Synthesis and immunological study of a glycosylated wall teichoic acid-based vaccine against Staphylococcus aureus

Staphylococcus aureus wall teichoic acids(WTAs) are attractive targets for antibacterial vaccine development. In this study, three core glycosylated WTA structure, including α-1,4-Glc NAc, β-1,4-Glc NAc andβ-1,3-Glc NAc modified ribitol phosphates containing a linker are chemically synthesized and conjugated with tetanus toxin(TT) carrier protein as vaccine candidates. In vivo immunological studies demonstrate that the synthesized glycosylated WTAs display high immunogenicity and all conjugates provoke strong immune responses and elicit high levels of specific IgG antibodies against the Glc NAc-modified WTA. Furthermore, antibodies elicited by the vaccine candidates remain the capability to recognize S. aureus cells and display significant opsonophagocytic activity to clear S. aureus. This study demonstrates that the core structure of glycosylated WTAs are effective antigens for constructing anti-S. aureus vaccines to prevent and control S. aureus infections.

Efficient biosynthesis of 2-keto-D-gluconic acid by fed-batch culture of metabolically engineered Gluconobacter japonicus

2-keto-D-gluconic acid(2-KGA)is a key precursor for synthesising vitamin C and isovitamin C.However,phage contamination is as constant problem in industrial production of 2-KGA using Pseudomonas fluorescens.Gluconobacter holds promise for producing 2-KGA due to impressive resistance to hypertonicity and acids,and high utilisation of glucose.In this study,the 2-KGA synthesis pathway was regulated to enhance production of 2-KGA and reduce accumulation of the by-products 5-keto-D-gluconic acid(5-KGA)and D-gluconic acid(D-GA)in the 2-KGA producer Gluconobacter japonicus CGMCC 1.49.Knocking out the ga5dh-1 gene from a competitive pathway and overexpressing the ga2dh-A gene from the 2-KGA synthesis pathway via homologous recombination increased the titre of 2-KGA by 63.81%in shake flasks.Additionally,accumulation of 5-KGA was decreased by 63.52%with the resulting G.japonicas-Δga5dh-1-ga2dh-A strain.Using an intermittent fed-batch mode in a 3 L fermenter,2-KGA reached 235.3 g L^−1 with a 91.1%glucose conversion rate.Scaling up in a 15 L fermenter led to stable 2-KGA titre with productivity of 2.99 g L^−1 h^−1,11.99%higher than in the 3 L fermenter,and D-GA and 5-KGA by-products were completely converted to 2-KGA.

Synthesis of DNP-modified GM3-based anticancer vaccine and evaluation of its immunological activities for cancer immunotherapy

Tumor-associated carbohydrate antigens(TACAs) are attractive targets for vaccine development. In this context, we described a strategy combining artificial TACA and glycoengineering for cancer vaccine development. A 2,4-ditrophenyl(DNP)-modified GM3 intermediate was synthesized chemoenzymatically and conjugated to keyhole limpet hemocyanin(KLH), and the resulting bioconjugate was tested for its potential as a vaccine candidate. Mice immunological studies revealed that the DNP-modified GM3(GM3-NHDNP) analog elicited strong and rapid immune responses by recruiting anti-DNP antibodies to facilitate the targeted delivery of the vaccine construct to antigen processing cells(APCs). Moreover, the endogenously produced anti-DNP antibodies, together with the elicited antibodies against GM3-NHDNP, may synergistically promote tumor binding and cancer cell death when the cancer cell surfaces are glycoengineered to express the GM3-NHDNP antigen.

MUC1 vaccines usingβ-cyclodextrin grafted chitosan(CS-g-CD)as carrier via host-guest interaction elicit robust immune responses

We construct MUC1 vaccines usingβ-cyclodextrin grafted chitosan(CS-g-CD)as carrier via host-guest interaction.These vaccines based on non-covalent assembling can provoke robust immune responses,including high level of specific antibodies and cytokines.The induced antibodies can specifically recognize tumor cells and mediate cytotoxicity against tumor cells.These results indicate that CS-g-CD with strong immunostimulatory activities can be a straightforward platform for peptide-based vaccine construction.