QCM : Flavivirus Biology and Disease Mechanisms — 12 questions

Questions et réponses du QCM

1. What does Flavivirus classification refer to?

A category of positive-sense single-stranded RNA viruses within Flaviviridae
A group of DNA viruses with segmented genomes
A class of non-enveloped double-stranded DNA viruses
A family of negative-sense RNA viruses

A category of positive-sense single-stranded RNA viruses within Flaviviridae

Explication

Flavivirus classification refers to the categorization of these viruses as positive-sense single-stranded RNA viruses within the Flaviviridae family, based on their genome structure and replication strategy, as explicitly stated in the source.

2. Which mosquito species are primarily responsible for transmitting flaviviruses such as Dengue and Zika?

Culex pipiens and Culex quinquefasciatus
Aedes aegypti and Aedes albopictus
Mansonia spp. and Coquillettidia spp.
Anopheles gambiae and Anopheles funestus

Aedes aegypti and Aedes albopictus

Explication

The primary vectors for transmitting flaviviruses like Dengue and Zika are Aedes aegypti and Aedes albopictus mosquitoes, as explicitly stated in the source content. These species are responsible for the majority of human infections through their blood-feeding behavior.

3. What is the primary purpose of flavivirus replication occurring within ER-derived vesicles in the host cell cytoplasm?

To promote integration of viral DNA into the host genome
To facilitate rapid viral RNA synthesis within a protected environment
To enable the virus to enter the nucleus for replication
To allow the virus to evade lysosomal degradation

To facilitate rapid viral RNA synthesis within a protected environment

Explication

The ER-derived vesicles provide a protected environment for viral RNA synthesis, allowing efficient replication while shielding the viral RNA from host immune responses.

4. When do the severe clinical manifestations of dengue, such as plasma leakage and hemorrhagic symptoms, typically occur during the course of the disease?

Before the onset of any symptoms, during the incubation period
During the initial febrile phase, within the first 1-2 days of symptom onset
During the convalescent phase, after symptoms have subsided
During the critical phase, usually between days 3 and 7 after symptom onset

During the critical phase, usually between days 3 and 7 after symptom onset

Explication

Severe dengue manifestations like plasma leakage and hemorrhagic symptoms typically occur during the critical phase, which usually happens between days 3 and 7 after symptom onset, following the initial febrile period.

5. How do the clinical manifestations of Zika virus infection differ from those of dengue virus infection?

Zika primarily causes congenital abnormalities like microcephaly, while dengue presents with febrile illness, hemorrhagic fever, and shock.
Zika infection is characterized by paralysis and encephalitis, while dengue causes only mild flu-like symptoms.
Zika causes severe hemorrhagic symptoms and shock, whereas dengue mainly results in mild febrile illness.
Both Zika and dengue primarily cause febrile illnesses with similar rash and joint pains, with no significant differences.

Zika primarily causes congenital abnormalities like microcephaly, while dengue presents with febrile illness, hemorrhagic fever, and shock.

Explication

The correct answer is that Zika primarily causes congenital abnormalities such as microcephaly and neurological syndromes, whereas dengue manifests with febrile illness, hemorrhagic symptoms, and shock. This reflects the key differences in their clinical presentations, with Zika's notable congenital effects and dengue's hemorrhagic and shock features.

6. Who is credited with formulating the current understanding of flavivirus cell entry mechanisms?

Research by the virology community
The CDC
The Pasteur Institute
The World Health Organization

Research by the virology community

Explication

The current understanding of flavivirus cell entry mechanisms, including receptor-mediated endocytosis and endosomal fusion, has been established through extensive research conducted by the global virology community, rather than a single individual or institution.

7. What is the effect of flavivirus genome replication occurring within ER-derived vesicles in the cytoplasm?

It facilitates efficient viral RNA synthesis and protects it from host immune responses.
It causes the viral genome to integrate into the host DNA.
It prevents the maturation of new virions.
It enhances immune detection of viral RNA.

It facilitates efficient viral RNA synthesis and protects it from host immune responses.

Explication

Replication within ER-derived vesicles allows flaviviruses to efficiently synthesize viral RNA while shielding it from host immune sensors, thus promoting successful infection and assembly.

8. In clinical practice, how can understanding the role of NS1 in flavivirus pathogenesis inform the management of severe cases such as dengue hemorrhagic fever?

Developing antiviral drugs that inhibit viral entry into host cells
Enhancing antibody responses to neutralize the virus
Targeting NS1 secretion to reduce endothelial dysfunction and vascular leakage
Improving mosquito control measures to prevent transmission

Targeting NS1 secretion to reduce endothelial dysfunction and vascular leakage

Explication

Understanding that NS1 induces endothelial dysfunction and vascular leakage helps in developing strategies to target NS1 secretion or activity, thereby potentially reducing vascular leakage and severity of disease in severe flavivirus infections like dengue hemorrhagic fever.

9. What is a key feature of antibody-dependent enhancement (ADE) in viral infections?

It is characterized by the production of high-affinity, neutralizing antibodies.
It results in the complete clearance of the virus by immune mechanisms.
It involves antibodies that neutralize the virus effectively at all titers.
It occurs at intermediate antibody titers, where antibodies facilitate viral entry into host cells.

It occurs at intermediate antibody titers, where antibodies facilitate viral entry into host cells.

Explication

ADE is characterized by the phenomenon where, at intermediate levels of cross-reactive antibodies, these antibodies do not neutralize the virus but instead help it enter host cells via Fc or complement receptors, thereby enhancing infection.

10. What is a key factor that influences the severity of dengue disease?

The patient's age at infection
Prior infection with dengue or Zika viruses
The presence of mosquito breeding sites nearby
The genetic variation of the dengue virus

Prior infection with dengue or Zika viruses

Explication

Prior infection with dengue or Zika viruses significantly influences dengue severity due to immune mechanisms like antibody-dependent enhancement and immune imprinting, which can increase the risk of severe disease.

11. What is a characteristic structural feature of picornaviruses?

They possess a lipid envelope with glycoprotein spikes
They have a complex, helical nucleocapsid structure
They have a T=3 icosahedral capsid and are non-enveloped
They are segmented RNA viruses with a spherical shape

They have a T=3 icosahedral capsid and are non-enveloped

Explication

Picornaviruses are characterized by their non-enveloped, T=3 icosahedral capsid structure, which provides stability outside the host and is a defining feature of this virus genus.

12. What is the primary role of poliovirus vaccines?

To prevent poliovirus infection and associated paralysis
To treat existing poliovirus infections
To cure paralysis caused by poliovirus
To diagnose poliovirus infections

To prevent poliovirus infection and associated paralysis

Explication

The primary role of poliovirus vaccines, such as IPV and OPV, is to induce immunity in individuals and populations, thereby preventing poliovirus infection and the paralysis that can result from the disease.

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Flaviviruses — classification?

Positive-sense ssRNA viruses in Flaviviridae.

Flavivirus genome — type?

Non-segmented, single polyprotein RNA.

Flavivirus replication — location?

Cytoplasm within ER-derived vesicles.

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