Co-reporter:Guochao Liao, Zhifang Zhou, Sharad Suryawanshi, Mohabul A. Mondal, and Zhongwu Guo
ACS Central Science 2016 Volume 2(Issue 4) pp:210
Publication Date(Web):April 4, 2016
DOI:10.1021/acscentsci.5b00364
α-2,9-Polysialic acid is an important capsular polysaccharide expressed by serotype C Neisseria meningitidis. Its protein conjugates are current vaccines against group C meningitis. To address some concerns about traditional protein conjugate vaccines, a new type of fully synthetic vaccines composed of oligosialic acids and glycolipids was explored. In this regard, α-2,9-linked di-, tri-, tetra-, and pentasialic acids were prepared and conjugated with monophosphoryl lipid A (MPLA). Immunological studies of the conjugates in C57BL/6J mouse revealed that they alone elicited robust immune responses comparable to that induced by corresponding protein conjugates plus adjuvant, suggesting the self-adjuvanting properties of MPLA conjugates. The elicited antibodies were mainly IgG2b and IgG2c, suggesting T cell dependent immunities. The antisera had strong and specific binding to α-2,9-oligosialic acids and to group C meningococcal polysaccharide and cell, indicating the ability of antibodies to selectively target the bacteria. The antisera also mediated strong bactericidal activities. Structure–activity relationship analysis of the MPLA conjugates also revealed that the immunogenicity of oligosialic acids decreased with elongated sugar chain, but all tested MPLA conjugates elicited robust immune responses. It is concluded that tri- and tetrasialic acid–MPLA conjugates are worthy of further investigation as the first fully synthetic and self-adjuvanting vaccines against group C meningitis.
Co-reporter:Guochao Liao, Zhifang Zhou, Jun Liao, Luning Zu, Qiuye Wu, and Zhongwu Guo
ACS Infectious Diseases 2016 Volume 2(Issue 2) pp:123
Publication Date(Web):December 19, 2015
DOI:10.1021/acsinfecdis.5b00104
With the rapid growth in fungal infections and drug-resistant fungal strains, antifungal vaccines have become an especially attractive strategy to tackle this important health problem. β-Glucans, a class of extracellular carbohydrate antigens abundantly and consistently expressed on fungal cell surfaces, are intriguing epitopes for antifungal vaccine development. β-Glucans have a conserved β-1,3-glucan backbone with sporadic β-1,3- or β-1,6-linked short glucans as branches at the 6-O-positions, and the branches may play a critical role in their immunologic functions. To study the immunologic properties of branched β-glucans and develop β-glucan-based antifungal vaccines, three branched β-glucan oligosaccharides with 6-O-linked β-1,6-tetraglucose, β-1,3-diglucose, and β-1,3-tetraglucose branches on a β-1,3-nonaglucan backbone, which mimic the structural epitopes of natural β-glucans, were synthesized and coupled with keyhole limpet hemocyanin (KLH) to form novel synthetic conjugate vaccines. These glycoconjugates were proved to elicit strong IgG antibody responses in mice. It was also discovered that the number, size, and structure of branches linked to the β-glucan backbone had a significant impact on the immunologic property. Moreover, antibodies induced by the synthetic oligosaccharide–KLH conjugates were able to recognize and bind to natural β-glucans and fungal cells. Most importantly, these conjugates elicited effective protection against systemic Candida albicans infection in mice. Thus, branched oligo-β-glucans were identified as functional epitopes for antifungal vaccine design and the corresponding protein conjugates as promising antifungal vaccine candidates.Keywords: carbohydrate; fungus; glycoconjugate; vaccine; β-glucan
Co-reporter:Zhifang Zhou, Guochao Liao, Satadru S. Mandal, Sharad Suryawanshi and Zhongwu Guo
Chemical Science 2015 vol. 6(Issue 12) pp:7112-7121
Publication Date(Web):22 Sep 2015
DOI:10.1039/C5SC01402F
Therapeutic cancer vaccines based on the abnormal glycans expressed on cancer cells, such as the globo H antigen, have witnessed great progress in recent years. For example, the keyhole limpet hemocyanin (KLH) conjugate of globo H has been on clinical trials as a cancer vaccine. However, such vaccines have intrinsic problems, such as inconsistence in eliciting T cell-mediated immunity in cancer patients and difficult quality control. To address the issue, a structurally defined fully synthetic glycoconjugate vaccine composed of globo H and monophosphoryl lipid A (MPLA) was developed. The new vaccine was shown to elicit robust IgG1 antibody responses and T cell-dependent immunity, which is desired for anticancer vaccines, and induce significantly faster and stronger immune responses than the globo H–KLH conjugate. Moreover, it was self-adjuvanting, namely, inducing immune responses without the use of an external adjuvant, thus MPLA was not only a vaccine carrier but also a build-in adjuvant. It was also found that antibodies induced by the new vaccine could selectively bind to and mediate strong complement-dependent cytotoxicity to globo H-expressing MCF-7 cancer cell. All of the results have demonstrated that the globo H–MPLA conjugate is a better cancer vaccine than the globo H–KLH conjugate under experimental conditions and is worth further investigation and development.
Co-reporter:Guochao Liao, Zhifang Zhou and Zhongwu Guo
Chemical Communications 2015 vol. 51(Issue 47) pp:9647-9650
Publication Date(Web):28 Apr 2015
DOI:10.1039/C5CC01794G
α-2,9-Di-, tri-, tetra-, and pentasialic acids were prepared and conjugated with a carrier protein. The resultant glycoconjugates elicited robust T cell-mediated immunity in mice. α-2,9-Trisialic acid was identified as a promising antigen for developing glycoconjugate vaccines against group C Neisseria meningitidis.
Co-reporter:Prolay K. Mondal, Guochao Liao, Mohabul A. Mondal, and Zhongwu Guo
Organic Letters 2015 Volume 17(Issue 5) pp:1102-1105
Publication Date(Web):February 12, 2015
DOI:10.1021/ol5036563
The structure of the capsular polysaccharide (CPS) of serotype Ia group B Streptococcus (GBS) has been characterized for years, but its repeating unit, which is a challenging pentasaccharide with a branch and a difficult α-sialic acid linkage, has not been synthesized yet. In this report, an effective synthesis was developed for the serotype Ia GBS CPS repeating unit, which had a reactive functionality linked to its main-chain reducing end to enable further elaboration, such as coupling with carrier proteins. The target molecule was accomplished by a convergent [2 + 3] glycosylation strategy employing a sialo-disaccharide as donor and a branched trisaccharide as acceptor. The strategy was designed to suit the synthesis of oligomers of the repeating unit.
Co-reporter:Guochao Liao, Zhifang Zhou, Srinivas Burgula, Jun Liao, Cheng Yuan, Qiuye Wu, and Zhongwu Guo
Bioconjugate Chemistry 2015 Volume 26(Issue 3) pp:466
Publication Date(Web):February 11, 2015
DOI:10.1021/bc500575a
Antifungal vaccines have recently engendered considerable excitement for counteracting the resurgence of fungal infections. In this context, β-glucan, which is abundantly expressed on all fungal cell surfaces, functionally necessary for fungi, and immunologically active, is an attractive target antigen. Aiming at the development of effective antifungal vaccines based on β-glucan, a series of its oligosaccharide derivatives was designed, synthesized, and coupled with a carrier protein, keyhole limpet hemocyanin (KLH), to form new semisynthetic glycoconjugate vaccines. In this article, a convergent and effective synthetic strategy using preactivation-based iterative glycosylation was developed for the designed oligosaccharides. The strategy can be widely useful for rapid construction of large oligo-β-glucans with shorter oligosaccharides as building blocks. The KLH conjugates of the synthesized β-glucan hexa-, octa-, deca-, and dodecasaccharides were demonstrated to elicit high titers of antigen-specific total and IgG antibodies in mice, suggesting the induction of functional T cell-mediated immunity. Moreover, it was revealed that octa-, deca-, and dodeca-β-glucans were much more immunogenic than the hexamer and that the octamer was the best among these. The results suggested that the optimal oligosaccharide sequence of β-glucan required for exceptional immunogenicity was a hepta- or octamer and that longer glucans are not necessarily better antigens, a finding that may be of general importance. Most importantly, the octa-β-glucan–KLH conjugate provoked protective immunity against Candida albicans infection in a systemic challenge model in mice, suggesting the great potential of this glycoconjugate as a clinically useful immunoprophylactic antifungal vaccine.
Co-reporter:Satadru S. Mandal, Guochao Liao and Zhongwu Guo
RSC Advances 2015 vol. 5(Issue 30) pp:23311-23319
Publication Date(Web):24 Feb 2015
DOI:10.1039/C5RA00759C
A derivative of the tumor-associated globo H antigen, a complex hexasaccharide, was synthesized by a convergent and efficient [3 + 2 + 1] strategy using various glycosylation methods. All glycosylation reactions afforded good to excellent yields and outstanding stereoselectivity, including the installation of cis α-linked D-galactose and L-fucose. The longest linear sequence for this synthesis was 11 steps from a galactose derivative 11 to give an overall yield of 2.6%. The synthetic target had a free and reactive amino group at the glycan reducing end, facilitating its conjugation with other molecules for various applications.
Co-reporter:Guochao Liao;Srinivas Burgula;Zhifang Zhou
European Journal of Organic Chemistry 2015 Volume 2015( Issue 13) pp:2942-2951
Publication Date(Web):
DOI:10.1002/ejoc.201500229
Abstract
β-Glucans are important carbohydrate antigens that are found on the surface of fungal cells, and they could be useful for the development of antifungal vaccines. This paper describes a highly convergent and efficient strategy for the synthesis of structurally defined branched β-glucan oligosaccharides that can be used for detailed studies of β-glucans and for the design of β-glucan-based vaccines. The strategy was highlighted by assembling three target compounds through preactivation-based glycosylation with thioglycosides as glycosyl donors. It was used to successfully prepare β-glucan oligosaccharides consisting of a β-1,3-linked nonaglucan backbone linked to a β-1,6-glucotetraose, a β-1,3-glucodiose, or a β-1,3-glucotetraose branch at the 6-O-position of the nonaglucan central sugar unit. The structure and size of the glycosyl donors and acceptors used in the syntheses did not significantly affect the efficiency of the glycosylation, which suggests that this strategy can be generally useful for the synthesis of more complex structures.
Co-reporter:Dr. Lili Lu;Dr. Jian Gao;Dr. Zhongwu Guo
Angewandte Chemie 2015 Volume 127( Issue 33) pp:9815-9818
Publication Date(Web):
DOI:10.1002/ange.201503814
Abstract
Glycosylphosphatidylinositol (GPI) anchoring of proteins to the cell surface is important for various biological processes, but GPI-anchored proteins are difficult to study. An effective strategy was developed for the metabolic engineering of cell-surface GPIs and GPI-anchored proteins by using inositol derivatives carrying an azido group. The azide-labeled GPIs and GPI-anchored proteins were then tagged with biotin on live cells through a click reaction, which allows further elaboration with streptavidin-conjugated dyes or other molecules. The strategy can be used to label GPI-anchored proteins with various tags for biological studies.
Co-reporter:Dr. Lili Lu;Dr. Jian Gao;Dr. Zhongwu Guo
Angewandte Chemie International Edition 2015 Volume 54( Issue 33) pp:9679-9682
Publication Date(Web):
DOI:10.1002/anie.201503814
Abstract
Glycosylphosphatidylinositol (GPI) anchoring of proteins to the cell surface is important for various biological processes, but GPI-anchored proteins are difficult to study. An effective strategy was developed for the metabolic engineering of cell-surface GPIs and GPI-anchored proteins by using inositol derivatives carrying an azido group. The azide-labeled GPIs and GPI-anchored proteins were then tagged with biotin on live cells through a click reaction, which allows further elaboration with streptavidin-conjugated dyes or other molecules. The strategy can be used to label GPI-anchored proteins with various tags for biological studies.
Co-reporter:Jian Gao, Guochao Liao, Lizhen Wang, and Zhongwu Guo
Organic Letters 2014 Volume 16(Issue 3) pp:988-991
Publication Date(Web):January 21, 2014
DOI:10.1021/ol4036903
An analog of Mycobacterium tuberculosis lipoarabinomannan (LAM) has been synthesized containing the characteristic structures of all of its three major components; that is, a mannosylated phosphatidylinositol moiety, an oligomannan, and an oligoarabinan. A highly convergent strategy was developed that is applicable to the synthesis of other LAM analogs. The synthetic miniature LAM should be useful for various biological studies.
Co-reporter:Zhifang Zhou, Mohabul Mondal, Guochao Liao and Zhongwu Guo
Organic & Biomolecular Chemistry 2014 vol. 12(Issue 20) pp:3238-3245
Publication Date(Web):11 Mar 2014
DOI:10.1039/C4OB00390J
A fully synthetic carbohydrate-based cancer vaccine is an attractive concept, but an important topic in the area is to develop proper vaccine carriers that can improve the immunogenicity and other immunological properties of tumor-associated carbohydrate antigens (TACAs). In this context, four monophosphoryl derivatives of Neisseria meningitidis lipid A were synthesized via a highly convergent and effective strategy and evaluated as vaccine carriers and adjuvants. The conjugates of these monophosphoryl lipid A (MPLA) derivatives with a modified form of the sTn antigen were found to elicit high titers of antigen-specific IgG antibodies, indicating a T cell-dependent immune response, in the absence of an external adjuvant. It was concluded that MPLAs could be utilized as potent vaccine carriers and built-in adjuvants to create fully synthetic self-adjuvanting carbohydrate-based cancer vaccines. The lipid composition and structure of MPLA were shown to have a significant influence on its immunological activity, and among the MPLAs examined, natural N. meningitidis MPLA exhibited the most promising properties. Moreover, Titermax Gold, a conventional vaccine adjuvant, was shown to inhibit, rather than promote, the immunological activity of MPLA conjugates, maybe via interacting with MPLA.
Co-reporter:Zhimeng Wu, Xueqing Guo, Jian Gao and Zhongwu Guo
Chemical Communications 2013 vol. 49(Issue 99) pp:11689-11691
Publication Date(Web):22 Oct 2013
DOI:10.1039/C3CC47229A
Green fluorescent protein and a glycosylphosphatidylinositol (GPI) anchor containing the common core structure and a lipid chain were synthesized and then coupled together in the promotion of bacterial sortase A (SrtA), which was the first example for the synthesis of a full-size GPI-anchored protein by SrtA, demonstrating that this can be a generally useful method for GPI-anchored protein synthesis.
Co-reporter:Zhimeng Wu, Xueqing Guo, Guofeng Gu, and Zhongwu Guo
Organic Letters 2013 Volume 15(Issue 22) pp:5906-5908
Publication Date(Web):October 22, 2013
DOI:10.1021/ol4028144
Analogs of the human CD52 and CD24 antigens carrying the common core structure of glycosylphosphatidylinositol (GPI) anchors and the intact polypeptide sequences of CD52 and CD24 were chemoenzymatically synthesized. CD52 and CD24 proteins were obtained by solid-phase peptide synthesis and then coupled to chemically synthesized GPI anchors under the influence of a bacterial enzyme, sortase A, to afford the target molecules in good yields.
Co-reporter:Shichong Yu, Zhongwu Guo, Charlie Johnson, Guofeng Gu, Qiuye Wu
Current Opinion in Chemical Biology 2013 17(6) pp: 1006-1013
Publication Date(Web):
DOI:10.1016/j.cbpa.2013.09.016
Co-reporter:Jian Gao and Zhongwu Guo
The Journal of Organic Chemistry 2013 Volume 78(Issue 24) pp:12717-12725
Publication Date(Web):November 22, 2013
DOI:10.1021/jo4021979
A convergent and efficient strategy was developed for the synthesis of lipomannan (LM), useful for vaccine development. Thioglycosides were employed as glycosyl donors to construct two key pseudotrisaccharide and tetramannose intermediates through preactivation-based glycosylation strategy. These building blocks were then successfully coupled to form the LM core, which was lapidated, phospholipidated, and finally globally deprotected to afford the target molecule. The intermediate LM core involved in this synthesis contained orthogonal protections, which would facilitate its variable modifications for the preparation of other complex LM derivatives and for the synthesis of LM conjugates as LM-based vaccines.
Co-reporter:Xueqing Guo, Zhimeng Wu, and Zhongwu Guo
Bioconjugate Chemistry 2012 Volume 23(Issue 3) pp:650
Publication Date(Web):February 28, 2012
DOI:10.1021/bc200694t
A new method was developed for site-specific modifications of liposomes by proteins via sortase A (SrtA)-mediated transpeptidation reactions. In this regard, the enhanced green fluorescent protein (eGFP) was biologically engineered to carry at its polypeptide C-terminus the LPATG motif recognized by SrtA and used as the protein donor for linking to liposomes that were decorated with phospholipids carrying a diglycine motif as the other SrtA substrate and the eGFP acceptor. Under the influence of SrtA, eGFP was efficiently attached to liposomes, as proved by analyzing the enzymatic reaction products and the resultant fluorescent liposomes. It was observed that increasing the concentration and the distance of the diglycine motif on and from the liposome surface could significantly improve the efficiency of liposome modification by proteins. It is anticipated that this strategy can be widely useful for the modification of liposomes by other proteins.
Co-reporter:Qianli Wang, Zhifang Zhou, Shouchu Tang, and Zhongwu Guo
ACS Chemical Biology 2012 Volume 7(Issue 1) pp:235
Publication Date(Web):October 20, 2011
DOI:10.1021/cb200358r
Tumor-associated carbohydrate antigens (TACAs) are useful targets in the development of therapeutic cancer vaccines. However, a serious problem with them is the poor immunogenicity. To overcome the problem, a monophosphorylated derivative of Neisseria meningitidis lipid A was explored as a potential carrier molecule and built-in adjuvant for the construction of structurally defined fully synthetic glycoconjugate vaccines. Some paradigm-shifting discoveries about the monophosphoryl lipid A (MPLA)-TACA conjugates were that they elicited robust IgG antibody responses, indicating T cell-mediated immunity, without an external adjuvant and that an external adjuvant, e.g., Titermax Gold, actually reduced rather than promoted the immunological activity of the conjugates. The induced antibodies were proved to bind selectively to target tumor cells. MPLA was therefore demonstrated to be a powerful built-in immunostimulant and adjuvant for an all new design of fully synthetic glycoconjugate cancer vaccines.
Co-reporter:Dr. Srinivas Burgula;Dr. Benjamin M. Swarts;Dr. Zhongwu Guo
Chemistry - A European Journal 2012 Volume 18( Issue 4) pp:1194-1201
Publication Date(Web):
DOI:10.1002/chem.201102545
Abstract
The first total synthesis of a glycosylphosphatidylinositol (GPI) anchor bearing a polyunsaturated arachidonoyl fatty acid is reported. This lipid is found in mammalian GPIs that do not undergo lipid remodeling, a process that has important implications in the localization and function of GPI-anchored proteins. Incorporation of the oxidation- and reduction-sensitive arachidonoyl lipid in the target GPI was accomplished by using the para-methoxybenzyl (PMB) group for permanent hydroxyl group protection, which featured a selective, rapid, and efficient global deprotection protocol. The flexibility of this synthetic strategy was further highlighted by the inclusion of two additional GPI core structural modifications present in the GPI anchor of the human lymphocyte CD52 antigen.
Co-reporter:Lei Qiu;Xi Gong;Qianli Wang;Jie Li;Honggang Hu;Qiuye Wu;Zhongwu Guo;Junping Zhang
Cancer Immunology, Immunotherapy 2012 Volume 61( Issue 11) pp:
Publication Date(Web):2012/11/01
DOI:10.1007/s00262-012-1224-6
Tumor-associated carbohydrate antigens (TACAs) are useful targets for the development of cancer vaccines or immunotherapies. However, a major obstacle in this application of TACAs is their poor immunogenicity. To overcome the problem, a new immunotherapeutic strategy combining synthetic vaccines made of artificial TACA derivatives and metabolic glycoengineering of cancer cells to express the artificial TACA derivatives was explored. Using a murine leukemia model FBL3 with GM3 antigen as the target, it was shown that artificial GM3 N-phenylacetyl derivative (GM3NPhAc) elicited robust antigen-specific T cell-dependent immunity and that N-phenylacetyl-d-mannosamine (ManNPhAc) as the biosynthetic precursor of GM3NPhAc selectively glycoengineered cancer cells to express GM3NPhAc both in vitro and in vivo. It was also demonstrated that GM3NPhAc-specific antisera and antibodies mediated strong cytotoxicity to ManNPhAc-treated FBL3 cell. Furthermore, vaccination with a conjugate vaccine made of GM3NPhAc followed by ManNPhAc treatment could significantly suppress tumor growth and prolong the survival of tumor-bearing mouse. These results have proved the feasibility of the new cancer immunotherapeutic strategy, as well as its efficacy to cure cancer, which is of general significance.
Co-reporter:Benjamin M. Swarts and Zhongwu Guo
Chemical Science 2011 vol. 2(Issue 12) pp:2342-2352
Publication Date(Web):06 Sep 2011
DOI:10.1039/C1SC00440A
Glycosylphosphatidylinositol (GPI) anchorage is a common posttranslational modification of eukaryotic proteins. Chemical synthesis of structurally defined GPIs and GPI derivatives is a necessary step toward understanding the properties and functions of these molecules in biological systems. In this work, the synthesis of several functionalized GPI anchors was accomplished using the para-methoxybenzyl (PMB) group for permanent hydroxyl protection, which allowed the incorporation of functionalities that are incompatible with permanent protecting groups traditionally used in carbohydrate synthesis. A flexible convergent–divergent assembly strategy enabled efficient access to a diverse set of target structures, including “clickable” alkyne- and azide-modified GPIs. For global deprotection, a one-pot reaction was employed to afford the target GPIs in excellent yields (85–97%). Fully deprotected clickable GPI derivatives were readily conjugated to imaging and affinity probes via Cu(I)-catalyzed and Cu-free strain-promoted [3 + 2] cycloaddition to result in GPI-Flour and GPI-Biotin conjugates, respectively.
Co-reporter:Zhimeng Wu, Xueqing Guo and Zhongwu Guo
Chemical Communications 2011 vol. 47(Issue 32) pp:9218-9220
Publication Date(Web):08 Jul 2011
DOI:10.1039/C1CC13322E
A chemoenzymatic method was developed for the synthesis of macrocyclic peptides and glycopeptides. Sortase A was found to mediate either head to tail cyclization or oligomerization and then head to tail cyclization of peptides and glycopeptides, depending on the peptide length, to produce 15-mer or higher cyclic peptides and glycopeptides.
Co-reporter:Qianli Wang and Zhongwu Guo
ACS Medicinal Chemistry Letters 2011 Volume 2(Issue 5) pp:373
Publication Date(Web):March 17, 2011
DOI:10.1021/ml100313d
To search for effective cancer vaccines based on sTn, a sialylated tumor-associated carbohydrate antigen (sialo-TACA) expressed by a number of tumors, four unnatural N-acyl sTn derivatives, including 5′-N-p-methylphenylacetyl sTn (sTnNMePhAc), 5′-N-p-methoxylphenylacetyl sTn (sTnNMeOPhAc), 5′-N-p-acetylphenylacetyl sTn (sTnNAcPhAc), and 5′-N-p-chlorophenylacetyl sTn (sTnNClPhAc), as well as their protein conjugates, were synthesized by a highly convergent procedure. The immunological properties of these sTn derivatives in the form of keyhole limpet hemocyanin conjugate were evaluated in mice and compared to that of sTnNPhAc, a sTn derivative previously investigated as a vaccine candidate. It was shown that sTnNMePhAc, sTnNMeOPhAc, sTnNAcPhAc, and sTnNClPhAc are all much more immunogenic than sTnNPhAc and that they provoked strong T cell-dependent IgG1 immune responses useful for cancer immunotherapy. It was concluded that sTnNClPhAc is a promising candidate for cancer vaccine development and is worthy of further investigation.Keywords: Cancer vaccine; glycoconjugate; immunology; sTn antigen; sTn derivative; tumor-associated carbohydrate antigen
Co-reporter:Shichong Yu, Qianli Wang, Junping Zhang, Qiuye Wu and Zhongwu Guo
MedChemComm 2011 vol. 2(Issue 6) pp:524-530
Publication Date(Web):18 Apr 2011
DOI:10.1039/C1MD00033K
GM3, a sialylated trisaccharide antigen expressed by a number of tumors, is an attractive target in the design of therapeutic cancer vaccines. However, a serious problem associated with GM3 is that it is poorly immunogenic. To overcome this problem for the development of GM3-based cancer vaccines, four GM3 derivatives, including 5′-N-p-methylphenylacetyl, 5′-N-p-methoxyphenylacetyl, 5′-N-p-acetophenylacetyl and 5′-N-p-chlorophenylacetyl GM3, were synthesized and then coupled to a carrier protein, keyhole limpet haemocyanin (KLH). The resultant glycoconjugates were evaluated as vaccines in mouse and compared to the KLH conjugate of 5′-N-phenylacetyl GM3 (GM3NPhAc), a highly immunogenic GM3 derivative that was previously investigated as a vaccine candidate. All of the four new GM3 derivatives were proved to be more immunogenic than GM3NPhAc and elicit very strong T cell-dependent immune responses desirable for cancer immunotherapy. It was concluded that the new GM3 derivatives can form promising vaccine candidates that may be used to combine with cell glycoengineering for cancer immunotherapy.
Co-reporter:Zhimeng Wu ; Xueqing Guo ; Qianli Wang ; Benjamin M. Swarts
Journal of the American Chemical Society 2010 Volume 132(Issue 5) pp:1567-1571
Publication Date(Web):January 15, 2010
DOI:10.1021/ja906611x
Several peptides/small proteins and glycosylphosphatidylinositol (GPI) derivatives were synthesized and compared as substrates of sortase A (SrtA), a bacterial transpeptidase, for enzymatic coupling. It was observed that peptides containing the LPKTGGS and LPKTGGRS sequences as sorting signals at the peptide C-terminus were effectively coupled to GPI derivatives having one or two glycine residues attached to the phosphoethanolamine group at the nonreducing end. This reaction was employed to prepare several analogues of the human CD52 and CD24 antigens, which are naturally GPI-anchored glycopeptides/glycoproteins. It was further observed that the trisaccharide GPI analogues 5 and 6 were better SrtA substrates than monosaccharide GPI analogue 4, suggesting that steric hindrance of the GPI analogues does not affect their peptidation reaction mediated by SrtA. Therefore, this synthetic strategy may be useful for the preparation of more complex GPI-anchored peptides, glycopeptides, proteins, and glycoproteins.
Co-reporter:Benjamin M. Swarts
Journal of the American Chemical Society 2010 Volume 132(Issue 19) pp:6648-6650
Publication Date(Web):April 27, 2010
DOI:10.1021/ja1009037
A GPI anchor bearing unsaturated fatty acid lipid chains (1) was synthesized by a highly convergent strategy employing the para-methoxybenzyl group for permanent hydroxyl protection. The final global deprotection was achieved by an efficient three-step, one-pot procedure to give an 81% isolated yield of the target structure.
Co-reporter:Zhimeng Wu, Xueqing Guo and Zhongwu Guo
Chemical Communications 2010 vol. 46(Issue 31) pp:5773-5774
Publication Date(Web):24 Jun 2010
DOI:10.1039/C0CC00828A
MUC1 glycopeptide was efficiently coupled to glycosylphosphatidylinositol (GPI) derivatives by sortase A (SrtA), verifying that SrtA can accept sterically hindered glycopeptide as substrate for ligation with GPIs. This work has established a practical method for the chemoenzymatic synthesis of GPI-linked glycopeptides.
Co-reporter:Shouchu Tang Dr.;Qianli Wang Dr. Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 4) pp:1319-1325
Publication Date(Web):
DOI:10.1002/chem.200902153
Abstract
Monophosphoryl lipid A is a safe and potent immunostimulant and vaccine adjuvant, which is potentially useful for the development of effective carbohydrate-based conjugate vaccines. This paper presents a convergent and efficient synthesis of a monophosphoryl derivative of E. coli lipid A that has an alkyne functionality at the reducing end, which is suitable for coupling with various molecules. The coupling of this derivative to an N-modified analogue of tumor-associated antigen GM3 through click chemistry is also presented.
Co-reporter:Xueqing Guo ; Qianli Wang ; Benjamin M. Swarts
Journal of the American Chemical Society 2009 Volume 131(Issue 29) pp:9878-9879
Publication Date(Web):July 7, 2009
DOI:10.1021/ja903231v
It is demonstrated that sortase A (SrtA) can catalyze efficient coupling of peptides to GPI analogues with a glycine residue attached to the phosphoethanolamine moiety at the nonreducing end to form GPI-linked peptides. This represents the first chemoenzymatic synthesis of GPI−peptide conjugates and is a proof-of-concept for the potential application of SrtA to the synthesis of more complex GPI-anchored peptides/glycopeptides and GPI-anchored proteins/glycoproteins.
Co-reporter:Qianli Wang, Jie Xue and Zhongwu Guo
Chemical Communications 2009 (Issue 37) pp:5536-5537
Publication Date(Web):27 Aug 2009
DOI:10.1039/B907351E
An efficient synthesis of a derivative of monophosphoryl lipid A suitable for coupling to various structures for the construction of glycoconjugate vaccines and its conjugation with an N-modified form of the tumor-associated antigen GM3 is presented.
Co-reporter:Honggang Hu, Jie Xue, Benjamin M. Swarts, Qianli Wang, Qiuye Wu and Zhongwu Guo
Journal of Medicinal Chemistry 2009 Volume 52(Issue 7) pp:2052-2059
Publication Date(Web):March 12, 2009
DOI:10.1021/jm801577r
An efficient and practical method for macrocyclic glycopeptide synthesis was developed and utilized to synthesize tyrocidine A and its glycosylated derivatives. The method is based on solid-phase peptide synthesis using 2-chlorotrityl resin as the solid-phase support and glycosyl amino acids as building blocks. After glycopeptides with fully protected glycans and side chains were released from the acid-labile resin, their C- and N-termini were intramolecularly coupled in solution to afford cyclic glycopeptides in quantitative yields. This synthetic method should be generally applicable to various macrocyclic glycopeptides. Biological studies of the synthetic tyrocidine A derivatives showed that linking glycans directly to the Asn residue of tyrocidine A diminished its antibacterial activity, but linking glycans to Asn via a simple spacer did not. These results revealed the important impact of glycans on the activities, and probably the structures, of glycopeptide antibiotics.
Co-reporter:Fei Yu, Zhongwu Guo
Bioorganic & Medicinal Chemistry Letters 2009 Volume 19(Issue 14) pp:3852-3855
Publication Date(Web):15 July 2009
DOI:10.1016/j.bmcl.2009.03.151
A facile and effective method was developed for large-scale syntheses of myo-inositol derivatives with the 1,2,6-O-positions differentiated from each other and from other positions as well. The syntheses started from methyl α-d-glucopyranoside, and the key steps are Ferrier rearrangement and a series of other regioselective and stereoselective reactions. The target compounds are key intermediates in the synthesis of GPIs.
Co-reporter:Xiaoming Wu, Zhihong Shen, Xiangqun Zeng, Shenhui Lang, Michael Palmer, Zhongwu Guo
Carbohydrate Research 2009 Volume 344(Issue 7) pp:952
Publication Date(Web):12 May 2009
DOI:10.1016/j.carres.2009.02.030
Co-reporter:Qianli Wang, Sandamali Amarasingha Ekanayaka, Jian Wu, Junping Zhang and Zhongwu Guo
Bioconjugate Chemistry 2008 Volume 19(Issue 10) pp:2060
Publication Date(Web):September 25, 2008
DOI:10.1021/bc800243f
5′-N-Phenylacetyl sTn (sTnNPhAc), an unnatural derivative of sTn antigen expressed by many tumors, and its α-linked protein conjugates were prepared and investigated to explore glycoconjugate cancer vaccines. sTnNPhAcα-KLH elicited a robust T cell dependent immunity. The antiserum derived from sTnNPhAcα- or sTnNPhAcβ-KLH-inoculated mice was similarly reactive to sTnNPhAcα and sTnNPhAcβ but showed very little reactivity to sTn, NeuNPhAcα(2,3)GalNAc—a regioisomer of sTnNPhAc, isolated phenylacetyl group, and the linker employed to conjugate sTnNPhAc and carrier protein. It was concluded that the sTnNPhAc-elicited immunity was specific for the whole antigen rather than the phenylacetyl group or other partial structures of sTnNPhAc and that the reducing end configuration or linkage of sTnNPhAc did not affect its immunological identity. It was also concluded that a new linker designed to conjugate carbohydrates and proteins did not provoke any immune reaction and that the linker, as well as the associated new and convenient coupling strategy, can be safely used for the development of glycoconjugate vaccines.
Co-reporter:Xiaoming Wu, Zhihong Shen, Xiangqun Zeng, Shenhui Lang, Michael Palmer, Zhongwu Guo
Carbohydrate Research 2008 Volume 343(10–11) pp:1718-1729
Publication Date(Web):21 July 2008
DOI:10.1016/j.carres.2008.03.033
Sperm CD52 GPI anchor and its derivatives containing different carbohydrate chains were prepared in a highly convergent fashion starting from the same properly protected phospholipidated pseudodisaccharide. Coupling this common key intermediate to various oligosaccharyl donors quickly afforded the framework of the synthetic targets, which was followed by global deprotection to furnish the desired structures. Preliminary studies on the biological properties of the synthetic GPI derivatives indicated that both the intact GPI anchor and the free phospholipidated pseudodisaccharide interacted strongly with CAMP factor, a pore-forming bacterial toxin.
Co-reporter:Qianli Wang, Junping Zhang, Zhongwu Guo
Bioorganic & Medicinal Chemistry 2007 Volume 15(Issue 24) pp:7561-7567
Publication Date(Web):15 December 2007
DOI:10.1016/j.bmc.2007.09.005
To verify the principal of a new immunotherapeutic strategy for cancer, a monoclonal antibody 2H3 against N-phenylacetyl GM3, an unnatural form of the tumor-associated antigen GM3, was prepared and employed to demonstrate that murine melanoma cell B16F0 could be effectively glycoengineered by N-phenylacetyl-d-mannosamine to express N-phenylacetyl GM3 and that 2H3 was highly cytotoxic to the glycoengineered B16F0 cell in the presence of complements. It was further demonstrated that B16F0 cell could be glycoengineered 4–5 times more effectively than 3T3 A31 cell, a normal murine embryo fibroblast cell, and that the antibody and complement mediated cytotoxicity was at least 200 times more potent to the glycoengineered B16F0 cell than to the N-phenylacetyl-d-mannosamine-treated 3T3 A31 cell. These results show the promise for developing useful melanoma immunotherapies based on vaccination against N-phenylacetyl GM3 followed by treatment with N-phenylacetyl-d-mannosamine.Melanoma cell was selectively glycoengineered, targeted, and killed.
Co-reporter:Qianli Wang, Jie Xue and Zhongwu Guo
Chemical Communications 2009(Issue 37) pp:
Publication Date(Web):
DOI:10.1039/B907351E
Co-reporter:Zhifang Zhou, Mohabul Mondal, Guochao Liao and Zhongwu Guo
Organic & Biomolecular Chemistry 2014 - vol. 12(Issue 20) pp:NaN3245-3245
Publication Date(Web):2014/03/11
DOI:10.1039/C4OB00390J
A fully synthetic carbohydrate-based cancer vaccine is an attractive concept, but an important topic in the area is to develop proper vaccine carriers that can improve the immunogenicity and other immunological properties of tumor-associated carbohydrate antigens (TACAs). In this context, four monophosphoryl derivatives of Neisseria meningitidis lipid A were synthesized via a highly convergent and effective strategy and evaluated as vaccine carriers and adjuvants. The conjugates of these monophosphoryl lipid A (MPLA) derivatives with a modified form of the sTn antigen were found to elicit high titers of antigen-specific IgG antibodies, indicating a T cell-dependent immune response, in the absence of an external adjuvant. It was concluded that MPLAs could be utilized as potent vaccine carriers and built-in adjuvants to create fully synthetic self-adjuvanting carbohydrate-based cancer vaccines. The lipid composition and structure of MPLA were shown to have a significant influence on its immunological activity, and among the MPLAs examined, natural N. meningitidis MPLA exhibited the most promising properties. Moreover, Titermax Gold, a conventional vaccine adjuvant, was shown to inhibit, rather than promote, the immunological activity of MPLA conjugates, maybe via interacting with MPLA.
Co-reporter:Zhimeng Wu, Xueqing Guo and Zhongwu Guo
Chemical Communications 2011 - vol. 47(Issue 32) pp:NaN9220-9220
Publication Date(Web):2011/07/08
DOI:10.1039/C1CC13322E
A chemoenzymatic method was developed for the synthesis of macrocyclic peptides and glycopeptides. Sortase A was found to mediate either head to tail cyclization or oligomerization and then head to tail cyclization of peptides and glycopeptides, depending on the peptide length, to produce 15-mer or higher cyclic peptides and glycopeptides.
Co-reporter:Benjamin M. Swarts and Zhongwu Guo
Chemical Science (2010-Present) 2011 - vol. 2(Issue 12) pp:NaN2352-2352
Publication Date(Web):2011/09/06
DOI:10.1039/C1SC00440A
Glycosylphosphatidylinositol (GPI) anchorage is a common posttranslational modification of eukaryotic proteins. Chemical synthesis of structurally defined GPIs and GPI derivatives is a necessary step toward understanding the properties and functions of these molecules in biological systems. In this work, the synthesis of several functionalized GPI anchors was accomplished using the para-methoxybenzyl (PMB) group for permanent hydroxyl protection, which allowed the incorporation of functionalities that are incompatible with permanent protecting groups traditionally used in carbohydrate synthesis. A flexible convergent–divergent assembly strategy enabled efficient access to a diverse set of target structures, including “clickable” alkyne- and azide-modified GPIs. For global deprotection, a one-pot reaction was employed to afford the target GPIs in excellent yields (85–97%). Fully deprotected clickable GPI derivatives were readily conjugated to imaging and affinity probes via Cu(I)-catalyzed and Cu-free strain-promoted [3 + 2] cycloaddition to result in GPI-Flour and GPI-Biotin conjugates, respectively.
Co-reporter:Zhifang Zhou, Guochao Liao, Satadru S. Mandal, Sharad Suryawanshi and Zhongwu Guo
Chemical Science (2010-Present) 2015 - vol. 6(Issue 12) pp:NaN7121-7121
Publication Date(Web):2015/09/22
DOI:10.1039/C5SC01402F
Therapeutic cancer vaccines based on the abnormal glycans expressed on cancer cells, such as the globo H antigen, have witnessed great progress in recent years. For example, the keyhole limpet hemocyanin (KLH) conjugate of globo H has been on clinical trials as a cancer vaccine. However, such vaccines have intrinsic problems, such as inconsistence in eliciting T cell-mediated immunity in cancer patients and difficult quality control. To address the issue, a structurally defined fully synthetic glycoconjugate vaccine composed of globo H and monophosphoryl lipid A (MPLA) was developed. The new vaccine was shown to elicit robust IgG1 antibody responses and T cell-dependent immunity, which is desired for anticancer vaccines, and induce significantly faster and stronger immune responses than the globo H–KLH conjugate. Moreover, it was self-adjuvanting, namely, inducing immune responses without the use of an external adjuvant, thus MPLA was not only a vaccine carrier but also a build-in adjuvant. It was also found that antibodies induced by the new vaccine could selectively bind to and mediate strong complement-dependent cytotoxicity to globo H-expressing MCF-7 cancer cell. All of the results have demonstrated that the globo H–MPLA conjugate is a better cancer vaccine than the globo H–KLH conjugate under experimental conditions and is worth further investigation and development.
Co-reporter:Guochao Liao, Zhifang Zhou and Zhongwu Guo
Chemical Communications 2015 - vol. 51(Issue 47) pp:NaN9650-9650
Publication Date(Web):2015/04/28
DOI:10.1039/C5CC01794G
α-2,9-Di-, tri-, tetra-, and pentasialic acids were prepared and conjugated with a carrier protein. The resultant glycoconjugates elicited robust T cell-mediated immunity in mice. α-2,9-Trisialic acid was identified as a promising antigen for developing glycoconjugate vaccines against group C Neisseria meningitidis.
Co-reporter:Zhimeng Wu, Xueqing Guo, Jian Gao and Zhongwu Guo
Chemical Communications 2013 - vol. 49(Issue 99) pp:NaN11691-11691
Publication Date(Web):2013/10/22
DOI:10.1039/C3CC47229A
Green fluorescent protein and a glycosylphosphatidylinositol (GPI) anchor containing the common core structure and a lipid chain were synthesized and then coupled together in the promotion of bacterial sortase A (SrtA), which was the first example for the synthesis of a full-size GPI-anchored protein by SrtA, demonstrating that this can be a generally useful method for GPI-anchored protein synthesis.
Co-reporter:Zhimeng Wu, Xueqing Guo and Zhongwu Guo
Chemical Communications 2010 - vol. 46(Issue 31) pp:NaN5774-5774
Publication Date(Web):2010/06/24
DOI:10.1039/C0CC00828A
MUC1 glycopeptide was efficiently coupled to glycosylphosphatidylinositol (GPI) derivatives by sortase A (SrtA), verifying that SrtA can accept sterically hindered glycopeptide as substrate for ligation with GPIs. This work has established a practical method for the chemoenzymatic synthesis of GPI-linked glycopeptides.
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