Viral Vectors and Gene Therapy Flashcards
Are patients that have received gene therapy able to pass their genes to their offspring? why or why not?
NO, The most commonly used method of gene therapy is SOMATIC gene therapy
- This only alters somatic cells and leaves the rest alone
How is gene therapy performed on cells ex vivo?
Cells are (e.g. from liver) are removed from the patient and incubated with the virus.
Cells that took up the vector are selected for and placed back into the patient (other are discarded)
What is the number one target in gene therapy today?
Cancer
What are the two strategies for applying gene therapy?
- describe them
- Therapeutic Strategy - Vector carries a gene that encodes a protein that is either defective or that is not present due to mutations(s) in the patients endogenous genes
- Cytolytic Strategy - Vector is designed to destroy or eliminate a diseased cell or tissue.
How can gancyclovir be used against human cells to treat cancer with the help of viral vectors?
Viral vector carries Thymidine Kinase (TK) from herpes Simplex Virus so that gancyclovir can be phosphorylated inside of cancer cells.
What is the 1st step in designing a viral vector gene therapy?
- Must identify gene (or genes) responsible for a particular disease state
What are the two primary strategies to designing Vectors?
- challenges associated with each of them?
- Challenges for both?
- Using attenuated or Modified versions of Viruses
- Challenge is to remove the disease-causing components of the virus and insert recombinant genes that will be therapeutic to the patient - Use non-viral vector like a Liposome
- Targeting to the correct place?
Both:
- We need long term expression and we need it expressed at the right place at the right time
- need to be sure the immune system doesn’t attack it
What kind of viral vectors is it most important to avoid immune response with? why?
Adenovirus (and any virus that does not insert into the host cell genome)
- Its important for these because if you have to re-administer the vector you might have an immune response built up against it and you could get a bad reaction
What are the two vectors that are used in the majority of gene therapy trials?
- Adenoviruses (that lack E1A and are replication-defective)
- Retroviruses (based on murine leukemia virus (MLV) or HIV
What is the reasoning behind why adenoviruses cause inflammation?
- They are a common cause of diseases that are encountered by humans (account for 5-10% of respiratory infections)
What is a packaging cell line?
- producer cell line?
Packaging Cell Line - cell that gets structural genes from the virus via a plasmid so that it can produce structural proteins
Producer Cell Line - is a packing cell line with therapeutic genes as well as the packing signals surrounding the therapeutic genes Inserted into the genome.
**Because the structural genes and packing genes are located at different parts of the cell, the structural genes won’t get transferred into the virus and it will be unable to infect new host cells
What 3 main problems need to be solved before gene therapy can become a true therapeutic tool for physicians?
- How to avoid immune response from the patient
- How to get genes into non-dividing cells like Liver, Muscle, and neurons
- How to get the gene integrated so that it will be replicated and expressed indefinitely and as needed.
What problems do antibodies pose to patients and vectors after receiving gene therapy?
- They provoke inflammation
- Antibodies will bind the vector when it is administered again
What is the advantage of using HIV over MLV-based retrovirus when it comes to overcoming the hurdle of being able to get genes into genomes of non-dividing cells?
HIV is a Lentivirus and this subset of retrovirus doesn’t require replication to get into the host cell genome
T or F: targeting is a major issue in viral gene therapy
True, viruses still want to just affect the cells that the normally affect
