Ch 13 Viruses general Flashcards
Do viruses have a lot or few enzymes?
few enzymes
The envelope of an Envelope Virus is made of _________.
phospholipid.
A more complex Envelope Virus has what structures, from inside out?
nucleic acid core
protein coat
envelope
spikes
Which parts of a complex Envelope Virus are antigenic?
protein coat, spikes, capsomeres
In 1892, Ivanowsky and Beijerink discovered what?
Infectious agent that still went thru a filter
In 1902, Twort & d’Herelle discovered what?
a virus that destroyed bacteria. They named it “bacteriophage”.
Few enzymes means what?
Few targets for antiviral drugs
Viruses are ____ ______ parasites.
obligate intracellular
A virus is
intracellular
A virion is
outside the cell
Capsomeres are
individual proteins that make up the protein coat
How does our immune system identify the cell as infected?
by the spikes
What is the matrix of a virus?
the space between the protein coat & envelope.
capsid
the protein coat surrounding the nucleic acid core that provides protection for viral nucleic acids and for recognition sites.
A bacteriophage is always _______.
complex.
The most important classification for viruses is what?
Host
after that is DNA or RNA.
family ends in
viridae
genus ends in
virus
________ is how we classify viruses in medicine.
Route of transmission
Ex’s of enteric viruses
coxsacievirus,
poliovirus
Ex’s of respiratory viruses
adenovirus, rhinovirus
Ex’s of zoonotic viruses
Rabies
Arbovirus
-West Nile
-St. Louis encephalitis
-Yellow FeverEx’s of sexually transmitted diseases
Herpes Virus II (HPV-2)
Papilloma virus (HPV)
HIV
What are the 3 types of bacteriophages?
- lytic
- temperate
- lysogenic
Lytic Bacteriophage, list the steps of replication.
- attachment
- genome entry
- synthesis
- assembly
- release
The receptors in the host of lytic bacteriophages are found in:
cell wall, flagella, fimbriae
The main difference between a Phage and an Animal Virus is:
Phage - only nucleic acid is injected into the bacterial cell.
Animal virus - the entire virus enters the animal cell.
A temperate phage is the same as
lysogenic phage
the Lambda phage is
a DNA virus; it’s host cell is E. Coli
A lysogenic bacteriophage that experiences environmental STRESS will
virus exits and enters the lytic cycle, causing a productive infection.
In the lysogenic cycle, the virus is
not going to kill the host cell; this allows the virus to go on and on.
Integrase is involved in the _____ cycle and allows what to happen?
lysogenic cycle; integrase allows the virus to catalyze/recombine viral and host DNA so they come together.
Viral DNA is called a _______.
prophage
Lysogenic immunity
lysogeny gives bacteria that carries the prophage immunity so it cannot be infected with that particular virus.
Specialized transduction
prophage excises itself with an adjacent piece of bacterial DNA. The virus always has some bacteria from the host on it. Daughter cells will have it, leading to a new strain.
Lysogenic conversion
daughters could carry a toxin.
prophage takes host bacterial DNA with it.
Ex’s of specialized transduction
Vibrio cholerae
Corynebacterium diphtheriae
Clostridium botulinum
Escherichia coli 0157:h7 - hemolytic uremic syndrome, shigella toxin
Streptococcus pyogenes - causes Scarlet fever
Salmonella enterica - food poisoning
generalized transduction
random; any piece of DNA could be picked up, not adjacent
Bacterial defenses include:
- DNA methylation (branding)
2. Restriction Enzymes (scissors cut DNA)
A researcher could count plaque forming units, or PFUs, to find
the viral titer
Lytic cycle steps in Animals:
- Attachment - virus binds to receptor
- Entire virus coat enters
envelope virus - membrane fusion
non-envelope virus - endocytosis - Uncoating - removal of protein coat
- Synthesis of DNA virus
DNA - nucleus, proofreading ability
RNA - cytoplasm, virus carries own RNA polymerase aka:
Replicase
Retrovirus - reverse transcriptase, no proofreading –> mutations - Assembly
budding for envelope viruses
Apoptosis for Naked Viruses
Structure of Naked Viruses
genetic material (DNA or RNA) protein coat
ex’s of enteric viruses
coxsacievirus
poliovirus
ex’s of respiratory viruses?
adenovirus
rhinovirus
ex’s of zoonotic viruses?
West Nile virus
Rabies
St. Louis encephalitis
Yellow Fever virus
Viral proteases are
enzymes that cut viral structures to assemble the virus properly.
also good targets for antiviral drugs
In an animal virus, release happens in what two ways?
budding (envelope)
apoptosis (naked)
char’s of an Acute viral infection
short duration, productive (viral particles)
give long lasting immunity
budding may produce longer symptoms
can detect viral particles
char’s of chronic/persistent infection
long duration
detect viral particles over time
Hep B, Hep C, HIV
Persistent/Latent viral infections
viral particles are NOT detected unless the infection becomes active.
DNA viruses
may/may not have symptoms, ie: Herpes virus
viruses that cause cancer
15% of all human cancers
insert selves into our DNA and turn on oncogenes
ex’s of virally induced cancers
Burkett's Lymphoma Hodgkins dz Kaposis sarcoma Cervical cancer Leukemia HTLV-1 and HTLV-2 Liver cancer: HBV, HCV
All ______ viruses are latent.
herpes simplex
HSV-1
cold sores
trigeminal nerve ganglia; cranial nerve 5
HSV-2
genital herpes
1/4 over age 30
inguinal nerves
Which drug is used to treat genital herpes?
Acyclovir, a nucleotide analog
HSV-3
chicken pox (early)
Varicella zoster (later) - “Shingles”
HSV-4
Epstein-Barr virus
infects the lymphatic system; assoc w/chronic fatigue syndrome
HSV-5
Cytomegalovirus
very common 80%
linked to low immunity
causes: encephalitis, eye infxn, birth defects
HSV-8
Kaposis sarcoma
cancer of blood vessels
seen in older men of Mediterranean descent
Which herpes virus causes Shingles?
HSV-3
Which herpes virus causes Epstein-Barr virus?
HSV-4
Which herpes virus causes chicken pox?
HSV-3
Which herpes virus causes genital warts?
HSV-2
Which herpes virus causes cold sores?
HSV-1
What is the acute form of Hepatitis?
Hep A
Which hepatitis can cause a chronic form of hepatitis?
Chronic Hep C, B
Which strains of HPV are associated with cancer?
16, 18
HPV infects the _____________.
mucus membranes
The function(s) of the viral capsid is?
protects nucleic acid
involved in recognition of host cell receptors
antigenic
A naked virus has ____________.
no phospholipds or envelope.
The protein subunits that make up a coat of a virus are ______.
capsomeres
A lytic phage does which of the following?
inserts its nucleic acid into bacteriophage
degrades host DNA early in infection
can bring pieces of chromosomal DNA from previous host into a new
host
A lytic cycle takes how long? This is called the _______.
30 min. / burst time
Which are true of a prophage?
it is replicated as the cell replicates
can be excised by viral enzymes
integrates into host chromosome at a specific site
Which can occur during lysogenic infection?
lysogenic conversion
lysogenic immunity
specialized transduction
