Podcast
Questions and Answers
What role do the surface proteins of enveloped viruses primarily play?
What role do the surface proteins of enveloped viruses primarily play?
Which of the following best describes the means by which a naked virus enters a host cell?
Which of the following best describes the means by which a naked virus enters a host cell?
Why do most RNA viruses replicate in the cytoplasm?
Why do most RNA viruses replicate in the cytoplasm?
Which virus requires host cell splicing enzymes located in the nucleus?
Which virus requires host cell splicing enzymes located in the nucleus?
Signup and view all the answers
What initiates the firm binding of a virus to a cell surface receptor?
What initiates the firm binding of a virus to a cell surface receptor?
Signup and view all the answers
In what manner do retroviruses replicate their genetic material?
In what manner do retroviruses replicate their genetic material?
Signup and view all the answers
What characterizes the entry mechanism of viruses that use caveolin-mediated endocytosis?
What characterizes the entry mechanism of viruses that use caveolin-mediated endocytosis?
Signup and view all the answers
Which stage follows the initial attachment during the viral entry process?
Which stage follows the initial attachment during the viral entry process?
Signup and view all the answers
Which of the following viruses has a unique entry mechanism involving clathrin-mediated endocytosis?
Which of the following viruses has a unique entry mechanism involving clathrin-mediated endocytosis?
Signup and view all the answers
What is the primary purpose of a virus modifying host behaviors?
What is the primary purpose of a virus modifying host behaviors?
Signup and view all the answers
Which of the following describes vertical transmission of viruses?
Which of the following describes vertical transmission of viruses?
Signup and view all the answers
What type of viruses are primarily transmitted by arthropod vectors?
What type of viruses are primarily transmitted by arthropod vectors?
Signup and view all the answers
Which factor is critical for a virus to successfully replicate within a permissive host cell?
Which factor is critical for a virus to successfully replicate within a permissive host cell?
Signup and view all the answers
Avian influenza virus transmission is primarily associated with which factor?
Avian influenza virus transmission is primarily associated with which factor?
Signup and view all the answers
How do some viruses overcome host cellular defenses during replication?
How do some viruses overcome host cellular defenses during replication?
Signup and view all the answers
Which of the following viruses is NOT transmitted via direct human behaviors such as sex or kissing?
Which of the following viruses is NOT transmitted via direct human behaviors such as sex or kissing?
Signup and view all the answers
Which disease is most likely associated with human travel and behaviors leading to its spread?
Which disease is most likely associated with human travel and behaviors leading to its spread?
Signup and view all the answers
What is a common mode of transmission for the Zika virus?
What is a common mode of transmission for the Zika virus?
Signup and view all the answers
Which of the following correctly identifies the requirement for a virus's survival?
Which of the following correctly identifies the requirement for a virus's survival?
Signup and view all the answers
What is the primary process that a virus undergoes to replicate its genome within a host cell?
What is the primary process that a virus undergoes to replicate its genome within a host cell?
Signup and view all the answers
Where does the RNA genome of a virus generally remain during the replication process?
Where does the RNA genome of a virus generally remain during the replication process?
Signup and view all the answers
What feature distinguishes naked viruses from enveloped viruses?
What feature distinguishes naked viruses from enveloped viruses?
Signup and view all the answers
Which viral process involves the interaction of the virus with host cellular machinery?
Which viral process involves the interaction of the virus with host cellular machinery?
Signup and view all the answers
During which stage does a virus capsize induce the host cell to alter its processes?
During which stage does a virus capsize induce the host cell to alter its processes?
Signup and view all the answers
What is a significant characteristic of the capsid structure in naked viruses?
What is a significant characteristic of the capsid structure in naked viruses?
Signup and view all the answers
What role does the envelope play in enveloped viruses that is not present in naked viruses?
What role does the envelope play in enveloped viruses that is not present in naked viruses?
Signup and view all the answers
What is the function of lysis in the viral replication cycle?
What is the function of lysis in the viral replication cycle?
Signup and view all the answers
What aspect of virus propagation is primarily characterized by the terms 'penetration' and 'uncoating'?
What aspect of virus propagation is primarily characterized by the terms 'penetration' and 'uncoating'?
Signup and view all the answers
What mechanism may be employed by viruses to delay the host's native translation processes during infection?
What mechanism may be employed by viruses to delay the host's native translation processes during infection?
Signup and view all the answers
Which statement correctly characterizes the uncoating process in virus replication?
Which statement correctly characterizes the uncoating process in virus replication?
Signup and view all the answers
Which factor is essential for transcription in DNA viruses?
Which factor is essential for transcription in DNA viruses?
Signup and view all the answers
What role do the 5’ methylated cap and 3’ poly(A) tail play in protein synthesis?
What role do the 5’ methylated cap and 3’ poly(A) tail play in protein synthesis?
Signup and view all the answers
How do RNA viruses transcribe their genome into mRNA?
How do RNA viruses transcribe their genome into mRNA?
Signup and view all the answers
In how many steps does the assembly of virions typically commence?
In how many steps does the assembly of virions typically commence?
Signup and view all the answers
What is the function of packaging signal sequences in viral genomes?
What is the function of packaging signal sequences in viral genomes?
Signup and view all the answers
Which type of capsid assembly begins with procapsid formation?
Which type of capsid assembly begins with procapsid formation?
Signup and view all the answers
What process describes how virions gain their envelope from host cells?
What process describes how virions gain their envelope from host cells?
Signup and view all the answers
What modification can alter protein conformation, activity, and stability?
What modification can alter protein conformation, activity, and stability?
Signup and view all the answers
Which of the following is a characteristic of poxviruses compared to most DNA viruses?
Which of the following is a characteristic of poxviruses compared to most DNA viruses?
Signup and view all the answers
Study Notes
Virus Transmission and Replication
- Students will be able to describe the mode of virus transmission and how viruses replicate within permissive cells after the lecture.
Virus Transmission
- A virus infects adjacent or distant cells to ensure its survival.
- To accomplish this, viruses modify host behaviors.
- Rabies: animals become aggressive, increasing the likelihood of being bitten by other animals, thus increasing transmission.
- Some viruses are transmitted directly during sex or kissing (EBV, HBV, HPV).
- Others are passed from parents to newborns (vertical transmission, HBV, HIV, MEV.)
Transmission Across Regions
- Animal migration (avian influenza virus).
- Human travel and behaviors (SARS coronavirus, SARS-CoV-2, COVID-19).
- Animal export and trading (monkeypox virus).
Vector-Borne Transmission
- Transmission occurs between hosts when organisms feed on them (vectors).
- Examples include dengue virus, Zika virus, yellow fever virus, and West Nile virus.
- Vectors are arthropods (ticks, insects, mites).
- Arboviruses are a type of vector-borne virus.
Virus Replication
- A permissive host cell is required for virus survival.
- The host cell must have suitable receptors for virus binding.
- The host cell produces transcription factors and enzymes necessary for virus replication.
- Host defenses against the virus are suppressed or the virus overcomes host defenses.
Virus Replication: General
- Attachment: Attachment of a virus to a host cell
- Penetration: The virus enters the host cell
- Uncoating : Removal of capsid from the virus particles
- Genome Replication: Viral genome replication (RNA or DNA)
- Protein Synthesis: Synthesis of viral proteins
- Assembly: Assembly of viral components
- Release : Release of viruses to infect other cells
Step 1: Attachment or Adsorption
- Naked viruses: Surface proteins are on capsids (depressions, ridges, fibers, spikes).
- Enveloped Viruses: Surface proteins are staggered along the lipid envelopes, often glycoproteins.
- Initially, a virion weakly binds to one or more receptors on the cell surface, becoming more firmly attached as more receptors and viral surface proteins bind.
Step 2: Virus Entry
- Membrane Fusion: Virion fuses directly with the plasma membrane.
- Endocytosis:
- Clathrin-mediated (adenoviruses).
- Caveolin-mediated (Simian virus 40) – low pH in endosome triggers release from envelope.
- Naked viruses utilize endocytosis.
Step 3: Genome Replication and Viral Protein Synthesis
-
Most RNA viruses replicate in cytoplasm; exceptions include influenza viruses (nucleus), and retroviruses (nucleus and cytoplasm).
- RNA viruses in the cytoplasm have the enzymes needed for replication within the cytoplasm.
-
Influenza viruses require host splicing enzymes in the nucleus.
-
Retroviruses reverse-transcribe RNA into DNA within the cytoplasm, which then moves into the nucleus during mitosis (when the nuclear membrane is weakened).
-
Most DNA viruses replicate in the nucleus, except poxviruses.
- Viral genomes are transported to the nuclear membrane by microtubules.
-
Uncoating: Partial or complete removal of the virus capsid.
-
Transcription: Binding of RNA polymerase to promoters and enhancers; DNA viruses use host RNA polymerase II; RNA viruses use their own RNA-dependent RNA polymerase.
Step 3: Protein Synthesis/Translation
- Protein synthesis/translation, mediated. by the 5' methylated cap and 3' poly(A) tail.
- 5' cap: Binding site for eukaryotic initiation factors (eIFs).
- Post-translational modifications: glycosylation, acylation, and phosphorylation.
- These modifications alter protein conformation, activity, localization, and/or stability
Step 4: Assembly
- Virion assembly begins when sufficient quantities of viral genomes and structural proteins have accumulated in infected cells.
- Nucleocaspid formation: Coating of viral genome with a helical capsid.
- Icosahedral capsid assembly: Begins with procapsid formation, carrying a viral genome and undergoing conformational change.
Step 5: Genome Packaging
- Virus packaging proteins are positively charged
- Packaging signal recognition differentiates viral genomes from cell genomes.
Step 6: Budding
-
Budding through host cell membranes.
- Virus glycoproteins accumulate on membranes, and are inserted in lipid bilayers.
-
Membranes pinch off and release virions.
-
Some viruses acquire envelopes from organelles other than the nucleus.
-
Virions are released when the host cell bursts (lysis) or are continually released without lysis.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the various modes of virus transmission and the mechanisms of replication within permissive cells. Students will learn about direct and indirect transmission methods, vector-borne infections, and the impact of animal and human behaviors on virus spread. Enhance your understanding of viral dynamics in different contexts.
