Volume 5(5); October

< Previous     Next >

Article Contents

Osong Public Health Res Perspect > Volume 5(5); 2014
Yun, Jeong, Wang, Lee, Han, Park, Lee, and Choi: Cloning and Expression of Recombinant Tick-Borne Encephalitis Virus-like Particles in Pichia pastoris



The purpose of this study was to verify the feasibility of using the glyceraldehyde-3-phosphate dehydrogenase (GAP) promotor based Pichia pastoris expression system to produce tick-borne encephalitis virus (TBEV) virus-like particles (VLPs).


The complementary DNA encoding the TBEV prM signal peptide, prM, and E proteins of TBEV Korean strain (KrM 93) was cloned into the plasmid vector pGAPZɑA, then integrated into the genome of P. pastoris, under the control of the GAP promoter. Expression of TBEV VLPs was determined by Western blotting using monoclonal antibody against TBEV envelope (E) protein.


Recombinant TBEV VLPs consisting of prM and E protein were successfully expressed using the GAP promoter-based P. pastoris expression system. The results of Western blotting showed that the recombinant proteins were secreted into the culture supernatant from the P. pastoris and glycosylated.


This study suggests that recombinant TBEV VLPs from P. pastoris offer a promising approach to the production of VLPs for use as vaccines and diagnostic antigens.


Pichia pastoris; tick-borne encephalitis virus; virus-like particles


Tick-borne encephalitis virus (TBEV) belongs to the Flavivirus genus of the Flaviviridae family and can cause fatal encephalitis in humans in Europe, Russia, and Far East Asia [1,2]. In South Korea, TBEV was first isolated from wild rodents in 2006 [3]. The flavivirus genome contains a single, long, open reading frame that encodes a polyprotein, which is cleaved into three structural proteins, i.e., the capsid (C), premembrane (prM) and envelope (E) proteins, and seven nonstructural (NS) proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) [4]. In flaviviruses, the prM and E proteins play crucial roles in the assembly and secretion of the virions [5–8]. Several studies have demonstrated that flavivirus virus-like particles (VLPs), consisting of the prM and E proteins, have been shown to be similar to the native virions in the structural and functional features for infection [5,9–12]. Thus, flavivirus VLPs can be substituted for native virions in investigations into the biological features of flavivirus, such as vaccine study for the prevention of flavivirus-induced diseases.
Until recently, various expression systems, including mammalian cells and insect cells, have been used to produce TBEV VLPs as antigens [10,13,14].
Pichia pastoris is one of the most widely used systems for producing recombinant protein by heterologous expression [15]. This system offers several advantages in comparison with other eukaryotic expression systems, such as the production of large-scale target proteins in their native conformation and cost-efficiency, and the proven safety of yeast-expressed VLPs vaccines such as hepatitis B virus VLPs [16] and human papillomavirus VLPs [17]. For this reason, the P. pastoris expression system has been used for the production of flavivirus proteins including VLPs [18–21]. However, there are no reports on the production of TBEV VLPs from P. pastoris. In the current study, we investigated the expression of TBEV VLPs using the glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter-based P. pastoris expression system.
To our knowledge, this is the first report on the successful expression of TBEV VLPs in P. pastoris.

Materials and methods

2.1 Viruses and cells

The TBEV Korean isolate, KrM 93 strain (GenBank accession No. HM535611), was propagated in the brains of suckling mice and BHK-21 cell as described previously [22]. The infected cell culture medium was used for RNA extraction.

2.2 Yeast strain and plasmid vector

The P. pastoris host strain X33 (Invitrogen, Carlsbad, CA, USA) was used as the expression host in this study. The expression vector pGAPZɑA (Invitrogen) contains the selectable marker Zeocin (Invitrogen), which is bifunctional in both P. pastoris and Escherichia coli, the GAP promoter, and the alcohol oxidase I (AOX1) transcription termination regions. E. coli transformants were selected on low salt Luria-Bertani agar plates containing 25 μg/mL Zeocin. P. pastoris transformants were selected on YPDS plates (1% yeast extract, 2% peptone, 2% dextrose, 1M sorbitol, 2% agar, and 100 μg/mL Zeocin) and P. pastoris liquid cell cultures were grown in YPD broth (1% yeast extract, 2% peptone, and 2% dextrose) with Zeocin.

2.3 Construction of recombinant expression vector

The coding sequence for the signal peptide of prM, prM, and E proteins was amplified from KrM 93 strain viral RNA by reverse transcription-polymerase chain reaction (RT-PCR) using SuperScript III First-strand synthesis system for RT-PCR (Invitrogen) and Ex Taq DNA polymerase (Takara, Shiga, Japan) according to the manufacturer's instructions, and the following primers: KrM93SS-F 5′-GAC TTC GAA ATG GTT GGC TTG CAA AAA-3′ (Bst BI site in bold and start codon in italics) and KrM93E-R 5′-GAA TCT AGA GCT GCC CCC ACT CCA AGG-3′ (Xba I site in bold). The PCR product (named as 93prM-E) was first cloned into pCR 2.1-TOPO plasmid (Invitrogen) and then subcloned into pGAPZɑA following enzymatic digestion using Bst BI and Xba I (New England BioLabs Inc., Beverley, MA, USA) to construct the full-length 93prM-E clone downstream of GAP promoter, which was designated as pGAPZɑA/93prM-E (Figure 1A). The plasmid inserts were confirmed by DNA sequencing.

2.4 Yeast transformation

The plasmid pGAPZɑA/93prM-E was linearized with Bgl II (New England BioLabs) and transformed into P. pastoris X33 using Pichia EasyComp Kit (Invitrogen) according to the manufacturer's instructions. The transformed yeast cells were incubated in YPDS agar containing 100 μg/mL Zeocin at 30°e for 3–4 days. Zeocin-resistant yeast colonies were selected and identification of the insert in these Zeocin-resistant transformants was checked by colony PCR.

2.5 Expression of recombinant TBEV E protein in P. pastoris

Positive transformants, selected as described previously, were inoculated in 5 mL YPD broth with 100 μg/mL Zeocin with shaking (250 rpm) at 30°C overnight. These cultures were transferred to 500 mL of YPD broth with Zeocin with shaking (250 rpm) at 30°C for 48 hours. The culture supernatant and cell pellet were collected by centrifugation at 10,000 × g for 10 minutes. The cell pellet was disrupted using Yeast PE LB (G-Biosciences, St. Louis, MO, USA) according to the manufacturer's instructions. The lysate was clarified by centrifugation at 20,000 × g for 30 minutes at 4°C. The culture supernatant was precipitated by using Amicon Ultra-15 Centrifugal Filter Units with 30 kDa membrane (Millipore, Billerica, MA, USA) according to the manufacturer's instructions.

2.6 Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis

The protein samples were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) on a reduced 4–12% Bis-Tris Gel (Invitrogen). Separated protein bands were transferred onto a 0.45-μm polyvinylidene difluoride membrane using the iBlot system (Invitrogen) according to the manufacturer's instructions. The membrane was blocked with 5% skim milk in Tris buffered saline with 0.05% Tween-20. TBEV E protein was detected using monoclonal anti-TBEV E antibody (8A7 mAb, in-house) as the primary antibody and horseradish peroxidase-conjugated goat anti-mouse immunoglobulin G (Promega, Madison, WI, USA) as the secondary antibody. The bands were visualized by enhanced chemiluminescence (GenDEPOT, Barker, TX, USA).

2.7 Analysis of glycosylation patterns of recombinant TBEV E protein

Glycosylation patterns of recombinant E protein in lysate and supernatant were analyzed by digestion using N-glycosidase F (PNGase F) and endoglycosidase H (Endo H; New England BioLabs) according to the manufacturer's instructions. Glycosidase-treated protein samples were analyzed by SDS-PAGE and Western blotting as described previously.


3.1 Construction of recombinant plasmid containing TBEV prM and E genes

The full-length prM and E genes of TBEV KrM 93 strain about 2 kb in size were amplified by using the RT-PCR method previously described. The 93prM-E fragment was then inserted into the yeast expression vector pGAPZɑA to construct a recombinant plasmid pGAPZɑA/93prM-E. The insert was confirmed by digestion with the restriction enzymes, Bst BI and Xba I (Figure 1B).

3.2 Expression of recombinant TBEV VLPS in P. pastoris

The pGAPZɑA/93prM-E plasmid was transformed into P. pastoris and positive clones were selected. Yeast cell lysate and culture supernatant were collected and analyzed for expression of E proteins by Western blotting using TBEV mAb 8A7. As shown in Figure 2, the specific recombinant E protein bands with a molecular mass of ∼55 kDa were detected in both the lysate and supernatant, but not in the plasmid-alone control. This result demonstrated that the recombinant TBEV VLPs were secreted into the culture supernatant from the yeast cell.
The glycosylation state of E protein in TBEV VLPs were examined with Endo H, which is specific for high mannose-type oligosaccharides and PNGase F, which cleaves both high mannose- and complex-type oligosaccharides. Comparison of glycosidase-treated recombinant TBEV E protein from yeast cell lysate and culture supernatant by SDS-PAGE and Western blotting indicated that the recombinant E protein was glycosylated in the P. pastoris expression system (Figure 3).


VLPs have been developed as effective vaccine candidates, because they mimic the organization and conformation of native virion without containing the viral full genome, and thus are a safe and highly immunogenic antigen. Among the various protein expression systems for VLPs production, the yeast expression system as an alternative eukaryotic expression system is a well-established platform for the efficient production of heterologous viral glycoproteins. Previous studies have reported that this system has been used for the generation of flaviviral glycoproteins [18–21]. Among the yeast expression systems, the protein expression level in the P. pastoris expression system was reportedly higher than that in another yeast Saccharomyces cerevisiae [23] and the GAP promoter based P. pastoris expression system can improve the protein yield compared to the P. pastoris by using methanol-inducible AOXI promoter [24]. We therefore have selected the P. pastoris expression system under the control of the GAP promoter to produce the TBEV VLPs in this study.
Here, we demonstrated the efficient production of TBEV VLPs, consisting of the prM and E proteins by using the GAP promoter-based P. pastoris expression system. The KrM 93 strain, which belongs to the Western subtype of TBEV isolated in South Korea [22], was used for production of recombinant proteins. As a main structural protein of flavivirus, the E protein plays important roles in receptor binding, membrane fusion activity, and immunogenicity [25,26]. The prM gene was included in the recombinant plasmid pGAPZɑA/93prM-E because E protein requires coexpression of the prM protein to maintain its native conformation and the protection of E protein from conformational alteration during transportation through the acidic compartments of the trans-Golgi network [27–29].
The results of Western blotting indicated that the TBEV VLPs were secreted into the culture supernatant from P. pastoris, suggesting that the signal peptide of prM can induce the secretion of TBEV VLPs, and coexpression of prM and E proteins in yeast cells may play an important role in virus particle release as shown in previous studies [5–9]. In addition, analysis of glycosylation of TBEV E protein in P. pastoris transformed with plasmid pGAPZɑA/93prM-E showed that the recombinant E protein from P. pastoris was glycosylated by eukaryotic posttranslational modifications (Figure 3).
This is the first study to report the successful cloning and expression of TBEV VLPs by using the GAP promoter-based P. pastoris expression system, and this study demonstrated that recombinant TBEV VLPs from P. pastoris offer a promising approach to the production of VLPs for use as vaccines and diagnostic antigens. Further study will be required for the purification of TBEV VLPs from P. pastoris and to identify the immunogenicity in a mouse model.

Conflicts of interest

The authors declare no conflicts of interest.


This research was funded by an intramural grant from the Korea National Institute of Health (grant number. 2013-NG53001-00).


This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.


1. Dumpis U., Crook D., Oksi J.. Tick-borne encephalitis. Clin Infect Dis 28(4):1999 Apr;882−890.
2. Ecker M., Allison S.L., Meixner T.. Sequence analysis and genetic classification of tick-borne encephalitis viruses from Europe and Asia. J Gen Virol 80(Pt 1):1999 Jan;179−185.
3. Kim S.Y., Yun S.M., Han M.G.. Isolation of tick-borne encephalitis viruses from wild rodents, South Korea. Vector Borne Zoonotic Dis 8(1):2008 Spring;7−13.
4. Chambers T.J., Hahn C.S., Galler R.. Flavivirus genome organization, expression, and replication. Annu Rev Microbiol 44:1990;649−688.
crossref pmid
5. Allison S.L., Stadler K., Mandl C.W.. Synthesis and secretion of recombinant tick-borne encephalitis virus protein E in soluble and particulate form. J Virol 69(9):1995 Sep;5816−5820.
6. Kim J.M., Yun S.I., Song B.H.. A single N-linked glycosylation site in the Japanese encephalitis virus prM protein is critical for cell type-specific prM protein biogenesis, virus particle release, and pathogenicity in mice. J Virol 82(16):2008 Aug;7846−7862.
7. Mackenzie J.M., Westaway E.G.. Assembly and maturation of the flavivirus Kunjin virus appear to occur in the rough endoplasmic reticulum and along the secretory pathway, respectively. J Virol 75(22):2001 Nov;10787−10799.
8. Goto A., Yoshii K., Obara M.. Role of the N-linked glycans of the prM and E envelope proteins in tick-borne encephalitis virus particle secretion. Vaccine 23(23):2005 Apr 27;3043−3052.
9. Wu C.J., Li T.L., Huang H.W.. Development of an effective Japanese encephalitis virus-specific DNA vaccine. Microbes Infect 8(11):2006 Sep;2578−2586.
10. Schalich J., Allison S.L., Stiasny K.. Recombinant subviral particles from tick-borne encephalitis virus are fusogenic and provide a model system for studying flavivirus envelope glycoprotein functions. J Virol 70(7):1996 Jul;4549−4557.
11. Zhang S., Liang M., Gu W.. Vaccination with dengue virus-like particles induces humoral and cellular immune responses in mice. Virol J 8:2011;333.
crossref pmid pmc
12. Wang P.G., Kudelko M., Lo J.. Efficient assembly and secretion of recombinant subviral particles of the four dengue serotypes using native prM and E proteins. PLoS One 4(12):2009;e8325.
crossref pmid pmc
13. Yoshii K., Hayasaka D., Goto A.. Enzyme-linked immunosorbent assay using recombinant antigens expressed in mammalian cells for serodiagnosis of tick-borne encephalitis. J Virol Methods 108(2):2003 Mar;171−179.
14. Liu Y.L., Si B.Y., Hu Y.. Expression of tick-borne encephalitis virus prM-E protein in insect cells and studies on its antigenicity. Zhonghua Shi Yan He Lin Chuang Bing Du Xue Za Zhi 19(4):2005 Dec;335−339. [Article in Chinese].

15. Macauley-Patrick S., Fazenda M.L., McNeil B.. Heterologous protein production using the Pichia pastoris expression system. Yeast 22(4):2005 Mar;249−270.
16. Leroux-Roels G., Desombere I., De Tollenaere G.. Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 1. Safety and immunogenicity in young, healthy adults. Vaccine 15(16):1997 Nov;1724−1731.
17. Bryan J.T.. Developing an HPV vaccine to prevent cervical cancer and genital warts. Vaccine 25(16):2007 Apr 20;3001−3006.
18. Tang Y.X., Jiang L.F., Zhou J.M.. Induction of virus-neutralizing antibodies and T cell responses by dengue virus type 1 virus-like particles prepared from Pichia pastoris. Chin Med J (Engl) 125(11):2012 Jun;1986−1992.

19. Kwon W.T., Lee W.S., Park P.J.. Protective immunity of Pichia pastoris-expressed recombinant envelope protein of Japanese encephalitis virus. J Microbiol Biotechnol 22(11):2012 Nov;1580−1587.
20. Liu W., Jiang H., Zhou J.. Recombinant dengue virus-like particles from Pichia pastoris: efficient production and immunological properties. Virus Genes 40(1):2010 Feb;53−59.
21. Sugrue R.J., Fu J., Howe J.. Expression of the dengue virus structural proteins in Pichia pastoris leads to the generation of virus-like particles. J Gen Virol 78(Pt 8):1997 Aug;1861−1866.
22. Yun S.M., Kim S.Y., Ju Y.R.. First complete genomic characterization of two tick-borne encephalitis virus isolates obtained from wild rodents in South Korea. Virus Genes 42(3):2011 Jun;307−316.
23. Cereghino J.L., Cregg J.M.. Heterologous protein expression in the methylotrophic yeast Pichia pastoris. FEMS Microbiol Rev 24(1):2000 Jan;45−66.
24. Vassileva A., Chugh D.A., Swaminathan S.. Expression of hepatitis B surface antigen in the methylotrophic yeast Pichia pastoris using the GAP promoter. J Biotechnol 88(1):2001 Jun 1;21−35.
25. McMinn P.C.. The molecular basis of virulence of the encephalitogenic flaviviruses. J Gen Virol 78(Pt 11):1997 Nov;2711−2722.
26. Gritsun T.S., Holmes E.C., Gould E.A.. Analysis of flavivirus envelope proteins reveals variable domains that reflect their antigenicity and may determine their pathogenesis. Virus Res 35(3):1995 Mar;307−321.
27. Konishi E., Mason P.W.. Proper maturation of the Japanese encephalitis virus envelope glycoprotein requires cosynthesis with the premembrane protein. J Virol 67(3):1993 Mar;1672−1675.
28. Heinz F.X., Stiasny K., Puschner-Auer G.. Structural changes and functional control of the tick-borne encephalitis virus glycoprotein E by the heterodimeric association with protein prM. Virology 198(1):1994 Jan;109−117.
29. Zhang Y., Corver J., Chipman P.R.. Structures of immature flavivirus particles. EMBO J 22(11):2003 Jun 2;2604−2613.
Figure 1
Construction of recombinant plasmid pGAPZɑA/93prM-E. (A) Scheme for cloning the 93prM-E fragment into the pGAPZɑA vector. (B) Confirmation of vector and insert by digestion with the restriction enzymes, Bst BI and Xba I. bp = base pairs, E = envelope protein; Lane M = 1 Kb DNA plus ladder; Lane 1 = pGAPZɑA/93prM-E digested with Bst BI and Xba I; prM = premembrane protein; S = the signal peptide of prM.
Figure 2
Western blot analysis on the expression of tick-borne encephalitis virus E protein in Pichia pastoris. Lane 1 = plasmid alone control; Lane 2 = sample from the cell lysate; Lane 3 = sample from the culture supernatant.
Figure 3
Analysis of glycosylation of tick-borne encephalitis virus E proteins in Pichia pastoris transformed with plasmid pGAPZɑA/93prM-E. Samples from (A) the cell lysate and (B) the cell supernatant were treated with Endo H (+) or PNGase F (+) and compared with untreated controls (−) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. fx1.gif = E protein; fx2.gif = deglycosylated E protein; Endo H = endoglycosidase H; PNGase = N-glycosidase F.

METRICS Graph View
  • 5 Crossref
  • 6 Scopus
  • 833 View
  • 4 Download

Close layer