Final Exam Flashcards
Taxonomy of Viruses
What do these suffixes refer to?
- virales
- viridae
- virinae
- virus
- virales: Orders
- viridae: Family
- virinae: subfamily
- virus: genera
Initial classification of viruses is made by ______ and how many of each are of clinical importance?
nucleic acid composition
RNA-14 families
DNA-6 families
Types of viral diseases
- Respiratory
- Enteric
- Exanthematous (skin eruptions)
- hepatitis
- persistent (latent)
Viruses are what type of pathogen?
obligate intracellular pathogen
cannot replicate outside of a host cell
What is tropism?
Viruses are host specific, meaning they have a limited number of hosts they can infect and survive in.
When are you considered contagious with a viral infection?
Varies
norovirus-from the time you display symptoms up yo 3 days after recovery
common cold-2-3 days after symptoms occur and lasts for a week
What is:
Antigenic Shift?
Antigenic Drift?
Antigenic Shift-infrequent major changes in the genetic structure of a virus (possibly incorporating host DNA into its viral genetic structure) creating a completely new virus
Antigenic Drift-minor changes in the genetic structure that occur during replication and this can occur all the time. The resulting virus is similar to the original with similar antigenic properties ( the immune system may still recognize it). Immunity can be lost over time due to the accumulation of the changes.
need for seasonal influenza vaccine
What is a virion?
It is measured in….
virus particle
nanometers
Viruses use ____ to replicate because they cannot _______.
- host cell machinery
- self replicate
Structural components of a virion
Genetic material (DNA or RNA) capsid (made of capsomeres)
Possible:
envelope
glycoprotein spikes
What are capsomeres?
repeating structural subunits that make up the capsid
What is a capsid?
Protein coat that encloses the virus’s genetic material.
genome + capsid=nucleocapsid
What is a virion envelope and what is it prone to?
A lipid membrane that surrounds the capsid of certain viruses.
Prone to drying, thus transmission is via direct contact (prevent exposure to environment)
What are vision glycoprotein spikes?
attached projections on the surface of a virion that aid in stabilization and may have some enzymatic activities.
These projections can change, which also impairs a need for seasonal influenza vaccines.
Modes of viral transmission:
Which one is considered the most common route?
- direct contact
- injection with contaminated fluids or blood
- organ transplantation
- fecal-oral
- respiratory (inhalation is the most common route)
Viral disease progression
1-acquisition 2-attachment 3-penetration 4-uncoating 5-replication 6-macromolecular synthesis 7-assembly 8-release
Viral disease progression
Acquisition
Entry into the body
viruses can enter the body via inhalation, but cause infection elsewhere in the body
Spreads via the blood or lymphatics
Symptoms of disease-due to tissue damage and host immune response
Viral disease progression
Attachment
Recognition/binding to host cell receptors
Tropism-infect only certain tissues due to recognition of limited numbers of host cells
Viral disease progression
Penetration
Process of entering host cell
Mechanism(s)
- fusion of viral envelope with host cell membrane
- penetrating host cell membrane with tail
Viral disease progression
Uncoating
releasing viral genetic material into the host cell
Viral disease progression
Macromolecular synthesis
production of nucleic acids/protein polymers
mRNA encodes early and late proteins
Early proteins: nonstructural, usually enzymes
Late proteins: structural
Viral disease progression
Assembly
arrangement of structures
Virion becomes intact and is ready for release
Viral disease progression
Release
Via host cell lysis OR budding with cytoplasmic membranes
Influenza virus-hemadsorption
Common cells used for detection of viruses
These are examined periodically to look for:
human diploid fibroblasts, human epidermoid, primary monkey kidney
examined to observe cytopathic effects