Influenza A: Antigenic Shift and Drift

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Questions and Answers

How does neuraminidase contribute to the pathogenesis of influenza following the inhalation of the virus?

By inhibiting the function of macrophages and T cells, thus suppressing the immune response.
By clearing the protective mucous layer, allowing viral access to respiratory tract cells. (correct)
By compromising the mucosal defenses of the respiratory tract, promoting bacterial adhesion.
By directly inducing the release of interferons, leading to systemic flu-like symptoms.

What is the primary mechanism by which neuraminidase inhibitors, such as oseltamivir and zanamivir, combat influenza infections?

By enhancing the host's interferon response, thereby amplifying the antiviral state.
By cleaving the sialic acid residues on the cell surface, thus preventing viral entry.
By preventing the virus from exiting infected cells. (correct)
By directly neutralizing the hemagglutinin protein, preventing viral attachment to host cells.

Why are live attenuated influenza vaccines contraindicated for pregnant women and immunocompromised individuals?

Because the vaccine can interfere with the development of protective antibodies against influenza.
Because the attenuated virus in the vaccine may cause illness in these individuals. (correct)
Because these vaccines contain viral antigens that may provoke an allergic reaction in susceptible individuals.
Because these vaccines can trigger an excessive inflammatory response, leading to severe tissue damage.

How does the antigenic shift in influenza A virus contribute to the potential for pandemic outbreaks, compared to antigenic drift?

Antigenic shift introduces drastically different hemagglutinin, neuraminidase proteins, which allows the virus to evade herd immunity. (C) Signup and view all the answers

What immunological mechanism provides protection against influenza re-infection?

The development of antibodies to hemagglutinin, as well as antibodies to neuraminidase. (C) Signup and view all the answers

A patient presents with symptoms including fever, myalgia, sore throat, and non-productive cough, 36 hours post exposure. Which diagnostic approach would allow for the most rapid and specific identification of the influenza strain?

Direct fluorescent antibody (DFA) or PCR testing of a respiratory sample. (D) Signup and view all the answers

Following an influenza outbreak, a research study reveals a novel mutation in the hemagglutinin protein of the circulating influenza A virus. Which immunological consequence is MOST likely to arise from this mutation within the population?

Reduced efficacy of existing antibodies against the mutated strain, leading to increased susceptibility. (A) Signup and view all the answers

A patient is diagnosed with influenza A and treated with oseltamivir. The patient returns 5 days later with continued symptoms and now presents with signs of bacterial pneumonia. What aspect of influenza pathogenesis MOST likely predisposed this patient to secondary bacterial pneumonia?

Viral-induced damage to the respiratory epithelium and impaired mucociliary clearance. (B) Signup and view all the answers

A study finds influenza B virus exhibits a different pattern of antigenic variation compared to influenza A virus. In terms of molecular mechanisms and epidemiological consequences, how does antigenic variation of influenza B typically differ from influenza A?

Influenza B exhibits only antigenic drift due to gradual mutations, resulting in less dramatic antigenic changes. (C) Signup and view all the answers

A child who has not been vaccinated against influenza develops a fever and is suspected of influenza B infection. To prevent the danger of Reye's syndrome, which medication should be avoided?

Aspirin to reduce fever. (B) Signup and view all the answers

Flashcards

Antigenic Shift

Major genetic change resulting in a completely new strain of influenza virus.

Antigenic Drift

Small, gradual mutations in the virus's surface proteins (hemagglutinin and neuraminidase) over time.