Expression, purification and characterization of the Hepatitis B virus entire envelope large protein in Pichia pastoris

Detection of Cell-Derived Exosomes Via Surface-Enhanced Raman Scattering Using Aggregated Silver Nanoparticles

Exosomes are small extracellular vesicles that contain RNA, lipids, and proteins and can act as cellular messengers, carrying information to cells and tissues in the body. Thus, sensitive, label-free, and multiplexed analysis of exosomes may help in early diagnosis of important diseases. Here, we describe the process of pretreatment of cell-derived exosomes, preparation of surface-enhanced Raman scattering (SERS) substrates, and label-free SERS detection of exosomes using sodium borohydride aggregators. This method can enable the observation of SERS signals of exosomes that are clear and stable and have a good signal-to-noise ratio.

Expression and immunogenic characterization of recombinant gp350 for developing a subunit vaccine against Epstein-Barr virus

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that is linked to the development of various malignancies. There is an urgent need for effective vaccines against EBV. EBV envelope glycoprotein gp350 is an attractive candidate for a prophylactic vaccine. This study was undertaken to produce the truncated (codons 1-443) gp350 protein (gp350(1-443)) in Pichia pastoris and evaluate its immunogenicity. The gp350(1-443) protein was expressed as a secretory protein with an N-terminal His-tag in P. pastoris and purified through Ni-NTA chromatography. Immunization with the recombinant gp350(1-443) could elicit high levels of gp350(1-443)-specific antibodies in mice. Moreover, gp350(1-443)-immunized mice developed strong lymphoproliferative and Th1/Th2 cytokine responses. Furthermore, the recombinant gp350(1-443) could stimulate CD4(+) and CD8(+) T cell responses in vaccinated mice. Collectively, these findings demonstrated that the yeast-expressed gp350(1-443) retained strong immunogenicity. This study will provide a useful source for developing EBV subunit vaccine candidates.

Expression of E2 gene of bovine viral diarrhea virus in Pichia pastoris: a candidate antigen for indirect Dot ELISA

The E2 gene containing the EcoR I and Not I sites of bovine viral diarrhea virus (BVDV) was amplified from the plasmid pMD-18T-E2 of the HB-bd isolated, and inserted into Pichia pastoris (P. pastoris) expression vector pPIC9K, and transfected into Escherichia coli DH5α. The recombinant plasmid pPIC9K-E2 was digested by the SalI restriction enzyme and transformed into the P. pastoris strain GS115 by electroporation. High copy integrative transformants were obtained by G418 screening and induced for expression with methanol. The expressed products in the culture medium were identified by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the Western blotting and the antibody test for immunity. An indirect Dot-ELISA for the detection of antibody against BVDV was established by the recombinant E2 protein as the coating antigen. The reaction conditions of the indirect Dot-ELISA were optimized. The coating concentration of the E2 recombinant protein antigen, the dilution of serum sample, the optimal concentration of HRP labeled antibody, the optimal blocking reagent and blocking time were studied. 100 sera samples from cows in the field were tested for the antibody against BVDV by the Dot-ELISA and the IDEXX HerdChek BVDV antibody ELISA kit simultaneously to compare the specificity, sensitivity and accuracy. The results showed that the expressed products in the culture medium resulted in single band of 44kDa by SDS-PAGE and Western blotting. The results of the immunogenicity assay indicated that the protein E2 expressed in P. pastoris could induce the experimental animals of the rabbit to produce BVDV specific antibodies. The results of the indirect Dot-ELISA showed that the optimal coating concentration of the E2 recombinant protein was 2.0μg/mL, the bovine serum dilution was 1:100, the optimal concentration of HRP-labeled rabbit anti-bovine antibody IgG was 1:500, and the optimal blocking reagent was 3% glutin-TBS and blocking for 45min. The indirect Dot-ELISA showed 96.7%, 92.5% and 95% in the terms of specificity, sensitivity and accuracy compared to the IDEXX ELISA test kit. The indirect Dot-ELISA using the E2 recombinant protein can be used for the detection of antibody against the BVDV and could be considered in the surveillance programs.

The twenty-year story of a plant-based vaccine against hepatitis B: stagnation or promising prospects?

Hepatitis B persists as a common human disease despite effective vaccines having been employed for almost 30 years. Plants were considered as alternative sources of vaccines, to be mainly orally administered. Despite 20-year attempts, no real anti-HBV plant-based vaccine has been developed. Immunization trials, based on ingestion of raw plant tissue and conjugated with injection or exclusively oral administration of lyophilized tissue, were either impractical or insufficient due to oral tolerance acquisition. Plant-produced purified HBV antigens were highly immunogenic when injected, but their yields were initially insufficient for practical purposes. However, knowledge and technology have progressed, hence new plant-derived anti-HBV vaccines can be proposed today. All HBV antigens can be efficiently produced in stable or transient expression systems. Processing of injection vaccines has been developed and needs only to be successfully completed. Purified antigens can be used for injection in an equivalent manner to the present commercial vaccines. Although oral vaccines require improvement, plant tissue, lyophilized or extracted and converted into tablets, etc., may serve as a boosting vaccine. Preliminary data indicate also that both vaccines can be combined in an effective parenteral-oral immunization procedure. A partial substitution of injection vaccines with oral formulations still offers good prospects for economically viable and efficacious anti-HBV plant-based vaccines.

Efficient and rapid purification of drug- and gene-carrying bio-nanocapsules, hepatitis B virus surface antigen L particles, from Saccharomyces cerevisiae

Bio-nanocapsules (BNCs) are hollow particles (approx. 50 nm diameter) consisting of hepatitis B virus surface antigen (HBsAg) large (L, pre-S1+pre-S2+S) proteins embedded in a unilamellar liposome, sharing the same transmembrane S region with an immunogen of hepatitis B vaccine (i.e., HBsAg small (S) protein particle). BNCs can incorporate drugs and genes into the hollow space and systemic administration of the BNCs can deliver the products to human liver via the human hepatocyte-specific receptor within the pre-S (pre-S1+pre-S2) region displayed on BNC's surface. Thus, BNCs are expected to offer efficient and safe non-viral nanocarriers to deliver human liver-specific genes and drugs. To date, BNCs have been purified from the crude extract of BNC-overexpressing yeast cells by fractionation with polyethylene glycol followed by one CsCl equilibrium and two sucrose density gradient ultracentrifugation steps. However, the process was inefficient in terms of yield and time, and was not suitable for mass production because of the ultracentrifugation step. Furthermore, trace contamination with yeast-derived proteinases degraded the pre-S region, which is indispensable for liver-targeting, during long-term storage. In this study, we developed a new purification method involving heat treatment and sulfated cellulofine column chromatography to facilitate rapid purification, completely remove proteinases, and enable mass production. In addition, the BNCs were functional for at least 14 months after lyophilization with 5% (w/v) sucrose as an excipient. This new process will significantly contribute to the development of forthcoming BNC-based nanomedicines as well as hepatitis B vaccines.

Use of the yeast Pichia pastoris as an expression host for secretion of enterocin L50, a leaderless two-peptide (L50A and L50B) bacteriocin from Enterococcus faecium L50

In this work, we report the expression and secretion of the leaderless two-peptide (EntL50A and EntL50B) bacteriocin enterocin L50 from Enterococcus faecium L50 by the methylotrophic yeast Pichia pastoris X-33. The bacteriocin structural genes entL50A and entL50B were fused to the Saccharomyces cerevisiae gene region encoding the mating pheromone alpha-factor 1 secretion signal (MFalpha1(s)) and cloned, separately and together (entL50AB), into the P. pastoris expression and secretion vector pPICZalphaA, which contains the methanol-inducible alcohol oxidase promoter (P(AOX1)) to express the fusion genes. After transfer into the yeast, the recombinant plasmids were integrated into the genome, resulting in three bacteriocinogenic yeast strains able to produce and secrete the individual bacteriocin peptides EntL50A and EntL50B separately and together. The secretion was efficiently directed by MFalpha1(s) through the Sec system, and the precursor peptides were found to be correctly processed to form mature and active bacteriocin peptides. The present work describes for the first time the heterologous expression and secretion of a two-peptide non-pediocin-like bacteriocin by a yeast.

Avian influenza A/H5N1 neuraminidase expressed in yeast with a functional head domain

The study reports heterologous expression in Pichia pastoris of active neuraminidase derived from avian influenza virus A/Viet Nam/DT-036/2005(H5N1). A gene encoding the neuraminidase N1 head domain (residues 63-449) was fused directly in-frame with the Saccharomyces cerevisiae alpha-factor secretion signal in pPICZ(A vector. Recombinant N1 neuraminidase was expressed in P. pastoris as a 72kDa secreted, soluble protein. Glycopeptidase F treatment generated a 45kDa product, indicating that the secreted recombinant N1 neuraminidase is an N-linked glycoprotein. Kinetic studies and inhibition tests with oseltamivir carboxylate demonstrated that the recombinant N1 neuraminidase has similar K(m) and K(i) values to those of the viral N1 neuraminidase. This yeast-based heterologous expression system provided functionally active recombinant N1 neuraminidase that should be useful in anti-influenza drug screening, and also as a potential protein-based vaccine.

Purification of Bionanoparticles

The recent demand for nanoparticulate products such as viruses, plasmids, protein nanoparticles, and drug delivery systems have resulted in the requirement for predictable and controllable production processes. Protein nanoparticles are an attractive candidate for gene and molecular therapy due to their relatively easy production and manipulation. These particles combine the advantages of both viral and non‐viral vectors while minimizing the disadvantages. However, their successful application depends on the availability of selective and scalable methodologies for product recovery and purification. Downstream processing of nanoparticles depends on the production process, producer system, culture media and on the structural nature of the assembled nanoparticle, i.e., mainly size, shape and architecture. In this paper, the most common processes currently used for the purification of nanoparticles, are reviewed.