Purification and analysis of polyhistidine-tagged human parvovirus B19 VP1 and VP2 expressed in insect cells

Screening for Human Parvovirus B19 Infection in Egyptian Family Replacement Blood Donors

Up till now, screening for human parvovirus B19 is not routine in national Egyptian blood bank strategy. Blood samples were collected from 500 healthy blood donors within the age range from 18 to 45 years old attending the blood bank of Suez Canal University Hospital, Ismailia, Egypt. Sera were separated and stored at - 20 °C. Serum samples were screened for anti-human parvovirus B19 IgM and IgG antibodies and B19 genome using ELISA and real-time PCR respectively. Frequency of B19 IgM and B19 IgG antibodies was 6.20%, and 80.20% respectively, and the prevalence of B19 genome was 3.00%. There is a high frequency of human parvovirus B19 among Egyptian blood donors; therefore, serological screening for B19 is warranted.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

Peptide presentation on primate erythroparvovirus 1 virus-like particles: In vitro assembly, stability and immunological properties

Virus-like particles (VLPs) have demonstrated to be valuable scaffolds for the display of heterologous peptides for vaccine development and other specific interactions. VLPs of primate erythroparvovirus 1, generally referred as parvovirus B19 (B19V), have already been produced in-vivo and in-vitro from the recombinant VP2 protein of this virus. In this study, chimeric forms of B19V VP2 were constructed, and their ability to assemble into VLPs was evaluated. Chimeras were composed of the VP2 protein fused, at its N-terminus, with two peptides derived from the fusion glycoprotein (F) of the respiratory syncytial virus (RSV). The chimeric proteins self-assembled into VLPs morphologically similar to B19V virions. Stability of these VLPs was analyzed under denaturation conditions with guanidinium chloride (GdnHCl). Our results indicate that the presence of the heterologous fragments increased the stability of VLPs assembled by any of the VP2 chimeras. Specific proteolysis assays shown that a fraction of the N-termini of the chimeric proteins is located on the outer surface of the VLPs. Immunogenicity of VLPs against RSV was evaluated and the results indicate that the particles can elicit a humoral immune response, although these antibodies did not cross-react with RSV in ELISA tests. These results provide novel insights into the localization of the N-termini of B19V VP2 protein after in vitro assembly into VLPs, and point them to be attractive sites to display peptides or proteins without compromise the assembly or stability of VLPs.

Next generation vaccines and vectors: Designing downstream processes for recombinant protein-based virus-like particles

In recent years, the development of novel recombinant virus-like particles (VLPs) has been generating new perspectives for the prevention of untreated and arising infectious diseases. However, cost-reduction and acceleration of manufacturing processes for VLP-based vaccines or vectors are key challenges for the global health system. In particular, the design of rapid and cost-efficient purification processes is a critical bottleneck. In this review, we describe and evaluate new concepts, development strategies and unit operations for the downstream processing of VLPs. A special focus is placed on purity requirements and current trends, as well as chances and limitations of novel technologies. The discussed methods and case studies demonstrate the advances and remaining challenges in both rational process development and purification tools for large biomolecules. The potential of a new era of VLP-based products is highlighted by the progress of various VLPs in clinical phases.

Immunogenicity of virus-like particles containing modified goose parvovirus VP2 protein

The major capsid protein VP2 of goose parvovirus (GPV) expressed using a baculovirus expression system (BES) assembles into virus-like particles (VLPs). To optimize VP2 gene expression in Sf9 cells, we converted wild-type VP2 (VP2) codons into codons that are more common in insect genes. This change greatly increased VP2 protein production in Sf9 cells. The protein generated from the codon-optimized VP2 (optVP2) was detected by immunoblotting and an indirect immunofluorescence assay (IFA). Transmission electron microscopy analysis revealed the formation of VLPs. These findings indicate that optVP2 yielded stable and high-quality VLPs. Immunogenicity assays revealed that the VLPs are highly immunogenic, elicit a high level of neutralizing antibodies and provide protection against lethal challenge. The antibody levels appeared to be directly related to the number of GP-Ag-positive hepatocytes. The variation trends for GP-Ag-positive hepatocytes were similar in the vaccine groups. In comparison with the control group, the optVP2 VLPs groups exhibited obviously better responses. These data indicate that the VLPs retained immunoreactivity and had strong immunogenicity in susceptible geese. Thus, GPV optVP2 appears to be a good candidate for the vaccination of goslings.

Expression of porcine parvovirus VP2 gene requires codon optimized E. coli cells

Porcine parvovirus (PPV) is a widespread infectious virus that causes serious reproductive diseases of swine and death of piglets. The gene coding for the capsid protein VP2 of PPV was amplified and inserted into the plasmid pET-32a (+), which was then used to transform Escherichia coli Rosetta, the capsid protein of PPV was fused to a polyhistidine tag, and the position of the affinity tag is in N-terminus. VP2 was expressed using different expression host bacteria, including E. coli BL21, and Rosetta, and different plasmid vectors, including pET-30a (+), pET-32a (+), and pGEX-6p-1. After selection, only the fusion protein inserted into pET-32a (+) was expressed well in E. coli Rosetta. The recombinant bacterium produced high quantities of the fusion protein VP2, about 8% in total. The expressed VP2 was antigenically similar to the native capsid protein according to a Western blot assay performed with polyclonal antibodies obtained from pigs vaccinated with PPV. A simple, easily commercialized procedure was used to purify this protein. This study provides a foundation for the application of VP2 protein in the clinical diagnosis of PPV and in the vaccination against PPV.

Purification of proteins from baculovirus-infected insect cells

Expression of recombinant proteins in the baculovirus/insect cell expression system is employed because it enables post-translational protein modification and high yields of recombinant protein. The system is capable of facilitating the functional expression of many proteins - either secreted or intracellularly located within infected insect cells. Strategies for the isolation and extraction of soluble proteins are presented in this chapter and involve selective cell lysis, precipitation and chromatography. Protein insolubility, following recombinant expression in insect cells, can occur. However, using the methods described herein, it is possible to extract and purify insoluble protein using affinity, ion-exchange and gel filtration chromatography. Indeed, protein insolubility often aids protein purification.

Production and purification of VP2 protein of porcine parvovirus expressed in an insect-baculovirus cell system

The porcine parvovirus (PPV) VP2 protein was expressed in an insect-baculovirus cell system and was purified using Ni-NTA affinity column chromatography. The recombinant 6-His-tagged VP2 protein with molecular mass (Mr) of about 64 kDa was detected by anti-his antibody and anti-PPV serum. Electron microscopy showed that the purified VP2 protein assembled into spherical particles with diameters ranging from 20 to 22 nm. The expressed VP2 was antigenically similar to the native capsid protein according to HA and a Western blotting assay performed with polyclonal antibodies collected from an outbreak of PPV in one farm. This study provides a foundation for the application of VP2 protein in the clinical diagnosis of PPV or in the vaccination against PPV in the future.

Expression of the capsid protein of Chikungunya virus in a baculovirus for serodiagnosis of Chikungunya disease

Chikungunya virus (CHIKV) causes endemic or epidemic outbreaks of CHIK fever, which typically manifests as a febrile illness. To develop a CHIKV-specific diagnostic test, CHIKV capsid protein was expressed using a baculovirus expression system. The seroreactvity of the recombinant CHIKV capsid protein was evaluated by ELISA and immuochromatographic assay (ICA), using 40 anti-CHIKV-positive and 20 anti-CHIKV-negative sera, an additional 20 normal sera samples from healthy Koreans, and 20 anti-Dengue virus sera samples. The sensitivity of the recombinant CHIKV capsid protein was 85% and 87.5% as measured by ELISA and ICA, respectively. The specificity of the recombinant CHIKV capsid protein was 100% both by ELISA and by ICA. No cross-reactivity of the capsid protein was seen with anti-Dengue virus sera samples. There was a significant correlation between the ELISA- and ICA-measured seroreactivities of the recombinant CHIKV capsid protein for anti-CHIKV IgM-positive sera samples. These results suggest that the recombinant CHIKV capsid protein could be used in a diagnostic test for identifying CHIKV disease.