Rotavirus vaccine design (e.g., Rotashield): which property of Rotavirus was crucial for constructing reassortant vaccine strains used in early live oral vaccines?
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AThe possession of a segmented RNA genome
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BA limited number of capsule types
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CThe ability of monkey Rotavirus strains to cause serious illness (diarrhea) in human beings
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DThe ability of the Rotavirus to be transmitted faster
Answer
Correct Answer: The possession of a segmented RNA genome
Explanation
Introduction: Live, oral rotavirus vaccines (such as the early Rotashield) exploited virologic features to generate reassortant strains combining human antigenic proteins with an attenuated animal backbone. This item tests recognition of the genome architecture that makes such reassortment feasible.
Given Data / Assumptions:
- Rotaviruses belong to the Reoviridae family.
- They have a segmented, double-stranded RNA genome.
- Segment exchange (reassortment) can occur during coinfection.
- Vaccine design aimed to present human-relevant antigens on an attenuated backbone.
Concept / Approach: Because Rotavirus has multiple genome segments, coinfection of a cell with animal and human strains allows segment swapping. Researchers selected reassortants that retained attenuation (from animal strains) while expressing human serotype antigens to induce protective immunity. Thus, the segmented RNA genome is the critical enabling property for constructing reassortant vaccine candidates.
Step-by-Step Solution: Recall Rotavirus genome: segmented dsRNA permits reassortment. Relate coinfection to segment mixing and selection of desired antigen combinations. Connect to Rotashield: rhesus-human reassortants presented human VP7/VP4 antigens. Choose the property that directly enables reassortant construction.
Verification / Alternative check: The broader principle mirrors that of other segmented viruses (e.g., influenza), where segment reassortment supports vaccine and research applications.
Why Other Options Are Wrong:
- Limited capsule types: Rotavirus has outer capsid proteins defining many types; limitation is not the key vaccine enabler.
- Ability of monkey strains to cause severe human illness: Not required; vaccine uses attenuated backbones.
- Faster transmission: Epidemiologic property, not a laboratory construction tool.
Common Pitfalls: Confusing attenuation source (animal strains) with the mechanism (reassortment) that installs human antigens onto that backbone.
Final Answer: The possession of a segmented RNA genome enabled reassortant vaccine construction.