Gene therapy Flashcards
(37 cards)
What is gene therapy?
The possibility of genetic alteration of the cells of affected persons to treat diseases
Gene therapy provides opportunities for improved understanding and diagnosis of many diseases.
What is somatic cell gene therapy?
The alteration of genes in human somatic cells to treat a specific disorder
It can be performed ex vivo (outside the body) or in vivo (inside the body).
What is gene replacement therapy?
Inserting a normal gene into somatic cells to replace a missing gene product
This approach is best for correcting loss-of-function mutations.
What are retroviral vectors?
RNA viruses that can insert copies of their genomes into the nuclei of host cells
They are commonly used as gene therapy vectors due to high transduction efficiency.
What is transduction?
The insertion of foreign DNA into a host cell via a viral vector
Retroviruses are noted for their efficiency in this process.
What are some advantages of retroviral vectors?
- Stable integration into the genome
- High efficiency of transduction
Retroviruses seldom provoke immune responses.
What are some disadvantages of retroviral vectors?
- Preferential integration near promoter sequences
- Ineffective in nondividing cells
This can lead to activation of proto-oncogenes and potential cancer.
What are adenoviral vectors?
Double-stranded DNA viruses that can transduce nondividing cells
They do not integrate into the host cell’s DNA, which reduces the risk of activating proto-oncogenes.
What is a key limitation of adenoviral vectors?
They often provoke an immune response and result in transient gene expression
This may require repeated administration of the vector.
What are adeno-associated viral vectors (AAVs)?
DNA viruses that require adenoviruses for replication and can transduce nondividing cells
AAVs elicit less immune response and can provide prolonged therapeutic expression.
What is a significant limitation of AAVs?
They can only accept a DNA insert of about 4.5 kb
This may be circumvented by splitting the insert into two parts.
What are lentiviral vectors?
Complex RNA retroviruses that can transduce nondividing cells
Examples include HIV, which can integrate stably into the genome.
What is a challenge in viral gene therapy?
Transient and low-level expression of the gene product
This can be due to low incorporation rates and regulatory sequence issues.
What are difficulties in targeting tissue for gene therapy?
Reaching or specifying target tissue can be challenging
Some disorders make it difficult to target affected neurons or specific cell types.
What are some adverse effects of gene therapy?
- Development of leukemia-like diseases
- Clonal T-cell proliferation
These can result from random insertion of retroviral vectors near proto-oncogenes.
What is the main goal of targeted genome editing using CRISPR/Cas9?
To induce double-strand DNA breaks and facilitate precise modifications in the target DNA sequence using a guide RNA
The process can involve either blocking disease-causing mutations or inserting normal DNA sequences through specific repair pathways.
What are some difficulties in targeting specific tissues for gene therapy?
Challenges include:
* Difficulty in reaching or specifying target tissue
* Modifying vectors to enter only desired cell types
Targeting affected neurons in central nervous system disorders is particularly challenging.
What is the potential risk associated with using retroviral vectors in gene therapy?
Insertional mutagenesis, which can lead to unpredictable and undesired consequences
Although rare, this risk has been documented in clinical cases.
What are the advantages of using nonviral vectors in gene therapy?
Advantages include:
* Lack of immune response
* Ability to accept large DNA inserts
* Potential for direct DNA insertion without a delivery vector
Liposomes are a common type of nonviral vector.
Define antisense therapy in gene therapy.
A method that uses oligonucleotides complementary to mRNA sequences to prevent translation of harmful proteins
This approach can also target double-stranded DNA to prevent transcription.
What is the purpose of exon skipping in treating Duchenne muscular dystrophy?
To remove an exon affected by a frameshift mutation, resulting in an intact reading frame for mRNA
This approach aims to produce a milder phenotype similar to Becker muscular dystrophy.
What is RNA interference (RNAi)?
A natural cellular process that destroys single-stranded RNA corresponding to double-stranded RNA, often used to silence gene expression
RNAi is being explored for various diseases, including cancer.
What is the significance of CAR T-cell therapy?
It involves genetically modifying T cells to express chimeric antigen receptors that target cancerous cells
This therapy has shown promise in treating refractory B-cell malignancies.
What is germline gene therapy?
A type of gene therapy that alters all cells of the body, including those that give rise to gametes
This could impact not only the patient but also future generations.
