Identification of fragments from Autographa californica polyhedrin protein essential for self-aggregation and exogenous protein incorporation

Comparison between different conditions for the incorporation of foreign proteins into Autographa californica multiple polyhedrovirus polyhedra for biotechnological purposes

The occlusion bodies of Autographa californica multiple nucleopolyhedrovirus are proteinaceous formations with significant biotechnological potential owing to their capacity to integrate foreign proteins through fusion with polyhedrin, their primary component. However, the strategy for successful heterologous protein inclusion still requires further refinement. In this study, we conducted a comparative assessment of various conditions to achieve the embedding of recombinant proteins within polyhedra. Two baculoviruses were constructed: AcPHGFP (polh+), with GFP as a fusion to wild type (wt) polyhedrin and AcΔPHGFP (polh+), with GFP fused to a fragment corresponding to amino acids 19 to 110 of polyhedrin. These baculoviruses were evaluated by infecting Sf9 cells and stably transformed Sf9, Sf9POLH, and Sf9POLHE44G cells. The stably transformed cells contributed another copy of wt or a mutant polyhedrin, respectively. Polyhedra of each type were isolated and characterized by classical methods. The fusion PHGFP showed more-efficient incorporation into polyhedra than ΔPHGFP in the three cell lines assayed. However, ΔPHGFP polyhedron yields were higher than those of PHGFP in Sf9 and Sf9POLH cells. Based on an integral analysis of the studied parameters, it can be concluded that, except for the AcΔPHGFP/Sf9POLHE44G combination, deficiencies in one factor can be offset by improved performance by another. The combinations AcPHGFP/Sf9POLHE44G and AcΔPHGFP/Sf9POLH stand out due to their high level of incorporation and the large number of recombinant polyhedra produced, respectively. Consequently, the choice between these approaches becomes dependent on the intended application.

Exploiting Nanomedicine for Cancer Polychemotherapy: Recent Advances and Clinical Applications

The most important limitations of chemotherapeutic agents are severe side effects and the development of multi-drug resistance. Recently, the clinical successes achieved with immunotherapy have revolutionized the treatment of several advanced-stage malignancies, but most patients do not respond and many of them develop immune-related adverse events. Loading synergistic combinations of different anti-tumor drugs in nanocarriers may enhance their efficacy and reduce life-threatening toxicities. Thereafter, nanomedicines may synergize with pharmacological, immunological, and physical combined treatments, and should be increasingly integrated in multimodal combination therapy regimens. The goal of this manuscript is to provide better understanding and key considerations for developing new combined nanomedicines and nanotheranostics. We will clarify the potential of combined nanomedicine strategies that are designed to target different steps of the cancer growth as well as its microenvironment and immunity interactions. Moreover, we will describe relevant experiments in animal models and discuss issues raised by translation in the human setting.

Involvement of the neddylation modification system in Bombyx mori nucleopolyhedrovirus replication

Neddylation is a posttranslational modification that is similar to ubiquitination, and involved in some critical biological processes, such as DNA repair, transcription regulation, and ubiquitin-proteasome pathway. Recently, it was found that neddylation inhibitor MLN4924 has potent antiviral activity against human viruses including herpes simplex virus (HSV)-1, HSV-2, and influenza viruses. Here, we report that MLN4924 could dramatically and dose-dependently inhibits the propagation, formation of budding virus (BV) and occlusion body (OB) of a lepidopteran virus-Bombyx mori nucleopolyhedrovirus (BmNPV), impaired OB assembly. In addition, the neddylation modification protein NEDD8 is colocalized with aggresome and autophagosome. Our findings suggest that inhibiting neddylation could be an antibaculovirus strategy and MLN4924 may be used as candidate drug for that purpose.

Easily purified baculovirus/insect-system-expressed recombinant hepatitis B virus surface antigen fused to the N- or C-terminus of polyhedrin

Baculoviruses are circular double-stranded DNA viruses that infect insects and are widely used as the baculoviral expression vectors (BEVs), which provide a eukaryotic milieu for heterologous expression. The most frequently used vector is based on Autographa californica multiple nucleopolyhedrovirus (AcMNPV). However, purification of recombinant proteins produced using BEVs is laborious, time-consuming, and often expensive. Numerous strategies have been explored to facilitate purification of heterologous proteins, such as fusion with occlusion body (OBs)-forming proteins like polyhedrin (Polh). Baculoviruses produce OBs in the late stages of infection to protect the virion in the cellular environment, and the main protein responsible for OB formation is Polh. In this study, we investigated the effect of fusing the gene that encodes the surface antigen (S-HBsAg) of hepatitis B virus (HBV) to either the N- or C-terminus of the AcMNPV Polh. The production of recombinant viruses and recombinant proteins was confirmed, and the ability to form chimeric S-HBsAg-containing OBs was accessed by light and scanning electron microscopy of infected cells. The fusion was found to affect the shape and size of the OBs when compared to wild-type OBs, with the N-terminal fusion producing less-amorphous OBs than the C-terminal construct. In addition, the N-terminal construct gave higher levels of expression than the C-terminal construct. Quantitative and qualitative immunoassays with human serum or plasma antibodies against HBsAg showed that the two forms of the antigen reacted differently. Although both reacted with the antibody, the N-terminal fusion protein reacted with more sensitivity (2.27-fold) and is therefore more suitable for quantitative assays than the C-terminal version. In summary, the BEVs represents a promising tool for the production of reagents for the diagnosis of HBV infection.

A self-aggregating peptide: implications for the development of thermostable vaccine candidates

BACKGROUND

The use of biomaterials has been expanded to improve the characteristics of vaccines. Recently we have identified that the peptide PH_(1-110) from polyhedrin self-aggregates and incorporates foreign proteins to form particles. We have proposed that this peptide can be used as an antigen carrying system for vaccines. However, the immune response generated by the antigen fused to the peptide has not been fully characterized. In addition, the adjuvant effect and thermostability of the particles has not been evaluated.

RESULTS

In the present study we demonstrate the use of a system developed to generate nano and microparticles carrying as a fusion protein peptides or proteins of interest to be used as vaccines. These particles are purified easily by centrifugation. Immunization of animals with the particles in the absence of adjuvant result in a robust and long-lasting immune response. Proteins contained inside the particles are maintained for over 1 year at ambient temperature, preserving their immunological properties.

CONCLUSION

The rapid and efficient production of the particles in addition to the robust immune response they generate position this system as an excellent method for the rapid response against emerging diseases. The thermostability conferred by the particle system facilitates the distribution of the vaccines in developing countries or areas with no electricity.

Incorporation of ORF2 from Porcine Circovirus Type 2(PCV2) into genetically encoded nanoparticles as a novel vaccine using a self-aggregating peptide

Porcine Circovirus Type 2 (PCV2) is one of the most important pathogens in pigs around the world. PCV2 is a non-enveloped virus and its capsid is formed by a single protein known as open reading frame 2 (ORF2). The aim of this study was to evaluate the antigenicity and immunogenicity of genetically-encoded protein nanoparticles (NPs) containing ORF2 from PCV2 fused to the first 110 amino acids of the N-terminus of polyhedrin from the insect virus Autographa californica nucleopolyhedrovirus (PH(1 -1 1 0)). Our group has previously described that some polyhedrin fragments self-aggregate forming polyhedra-like particles. We identified a self-aggregating signal within the first 110 amino acids from polyhedrin (PH(1 -1 1 0)). Fusing the ORF2 from PCV2 to the carboxyl terminus from PH(1 -1 1 0) results in the formation of NPs which incorporate the antigen of interest. Using this system we synthesized NPs containing PH(1 -1 1 0) fused to ORF2 (PH(1 -1 1 0)PCV2) and purify them to immunize pigs and evaluate the humoral immune response generated by these NPs comparing them to a commercially available vaccine. Pigs immunized with PH(1 -1 1 0)PCV2 NPs produced antibodies against ORF2 from PCV2 as indicated by western blot and ELISA analysis. Antibodies obtained with PH(1 -1 1 0)PCV2 NPs were comparable to those obtained using a commercial PCV2 vaccine. These antibodies neutralized the infection of a recombinant PCV2 expressing the green fluorescent protein (GFP). These results together suggest that the self-aggregating peptide PH(1 -1 1 0) can be used for the synthesis of subunit vaccines against PCV2.

Recombinant occlusion bodies of baculovirus as carriers of a non-structural protein of foot-and-mouth disease virus

Here, we developed a diagnostic ELISA for foot-and-mouth disease using recombinant occlusion bodies (rOBs) of baculovirus. We fused Δ3AB_1-3, a polypeptide derived from non-structural proteins of foot-and-mouth disease virus, to polyhedrin (POLH), the major constituent of OBs, under polh promoter. To further assess the most convenient strategy to improve yields, we designed two recombinant baculoviruses, vPOLH and vPOLH_E44G. These carried the sequence of the fusion protein POLH-Δ3AB_1-3 with an additional copy in cis of polh or polh _E44G , respectively, under p10 promoter. Our results show that both viruses expressed POLH-Δ3AB_1-3, which was detected by western blot in purified rOBs with anti-POLH and anti-3AB1 antibodies. We also found that vPOLH_E44G produced larger polyhedra and a significant increase of antigen yield (p < 0.01). Furthermore, the chimeric protein POLH-Δ3AB_1-3 was recognized by sera from experimentally infected animals, showing that translational fusion to POLH does not alter the antigenicity of Δ3AB_1-3. Finally, the rOBs were successfully used in an ELISA test to differentiate infected from vaccinated animals. Taken together, these results demonstrate the great potential of rOBs to develop diagnostic schemes adaptable to animal infectious diseases.

Induction of adaptive immune response by self-aggregating peptides

INTRODUCTION

Recently, subunit vaccines are replacing some of the traditional vaccines because they offer a higher margin of safety. However, generally subunit vaccines have low antigenicity. Adjuvants are used in vaccine formulations to increase their immunogenicity, but current research suggests that adjuvants could induce serious side effects in susceptible individuals; therefore, the improvement of antigens and adjuvants is important.

AREAS COVERED

Here we reviewed some self-aggregating peptides (SAPs) used as antigen delivery systems. SAPs are based on a short sequence of amino acids, which have self-aggregating properties, inducing self-interaction among peptide molecules by means of non-covalent interactions to generate nanoparticles (NPs).

EXPERT COMMENTARY

SAPs increase the immunogenicity of fused/conjugated antigens because they can interact with antigen-presenting cells and induce adaptive immunity based on both humoral and cellular responses. As an example, we report an antigen delivery system based on SAPs forming NPs. These NPs are synthesized using a recombinant baculovirus. We fused the green fluorescent protein to the first 110 amino acids of polyhedrin protein from Autographa californica nucleopolyhedrovirus, which has self-aggregating properties. We showed that these NPs prompt high antibody levels without inducing inflammation, similarly to some SAPs reported here.

Novel biotechnological platform based on baculovirus occlusion bodies carrying Babesia bovis small antigenic peptides for the design of a diagnostic enzyme-linked immunosorbent assay (ELISA)

Baculoviruses are large DNA virus of insects principally employed in recombinant protein expression. Its ability to form occlusion bodies (OBs), which are composed mainly of polyhedrin protein (POLH), makes them biotechnologically attractive, as these crystals (polyhedra) can incorporate foreign peptides and can be easily isolated. On the other hand, peptide microarrays allow rapid and inexpensive high-throughput serological screening of new candidates to be incorporated to OBs. To integrate these 2 biotechnological approaches, we worked on Babesia bovis, one of the causative agents of bovine babesiosis. Current molecular diagnosis of infection with B. bovis includes enzyme-linked immunosorbent assay (ELISA) techniques, which use merozoite lysate obtained from infected bovine erythrocytes. However, it is important to produce recombinant antigens that replace the use of crude antigens. Here, we describe a new biotechnological platform for the design of indirect ELISAs based on 5 antigenic peptides of 15 amino acid residues of B. bovis (ApBb), selected from a peptide microarray and expressed as a fusion to POLH. An Sf9POLH_E44G packaging cell line infected with recombinant baculoviruses carrying POLH-ApBb fusions yielded higher levels of chimeric polyhedra, highlighting the advantage of a trans-contribution of a mutant copy of polyhedrin. Finally, the use of dissolved recombinant polyhedra as antigens was successful in an ELISA assay, as B. bovis-positive sera recognized the fusion POLH-ApBb. Thus, the use of this platform resulted in a promising alternative for molecular diagnosis of relevant infectious diseases.

In vivo production of recombinant proteins using occluded recombinant AcMNPV-derived baculovirus vectors

Trichoplusia ni insect larvae infected with vectors derived from the Autographa californica multiple nucleopolyhedrovirus (AcMNPV), are an excellent alternative to insect cells cultured in conventional bioreactors to produce recombinant proteins because productivity and cost-efficiency reasons. However, there is still a lot of work to do to reduce the manual procedures commonly required in this production platform that limit its scalability. To increase the scalability of this platform technology, a current bottleneck to be circumvented in the future is the need of injection for the inoculation of larvae with polyhedrin negative baculovirus vectors (Polh-) because of the lack of oral infectivity of these viruses, which are commonly used for production in insect cell cultures. In this work we have developed a straightforward alternative to obtain orally infective vectors derived from AcMNPV and expressing recombinant proteins that can be administered to the insect larvae (Trichoplusia ni) by feeding, formulated in the insect diet. The approach developed was based on the use of a recombinant polyhedrin protein expressed by a recombinant vector (Polh+), able to co-occlude any recombinant Polh- baculovirus vector expressing a recombinant protein. A second alternative was developed by the generation of a dual vector co-expressing the recombinant polyhedrin protein and the foreign gene of interest to obtain the occluded viruses. Additionally, by the incorporation of a reporter gene into the helper Polh+ vector, it was possible the follow-up visualization of the co-occluded viruses infection in insect larvae and will help to homogenize infection conditions. By using these methodologies, the production of recombinant proteins in per os infected larvae, without manual infection procedures, was very similar in yield to that obtained by manual injection of recombinant Polh- AcMNPV-based vectors expressing the same proteins. However, further analyses will be required for a detailed comparison of production yields reached by injection vs oral infections for different recombinant proteins. In conclusion, these results open the possibility of future industrial scaling-up production of recombinant proteins in insect larvae by reducing manual operations.

Protein composition analysis of polyhedra matrix of Bombyx mori nucleopolyhedrovirus (BmNPV) showed powerful capacity of polyhedra to encapsulate foreign proteins

Polyhedra can encapsulate other proteins and have potential applications as protein stabilizers. The extremely stable polyhedra matrix may provide a platform for future engineered micro-crystal devices. However, the protein composition of the polyhedra matrix remains largely unknown. In this study, the occlusion-derived virus (ODV)-removed BmNPV polyhedra matrix fraction was subjected to SDS-PAGE and then an LC-ESI-MS/MS analysis using a Thermo Scientific Q Exactive mass spectrometer. In total, 28 host and 91 viral proteins were identified. The host components were grouped into one of six categories, i.e., chaperones, ubiquitin and related proteins, host helicases, cytoskeleton-related proteins, RNA-binding proteins and others, according to their predicted Pfam domain(s). Most viral proteins may not be essential for polyhedra assembly, as evidenced by studies in the literature showing that polyhedra formation occurs in the nucleus upon the disruption of individual genes. The structural role of these proteins in baculovirus replication will be of significant interest in future studies. The immobilization of enhanced green fluorescent protein (eGFP) into the polyhedra by fusing with the C-terminus of BM134 that is encoded by open reading frame (ORF) 134 suggested that the polyhedra had a powerful capacity to trap foreign proteins, and BM134 was a potential carrier for incorporating proteins of interest into the polyhedra.