What is a prion?
Not a virus, or any other recognized infectious agent
- it is a misfolded protein
What is the purpose of the capsid and envelope (when present)?
Serve to protect the genome (DNA &RNA)
What are the components of a virus?
- nuclei acid core
- capsid (an outer glycoprotein coating)
- an outer envelope (sometimes)
The function of the capsid is to protect the fragile nucleic acid genome from:
- physical damage: shearing my mechanical forces
- chemical damage: UV irritation leading to chemical modification
- enzymatic damage: nucleases derived from dead or leaky cells or deliberately secreted by vertebrates as defense against infection
List some properties of viruses that are important relative to disinfection and transmission
- heat sensitivity
- pH sensitivity
- lipid solvents
- chemicals
- radiation and UV light
- humidity
What are the two types of symmetric viral structure?
Isometric (icosahedral): constructed of 20 equilateral triangular faces
Helical: tubular construction with the subunits arranged around the nucleic acid in a coil
What are the two viral structures with no recognized symmetry?
Complex (looks like a little rocket)
Filamentous (Ebola, looks like Mickey mouse with a tail)
Viral taxonomy is based upon what 4 characteristics?
- morphology of iron, capsid, and envelope
- genome (RNA, DNA, SS, DS etc)
- serological relationships (stereotypes)
- replication strategy
What are some characteristics of structural proteins in a virus
- important for viral stability and attachment
- antibodies are generally formed against the structural proteins
What are some characteristics of non-structural proteins in a virus
- enzymes involved in viral replication
- when antibodies are found against the non-structural proteins this may help in differentiating animals vaccinated with inactivated recombinant vaccines from those naturally infected (DIVA principle)
The capsid and envelope of the virus is responsible for what?
Recognition of the host cell (Receptor binding)
Differentiate between promiscuous and plastic
- promiscuous: capable of infecting several species
- plastic: exhibiting adaptability to change or variety in the environment
A well characterized virus is known as a ______.
Strain
Different strains may have different properties, such as ______.
Virulence
An ____ refers to the virus recovered from a specific host or location
Isolate
________ generally means that immunity is not conferred by previous exposure to a different type
Serotype
How are enteric viruses acquired?
By ingestion (fecal-oral transmission) and replicate primarily in the intestinal tract
How are respiratory viruses acquired?
Acquired by inhalation or fomites (inanimate objects carrying virus contagion) and replicate primarily in the respiratory tract
How are arboviruses transmitted?
Replicate in their hematophagous (blood-feeding) arthropod hosts and are then transmitted by bite to vertebrate hosts
How are oncogenic viruses transmitted?
Acquired by close contact, injection fomites, and unknown means
What are the steps of virus replication
Attachment
Penetration
Uncoating
Transcription
Translation
Replication
Assembly (maturation)
Release
