Gene therapy: transfer techniques and clinical applications MCQs With Answer

Gene therapy: transfer techniques and clinical applications MCQs With Answer

Introduction: This quiz collection is designed for M.Pharm students to reinforce understanding of gene therapy delivery methods and clinical applications. It covers viral and non-viral transfer systems, ex vivo and in vivo strategies, genome editing tools, vector design principles, safety concerns such as immunogenicity and insertional mutagenesis, and examples of approved therapies. Questions emphasize mechanistic insights, vector capacities, tropism, and translational considerations relevant to pharmacology and therapeutics. Use these MCQs to test conceptual knowledge, prepare for exams, and identify areas for deeper study in cellular and molecular pharmacology of gene-based treatments.

Q1. Which viral vector is most commonly associated with stable integration into the host genome and long-term expression in dividing cells?

• Adeno-associated virus (AAV)
• Retrovirus (gamma-retrovirus)
• Adenovirus
• Non-viral plasmid DNA

Correct Answer: Retrovirus (gamma-retrovirus)

Q2. Which feature distinguishes lentiviral vectors from gamma-retroviral vectors in gene transfer?

• Lentiviral vectors can transduce non-dividing cells efficiently
• Lentiviral vectors have no risk of insertional mutagenesis
• Lentiviral vectors are single-stranded DNA viruses
• Lentiviral vectors are naturally non-integrating

Correct Answer: Lentiviral vectors can transduce non-dividing cells efficiently

Q3. Which property of adeno-associated virus (AAV) vectors most limits the size of therapeutic transgenes that can be delivered?

• High immunogenicity of the capsid
• Limited packaging capacity (~4.7 kb)
• Integration into active oncogenes
• Requirement for helper virus during production

Correct Answer: Limited packaging capacity (~4.7 kb)

Q4. Which delivery technique is best described as transiently increasing cell membrane permeability using electrical pulses to allow plasmid DNA entry?

• Lipofection
• Electroporation
• Viral transduction
• Hydrodynamic tail vein injection

Correct Answer: Electroporation

Q5. In ex vivo gene therapy for hematopoietic stem cells, which step is critical to minimize insertional oncogenesis risk?

• Using integrating gamma-retroviral vectors without modification
• Expanding cells extensively before reinfusion to ensure engraftment
• Applying self-inactivating (SIN) vector designs and internal promoters
• Delivering via systemic intravenous infusion immediately after modification

Correct Answer: Applying self-inactivating (SIN) vector designs and internal promoters

Q6. Which clinically approved gene therapy uses an AAV vector to deliver a functional RPE65 gene for inherited retinal dystrophy?

• Strimvelis
• Luxturna
• Zolgensma
• Kymriah

Correct Answer: Luxturna

Q7. What is the primary therapeutic mechanism of CAR-T cell therapy in oncology?

• Delivery of oncolytic viral genomes to tumor cells to cause lysis
• Systemic administration of siRNA to silence oncogenes in tumors
• Genetic modification of patient T cells to express a chimeric antigen receptor targeting tumor antigens
• Introducing suicide genes into tumor cells to trigger apoptosis upon prodrug administration

Correct Answer: Genetic modification of patient T cells to express a chimeric antigen receptor targeting tumor antigens

Q8. Which of the following is a major advantage of non-viral lipid nanoparticle (LNP) delivery for nucleic acid therapeutics?

• Unlimited cargo size for DNA constructs
• Completely avoids innate immune activation
• Simplified large-scale manufacturing and lower immunogenicity compared to some viral vectors
• Guaranteed nuclear integration and permanent expression

Correct Answer: Simplified large-scale manufacturing and lower immunogenicity compared to some viral vectors

Q9. Which genome editing system relies on a guide RNA directing an endonuclease to create double-strand breaks for targeted edits?

• Zinc finger nucleases (ZFNs)
• Transposase-based systems
• CRISPR-Cas9
• Antisense oligonucleotides

Correct Answer: CRISPR-Cas9

Q10. Which clinical application exemplifies in vivo gene therapy administered systemically to correct a monogenic disease in infants?

• Strimvelis for ADA-SCID via ex vivo hematopoietic stem cell modification
• Luxturna for RPE65 mutation via subretinal injection
• Zolgensma for spinal muscular atrophy delivered as systemic AAV vector
• Kymriah for B-cell malignancies using autologous CAR-T cells

Correct Answer: Zolgensma for spinal muscular atrophy delivered as systemic AAV vector

Q11. Which factor most directly affects tissue tropism of a viral vector?

• Size of the transgene cassette
• Promoter strength used in the expression cassette
• Viral capsid or envelope proteins interacting with specific cellular receptors
• Purification method used during vector manufacturing

Correct Answer: Viral capsid or envelope proteins interacting with specific cellular receptors

Q12. What is the primary safety concern associated with integrating vectors used in gene therapy?

• Transient expression leading to frequent redosing needs
• Risk of insertional mutagenesis activating oncogenes or disrupting tumor suppressors
• Excessive packaging capacity causing host cell stress
• Immediate cytolysis of transduced cells

Correct Answer: Risk of insertional mutagenesis activating oncogenes or disrupting tumor suppressors

Q13. Which modification to adenoviral vectors reduces expression of viral genes and prolongs transgene expression by lowering host immune responses?

• Using first-generation adenovirus with E1 and E3 deleted only
• Helper-dependent (gutless) adenoviral vectors with almost all viral coding sequences removed
• Using wild-type adenovirus at lower doses
• Pseudotyping adenovirus with a different viral envelope

Correct Answer: Helper-dependent (gutless) adenoviral vectors with almost all viral coding sequences removed

Q14. In the context of RNA therapeutics, what is the main mechanism of action of small interfering RNA (siRNA) delivered by LNPs?

• Promoting genomic integration of therapeutic sequences
• Recruiting DNA repair machinery to correct mutations
• Inducing sequence-specific degradation of target mRNA via the RNA-induced silencing complex (RISC)
• Blocking translation by steric hindrance at the ribosomal exit tunnel

Correct Answer: Inducing sequence-specific degradation of target mRNA via the RNA-induced silencing complex (RISC)

Q15. Which clinical gene therapy approval involved ex vivo correction of autologous hematopoietic stem cells for adenosine deaminase deficiency?

• Luxturna
• Strimvelis
• Onasemnogene abeparvovec (Zolgensma)
• Imlygic (oncolytic HSV)

Correct Answer: Strimvelis

Q16. Which strategy is used to achieve tissue-specific expression from a viral vector without restricting vector tropism?

• Using a tissue-specific promoter driving the transgene
• Increasing vector dose to saturate non-target tissues
• Injecting vector systemically without targeting modifications
• Relying on random integration for selective expression

Correct Answer: Using a tissue-specific promoter driving the transgene

Q17. What is pseudotyping in the context of lentiviral vector design?

• Altering the promoter within the vector to change expression level
• Replacing the native viral envelope glycoprotein with that from another virus to modify tropism
• Deleting packaging signals to prevent replication
• Inserting a tissue-specific enhancer to improve expression

Correct Answer: Replacing the native viral envelope glycoprotein with that from another virus to modify tropism

Q18. Which delivery method is characterized by rapid intravenous injection of a large volume solution to achieve high gene transfer to the liver in rodent models?

• Hydrodynamic tail vein injection
• Intra-arterial catheter infusion
• Electroporation of muscle followed by IM injection
• Subretinal injection

Correct Answer: Hydrodynamic tail vein injection

Q19. Which of the following is a common approach to reduce immune recognition of viral vectors upon systemic administration?

• Delivering vectors at higher doses to overwhelm immune cells
• Using serotype switching, capsid engineering, or transient immunosuppression
• Co-administering plasmid DNA to distract immune sensors
• Encoding luciferase in the vector to saturate antigen presentation

Correct Answer: Using serotype switching, capsid engineering, or transient immunosuppression

Q20. For therapeutic gene addition versus genome editing approaches, which statement best contrasts their long-term outcomes?

• Gene addition always ensures physiological regulation of the transgene identical to the native gene
• Genome editing can restore endogenous gene regulation and correct mutations, while gene addition typically provides ectopic expression from introduced cassettes
• Gene addition never elicits immune responses, whereas genome editing always does
• Genome editing requires larger vectors than gene addition in all cases

Correct Answer: Genome editing can restore endogenous gene regulation and correct mutations, while gene addition typically provides ectopic expression from introduced cassettes

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