Structure of the influenza virus and surface proteins
Influenza viruses belong to the family Orthomyxoviridae and contain single-stranded segmented RNA. The internal structure is represented by a ribonucleoprotein surrounded by the matrix protein M1. The outer lipid envelope (supercapsid) contains surface glycoproteins that determine the viral subtype and act as antigens.
Key surface structures include:
- Hemagglutinin (H) — ensures adhesion of the virion to sialic acids of respiratory epithelial cells.
- Neuraminidase (N) — breaks the bonds between hemagglutinin and cellular receptors, helping the virus enter and release after replication.
Adsorption, penetration, and the role of the M2 protein
The infectious process begins with the attachment of the virus to the target cell through the interaction of hemagglutinin with sialic acids. Then the virion penetrates inside via endocytosis, forming an endosome.
Inside the endosome, the medium becomes acidified. Hydrogen ions enter the viral particle through the proton channel formed by the M2 protein. This process leads to the dissociation of the matrix protein and ribonucleoproteins — deproteinization occurs, and the viral RNA enters the cytoplasm.
The pharmacological agent rimantadine selectively blocks M2 ion channels, preventing acidification of the virion and its "uncoating".
Intracellular synthesis, assembly, and virion release
The released viral RNA is transported into the nucleus of the host cell, where genome replication and viral mRNA transcription occur using viral RNA polymerase. The resulting mRNA enters the cytoplasm, where necessary proteins are synthesized on ribosomes.
The assembly of new virions occurs at the cell membrane, after which viral particles bud off. At the final stage, hemagglutinin holds new virions on the surface of the infected cell.
The enzyme neuraminidase breaks this bond, ensuring the final detachment of viral particles. The drug oseltamivir inhibits neuraminidase, blocking the spread of infection.
M2 — Bear outpost (blocked by rimantadine), Neuraminidase — Scissors (cut the bond with the cell, blocked by oseltamivir).
Class and exam questions
What is the function of the M2 protein in the influenza virus?
The M2 protein forms a specific ion channel in the viral envelope. Through it, hydrogen ions penetrate inside the virion during endosome acidification, which triggers the deproteinization process.
Which drug blocks M2 ion channels and what is its effect?
Rimantadine blocks the function of M2 ion channels. This disrupts proton transport into the virion and prevents its "uncoating".
What is the role of neuraminidase in the viral life cycle?
Neuraminidase breaks the bond of hemagglutinin with sialic acids of the cell membrane. This ensures the detachment of new virions from the infected cell and their release to infect other cells.
Where do replication and transcription of the influenza virus take place?
The processes of viral genome replication and mRNA transcription occur in the nucleus of the host cell.
What else to study on this topic
- Classification and structure of influenza virus types A, B, and C
- Structure of segmented RNA and ribonucleoproteins
- The role of the M1 matrix protein in the virion structure
- Mechanisms of endocytosis and endosome formation
- Processes of viral protein translation on host cell ribosomes
Master the entire topic in the «Pharmacology» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Anti-influenza drugs" and another 5,304 subject pages
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 116 video lessons on the subject
Other topics in the "Antivirals" section
Free video lessons: pharmacologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.