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Helper-Dependent Adenoviral Vectors Service

Helper-dependent adenoviral vectors (HDAd) lack all viral genes and they can efficiently transduce a wide variety of dividing and non-dividing cells to mediate high levels of transgene expression. The absence of viral genes in HDAd results in long-term transgene expression without chronic toxicity and has a great clonal capacity. Thus, HDAd offers tremendous potential for in vivo gene therapy. Creative Biolabs has focused on the development of biotechnology for many years and has established excellent adenovirus vector construction platforms for gene therapy. We provide a variety of adenovirus vectors constructions to meet the diverse needs of our customers.

Introduction to Helper-Dependent Adenoviral Vectors

First or second-generation adenoviral vectors are effective vectors for gene transfer in vivo. However, the leakage expression of adenoviral genes from the vector backbone causes destruction of the transduced cells resulting in short-term transgene expression and chronic toxicity. To avoid this, all the viral genes were removed from the vector backbone to produce HDAds. As a result, these HDAds are able to mediate high-level, long-term transgene expression in the absence of chronic toxicity. Furthermore, the HDAd genome is maintained episomally, thus minimizing insertional mutagenesis and germline transmission.

Because HDAds are missing all viral coding sequences, a helper virus is required for their propagation. The efficient method for generating HDAds was the Cre-loxP system, in which HDAd genome is constructed in a bacterial plasmid. Minimally, the HDAd genome contains the expression cassette of interest, 500 bp of cis-acting adenoviral vector sequences, and “stuffer” DNA. The “stuffer” DNA is typically a noncoding mammalian DNA with minimal repetitive sequences. To rescue the HDAd, the plasmid is firstly digested with the appropriate restriction enzyme to liberate the HDAd genome from the bacterial plasmid sequences. 293 cells expressing the site-specific recombinase Cre are then transfected with the linearized HDAd genome and subsequently infected with the helper virus. The titer of the HDAd is amplified by serial coinfection of 293Cre cells with the HDAd and the helper virus, and the HDAd is finally purified by CsCl ultracentrifugation.

The Cre-loxP system for producing HDAds. Figure 1. The Cre-loxP system for producing HDAds. (Palmer, 2005)

The Service of Helper-Dependent Adenoviral Vectors

Helper-dependent adenoviral vectors possess a number of characteristics that make them attractive gene therapy vectors. These vectors are completely devoid of viral coding sequences and are able to mediate high-efficiency transduction in vivo to direct sustain high-level transgene expression with negligible chronic toxicity. Therefore, we offer a variety of adenovirus vector construction services, including helper-dependent adenoviral vectors with Cre-loxP system, or other site-specific recombination and the helper viruses.

Creative Biolabs has been involved in the field of gene therapy for many years and we are committed to completing your project with high quality. We have accumulated a wealth of scientific experience from our completed projects and provide you with the best adenoviral vector construction services to ensure your requirements are met. If you are interested in our services, please contact us for more details.


  1. Palmer, D.; et al. (2005). Helper-Dependent Adenoviral Vectors for Gene Therapy. Human Gene Therapy. 16(1):1-16.

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