Chimeric Adenovirus Vector Construction Service

Adenovirus (Ad) vectors are potent gene delivery vectors that cause mucosal and systemic immune responses. However, the presence of circulating antibodies to Ad capsid proteins is a barrier to gene therapy. By modifying the Ad fibrin, for example, by constructing a chimeric Ad vector, the properties of the fibrin can be altered, thereby increasing the efficiency of the vector in gene therapy. Creative Biolabs is a biotechnology company specializing in custom Ad vector production services. We offer a wide range of services for the construction of chimeric Ad vectors.

Chimeric Ad Vector Construction

Chimeric pseudo-vectors are commonly used to modify Ad tropism by replacing fibrin. The overall method towards constructing a chimeric virus is firstly to assemble the complete E1-deletion-virus DNA into a single plasmid, digest the plasmid DNA with an appropriate restriction enzyme to release the viral DNA ends, and transfect the DNA into a cell line such as HEK 293 to determine whether viable chimeric Ad can be rescued. Creative Biolabs has successfully constructed a chimeric Ad vector to construct all recombinant Ads by assembling a complete recombinant Ad genome in a single plasmid, which is flanked by a PacI site for the release of recombinant viral genomes from the plasmid backbone. Then, it is transfected into 293 cells to rescue the recombinant adenovirus. Most of the capsid proteins of this chimeric vector are derived from one adenovirus species and the flanking E1 and E4 regions are from another.

Figure 1. Cloning and rescue of recombinant adenoviral vectors.¹

Taking the most widely used group B (Ad3) and group C (Ad5) Ads as example, the chimeric fiber cDNA containing the head domain of Ad3 fiber fused with the tail and shaft of Ad5 fiber was integrated into the genome of an Ad vector, where E1 and E3 were deleted to encode beta-galactosidase to produce an Ad particle which contains a chimeric fibrin. Transduction experiments with fibrin competitors showed that the altered receptor tropism of chimeric fibrin vector is comparable with parental vector. Vector containing Ad3 fiber is more efficient than Ad5 fiber in transducing three cell lines (THP-1, MRC-5 and FaDu). These results suggest that the exchange of fiber head domains is a feasible method to produce Ad vectors with cell type selective transduction characteristics. Therefore, this method of constructing chimeric Ad vectors can be extended to use ligands for a series of different cell receptors in order to target gene transfer to specific cell types at the transduction level.

Why Go Chimeric? — The Essential Solution to a Critical Bottleneck

Conventional gene therapy vectors are frequently based on human adenovirus species C, particularly serotype 5 (HAdV-5). Yet, a majority of adults possess neutralizing antibodies against Ad5. This effectively cloaks the vector, rendering it invisible and leading to its rapid clearance by the immune system before it can reach target cells, resulting in failed therapy and inefficient transgene expression.

The chimeric adenovirus vector was engineered precisely to address this core challenge. Its central concept is a sophisticated "genetic graft" of the viral capsid proteins, particularly the fiber protein. This allows the vector to retain its potent infectivity while completely altering its immunological identity, enabling it to evade pre-existing immunity.

Specifically, the chimeric vectors we construct derive most of their structural proteins from an adenovirus serotype with low seroprevalence in humans. This clever design preserves all the critical protein-protein interactions required for proper capsid assembly, ensuring the production of stable, high-titer viral particles. Simultaneously, the key fiber protein is replaced with a corresponding domain from a different serotype, bestowing upon the vector a novel receptor specificity.

This elegant "recombination" strategy empowers your vector to:

• Regain "Stealth" Capabilities: By evading circulating antibodies, the vector achieves significantly higher in vivo gene delivery efficiency.
• Expand the "Attack" Range: Altering the virus's natural tropism allows it to efficiently transduce previously resistant or difficult cell types, such as specific tumor cells or primary cell lines.
• Enable "Precision" Targeting: It opens the door for targeting specific cellular receptors, paving the way for the next generation of targeted gene therapies.

Our Services

Chimeric Ad vectors for gene therapy are mainly used to increase the host range, expand the capacity and the titer of transgenic gene production, and combine gene elements to prolong the time of gene expression. At Creative Biolabs, we can provide you a series of chimeric Ad vector construction services, with the following advantages:

• Customization service: cloning scheme can be determined according to the original plasmid information provided by customers;
• Short turnaround time: the construction of viral DNA from the original plasmid can be completed in a short time;
• High cloning positive rate, reliable quality, stable packaging, rapid toxic and high titer.

Our Core Technology: A Precise, Efficient, and Flexible Construction Strategy

Creative Biolabs possesses a mature and validated technology platform for chimeric adenovirus vector construction. Our approach is built on a modular strategy centered around a single-plasmid rescue system, ensuring the entire process is efficient, precise, and highly reproducible.

Taking the well-characterized modification of Ad5 (species C) with Ad3 (species B) fiber as a classic example, our service workflow demonstrates unparalleled flexibility and control:

1. Gene Design & Synthesis: Based on your specific requirements, we design and synthesize the chimeric fiber gene. For instance, we precisely fuse the knob domain of the Ad3 fiber (responsible for receptor recognition) with the tail and shaft domains of the Ad5 fiber (responsible for anchoring into the viral particle). This design guarantees the chimeric fiber is correctly assembled onto a viral particle whose major coat proteins are derived from Ad5.
2. Full-Genome Plasmid Assembly: We integrate the engineered chimeric gene, along with your desired transgene expression cassette (e.g., a therapeutic gene or a reporter like beta-galactosidase), into a single, optimized plasmid containing the complete recombinant adenovirus genome. This plasmid is flanked by unique PacI restriction sites to facilitate subsequent linearization and virus rescue.
3. Virus Rescue & Amplification: The linearized plasmid is transfected into a highly efficient packaging cell line (e.g., HEK 293 cells). Inside these cells, the recombinant viral genome is replicated and packaged, ultimately producing infectious recombinant adenovirus particles displaying the engineered chimeric fiber protein.
4. Functional Validation & Characterization: We rigorously quality-control every rescued virus. Through transduction experiments using specific fiber protein competitors, we can definitively validate that the receptor tropism of the chimeric vector has indeed been altered as designed. Importantly, its transduction efficiency is comparable to, and often exceeds, that of the parental vector. Data demonstrates that vectors containing the Ad3 fiber transduce cell lines like THP-1, MRC-5, and FaDu significantly more efficiently than traditional Ad5 vectors.

Applications: Opening a New Chapter in Targeted Gene Therapy

The potential of chimeric adenovirus vectors extends far beyond simply evading immune responses. The vectors constructed through our service open the door to a vast landscape of advanced applications:

• Targeted Gene Therapy: By replacing the fiber knob with ligands that recognize tumor-specific antigens or receptors on particular cell types, you can create "smart" vectors that precisely target diseased cells while minimizing effects on healthy tissue.
• Vaccine Development: Using chimeric vectors based on rare serotypes to deliver antigen genes can overcome pre-existing immunity in the population, eliciting stronger and more durable humoral and cellular immune responses. This provides a powerful tool for developing next-generation, highly effective vaccines.
• Functional Genomics & Gene Editing: Efficient, broad-tropism chimeric vectors enable high-efficiency gene delivery into difficult-to-transduce cells, such as primary immune cells or stem cells, greatly facilitating cutting-edge research like gene function studies and CRISPR-based genetic screens.

Our Advantages

Choosing Creative Biolabs' chimeric adenovirus vector construction service provides you with more than just a viral particle. You gain a fully tailored solution, backed by top-tier scientists and a cutting-edge platform, designed to empower your specific research goals.

• Deep Customization, Infinite Possibilities
  We understand that every research project is unique. Therefore, we offer truly bespoke services. Whether you aim to replace a fiber knob to target a specific receptor, combine capsid proteins from different serotypes to optimize the immune evasion profile, or need to package a large or complex transgene with special regulatory elements, our scientists will collaborate closely with you to devise the most scientifically sound cloning strategy. Simply provide your original plasmid information or research concept, and we will handle the rest.
• Rapid Turnaround, Accelerated Discovery
  In the competitive landscape of research, time is critical. Our optimized processes and experienced team ensure high project efficiency. From the moment you provide the starting plasmid to the completion of viral DNA construction and initial validation, we commit to delivering results within the shortest possible turnaround time, keeping your research progress ahead of the curve.
• Superior Quality, Unwavering Reliability
  Quality is the cornerstone of our service. We pride ourselves on achieving an exceptionally high cloning positive rate and utilizing a stable, reliable virus packaging system. Every step is subject to stringent quality control, guaranteeing that the final product you receive is a high-titer, potent, and genetically stable chimeric adenovirus vector. Whether for in vitro functional studies or complex in vivo animal models, our products provide the most solid foundation for your data.

Frequently Asked Questions

Partner with Us

The future of gene therapy lies in continuously pushing boundaries to achieve delivery that is more efficient, safer, and more precise. Creative Biolabs is your committed partner, ready to transform your innovative ideas into tangible realities, backed by our profound expertise and continuous innovation in adenovirus vector construction. Do not let the barrier of pre-existing immunity hinder your path to discovery. Contact us today to discuss your project requirements with our expert team. Together, we can design the ideal vector to unlock the full therapeutic potential of your gene therapy program.

Reference

1. Sallard E, Zhang W, Aydin M, et al. The adenovirus vector platform: novel insights into rational vector design and lessons learned from the COVID-19 vaccine. Viruses, 2023, 15(1): 204. https://doi.org/10.3390/v15010204 Distributed under Open Access license CC BY 4.0, without modification.