Codon-Optimized Expression and Purification of Truncated ORF2 Protein of Hepatitis E Virus in Escherichia coli

High prevalence of hepatitis E among regular hemodialysis patients in South of Iran

OBJECTIVE

Hepatitis E virus (HEV) is one of the prevalent nosocomially transmitted agents among patients on maintenance hemodialysis due to parenteral transmission of HEV and immunocompromised condition of chronic hemodialysis patients. Therefore, this study aimed to investigate prevalence, risk factors, and genotypic pattern of HEV infection among hemodialysis patients in South of Iran.

METHODS

All patients on maintenance hemodialysis attending the hemodialysis centers of Bushehr, Borazjan, and Genaveh cities for regular hemodialysis were enrolled in this study. Serum samples were tested for the presence of anti-HEV antibodies using ELISA kit. The serum samples were further tested for detection of HEV RNA using nested RT-PCR.

RESULTS

Of 226 hemodialysis patients, 155 patients (68.6%, 95% CI: 62.3%-74.3%) were positive for anti-HEV IgG antibody, of which 33 patients (14.6%, 95% CI: 10.6%-19.8%) had anti-HEV IgM antibody. The prevalence of anti-HEV IgG and anti-IgM antibodies in non-hemodialysis controls were 65.1% and 9.6%, respectively. Although the hemodialysis patients had higher prevalence of HEV than the controls, the difference was not significant. All samples were negative for HEV RNA. HEV seroprevalence among hemodialysis patients was not significantly associated with place of residency, ethnicity, level of education, gender distribution, hemodialysis duration, and levels of liver enzymes. HEV seropositive patients had significantly higher mean age compared to seronegative patients.

CONCLUSION

This study reports the highest seroprevalence of HEV among hemodialysis patients in Iran. Inapparent HEV infection in the dialysis setting calls for regular screening of hemodialysis patients regardless of the hemodialysis duration, clinical symptoms, and liver function parameters.

Effect of different cloning strategies in pET-28a on solubility and functionality of a staphylococcal phage endolysin

Endolysins have been studied intensively as an alternative to antibiotics. In this study, endolysin derived from a phage which infects methicillin-resistant Staphylococcus aureus (MRSA) was cloned and expressed in Escherichia coli pET28a. Initially, the endolysin was cloned using BamHI/XhoI, resulting in expression of a recombinant endolysin which was expressed in inclusion bodies. While solubilization was successful, the protein remained nonfunctional. Recloning the endolysin using NcoI/XhoI resulted in expression of soluble and functional proteins at 18°C. The endolysin was able to form halo zones on MRSA plates and showed a reduction in turbidity of MRSA growth. Therefore, cloning strategies should be chosen carefully even in an established expression system as they could greatly affect the functionality of the expressed protein.

In-silico design and production of a novel antigenic chimeric Shigella IpaB fused to C-terminal of Clostridium perfringens enterotoxin

The emergence of antibiotic-resistant phenotypes in Shigella serotypes and the high mortality rate, approximately one million dead annually, in affected patients announce a global demand for an effective serotype-independent vaccine against Shigella. This study aims to design, express, and purify a novel chimeric protein, as a serotype-independent vaccine candidate against Shigella containing full-length Shigella invasion plasmid antigen B (IpaB) and a C-terminal fragment (residues 194-319) of Clostridium perfringens enterotoxin (C-CPE) as a mucosal adjuvant. Several online databases and bioinformatics software were utilized to design the chimeric protein and the relative recombinant gene. The recombinant gene encoding IpaB-CPE_194-319 was synthesized, cloned into pACYCDuet-1 expression vector, and transferred to E. coli Bl21 (DE3) cells. IpaB-CPE_194-319 was then expressed in auto-induction medium, purified and characterized using MALDI-TOF-TOF mass spectrometry. Followed by subcutaneous injection of the purified IpaB-CPE_194-319 to BALB/c mice, antigenicity of this chimeric protein was determined through performing dot-blot immunoassay on nitrocellulose membrane using mice sera. The outcomes of this study show the successful design, efficient expression, and purification of IpaB-CPE_194-319 divalent chimeric protein under mentioned conditions. The obtained results also demonstrate the intrinsic antigenic property of IpaB-CPE_194-319.

In-silico design, expression, and purification of novel chimeric Escherichia coli O157:H7 OmpA fused to LTB protein in Escherichia coli

E. coli O157:H7, one of the major EHEC serotypes, is capable of developing bloody diarrhea, hemorrhagic colitis (HC), and fatal hemolytic uremic syndrome (HUS) and is accompanied by high annual economic loss worldwide. Due to the increased risk of HC and HUS development following antibiotic therapy, the prevention of infections caused by this pathogen is considered to be one of the most effective ways of avoiding the consequences of this infection. The main aim of the present study was to design, express, and purify a novel chimeric protein to develope human vaccine candidate against E. coli O157:H7 containing loop 2–4 of E. coli O157:H7, outer membrane protein A (OmpA), and B subunit of E. coli heat labile enterotoxin (LTB) which are connected by a flexible peptide linker. Several online databases and bioinformatics software were utilized to choose the peptide linker among 537 analyzed linkers, design the chimeric protein, and optimize the codon of the relative gene encoding this protein. Subsequently, the recombinant gene encoding OmpA-LTB was synthesized and cloned into pET-24a (+) expression vector and transferred to E. coli BL21(DE3) cells. The expression of OmpA-LTB chimeric protein was then carried out by induction of cultured E. coli Bl21 (DE3) cells with 1mM isopropyl-β-D-thiogalactopyranoside (IPTG). The purification of OmpA-LTB was then performed by nickel affinity chromatography. Expression and purification were analyzed by sodium dodecyl sulphate poly acrylamide gel electrophoresis. Moreover, the identity of the expressed protein was analyzed by western blotting. SDS-PAGE and western immunoblotting confirmed the successful expression of a 27 KDa recombinant protein after 24 hours at 37°C post-IPTG induction. OmpA-LTB was then successfully purified, using nickel affinity chromatography under denaturing conditions. The yield of purification was 12 mg per liter of culture media. Ultimately, we constructed the successful design and efficient expression and purification of OmpA-LTB divalent under the above-mentioned conditions.

Designing, Construction and Expression of a Recombinant Fusion Protein Comprising the Hepatitis E Virus ORF2 and Rotavirus NSP4 in the Baculovirus Expression System

Background

The hepatitis E virus (HEV) accounts for hepatitis E infection with relatively high mortality rate in pregnant women that can lead to fulminant hepatitis. The baculovirus expression system (BES) has the capability to produce high-level recombinant proteins and could be useful for vaccine designing.

Objectives

The aim of this study was designing a recombinant hepatitis E virus ORF2 and Rotavirus NSP4 (ORF2-NSP4) and to evaluating construction these recombinant proteins in the BES.

Methods

The truncated ORF2 gene (112-607) and truncated ORF2-NSP4 were subcloned in pFastBac1 plasmid, separately, followed by digestion and confirmed by digestion and sequencing. Then the products were transformed into Escherichia coli DH5α and retransformed in DH10Bac competent cells. Finally the white colonies containing Bacmid DNA subjected to PCR for confirming transformation. Bacmid DNA containing HEV truncated ORF2 and HEV truncated ORF2-NSP4 genes were transfected into SF9 cells using BES. The expressed proteins in the cell lysate were evaluated by SDS-PAGE and determined by the western blot assay.

Results

The lengths of subcloned genes, truncated ORF2 and truncated ORF2-NSP4 were 1500 and 2000bp, respectively. After retransforming in DH10Bac, the size of PCR products were 300 bp in Bacmid DNA without recombination while it was 4300 and 3800 bp in Bacmid truncated ORF2-NSP4 and Bacmid truncated ORF2 PCR products. The analysis of protein expression by SDS-PAGE and immunoblotting revealed the presence of 56 KDa for truncated ORF2 and 74.5 KDa for truncated ORF2-NSP4 proteins.

Conclusions

The results of the present study showed that the baculovirus expression system (SF9 cells) was able to express truncated ORF2 and truncated ORF2-NSP4 proteins as a potential candidate vaccine.

Epidemiology of Hepatitis E in Pregnant Women and Children in Iran: A General Overview

From an epidemiological point of view, hepatitis E is an old infection in Iran, but only recently has its importance as a public health concern been considered from research and public health standpoints. As such, there is still a long road ahead to clarify the real burden of hepatitis E virus (HEV) infection in Iran. According to the available epidemiological studies, the seroprevalence of HEV infection among pregnant women is between 3.6% and 7.4%, and among Iranian children is between 0.9% to 8.5%, varying by geographic regions within the country and directly dependent upon the sanitary status of each. In addition to evaluating the sanitation level of a society, community-based seroprevalence studies of HEV infection demonstrate the most prevalent risk factors, the major routes of transmission, and the epidemiological patterns of HEV among that country's population. In this review, the current knowledge about the pathogenesis and epidemiology of HEV infection in pregnant women and children in Iran, as well as the recent advances in diagnosis, prevention and treatment of HEV infection have been summarized.

Epidemiology of hepatitis E virus in Iran

Iran is known as an endemic country for hepatitis E virus (HEV) infection, while there are variations in the epidemiology of HEV infection throughout the country. The available epidemiological studies in different regions of Iran show HEV seroprevalence of 1.1%-14.2% among general population, 4.5% -14.3% among blood donors, 6.1%-22.8% among injecting drug users, 6.3%-28.3% among hemodialysis patients, 1.6%-11.3% among patients infected with other hepatitis viruses, 27.5% among patients with chronic liver disease, 30.8% among kidney transplant recipient patients, and 10%-16.4% among human immunodeficiency virus-infected patients. These variations reflect differences in the status of public health and hygiene, risk factors, and routes of transmission in different regions and groups. Therefore, it is necessary to review the epidemiology of HEV infection to determine the most prevalent risk factors and routes of transmission, and to evaluate the effectiveness of preventive strategies employed in the public health services of the country. Moreover, the other epidemiological aspects of HEV, including the genotypic pattern, extra hepatic manifestations, and incidence of chronic infection need to be investigated among Iranian population to expand the current knowledge on the epidemiology of HEV and to clarify the real burden of HEV infection. Therefore, this review was performed to provide a general overview regarding the epidemiology of HEV in Iran.

Production and characterization of a Brazilian candidate antigen for Hepatitis E Virus genotype 3 diagnosis

Hepatitis E, caused by hepatitis E virus (HEV), is a viral infectious pathology of great importance in the public health. Hepatitis E outbreaks were registered in developing countries with poor or no sanitation, where drinking water was contaminated with fecal material, but also in many industrialized countries probably due to consumption of HEV-positive swine meat. In this study, we present the development and characterization of a recombinant antigen from ORF2 HEV genotype 3. Viral RNA was extracted from swine feces infected with the native virus. A total of 267 residues from the C-terminal ORF2((394-661)) coding sequence were cloned into the pET20a vector and expressed in Escherichia coli ER2566. Recombinant protein was purified by liquid chromatography and the fragment obtained a 98% homology against other human or swine HEV genotype 3 ORF2 sequences. Wistar rats were inoculated with ORF2p, developing antibodies able to recognize both the homologous antigen and the native HEV genotype 3 ORF2 present in infected stool. In parallel, HEV-negative swine were experimentally challenged with HEV genotype 3. ORF2 was detected by PCR 14 days post-inoculation in three-fourth piglets' feces and one week later by dot blot. In conclusion, this study proved the immunogenic and antigenic properties of the recombinant protein ORF2p.

Enhanced expression of soluble human papillomavirus L1 through coexpression of molecular chaperonin in Escherichia coli

The major recombinant capsid protein L1 of human papillomavirus (HPV) is widely used to produce HPV prophylactic vaccines. However, the quality of soluble and active expression of L1 in Escherichia coli was below the required amount. Coexpression with the chaperonin GroEL/ES enhanced L1 expression. Overexpressing GroEL/ES increased the soluble expression level of glutathione S-transferase-fused L1 (GST-L1) by approximately ∼3 fold. The yield of HPV type 16 L1 pentamer (L1-p) was ∼2 fold higher than that in a single expression system after purification through size-exclusion chromatograph. The expression and purification conditions were then optimized. The yield of L1-p was enhanced by ∼5 fold, and those of HPV types 18 and 58 L1-p increased by ∼3 and ∼2 folds, respectively, compared with that in the single expression system. Coexpressing the mono-site mutant HPV16 L1 L469A with GroEL/ES increased L1-p yield by ∼7 fold compared with strains expressing the wild-type L1 gene. L1-p was then characterized using circular dichroism spectra, UV-vis cloud point, dynamic light scattering and transmission electron microscope analyses. Results indicated that the conformation and biological characteristics of L1-p were identical to that of native L1. Hence, overexpressing chaperonin in E. coli can increase the expression level of GST-L1 and L1-p production after purification. This finding may contribute to the development of a platform for prophylactic HPV vaccines.

Design, Construction and Cloning of Truncated ORF2 and tPAsp-PADRE-Truncated ORF2 Gene Cassette From Hepatitis E Virus in the pVAX1 Expression Vector

BACKGROUND

Hepatitis E Virus (HEV) is the causative agent of enterically transmitted acute hepatitis and has high mortality rate of up to 30% among pregnant women. Therefore, development of a novel vaccine is a desirable goal.

OBJECTIVES

The aim of this study was to construct tPAsp-PADRE-truncated open reading frame 2 (ORF2) and truncated ORF2 DNA plasmid, which can assist future studies with the preparation of an effective vaccine against Hepatitis E Virus.

MATERIALS AND METHODS

A synthetic codon-optimized gene cassette encoding tPAsp-PADRE-truncated ORF2 protein was designed, constructed and analyzed by some bioinformatics software. Furthermore, a codon-optimized truncated ORF2 gene was amplified by the polymerase chain reaction (PCR), with a specific primer from the previous construct. The constructs were sub-cloned in the pVAX1 expression vector and finally expressed in eukaryotic cells.

RESULTS

Sequence analysis and bioinformatics studies of the codon-optimized gene cassette revealed that codon adaptation index (CAI), GC content, and frequency of optimal codon usage (Fop) value were improved, and performance of the secretory signal was confirmed. Cloning and sub-cloning of the tPAsp-PADRE-truncated ORF2 gene cassette and truncated ORF2 gene were confirmed by colony PCR, restriction enzymes digestion and DNA sequencing of the recombinant plasmids pVAX-tPAsp-PADRE-truncated ORF2 (aa 112-660) and pVAX-truncated ORF2 (aa 112-660). The expression of truncated ORF2 protein in eukaryotic cells was approved by an Immunofluorescence assay (IFA) and the reverse transcriptase polymerase chain reaction (RT-PCR) method.

CONCLUSIONS

The results of this study demonstrated that the tPAsp-PADRE-truncated ORF2 gene cassette and the truncated ORF2 gene in recombinant plasmids are successfully expressed in eukaryotic cells. The immunogenicity of the two recombinant plasmids with different formulations will be evaluated as a novel DNA vaccine in future investigations.

Cytokine Profiles and Cell Proliferation Responses to Truncated ORF2 Protein in Iranian Patients Recovered from Hepatitis E Infection

Background. The aim of this study was to evaluate hepatitis E virus (HEV) specific cellular immune responses to truncated ORF2 protein in Iranian patients recovered from HEV infection. Information about HEV-specific immune responses could be useful in finding an effective way for development of HEV vaccine. Methods. A truncated form of HEV ORF2 protein containing amino acids 112-608 was used to stimulate peripheral blood mononuclear cells (PBMCs) separated from HEV-recovered and control groups. Finally, the levels of four cytokines, IFN-γ ELISPOT, and cell proliferative responses following stimulation with the truncated ORF2 protein were assessed in the both groups. Results. The truncated ORF2 protein was able to induce IFN-γ ELISPOT and cell proliferation responses and to produce significant amounts of IFN-γ and IL-12 cytokines, but low amounts of IL-10 and IL-4 cytokines in vitro. These responses were significantly higher in the recovered group compared to the control group. These results indicate the antigenic nature of the truncated ORF2 protein and production of T helper type 1 cytokines. Conclusion. The truncated ORF2 protein can effectively induce significant cellular immune responsesand can be introduced as a potential vaccine candidate. However, further studies are required to evaluate this protein in vivo.

Prevalence of Hepatitis E Virus among Adults in South-West of Iran

Background. Knowledge regarding prevalence of HEV in general population can be an indicator of the public health and hygiene. Therefore, this study was conducted to evaluate the prevalence of HEV among adults in South-West of Iran. Methods. Blood samples were taken from 510 participants, 206 (40.4%) males and 304 (59.6%) females from February to July 2014. Detection of anti-HEV IgG and IgM antibodies was carried out by ELISA test. Results. The overall anti-HEV IgG and IgM prevalence rates were 46.1% and 1.4%, respectively. Anti-HEV IgG and IgM seropositivity were not statistically associated with gender and race/ethnicity. Meanwhile, there were significant differences between the age groups regarding HEV IgG and IgM seropositivity. HEV IgG seroprevalence increased with age from 14.3% in subjects aged 18-30 years to 71.4% in persons over 71 years old, and considerably individuals aged 61 to 70 years had the highest HEV prevalence (90.9%). Also, 5.7% in the age group 18-30 years and 2.2% in the age group 31-40 years were positive for anti-HEV IgM antibodies and the highest rate was observed in subjects aged 18-30 years. Conclusion. In conclusion, high HEV IgG seroprevalence of 46.1% was observed among adults in South-West of Iran.

Design and production of a multiepitope construct derived from hepatitis E virus capsid protein

The aim of this study was to design a high density multiepitope protein, which can be a promising multiepitope vaccine candidate against Hepatitis E virus (HEV). Initially, conserved and antigenic helper T‐lymphocyte (HTL) epitopes in the HEV capsid protein were predicted by in silico analysis. Subsequently, a multiepitope comprising four HTL epitopes with high‐affinity binding to the HLA molecules was designed, and repeated four times as high density multiepitope construct. This construct was synthesized and cloned into pET‐30a (+) vector. Then, it was transformed and expressed in Escherichia coli BL21 cells. The high density multiepitope protein was purified by Ni‐NTA agarose and concentrated using Amicon filters. Finally, the immunological properties of this high density multiepitope protein were evaluated in vitro. The results showed that the high density multiepitope construct was successfully expressed and purified. SDS‐PAGE and Western blot analyses showed the presence of a high density multiepitope protein band of approximately 33 kDa. Approximately 1 mg of the purified protein was obtained from each liter of the culture media. Moreover, the purified multiepitope protein was capable of induction of proliferation responses, IFN‐γ ELISPOT responses and IFN‐γ and IL‐12 cytokines production in a significant level in peripheral blood mononuclear cells (PBMCs) isolated from HEV‐recovered individuals compared to the control group. In conclusion, the newly produced multiepitope protein can induce significant T helper type 1 responses in vitro, and can be considered as a novel strategy for the development of HEV vaccines in the future. J. Med. Virol. 87:1225–1234, 2015. © 2015 Wiley Periodicals, Inc.