Vaccine delivery systems: uptake of antigens MCQs With Answer

Vaccine delivery systems: uptake of antigens MCQs With Answer are designed to help M. Pharm students master how delivery platforms engineer antigen entry into antigen-presenting cells (APCs) to shape protective immunity. This set focuses on cellular uptake pathways (phagocytosis, macropinocytosis, receptor-mediated endocytosis), receptor targeting (mannose receptor, DC-SIGN, Clec9A), lymphatic trafficking influenced by particle size and charge, and strategies enabling cross-presentation on MHC I. You will also test your understanding of adjuvants (alum, emulsions, TLR agonists), mucosal transcytosis (M cells, FcRn), microneedle-based intradermal delivery, and smart materials (pH-responsive polymers, saponin ISCOMs). Each MCQ highlights critical design rules that connect formulation attributes with antigen uptake, processing, and resulting immune responses.

Q1. Which cellular uptake pathway most efficiently internalizes particulate antigens larger than ~500 nm in dendritic cells?

• Phagocytosis
• Receptor-mediated endocytosis via clathrin
• Caveolae-mediated endocytosis
• Passive diffusion across membranes

Correct Answer: Phagocytosis

Q2. Decorating nanoparticles with mannose ligands primarily enhances uptake by APCs through which receptor?

• Mannose receptor (CD206)
• Neonatal Fc receptor (FcRn)
• CXCR5
• CD40

Correct Answer: Mannose receptor (CD206)

Q3. After subcutaneous administration, which particle size range is most favorable for rapid passive lymphatic drainage to draining lymph nodes?

• Approximately 10–50 nm
• Approximately 1–5 nm
• Approximately 300–500 nm
• Greater than 5 μm

Correct Answer: Approximately 10–50 nm

Q4. What is a key advantage of cationic liposomes for vaccine antigen delivery?

• Increased electrostatic interaction with cell membranes and enhanced APC uptake
• Reduced complement opsonization
• Improved long-circulation via stealth properties
• Exclusive presentation on MHC I

Correct Answer: Increased electrostatic interaction with cell membranes and enhanced APC uptake

Q5. In the cytosolic pathway of cross-presentation, which event enables exogenous antigens to be displayed on MHC class I?

• Antigen escapes endosomes to cytosol, undergoes proteasomal degradation, and peptides are loaded onto MHC I
• Antigen is loaded onto MHC II in endolysosomes
• Antigen is presented exclusively by B cells to CD4+ T cells
• IgG-mediated transcytosis across endothelium by FcRn

Correct Answer: Antigen escapes endosomes to cytosol, undergoes proteasomal degradation, and peptides are loaded onto MHC I

Q6. How do TLR agonist adjuvants (e.g., CpG, MPLA) most directly enhance antigen uptake and presentation?

• Activate dendritic cells, upregulate costimulatory molecules, and promote antigen processing/cross-presentation
• Increase antigen diffusion away from the injection site, reducing APC contact
• Inhibit endocytosis to favor phagocytosis
• Neutralize lysosomal proteases to prevent degradation

Correct Answer: Activate dendritic cells, upregulate costimulatory molecules, and promote antigen processing/cross-presentation

Q7. Which route/formulation combination best exploits high APC density to reduce antigen dose?

• Intradermal delivery using microneedles
• Intramuscular injection in deep muscle
• Intravenous infusion
• Oral delivery of soluble antigen

Correct Answer: Intradermal delivery using microneedles

Q8. M-cell–mediated transcytosis is a key uptake mechanism for vaccines delivered via which route?

• Oral route targeting intestinal Peyer’s patches
• Intranasal delivery to the lower respiratory tract
• Intravaginal delivery
• Intradermal delivery

Correct Answer: Oral route targeting intestinal Peyer’s patches

Q9. What is a common effect of PEGylating vaccine nanoparticles on antigen uptake?

• Reduced opsonization and cellular uptake with increased circulation time
• Markedly increased dendritic cell uptake
• Specific targeting to the mannose receptor
• Direct activation of the NLRP3 inflammasome

Correct Answer: Reduced opsonization and cellular uptake with increased circulation time

Q10. Which mechanism best explains how alum-based adjuvants enhance antigen uptake?

• Depot effect and particulate adsorption that favor phagocytosis by APCs
• Immediate cytosolic delivery via membrane fusion
• Opening epithelial tight junctions to increase paracellular transport
• FcRn-mediated transcytosis across epithelia

Correct Answer: Depot effect and particulate adsorption that favor phagocytosis by APCs

Q11. pH-responsive materials designed to promote endosomal escape should become membrane-active at approximately which pH?

• pH 5–6 (endosomal acidification)
• pH 7.4 (physiological)
• pH 9 (alkaline)
• Endosomal escape is pH-independent

Correct Answer: pH 5–6 (endosomal acidification)

Q12. Targeting which receptor is particularly useful for delivering antigen to cross-presenting cDC1 dendritic cells?

• Clec9A (DNGR-1)
• CD206
• CD40
• TLR4

Correct Answer: Clec9A (DNGR-1)

Q13. What feature of saponin-based ISCOMs supports enhanced antigen uptake and cross-presentation?

• Formation of cholesterol-containing nanoparticles that facilitate membrane permeabilization and cytosolic delivery
• Strictly soluble macromolecular complexes with no particulate behavior
• Inhibition of complement activation on particle surfaces
• Specific binding to FcRn for epithelial transcytosis

Correct Answer: Formation of cholesterol-containing nanoparticles that facilitate membrane permeabilization and cytosolic delivery

Q14. Fc-fusion of antigens can improve mucosal vaccine uptake by exploiting which transport pathway?

• FcRn-mediated transcytosis across epithelial cells
• CCR7-driven dendritic cell migration
• CD28-mediated T-cell costimulation
• P-glycoprotein efflux

Correct Answer: FcRn-mediated transcytosis across epithelial cells

Q15. Compared with soluble antigens, surface-displayed antigens on nanoparticles are more likely to:

• Cross-link B-cell receptors and enhance B cell uptake
• Avoid recognition by B cells
• Be completely degraded before reaching APCs
• Activate only T cells, not B cells

Correct Answer: Cross-link B-cell receptors and enhance B cell uptake

Q16. Which design attribute favors retention at the injection site with subsequent uptake by infiltrating APCs rather than immediate lymphatic drainage?

• Larger particle size (~200–1000 nm)
• Ultrafine size (~5 nm)
• Neutral, highly hydrophilic small molecules
• Fully soluble antigen

Correct Answer: Larger particle size (~200–1000 nm)

Q17. For intranasal vaccines targeting NALT, which formulation most effectively increases residence time and epithelial penetration for improved uptake?

• Mucoadhesive chitosan nanoparticles
• PEGylated micelles with minimal surface charge
• Oil-in-water emulsion lacking mucoadhesive properties
• Plain saline solution

Correct Answer: Mucoadhesive chitosan nanoparticles

Q18. Which statement best describes antigen uptake dynamics in intramuscular vaccination?

• Muscle has relatively low resident APC density
• Adjuvants recruit and activate dendritic cells to the site
• Both statements are correct
• Neither statement is correct

Correct Answer: Both statements are correct

Q19. Complement opsonization of antigen–nanoparticle complexes enhances uptake predominantly through which receptors on phagocytes?

• CR3/CR4 (complement receptors)
• FcRn
• DEC-205
• CXCR4

Correct Answer: CR3/CR4 (complement receptors)

Q20. What is a key safety concern when using highly cationic carriers to boost cellular uptake of vaccine antigens?

• Increased cytotoxicity and excessive inflammatory responses
• Accelerated renal clearance due to small hydrodynamic size
• Loss of endosomal escape capability
• Antigen denaturation occurs only at neutral pH

Correct Answer: Increased cytotoxicity and excessive inflammatory responses

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