A retrovirus is any virus belonging to the viral family Retroviridae. All The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be considered part of the genetic material of the host cell. Retrovirus genomes commonly contain these three open reading frames that encode for proteins that can be found in the mature virus. Group-specific antigen (gag) codes for core and structural proteins of the virus, polymerase (pol) codes for reverse transcriptase, protease and integrase, and envelope (env) codes for the retroviral coat proteins (see figure 1).Figure 1. Genome organisation of retroviruses.
The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell (the chromosomes). This process is done by another enzyme carried in the virus called integrase (see figure 2).
Now that the genetic material of the virus is incorporated and has become part of the genetic material of the host cell, we can say that the host cell is now modified to contain a new gene. If this host cell divides later, its descendants will all contain the new genes. Sometimes the genes of the retrovirus do not express their information immediately.
Retroviral vectors are created by removal op the retroviral gag, pol, and env genes. These are replaced by the therapeutic gene. In order to produce vector particles a packaging cell is essential. Packaging cell lines provide all the viral proteins required for capsid production and the virion maturation of the vector. These packaging cell lines have been made so that they contain the gag, pol and env genes. Early packaging cell lines contained replication competent retroviral genomes and a single recombination event between this genome and the retroviral DNA vector could result in the production of a wild type virus. Following insertion of the desired gene into in the retroviral DNA vector, and maintainance of the proper packaging cell line, it is now a simple matter to prepare retroviral vectors (see figure 3).
One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus in any arbitrary position in the genome of the host. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. This problem has recently begun to be addressed by utilizing zinc finger nucleases or by including certain sequences such as the beta-globin locus control region to direct the site of integration to specific chromosomal sites.
Gene therapy trials to treat severe combined immunodeficiency (SCID) were halted or restricted in the USA when leukemia was reported in three of eleven patients treated in the French X-linked SCID (X-SCID) gene therapy trial. Ten X-SCID patients treated in England have not presented leukemia to date and have had similar success in immune reconstitution. Gene therapy trials to treat SCID due to deficiency of the Adenosine Deaminase (ADA) enzyme continue with relative success in the USA, Italy and Japan.
As a reaction to the adverse events in the French X-SCID gene therapy trial, the Recombinant DNA Advisory Committee (RAC) sent a letter to Principal Investigators Conveying RAC Recommendations in 2003. In addition, the RAC published conclusions and recommendations of the RAC Gene Transfer Safety Symposium in 2005. A joint working party of the Gene Therapy Advisory Committee and the Committee on Safety of Medicines (CSM) in the UK lead to the publication of an updated recommendations of the GTAC/CSM working party on retroviruses in 2005.
Original post:
Gene Therapy Retrovirus Vectors Explained
- Dosing paused in Pfizer DMD gene therapy trial after patient death - Muscular Dystrophy News - May 14th, 2024
- Astellas CEO Q&A (Part 1): There Is No Playbook on Cell and Gene Therapies - MedCity News - May 14th, 2024
- Bluebird: Cells collected from 1st sickle cell patient having... - Sickle Cell Disease News - May 14th, 2024
- Regeneron Gene Therapy Reaches New Heights In Restoring Hearing - Scrip - May 14th, 2024
- Young participant in Pfizer's DMD gene therapy trial dies - Fierce Biotech - May 14th, 2024
- Boy Dosed with Pfizer DMD Gene Therapy Dies a Year after Phase II Trial - Genetic Engineering & Biotechnology News - May 14th, 2024
- Gene therapy trials treat inherited blindness and deafness - DW (English) - May 14th, 2024
- Deaf girl is cured in world first gene therapy trial - The Independent - May 14th, 2024
- beyond-the-lab-cell-and-gene-therapy - Drug Target Review - May 14th, 2024
- Child who was born deaf can now hear whispers and parents clapping for first time thanks to 'mind-blowing' gene therapy - New York Post - May 14th, 2024
- White Paper: Navigating the regulatory path of CRISPR-based therapeutics 13 May 2024 - SelectScience - May 14th, 2024
- Krystal Biotech touts topical gene therapy uptake, plots overseas launches - FiercePharma - May 14th, 2024
- Pharming uproots angioedema gene therapy collab with Orchard - Fierce Biotech - May 14th, 2024
- Deaf toddler playing piano and dancing after world-first gene therapy - The Telegraph - May 14th, 2024
- New gene therapy allows deaf child to hear DW 05/09/2024 - DW (English) - May 14th, 2024
- Our Mission at Voyager Therapeutics: Define the Future of Neurogenetic Medicines - BioSpace - May 14th, 2024
- Gene therapy provision would make life-saving treatment more accessible and equitable - Star Tribune - May 14th, 2024
- British girl's hearing restored in pioneering gene therapy trial - Sky News - May 14th, 2024
- ASGCT24: Translational Research Powering Potentially Transformative Therapies - BioSpace - May 14th, 2024
- Advancing Delivery of AAV Vector-Based Gene Therapies Using Bispecific Antibodies (ASGCT 2024) - BioPharm International - May 14th, 2024
- Krystal Biotech Inc (KRYS) Reports Strong Q4 and Full Year 2023 Financial Results - Yahoo Finance - February 27th, 2024
- New sickle cell gene therapies are a breakthrough, but solving how to pay their high prices is a struggle - CNBC - February 27th, 2024
- 10 gene therapy companies you should know about - Labiotech.eu - February 27th, 2024
- Former Penn employee sues Gene Therapy Program director, alleging 'unethical and illegal conduct' - The Daily Pennsylvanian - February 27th, 2024
- Gene therapy can't cure deafness because it doesn't need to be cured - The Philadelphia Inquirer - February 27th, 2024
- Fetal surgery expert Tippi MacKenzie shifts to in-utero gene therapy - STAT - February 27th, 2024
- Therapeutic Solutions International Files Patent on Facilitating Effects of JadiCells on Gene Therapy Mediated Cell ... - Business Wire - February 27th, 2024
- CU Anschutz Set to Launch Gene Therapy Trials for Heart Disorder - University of Colorado Anschutz Medical Campus - February 27th, 2024
- ICH targets cell and gene therapies, real-world data as topics ripe for harmonization - Regulatory Focus - February 27th, 2024
- Encoded Therapeutics Announces UK CTA Approval for Dravet Syndrome Gene Therapy Candidate ETX101 - Business Wire - February 27th, 2024
- Voyager Therapeutics Announces Selection of Gene Therapy Development Candidate for Friedreich's Ataxia in ... - GlobeNewswire - February 27th, 2024
- Therapeutic Solutions International Files Patent on Facilitating Effects of JadiCells on Gene Therapy Mediated Cell ... - The Bakersfield Californian - February 27th, 2024
- Ring Therapeutics, a Flagship gene therapy startup, lays off 20% of staff - STAT - February 27th, 2024
- Ed Silverman on new gene therapies, biosimilars, coffee, and more - STAT - STAT - February 27th, 2024
- Combatting HIV using gene therapy - Drug Target Review - February 27th, 2024
- NCDHHS working with federal government on increasing access to sickle cell disease treatment - WECT - February 27th, 2024
- Cell Therapy Weekly: FDA Approves First Cell Therapy For Solid Tumors - RegMedNet - February 27th, 2024
- Rejuvenate Bio Announces Gene Therapy-Mediated Partial Reprogramming Extends Lifespan and Reverses Age ... - Business Wire - February 27th, 2024
- New sickle cell therapy uses gene editing at MUSC | Health | postandcourier.com - The Post and Courier - February 27th, 2024
- Long-term and real-world safety and efficacy of retroviral gene therapy for adenosine deaminase deficiency - Nature.com - February 18th, 2024
- Gene therapy, blood transfusions, stool monitoring: The Sydneysiders trying to escape death - Sydney Morning Herald - February 18th, 2024
- Not too late to repair: gene therapy improves advanced heart failure in animal model - Baylor College of Medicine | BCM - February 18th, 2024
- Direct Administration of CRISPR-Cas9: Tools for Cell and Gene Therapy - Forbes - February 18th, 2024
- Gene therapy's promise seen in its success for AADC deficiency - AADC News - February 18th, 2024
- First Patient Randomized in AskBio Phase II Gene Therapy Trial for Congestive Heart Failure Treatment - Diagnostic and Interventional Cardiology - February 18th, 2024
- FDA to review expanded use of Sarepta Duchenne gene therapy - Yahoo Finance - February 18th, 2024
- How gene therapy can help treat a rare blood disorder - KUTV 2News - February 18th, 2024
- CRISPR gene therapy Casgevy secures approval in Europe - Pharmaceutical Technology - February 18th, 2024
- FDA Updates for the Week of Feb. 12, 2024: New Approvals, an Extended Review and Goal Dates Set - Managed Healthcare Executive - February 18th, 2024
- First Patient Randomized in AskBio Phase II Gene Therapy Trial for Congestive Heart Failure - Business Wire - February 18th, 2024
- Lisa Jarvis: A cure for some kinds of hearing loss? Gene therapies are getting closer - St. Paul Pioneer Press - February 18th, 2024
- Spinal Muscular Atrophy Market: Navigating Therapeutic Advances towards USD 5.6 Billion by 2034, with a CAGR of ... - Yahoo Finance - February 18th, 2024
- Crispr Therapeutics' Gene Therapy Wins EU Approval - TipRanks.com - TipRanks - February 18th, 2024
- Revolutionizing Gene Therapy: A Novel Technique for In Vivo CAR T Cells - Medriva - February 18th, 2024
- How Stella Vnook is 'infusing innovation' into cell therapies with Likarda's technology - BioPharma-Reporter.com - February 18th, 2024
- Using cancer's 'superpower' to boost T-cell therapies in mice - FierceBiotech - February 18th, 2024
- Parkinson's Disease Patient Identification and Education Will Need to Improve When New Disease Modifying ... - Yahoo Finance - February 18th, 2024
- CRISPR (CRSP) to Report Q4 Earnings: What's in the Cards? - Yahoo Finance - February 18th, 2024
- Gene Therapy: A Ray of Hope for Heart Failure Treatment | Health News - Medriva - February 18th, 2024
- Gene therapy trials restore hearing to children born deaf - The Hill - February 2nd, 2024
- Early Trial Success for Inherited Deafness Gene-Therapy - RegMedNet - February 2nd, 2024
- Sickle cell gene therapy first focus of Medicaid pay model - Modern Healthcare - February 2nd, 2024
- Beyond chemotherapy: Navigating the promise and perils of CAR-T therapy in pediatric cancer - BioPharma-Reporter.com - February 2nd, 2024
- Angiodema: Gene therapy blocks painful hereditary disorder - BBC - February 2nd, 2024
- FDA: Genome editing therapies may use accelerated approval pathway - Regulatory Focus - February 2nd, 2024
- CRISPR tech treats severe hereditary condition successfully - Interesting Engineering - February 2nd, 2024
- Gene Therapy Restores Hearing in Small Trial for Kids With Hereditary Deafness - Technology Networks - February 2nd, 2024
- Gene-based therapy may slow development of life-threatening heart condition - Medical Xpress - February 2nd, 2024
- Jaguar Gene Therapy Announces FDA Clearance of IND to Study JAG201 in a Genetic Form of Autism Spectrum ... - Business Wire - February 2nd, 2024
- Replacing the PKP2 gene prolongs survival in ARVC patients - Drug Target Review - February 2nd, 2024
- Cell and gene therapies top pharmaceutical industry trend to watch for 2024 - Pharmaceutical Technology - February 2nd, 2024
- Gene Therapy Restores Hearing in Children with Hereditary Deafness - The Hearing Review - February 2nd, 2024
- 2 Dutch among 10 "functionally cured" of hereditary swelling disease by new gene therapy - NL Times - February 2nd, 2024
- FDA publishes final industry guidance for CAR-T and gene therapies - PMLiVE - February 2nd, 2024
- Gene therapy cures hereditary deafness in two people - Advanced Science News - February 2nd, 2024
- Hearing Restored in Deaf Children in Gene Therapy Clinical Trial - Securities.io - February 2nd, 2024
- Vivet Therapeutics Receive 4.9 Million to Advance Development of Gene Therapy - European Pharmaceutical Manufacturer - February 2nd, 2024
- Adverum Biotechnologies will Host Webcast to Review LUNA Phase 2 Preliminary Efficacy and Safety Results on ... - GlobeNewswire - February 2nd, 2024
- Allogene parks Notch CARs, leaving one on the road - FierceBiotech - February 2nd, 2024
- Experimental gene therapy allows kids with inherited deafness to hear - The Associated Press - January 25th, 2024