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Questions and Answers
What is the typical duration of a fever associated with influenza, assuming no complications arise?
What is the typical duration of a fever associated with influenza, assuming no complications arise?
Which of the following processes contributes most significantly to local symptoms of influenza?
Which of the following processes contributes most significantly to local symptoms of influenza?
What is the primary mechanism by which the influenza virus causes damage to the respiratory tract?
What is the primary mechanism by which the influenza virus causes damage to the respiratory tract?
Which of the following is LEAST likely to be directly a part of influenza infections in adults?
Which of the following is LEAST likely to be directly a part of influenza infections in adults?
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How long can the regeneration of the respiratory epithelium take after an influenza infection subsides?
How long can the regeneration of the respiratory epithelium take after an influenza infection subsides?
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Which of the following is a characteristic of the Orthomyxoviridae family?
Which of the following is a characteristic of the Orthomyxoviridae family?
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What is the function of the hemagglutinin (HA) protein in Orthomyxoviridae viruses?
What is the function of the hemagglutinin (HA) protein in Orthomyxoviridae viruses?
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How many RNA segments are found in the genome of influenza A and B viruses?
How many RNA segments are found in the genome of influenza A and B viruses?
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What is the role of the neuraminidase (NA) protein in the lifecycle of Orthomyxoviridae viruses?
What is the role of the neuraminidase (NA) protein in the lifecycle of Orthomyxoviridae viruses?
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Which of the following describes how the Orthomyxoviridae RNA genome is replicated?
Which of the following describes how the Orthomyxoviridae RNA genome is replicated?
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What is the nucleoprotein (NP) associated with in Orthomyxoviridae viruses?
What is the nucleoprotein (NP) associated with in Orthomyxoviridae viruses?
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Which viral proteins are responsible for the transcription of the Orthomyxoviridae genome?
Which viral proteins are responsible for the transcription of the Orthomyxoviridae genome?
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From which surface of the infected cell does the Orthomyxoviridae virus preferentially bud?
From which surface of the infected cell does the Orthomyxoviridae virus preferentially bud?
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Which of the following is a complication directly caused by influenza viral replication in alveolar epithelial cells?
Which of the following is a complication directly caused by influenza viral replication in alveolar epithelial cells?
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What mechanism of action do zanamivir and oseltamivir share in combating influenza?
What mechanism of action do zanamivir and oseltamivir share in combating influenza?
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Which diagnostic method is MOST likely to be used for influenza virus detection in severe cases or hospitalized patients?
Which diagnostic method is MOST likely to be used for influenza virus detection in severe cases or hospitalized patients?
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What is a primary reason annual influenza vaccines are updated each year?
What is a primary reason annual influenza vaccines are updated each year?
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Secondary bacterial pneumonia that occurs after influenza infection is usually due to which of the following factors?
Secondary bacterial pneumonia that occurs after influenza infection is usually due to which of the following factors?
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What is the primary cause of antigenic shift in influenza A viruses?
What is the primary cause of antigenic shift in influenza A viruses?
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Which type of influenza virus is MOST likely to undergo antigenic shift?
Which type of influenza virus is MOST likely to undergo antigenic shift?
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What is a key consequence of antigenic shift in influenza A viruses?
What is a key consequence of antigenic shift in influenza A viruses?
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What is characteristic of antigenic drift in influenza viruses?
What is characteristic of antigenic drift in influenza viruses?
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How are influenza A subtypes classified?
How are influenza A subtypes classified?
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Which of the following is a common characteristic of strains of influenza B?
Which of the following is a common characteristic of strains of influenza B?
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What are the two primary surface proteins used to classify influenza A virus subtypes?
What are the two primary surface proteins used to classify influenza A virus subtypes?
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What is the significance of the pig as a host in the context of influenza virus evolution?
What is the significance of the pig as a host in the context of influenza virus evolution?
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Where does the influenza virus typically replicate within the human body?
Where does the influenza virus typically replicate within the human body?
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Which of the following is true regarding influenza B virus infection in humans?
Which of the following is true regarding influenza B virus infection in humans?
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Study Notes
Orthomyxoviridae Family
- The family of viruses that includes influenza viruses
- Genome is segmented, single-stranded (ss) negative-sense RNA
- Pleomorphic capsid
- Enveloped viruses (80-120 nm diameter)
Influenza Virus Structure
- Contains proteins crucial to the virus's function
- Hemagglutinin (HA): spike-shaped trimer, binds to sialic acid receptor, promotes fusion with endosome, elicits neutralizing antibodies
- Neuraminidase (NA): tetramer, cleaves sialic acid residues on host cells, which helps release new virions from infected cells
- M2: membrane protein
- M1: matrix protein
- NP: nucleoprotein, associated with RNA segments
- NS: nuclear export protein
- The genome segments are associated with NP (RNP) and the transcribed RNA polymerase (components PB1, PB2, PA)
- Influenza A and B viruses possess 8 different segments, while Influenza C contains 7
- The images in the document show the structural components of the influenza A and B viruses.
- Different types have different proteins (A, B, C)
Types of influenza Viruses
- Influenza A: causes most human illness and flu season
- Subtypes (H1N1), (H3N2) and others based on HA and NA protein subtypes. -Lineages: (Victoria), (Yamagata) and others -Multiple Clades and sub-clades in the tree
- Influenza B: infects only humans -Lineages: (Victoria), (Yamagata) and and others
- Influenza C: infects humans more rarely
Influenza Virus Replication Cycle
- Viral attachment, internalization into vesicles
- Acidification of endosome; Membrane fusion and nucleocapsid release
- Viral mRNA transcription occurs
- Viral mRNA translation
- Genome replication in the nucleus; assembly process
- Budding of new virions
Antigenic Shift and Drift
- Shift: Major change in HA and/or NA proteins, caused by reassortment between animal and human viruses, leading to pandemic strains
- Drift: Smaller changes in HA and NA proteins continually occurring as the virus replicates over time. Accumulated mutations lead to antigenically different viruses the antibodies cannot recognize.
Influenza Virus Pathogenesis
- Infection of epithelial cells (upper and lower respiratory tract)
- Viral replication causes damage to these cells
- Loss of cells lining respiratory tract; secondary infections
- Symptoms such as cough, fever, body aches - Local symptoms (from damaged epithelial cells) - Systemic symptoms (from interferon and cytokine response to the virus)
Diagnosis of Influenza
- Molecular methods (RT-PCR): amplifying viral genome in respiratory samples.
Antiviral Therapy
- Inhibitors of viral neuraminidase activity(Zanamivir, Oseltamivir)
- Inhibitors of the viral M2 protein ion channels (Amantadine, Rimantadine)
Influenza Vaccine
- Vaccines should contain antigens of prevalent A and B strains.
- Egg and Recombinant-based vaccines are highlighted.
- Different specific influenza strains are listed, with examples of vaccines used.
Severe Complications
- Primary and secondary viral pneumonia
- Myocarditis and pericarditis
- Myositis
- Encephalopathy
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Description
Explore the intricate structure and function of the influenza virus, focusing on its proteins and segmented RNA genome. This quiz delves into the Orthomyxoviridae family and details the key components essential for the virus's lifecycle. Test your understanding of hemagglutinin, neuraminidase, and more.
