that Cdc42, in a prenylation-dependent manner, targets MLK3 from a perinuclear region to membranes, including the plasma membrane. Cdc42-induced membrane targeting of MLK3 is independent of MLK3 catalytic activity but depends upon an intact Cdc42/Rac-interactive binding motif, consistent with MLK3 membrane translocation being mediated through direct binding of Cdc42. Phosphorylation of the activation loop of MLK3 requires MLK3 catalytic activity and is induced by Cdc42 in a prenylation-independent manner, arguing that Cdc42 binding is sufficient for activation loop autophosphorylation of MLK3. However, membrane targeting is necessary for full activation of MLK3 and maximal signaling to JNK. We previously reported that MLK3 is autoinhibited through an interaction between its N-terminal SH3 domain and a proline-containing sequence found between the leucine zipper and the CRIB motif of MLK3. Thus we propose a model in which GTP-bound Cdc42/Rac binds MLK3 and disrupts SH3-mediated autoinhibition leading to dimerization and activation loop autophosphorylation. Targeting of this partially active MLK3 to membranes likely results in additional phosphorylation events that fully activate MLK3 and its ability to maximally signal through the JNK pathway.     

Synthesis of new, potent avermectin-like insecticidal agents

4'-Modified avermectin derivatives were designed and synthesized. Some of the new synthetic compounds showed excellent in vivo bioactivity against cabbage larvae when compared to commercially available avermectin B1a. In this synthesis, uncommon thioglycosyl sugar donors, prepared from the hydrolysis of natural antibiotics, proved compatible with sugar-macrolide synthesis in the presence of N-iodosuccinimide (NIS) or I2 in N-methylpyrrolidone at room temperature.     

Synthesis of a C3-symmetric (1-->6)-N-acetyl-beta-D-glucosamine octadecasaccharide using click chemistry

A C3-symmetric (1-->6)-N-acetyl-beta-D-glucosamine octadecasaccharide was convergently synthesized on the basis of a copper(I)-catalyzed 1,3-dipolar cycloaddition reaction of azide and alkyne. The target octadecasaccharide showed good antitumor activity against H22 in the preliminary mice tests.