Viral and nonviral gene transfer MCQs With Answer

Viral and nonviral gene transfer MCQs With Answer

This collection of multiple-choice questions is tailored for M.Pharm students studying Molecular Pharmaceutics / NTDS (MPH 201T). The quiz focuses on principles, mechanisms, vector characteristics, delivery strategies and safety considerations of viral and nonviral gene transfer systems. Questions are designed to test both conceptual understanding and practical knowledge relevant to vector selection, design limitations (packaging capacity, tropism, immunogenicity), delivery challenges (endosomal escape, nuclear entry) and clinical translation issues (insertional mutagenesis, neutralizing antibodies, regulatory safety). Use these MCQs to reinforce learning, prepare for exams and identify areas for deeper study in advanced gene delivery techniques and therapeutics.

Q1. Which statement best distinguishes ‘transduction’ from ‘transfection’ in gene delivery?

• Transduction uses nonviral chemical reagents while transfection uses mechanical methods
• Transduction refers to introduction of genetic material by viral vectors; transfection refers to nonviral delivery methods
• Transduction always results in genomic integration; transfection never leads to expression
• Transduction is only used in bacteria; transfection only in mammalian cells

Correct Answer: Transduction refers to introduction of genetic material by viral vectors; transfection refers to nonviral delivery methods

Q2. What is the approximate maximum packaging capacity of wild-type adeno-associated virus (AAV) vectors for therapeutic cargo?

• ~36 kilobases
• ~4.7 kilobases
• ~25 kilobases
• ~100 kilobases

Correct Answer: ~4.7 kilobases

Q3. Which viral vector is most associated with stable integration into the host genome and is therefore commonly used for long-term expression in dividing cells?

• Adeno-associated virus (AAV)
• Adenovirus
• Lentivirus
Herpes simplex virus (HSV)

Correct Answer: Lentivirus

Q4. Which nonviral delivery mechanism primarily relies on creating transient pores in the cell membrane using an electric field to enhance DNA uptake?

• Lipofection with cationic lipids
• Electroporation
• Calcium phosphate precipitation
• Polymeric nanoparticle endocytosis

Correct Answer: Electroporation

Q5. What is the principal safety concern uniquely associated with integrating viral vectors such as gamma-retroviruses?

• Generation of neutralizing antibodies
• Insertional mutagenesis leading to oncogene activation
• Poor cellular uptake
• Rapid episomal loss in nondividing cells

Correct Answer: Insertional mutagenesis leading to oncogene activation

Q6. Which feature of polyethyleneimine (PEI) contributes to its capability to facilitate endosomal escape of nucleic acids?

• Hydrophobic tail-mediated membrane fusion
• Proton sponge effect due to high buffering capacity
• Specific receptor-mediated uptake by hepatocytes
• Double-stranded RNA binding activity

Correct Answer: Proton sponge effect due to high buffering capacity

Q7. Pseudotyping a lentiviral vector with vesicular stomatitis virus G protein (VSV-G) primarily changes which characteristic?

• Replication competence of the vector
• Genome packaging capacity
• Tropism and stability of the viral particle
• Integration site preference in the host genome

Correct Answer: Tropism and stability of the viral particle

Q8. Which viral vector is most commonly associated with strong innate and adaptive immune responses limiting repeat dosing, but can carry relatively large payloads (including entire genes and regulatory elements)?

• Adenovirus
• AAV
• Lentivirus
• Retrovirus (MLV)

Correct Answer: Adenovirus

Q9. Self-complementary AAV (scAAV) vectors provide faster onset of expression by delivering double-stranded DNA but what is the primary trade-off?

• Increased immunogenicity compared to single-stranded AAV
• Reduced packaging capacity roughly half that of conventional AAV
• Inability to transduce nondividing cells
• Higher rate of genome integration

Correct Answer: Reduced packaging capacity roughly half that of conventional AAV

Q10. In the context of in vivo gene delivery, PEGylation of nanoparticles is used mainly to achieve which outcome?

• Increase endosomal escape by proton sponge effect
• Mask surface charge to reduce opsonization and extend circulation time
• Enhance specific receptor-mediated uptake by tumor cells
• Increase payload density inside the particle

Correct Answer: Mask surface charge to reduce opsonization and extend circulation time

Q11. Which clinical gene therapy example used an AAV vector to deliver a functional RPE65 gene to treat inherited retinal dystrophy?

• Glybera
• Strimvelis
• Luxturna
• Zolgensma

Correct Answer: Luxturna

Q12. Which nonviral carrier type uses cationic lipids to form complexes (lipoplexes) with DNA and facilitates cellular uptake primarily via endocytosis?

• Dendrimers
• Liposomes
• Gold nanoparticles delivered by gene gun
• Viral-like particles

Correct Answer: Liposomes

Q13. Which property of a promoter is most important when designing a vector for ubiquitous high-level transgene expression across many tissues?

• Tissue-specific enhancer elements
• Strong constitutive promoter such as CMV
• Minimal core promoter to avoid immune detection
• Presence of intronic shRNA sequences

Correct Answer: Strong constitutive promoter such as CMV

Q14. Which method is commonly used to quantify infectious titer of a viral vector preparation in vitro?

• qPCR of packaged genome only
• Plaque assay or transducing units per mL (TU/mL) using indicator cells
• Mass spectrometry for capsid proteins
• Electron microscopy particle counting

Correct Answer: Plaque assay or transducing units per mL (TU/mL) using indicator cells

Q15. A researcher plans to deliver CRISPR-Cas9 components for genome editing using a single AAV vector but the SpCas9 gene plus guide RNA exceed AAV capacity. Which practical alternative addresses this size limitation?

• Use helper-dependent adenovirus only because it is nonintegrating
• Switch to a smaller Cas9 ortholog (e.g., SaCas9) or use dual-AAV split-intein strategy
• Deliver plasmid DNA by passive diffusion across the cell membrane
• Reduce promoter strength to shrink the genetic payload

Correct Answer: Switch to a smaller Cas9 ortholog (e.g., SaCas9) or use dual-AAV split-intein strategy

Q16. Which statement best describes the ‘proton sponge’ hypothesis as it relates to polymeric gene carriers?

• Polymers bind protons on the cell surface to trigger receptor-mediated endocytosis
• High buffering capacity polymers absorb protons in endosomes, causing osmotic swelling and endosomal rupture to release cargo
• Polymers create a low-pH environment that stabilizes DNA in lysosomes
• Polymers directly form pores in the nuclear envelope enabling nuclear entry

Correct Answer: High buffering capacity polymers absorb protons in endosomes, causing osmotic swelling and endosomal rupture to release cargo

Q17. Which regulatory element in viral vector design reduces the risk of unintended expression by blocking enhancer–promoter interactions and improving safety?

• Polyadenylation signal
• Insulator sequences such as cHS4
• Internal ribosome entry site (IRES)
• LTR enhancer sequences

Correct Answer: Insulator sequences such as cHS4

Q18. What is a major advantage of nonviral lipid nanoparticles (LNPs) that was demonstrated in recent mRNA vaccine platforms?

• They guarantee permanent genomic integration
• Rapid scalable manufacture and potent transient expression without integration
• Unlimited cargo size for any nucleic acid
• Complete absence of innate immune activation

Correct Answer: Rapid scalable manufacture and potent transient expression without integration

Q19. Neutralizing antibodies against AAV capsid in a patient limit repeat systemic administration. Which strategy can mitigate this problem?

• Administer higher AAV dose to overcome antibodies
• Use a different AAV serotype or transiently immunosuppress the patient
• Switch to the same serotype but alter the promoter sequence
• Use plasmid DNA via hydrodynamic injection in humans

Correct Answer: Use a different AAV serotype or transiently immunosuppress the patient

Q20. Multiplicity of infection (MOI) is a critical parameter in viral transduction. What does MOI represent?

• The number of viral particles required to lyse one cell
• The ratio of infectious viral particles to target cells in an infection experiment
• The percentage of cells expressing the transgene after transduction
• The time required for viral genome integration into host DNA

Correct Answer: The ratio of infectious viral particles to target cells in an infection experiment

Download