Tools for the targeted genetic modification of poxvirus genomes

Advancing ORFV-Based Therapeutics to the Clinical Stage

The Orf virus (ORFV) is the prototype member of the parapoxvirus family and has long been recognized for its robust immunogenicity, favourable safety profile and its ability to stimulate both cellular and humoural immune responses without inducing significant anti-vector immunity. Despite these inherent advantages, early applications of ORFV-based technologies were limited by challenges in manufacturing scalability and uncertainties regarding clinical safety in humans. However, recent breakthroughs have transformed this therapeutic landscape. A landmark achievement is the development of Prime-2-CoV, an ORFV-based anti-COVID-19 vaccine that has advanced into human clinical trials, providing the first clinical evidence of live ORFV's feasibility, safety and immunogenicity. This milestone, together with the establishment of a good manufacturing practice (GMP)-compliant production process and comprehensive preclinical evaluations, has laid a robust foundation for broader clinical applications of ORFV-based therapeutics. Moreover, the use of ORFV as an oncolytic virus therapy has shown promising results, effectively converting immunologically 'cold' tumours into 'hot' ones, underscoring its versatility as a therapeutic platform. In this review, we critically assess recent advances in ORFV-based therapeutics, with a particular focus on vaccine development and oncolytic virotherapy (OVT). We thoroughly discuss the milestones and impact of the first ORFV-based clinical trial, outline strategies for optimizing the technology and provide insights into overcoming remaining challenges. Collectively, these advancements position ORFV as a highly promising and versatile platform for next-generation prophylactic and therapeutic interventions in both human and veterinary medicine, while also providing a roadmap for future innovations.

Vaccinia virus-mediated oncolytic immunotherapy: Emerging strategies for gastrointestinal cancer treatment at dawn

Oncolytic vaccinia virus (VVs) based immunotherapy is a rapidly developing treatment for gastrointestinal (GI) cancers. Conventional treatments, such as chemotherapy, radiotherapy and surgery achieve good effects in early-stage GI cancers, but effects are limited in advanced disease. Immunotherapy has limited efficacy in GI cancers due to tumor heterogeneity and complex immunosuppressive mechanisms. Oncolytic VV immunotherapy is a novel treatment approach showing promising results in preclinical and clinical trials. Oncolytic VV's intracytoplasmic replication and assembly mechanism, diverse mature forms, and use methods make it extremely safe and versatile for drug delivery. Combining oncolytic VV with conventional therapies and immunotherapy (e.g., ICIs, CAR-T) enhances tumor regression and survival compared to monotherapies. Researchers are establishing response protocols and improvement strategies, rapidly developing VV tumor oncolytic immunotherapy. This article focuses on oncolytic vaccinia development and outlook in gastrointestinal cancer therapy, advantages when combined with other drugs to improve clinical survival, safety, and risk reduction for patients.

Evaluation of Vaccinia Virus Infection in Mice Using Two-Reporter Recombinant Virus

The family Poxviridae comprises multiple viruses with large double-stranded (ds) DNA genomes that can infect numerous vertebrate and invertebrate hosts, including humans. The development of genetic engineering methods for Vaccinia virus (VACV), the prototypic member in the family, have allowed the manipulation of the genomes of poxviruses for the generation of recombinant (r)VACV expressing easily traceable luciferase and/or fluorescent reporter genes. These recombinant viruses have significantly contributed to progress in the field of poxvirus research and accelerated the development of novel prophylactic vaccines and therapeutic antiviral treatments. Recently, we described two reporter rVACV expressing luciferase (Nluc) and fluorescent (GFP or Scarlet) proteins to easily track viral infections in different systems, overcoming the limitations associated with the use of rVACV expressing a single luciferase or fluorescent reporter gene. Here, we describe the experimental procedures to carry out in vitro, in vivo and ex vivo studies using these novel bireporter-expressing rVACV, which also represent an excellent option to study the biology of VACV, including the use of these reporter viruses for testing new antivirals and vaccines, using cultured cells and/or well-characterized animal models of infection.

Creation of poxvirus expressing foot-and-mouth and peste des petits ruminant disease virus proteins

OBJECTIVE

Foot-and-mouth disease (FMD) and Peste des petits ruminant disease (PPR) are acute and severe infectious diseases of sheep and are listed as animal diseases for compulsory immunization. However, there is no dual vaccine to prevent these two diseases. The Modified Vaccinia virus Ankara strain (MVA) has been widely used in the construction of recombinant live vector vaccine because of its large capacity of foreign gene, wide host range, high safety, and immunogenicity. In this study, MVA-GFP recombinant virus skeleton was used to construct dual live vector vaccines against FMD and PPR.

METHODS

The recombinant plasmid pUC57-FMDV P1-2A3CPPRV FH was synthesized and transfected into MVA-GFP infected CEF cells for homologous recombination.

RESULTS

The results showed that a recombinant virus without fluorescent labeling was obtained after multiple rounds of plaque screening. The recombinant virus successfully expressed the target proteins, and the empty capsid of FMDV could be observed by transmission electron microscope (TME), and the expression levels of foreign proteins (VP1 and VP3) detected by ELISA were like those detected in FMDV-infected cells. This study laid the foundation for the successful construction of a live vector vaccine against FMD and PPR.

KEY POINTS

• A recombinant MVA expressing FMDVP12A3C and PRRV HF proteins • Both the FMDV and PRRV proteins inserted into the virus were expressed • The proteins expressed by the recombinant poxvirus were assembled into VLPs.

Advances in vaccinia virus-based vaccine vectors, with applications in flavivirus vaccine development

Historically, virulent variola virus infection caused hundreds of millions of deaths. The smallpox pandemic in human beings has spread for centuries until the advent of the attenuated vaccinia virus (VV) vaccine, which played a crucial role in eradicating the deadly contagious disease. Decades of exploration and utilization have validated the attenuated VV as a promising vaccine vehicle against various lethal viruses. In this review, we focus on the advances in VV-based vaccine vector studies, including construction approaches of recombinant VV, the impact of VV-specific pre-existing immunity on subsequent VV-based vaccines, and antigen-specific immune responses. More specifically, the recombinant VV-based flaviviruses are intensively discussed. Based on the publication data, this review aims to provide valuable insights and guidance for future VV-based vaccine development.

Poxvirus Recombination

Genetic recombination is used as a tool for modifying the composition of poxvirus genomes in both discovery and applied research. This review documents the history behind the development of these tools as well as what has been learned about the processes that catalyze virus recombination and the links between it and DNA replication and repair. The study of poxvirus recombination extends back to the 1930s with the discovery that one virus can reactivate another by a process later shown to generate recombinants. In the years that followed it was shown that recombinants can be produced in virus-by-virus crosses within a genus (e.g., variola-by-rabbitpox) and efforts were made to produce recombination-based genetic maps with modest success. The marker rescue mapping method proved more useful and led to methods for making genetically engineered viruses. Many further insights into the mechanism of recombination have been provided by transfection studies which have shown that this is a high-frequency process associated with hybrid DNA formation and inextricably linked to replication. The links reflect the fact that poxvirus DNA polymerases, specifically the vaccinia virus E9 enzyme, can catalyze strand transfer in in vivo and in vitro reactions dependent on the 3'-to-5' proofreading exonuclease and enhanced by the I3 replicative single-strand DNA binding protein. These reactions have shaped the composition of virus genomes and are modulated by constraints imposed on virus-virus interactions by viral replication in cytoplasmic factories. As recombination reactions are used for replication fork assembly and repair in many biological systems, further study of these reactions may provide new insights into still poorly understood features of poxvirus DNA replication.

Vaccinia Virus Attenuation by Codon Deoptimization of the A24R Gene for Vaccine Development

Poxviruses have large DNA genomes, and they are able to infect multiple vertebrate and invertebrate animals, including humans. Despite the eradication of smallpox, poxvirus infections still remain a significant public health concern. Vaccinia virus (VV) is the prototypic member in the poxviridae family and it has been used extensively for different prophylactic applications, including the generation of vaccines against multiple infectious diseases and/or for oncolytic treatment. Many attempts have been pursued to develop novel attenuated forms of VV with improved safety profiles for their implementation as vaccines and/or vaccines vectors. We and others have previously demonstrated how RNA viruses encoding codon-deoptimized viral genes are attenuated, immunogenic and able to protect, upon a single administration, against challenge with parental viruses. In this study, we employed the same experimental approach based on the use of misrepresented codons for the generation of a recombinant (r)VV encoding a codon-deoptimized A24R gene, which is a key component of the viral RNA polymerase. Similar to our previous studies with RNA viruses, the A24R codon-deoptimized rVV (v-A24cd) was highly attenuated in vivo but able to protect, after a single intranasal dose administration, against an otherwise lethal challenge with parental VV. These results indicate that poxviruses can be effectively attenuated by synonymous codon deoptimization and open the possibility of using this methodology alone or in combination with other experimental approaches for the development of attenuated vaccines for the treatment of poxvirus infection, or to generate improved VV-based vectors. Moreover, this approach could be applied to other DNA viruses. IMPORTANCE The family poxviridae includes multiple viruses of medical and veterinary relevance, being vaccinia virus (VV) the prototypic member in the family. VV was used during the smallpox vaccination campaign to eradicate variola virus (VARV), which is considered a credible bioterrorism threat. Because of novel innovations in genetic engineering and vaccine technology, VV has gained popularity as a viral vector for the development of vaccines against several infectious diseases. Several approaches have been used to generate attenuated VV for its implementation as vaccine and/or vaccine vector. Here, we generated a rVV containing a codon-deoptimized A24R gene (v-A24cd), which encodes a key component of the viral RNA polymerase. v-A24cd was stable in culture cells and highly attenuated in vivo but able to protect against a subsequent lethal challenge with parental VV. Our findings support the use of this approach for the development of safe, stable, and protective live-attenuated VV and/or vaccine vectors.

CAQK modification enhances the targeted accumulation of metformin-loaded nanoparticles in rats with spinal cord injury

Spinal cord injury (SCI) often causes neuronal membrane rupture and immediate death of neurons, followed by complicated secondary injuries. Treatment of SCI still remains a major challenge in clinical practice; thus, a great advance is urgently needed in this field. Metformin (MET) has anti-oxidant, anti-inflammatory, anti-apoptotic and neuroprotective properties, which may exert a potential therapeutic effect on SCI. In this study, we established a zein-based MET-loaded nanodrug system (CAQK-MET-NPs) for the targeted drug delivery for SCI. The results showed that MET could be effectively encapsulated into zein to obtain the zein-based spherical nanoparticles. Pharmacokinetic analysis indicated that CAQK-MET-NPs exhibited sustained-release and long-term therapeutic effects. The fluorescence imaging and tissue distribution experiments showed that CAQK-MET-NPs could efficiently accumulate at the lesion site of SCI rats. In conclusion, CAQK-MET-NPs may be a promising nanodrug for the treatment of SCI.