Tae-Yeon Kim

Immunogenicity of synthetic HIV-1 V3 loop peptides by MPL adjuvanted pH-sensitive liposomes.

A successful HIV-1 vaccine should be capable of generating humoral and cellular immune responses at the same time. The only response shown to be effective in this regard is virus-neutralization antibodies and virus-specific cytotoxic T-lymphocytes (CTL) directed against the viral antigens. In the present study, it is shown that V3 peptides encapsulated pH-sensitive liposomes elicit the virus neutralization antibodies and virus specific CTL response at the same time in Balb/c mice. None of the immunization protocols elicited an antibody response and CTL response when R15K and T26K was used as immunogen without liposomes. In contrast, antibodies and CTL response were detectable in the mice which were immunized with peptide encapsulated pH-sensitive liposomes. Antibody production was confirmed by virus neutralizing assay. CD4+ T-cells are involved in target cell lysis to some degree but CTL activity is mainly due to the CD8 + T-cells. The consistency of the antibody and CTL response was related to the V3 loop peptides size. The T26K (26mer) peptide induced a stronger antibody and CTL response than R15K (15mer) in vivo. Based on the results of this study, T26K was used as a potentially effective HIV-1 vaccine component and T26K encapsulated pH-sensitive liposomes composed of phosphatidylethanolamine-beta-oleoyl-gamma-palmitoyl (POPE)/cholesterol hemisuccinate (CHOH)/monophosphoryl lipid A (MPL) (7:3:0.1, mole ratio) may be used as a potentially immunomodulating adjuvant system for the development of HIV and other viral vaccines.

Characterization of GCY1 in Saccharomyces cerevisiae by metabolic profiling

The analytical study of intracellular (IC) metabolites has developed with advances in chromatography‐linked mass spectrometry and fast sampling procedures. We applied the IC metabolite analysis to characterize the role of GCY1 in the glycerol (GLY) catabolic pathway in Saccharomyces cerevisiae.

Gentiobiose synthesis from glucose using recombinant β-glucosidase fromThermus caldophilus GK24

Recombinant β-glucosidase fromThermus caldophilus GK24 was easily purified partially by a heat treatment procedure, resulting in 8-fold and recovery yield of 80% from crude enzyme. When the β-glucosidase was incubated with a 80% glucose solution (w/w), gentiobiose (β1,6-glucobiose) was the major product in the reaction mixture. The optimal conditions for producing gentiobiose (11% yields of total sugar) were pH 8–9 and 70°C for 72 h.

Effect of Dehydration and Rehydration of the pH-Sensitive Liposomes Containing Chimeric gag-V3 Virus Like Particle on Their Long-term Stability

One of the practical limitations with the use of liposomes for delivery of the pharmaceutical substances such as antigens is that liposomes are relatively unstable in storage. In order to extend the stability of liposome in storage without affecting their functional activity, solution-type liposomes were dehydrated to form a structurally intact dry liposomes. Comparative immunological evaluation was carried out for both dry and solution-type liposomes containing gag-V3 chimera, consequently it was found that dry liposomes elicited both humoral and cellular response as efficiently as solution-type liposomes did against the same gag-V3 antigen. Especially, long-term stability of the liposomes was remarkably enhanced by the dehydration made to liposomes without a significant change in its ability to elicit immune responsein vivo. These results indicate that dry pH-sensitive liposome may become an effective delivery and adjuvant system for general vaccine development.

Improved resistance against oxidative stress of engineered cellobiose-fermenting Saccharomyces cerevisiae revealed by metabolite profiling

Cellobiose has garnered attention as an alternative carbon source for numerous biotechnological processes because it is produced when lignocellulosic biomass is treated with endo and exo-glucanases. An engineered Saccharomyces cerevisiae (CEL), expressing cellobiose transporter and intracellular beta-glucosidase utilized cellobiose efficiently. As compared to the culture using glucose, the CEL strain grown on cellobiose produced a similar yield of ethanol with slightly reduced growth rate. In this study, concentrations of central metabolites were monitored at mid-log phase with GC/MS to compare cellobiose- and glucose-grown CEL strain. When the CEL strain was grown on cellobiose, intracellular trehalose concentration increased 6-fold as compared with the glucosegrown cells. Interestingly, the higher level of trehalose in cells grown on cellobiose resulted in physiological changes which might be beneficial for biotechnological processes. We observed higher resistance against oxidative stress when cellobiose was used. Oxidative stress is commonly occurred by the byproducts of pretreatment process of lignocellulosic biomass, such as 2-furaldehyde (furfural) and 5-hydroxymethylfurfural (HMF). Our study demonstrated that intracellular metabolite profiling of yeast strains can be employed for linking intracellular concentrations of metabolite with physiological changes of cells upon genetic and environmental perturbations.