Introduction: DNA vaccines MCQs With Answer is a concise question bank tailored for M.Pharm students studying Immunotechnology. This collection emphasizes the molecular design, delivery strategies, immune mechanisms, evaluation methods, advantages and limitations of DNA-based vaccines. Questions probe deeper aspects such as plasmid backbone elements, promoter selection, codon optimization, immune presentation pathways, and technological enhancements like electroporation and molecular adjuvants. Clinical and safety considerations including integration risk, anti-DNA responses, and regulatory aspects are also covered. Use these MCQs for exam preparation, self-assessment, and refining conceptual understanding necessary for research or development roles in vaccine biotechnology.
Q1. What is the primary mechanism by which DNA vaccines induce cytotoxic T lymphocyte (CTL) responses?
- Direct activation of B cells to produce antigen-specific antibodies
- Uptake of plasmid DNA by antigen-presenting cells and endogenous antigen expression with presentation on MHC class I
- Extracellular antigen capture and presentation on MHC class II to CD4+ T cells exclusively
- Complement-mediated lysis of infected cells leading to cross-priming
Correct Answer: Uptake of plasmid DNA by antigen-presenting cells and endogenous antigen expression with presentation on MHC class I
Q2. Which plasmid element is most critical for high-level transgene expression in mammalian cells?
- Origin of replication for bacterial propagation (ori)
- Antibiotic resistance gene
- Cytomegalovirus (CMV) immediate-early promoter
- Multicloning site
Correct Answer: Cytomegalovirus (CMV) immediate-early promoter
Q3. Codon optimization in DNA vaccine design primarily aims to:
- Increase plasmid replication rate in bacteria
- Enhance transgene protein translation efficiency in host cells
- Reduce plasmid size for easier purification
- Increase CpG content to stimulate innate immunity
Correct Answer: Enhance transgene protein translation efficiency in host cells
Q4. Which delivery method increases DNA uptake by skeletal muscle and improves immunogenicity via transient membrane permeabilization?
- Needle-free jet injection
- Liposome encapsulation
- Electroporation
- Oral administration with enteric coating
Correct Answer: Electroporation
Q5. CpG motifs in plasmid DNA act as:
- Sequences that enhance plasmid replication in mammalian cells
- Toll-like receptor 9 (TLR9) agonists that promote innate immune activation
- Promoter elements driving transgene expression
- Mammalian splice donor sites to increase mRNA stability
Correct Answer: Toll-like receptor 9 (TLR9) agonists that promote innate immune activation
Q6. Which safety concern is most frequently discussed regarding DNA vaccines?
- High risk of immediate anaphylaxis in all recipients
- Integration of plasmid DNA into the host genome potentially causing insertional mutagenesis
- Production of replication-competent viruses from the plasmid
- Transmission of antibiotic resistance to human gut flora from intramuscular injection
Correct Answer: Integration of plasmid DNA into the host genome potentially causing insertional mutagenesis
Q7. A molecular adjuvant frequently co-delivered with DNA vaccines to enhance cellular immunity is:
- Alum (aluminum salts)
- Recombinant GM-CSF expression plasmid
- Freund’s complete adjuvant
- Polysaccharide capsule conjugate
Correct Answer: Recombinant GM-CSF expression plasmid
Q8. Which antigen design strategy favors induction of both humoral and CD8+ T-cell responses when encoded in a DNA vaccine?
- Secreted soluble antigen without targeting sequences
- Antigen fused to a leader sequence for secretion and to a transmembrane domain for cell-surface display
- Antigen truncated to remove all epitopes
- Antigen expressed as bacterial inclusion bodies
Correct Answer: Antigen fused to a leader sequence for secretion and to a transmembrane domain for cell-surface display
Q9. Which assay is most appropriate to quantify antigen-specific IFN-γ–producing T cells after DNA vaccination?
- ELISA for serum IgG
- ELISPOT for IFN-γ
- Western blot of muscle lysates
- Hemagglutination inhibition assay
Correct Answer: ELISPOT for IFN-γ
Q10. In prime-boost strategies, a DNA prime followed by a viral-vectored boost is used primarily because:
- DNA prime induces stronger neutralizing antibodies than viral vectors alone
- DNA primes induce T-cell memory that is potently expanded by a heterologous viral boost
- Viral vector boosts remove pre-existing immunity against the DNA plasmid
- This approach reduces the need for adjuvants in both doses
Correct Answer: DNA primes induce T-cell memory that is potently expanded by a heterologous viral boost
Q11. Which promoter feature is desirable in a DNA vaccine vector to minimize promoter silencing in vivo?
- Presence of high-CpG island density in the promoter
- Use of tissue-specific promoter with minimal methylation-prone sequences
- Inclusion of multiple bacterial promoters in tandem
- Use of prokaryotic ribosomal promoters
Correct Answer: Use of tissue-specific promoter with minimal methylation-prone sequences
Q12. Which animal model characteristic is most important when preclinically evaluating immunogenicity of a DNA vaccine intended for human use?
- Identical body weight to humans
- Expression of human-relevant MHC molecules (HLA transgenic models)
- Ability to tolerate high volumes of intramuscular injection
- Absence of innate immune receptors like TLRs
Correct Answer: Expression of human-relevant MHC molecules (HLA transgenic models)
Q13. Which manufacturing consideration is unique or particularly important for plasmid DNA vaccines compared with protein vaccines?
- Requirement for sterile filtration of a proteinaceous final product
- Removal of endotoxin (LPS) from bacterial-derived plasmid preparations
- Need for glycosylation profiling
- Complex refolding steps to obtain active antigen
Correct Answer: Removal of endotoxin (LPS) from bacterial-derived plasmid preparations
Q14. The use of antibiotic resistance genes in plasmid backbones is discouraged mainly because:
- They increase plasmid size reducing transfection efficiency
- Risk of horizontal gene transfer to microbial flora and regulatory concerns
- They reduce antigen expression in mammalian cells
- They trigger immediate hypersensitivity reactions in humans
Correct Answer: Risk of horizontal gene transfer to microbial flora and regulatory concerns
Q15. Which route of administration is often used for DNA vaccines to target skin-resident antigen-presenting cells and can be performed with microneedles?
- Intravenous injection
- Intradermal delivery
- Oral gavage
- Subconjunctival injection
Correct Answer: Intradermal delivery
Q16. Which characteristic of DNA vaccines contributes to their thermal stability compared to many protein vaccines?
- Requirement for cold chain below -80°C
- Plasmid DNA’s relatively stable double-stranded structure that tolerates higher temperatures
- Dependence on live-attenuated carriers to maintain antigen integrity
- Obligate requirement for lipid nanoparticles to prevent degradation
Correct Answer: Plasmid DNA’s relatively stable double-stranded structure that tolerates higher temperatures
Q17. Which immune polarization is most commonly desired when designing DNA vaccines against intracellular pathogens and tumors?
- Strong Th2-biased humoral response with IgE production
- Balanced Th17/Th2 response favoring mucosal IgA
- Th1-biased cellular immunity with strong CD8+ T-cell responses and IFN-γ production
- Regulatory T-cell induction to suppress inflammation
Correct Answer: Th1-biased cellular immunity with strong CD8+ T-cell responses and IFN-γ production
Q18. Which modification to a DNA vaccine transgene can increase MHC class I presentation and CD8+ T-cell recognition?
- Fusion of the antigen to an endoplasmic reticulum retention signal (KDEL)
- Targeting the antigen for proteasomal degradation by adding ubiquitin or degradation signals
- Secretion of the antigen as an extracellular soluble protein
- Glycosylation to mask T-cell epitopes
Correct Answer: Targeting the antigen for proteasomal degradation by adding ubiquitin or degradation signals
Q19. During clinical evaluation, which assay combination best assesses both humoral and cell-mediated responses elicited by a DNA vaccine?
- Neutralization assay for antibodies and IFN-γ ELISPOT for T cells
- Complete blood count and liver function tests
- Endotoxin quantification and agarose gel electrophoresis
- Mass spectrometry proteomics of vaccine batch
Correct Answer: Neutralization assay for antibodies and IFN-γ ELISPOT for T cells
Q20. Which regulatory consideration is particularly relevant for DNA vaccines containing sequences of human origin or oncogenes?
- They are exempt from preclinical safety testing
- Enhanced assessment for potential oncogenicity and insertional mutagenesis, with stricter containment and safety studies
- No requirement to assess biodistribution of plasmid DNA
- They must be formulated with adjuvants like alum by default
Correct Answer: Enhanced assessment for potential oncogenicity and insertional mutagenesis, with stricter containment and safety studies
