Adenovirus-based studies

Adenoviruses are one of the most genetically diverse DNA viruses, occuring naturally in a range of hosts and causing only mild infections. Adenoviruses are also excellent vectors for delivering genes or vaccine antigens to the target host tissues and are being tested in several vaccine and gene therapy studies. Adenovirus-based vectors offer several advantages over other viral vectors such as broad range of tissue tropism, well-characterized genome, ease of genetic manipulation including acceptance of large transgene DNA insertions, inherent adjuvant properties, ability to induce robust transgene-specific T cell and antibody responses, non-replicative nature in host, and ease of production at large scale. However, several studies have highlighted major drawbacks to using adenovirus as vaccine and gene therapy vectors. These include pre-existing immunity in humans, inflammatory responses, sequestering of the vector to liver and spleen, and immunodominance of the vector genes over transgenes. That is why it is of paramount importance to tests for their efficacy and safety.

Adenoviruses have a unique ability to infect a broad range of cell types. Therefore, adenovirus-based vectors can be used to transduce and deliver transgenes to different cell types including both replicating and quiescent cell populations. This property of adenoviral vectors is extremely important in gene therapy and puts adenoviral vectors on top of viral vectors for gene delivery. Furthermore, adenovirus vectors do not integrate into host genomes but stay as episomal DNA in the nucleus of host cells. Modern adenoviral vectors can take multiple gene cassettes, up to 36 kb of foreign DNA, which make them suitable for delivering virtually any size of gene.

At the same time, adenoviruses must be engineered in a way to ensure they are safe and efficient for human use as vaccine and gene therapy vectors, Usually, it is accomplished by deleting certain AdV genome sequences so that they become replication-defective. In some specific cases – like in cancer gene therapy – a natural proces of lytic virus replication is harnessed, when replication-competent (oncolytic) vectors are used to specifically target, replicate-in and destroy cancer cells.

In addition, adenoviruses activate several innate immune signaling pathways that result in the secretion of a number of proinflammatory cytokines. These proinflammatory cytokines pave the way for effective immune cell stimulation and result in the induction of robust adaptive humoral and cellular immune responses. To resolve infections with intracellular pathogens such as viruses, CD8+ cytotoxic T lymphocyte (CTL) responses are critical. Transgene antigens carried by adenoviral vectors are presented to T cells via MHC class I molecules, and therefore, they induce efficient and robust CTL responses. The CTLs efficiently recognize and kill virus-infected cells, intracellular pathogens, and cancerous cells. These properties make adenoviral vectors promising as vaccine vectors.(1)

More than 400 gene therapy trials have been or are being conducted with human Ad vectors (2). Most of these trials are for treatment of cancer, although some are for use of Ad vectors as vaccines in which the vector expresses a foreign antigenic protein or for gene therapy in which the vector expresses a non-mutant protein to correct a genetic defect.

We at GENERI BIOTECH have so far taken part in ….

  1. Development of a detection system for AdV5 ONCOS-102 for Oncos
    • Development and validation of AdV5 assay (2012)
    • qPCR analysis of CGTG-102 adenovirus sequence in human blood samples after application of CGTG-102 virus (2013)
    • qPCR analysis of CGTG-102 adenovirus sequence in human blood samples, buccal swabs, urine after application of CGTG-102 virus (2013)
    • GMP-development of analytical method for CGTG-102 quantification in blood, urine and buccal swabs (2014)
  2. Quality control tests for Oncos
    • Analysis of presence of wild type virus Ad5 (2012)
  3. First validation study for Targovax (2016)
    • Method validation for quantification of ONCOS-102 in stool, urine, swab and blood human samples and sample analysis from following studies
      Oncos C719 = A Randomised Phase II Open-label Study With a Phase Ib Safety lead-in Cohort of ONCOS-102, an Immune-priming GM-CSF Coding Oncolytic Adenovirus, and Pemetrexed/Cisplatin in Patients With Unresectable Malignant Pleural Mesothelioma
      Oncos C824 = A Pilot Study of Sequential ONCOS-102, an Engineered Oncolytic Adenovirus Expressing GMCSF, and Pembrolizumab in Patients With Advanced or Unresectable Melanoma Progressing After Programmed Cell Death Protein 1 (PD1) Blockade
      SP015 = A phase I/II, single-arm clinical trial to evaluate the safety and immune activation of the combination of DCVAC/PCa, an active cellular immunotherapy, and ONCOS-102, an immune-priming adenovirus, in men with advanced metastatic castration-resistant prostate cancer.
    • Method validation for quantification of ONCOS-102 in swabs in UTM medium (2018, 2019)
  4. Quality control of the product for Targovax
    • Determination of wild-type adenoviral E1A sequence in ONCOS-102 sample (2016)
  5. Characterization of the production cell line for Targovax
    • cGMP Residual RNA
  6. Preclinical study for Biotest
    • GLP biodistribution study of the CGTG-102 in Syrian hamsters (2012)

(1) Adenoviral Vector-Based Vaccines and Gene Therapies: Current Status and Future Prospects

By Shakti Singh, Rakesh Kumar and Babita Agrawal

Submitted: February 15th 2018Reviewed: June 21st 2018Published: November 5th 2018

DOI: 10.5772/intechopen.79697


(2) Wold WSM, Ison MG. Adenoviruses. In: Knipe DM, How-ley PM, editors. Fields Virology. Philadelphia, PA: Lippincott Williams & Wilkins; 2013. pp. 1732–1767. [Google Scholar]