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9.16 Introduction to Virology
by Dr. Amedee at 10am
118
Microbiology
Professional
09/19/2011

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Term
What is a virus?
Definition
originally defined as a filterable agent but now they are defined as obligate intracellular parasites with an RNA or DNA genome
Term
T/F Human genome contains viral DNA.
Definition
true
Term
T/F Rabies, polio, smallpox, yellow fever, and measles are all relatively recent viral diseases in the history of humans.
Definition
False, they are considered "ancient diseases" because they have been around for a long time
Term
The term virus is derived from a Latin word meaning...
Definition
a slimy liquid or a poisonous liquid
Term
What was the first human virus discovered?
Definition
yellow fever in 1901
Term
How are viruses classified?
Definition
by the disease they cause, their mode of transmission, structure, and biochemical characteristics
Term
How big are viruses?
Definition
anywhere from 20 nm to 300 nm
Term
Nucleocapsid and capsid proteins are typical of what kinds of viruses?
Definition
enveloped viruses
Term
Which DNA virus is bigger: a parvovirus or a poxvirus?
Definition
poxvirus (300 versus 25 nm)
Term
Which RNA virus is bigger a picornavirus or a paramyxovirus?
Definition
a paramyxovirus
Term
What is the genome of parvoviruses?
Definition
SS linear DNA
Term
What is the genome of a hepadnavirus?
Definition
DS circular DNA
Term
What is the genome of a papovavirus?
Definition
DS circular DNA
Term
What is the genome of an adenovirus?
Definition
DS linear DNA
Term
What is the genome of a herpes virus?
Definition
DS linear DNA
Term
What is the DNA of a poxvirus?
Definition
DS linear DNA
Term
What is the genome of a picornavirus?
Definition
SS+ RNA
Term
What is the genome of a calicivirus?
Definition
SS+ RNA
Term
What is the genome of a reovirus?
Definition
DS (+/-) RNA
Term
What is the genome of a togavirus?
Definition
ss+
Term
What is the genome of a flavivirus?
Definition
SS+ RNA
Term
What is the genome of a rhabdovirus?
Definition
SS- RNA
Term
What is the genome of a paramyxovirus?
Definition
SS- RNA
Term
What is the genome of an orthomyxovirus?
Definition
SS- RNA
Term
What is the genome of a retrovirus?
Definition
SS+ RNA (two identical)
Term
What is the genome of a filovirus?
Definition
SS- RNA
Term
What is the genome of an arenavirus?
Definition
SS- RNA
Term
What is the genome of a bunyavirus?
Definition
SS- RNA
Term
What is the genome of a coronavirus?
Definition
SS+ RNA
Term
Name the two simplest capsid structures.
Definition
helical and icosahedral
Term
Describe the icosahedral capsid structure.
Definition
20 triangular faces; 5:3:2 symmetry
Term
What are the parts formed together to make a mature capsid?
Definition
protomers -> capsomers -> procapsid -> mature capsid
Term
What is a capsid?
Definition
the protein coat surrounding the nucleic acid genome
Term
What's the difference between capsomers and protomers?
Definition
capsomers are the repeating protein subunits that make up the capsid. Protomers are the polypeptide chains which make up the capsomers
Term
What do you call capsids composed of multiple copies of a single kind of protein subunit in a close-packed helix?
Definition
helical capsids
Term
What are some examples of helical capsids?
Definition
rhabdovirus (VSV), influenza, tobacco mosaic virus
Term
What is a virion?
Definition
the complete virus particle
Term
What is a nucleocapsid?
Definition
the capsid proteins associated with the viral nucleic acid
Term
What is a nucleoprotein?
Definition
proteins associated with the viral nucleic acid
Term
What is the viral envelope?
Definition
membrane composed of lipids, proteins and glycoproteins that is obtained from the cellular membranes. Virus encoded envelope proteins or "spikes" serve as the viral attachment proteins
Term
What type of capsid does the adenovirus have?
Definition
icosahedral
Term
Describe the outer coverings of a herpes virus?
Definition
enveloped icosahedral
Term
Describe the outer coverings of the influenza virus?
Definition
enveloped helical virus
Term
Describe the outer coverings of HIV?
Definition
enveloped icosahedral
Term
Describe the different ways a virus can enter a cell?
Definition
fusion with the cell membrane either at cell membrane or in an endosome or receptor mediated endocytosis
Term
What are the different types of RNA viruses?
Definition
can be + or - polarity, single-stranded or double-stranded, circular or linear, unimolecular or segmented.
Term
Where do RNA viruses generally replicate?
Definition
in the cytoplasm (retrovirus and influenza are exceptions)
Term
What does it mean for an RNA virus to be negative or positive?
Definition
+ means the genome is used as mRNA, - means the viral polymerase produces mRNA
Term
What are the different types of DNA genomes?
Definition
single-stranded, double stranded, circular and linear
Term
Where do DNA viruses generally replicate?
Definition
in the nucleus (poxvirus is the exception)
Term
In general which viruses are more dependent on host machinery and which are more independent and encode thier own enzymes and proteins?
Definition
smaller is more dependent, larger encodes its own
Term
What are the different classes of genes in the life cycle of herpesvirus?
Definition
imediate early, early and late
Term
Describe the herpes life cycle.
Definition
1) Circularization of genome oand transcription of immediate-early genes
2) alpha proteins, products of immediate-early genes, stimulate transcription of early genes
3) beta-proteins, products of early genes, function in DNA replication, yielding concatemeric DNA. Late genes are trnascribed
4) gamma proteins, products of late genes, participate in virion assembly
Term
Hepatitis is caused by what viruses?
Definition
HAV, HBV, HCV, HDV, HEV, CMV, and EBV
Term
What viruses cause encephalitis?
Definition
HSV, togaviruses, vlaviviruses, rabies, picornaviruses
Term
What viruses cause meningitis?
Definition
enteroviruses, mumps, HSV-2 and VZV
Term
Rotavirus, caliciviruses, and adenoviruses (40-41) all cause disease the in...
Definition
GI tract
Term
Which viruses cause the common cold?
Definition
rhinoviruses, coronaviruses, and adenoviruses
Term
What viruses cause disease in the lower respiratory tract?
Definition
influenza, parainfluenza, ReSV, adenoviruses
Term
What viruses cause congenital and neonatal infections?
Definition
CMV, parvovirus B19, rubella, HSV, HIV, and lymphocytic choriomeningitis
Term
What viruses cause congenital and neonatal infections?
Definition
CMV, parvovirus B19, rubella, HSV, HIV, and lymphocytic choriomeningitis
Term
What are examples of viruses that present as localized infections of the respiratory tract?
Definition
influenza and the common cold (rhinoviruses, coronaviruses, adenoviruses)
Term
What viruses can cause disseminated infections via respiratory transmission?
Definition
varicella-zoster virus, measles
Term
What is an early physical sign of disseminated infection with the measles virus?
Definition
koplik's spots (white spots on the buccal mucosa)
Term
What type of virus is the measles?
Definition
paramyxovirus
Term
Which virus causes the chicken pox and shingles?
Definition
varicella zoster virus (HHV-3)
Term
Name the important viruses that are spread fecal-orally.
Definition
picornavirus, rotavirus, reovirus, caliciviruses, astrovirus, adenovirus
Term
What virus is a frequent cause of acute disease outbreaks on cruise ships and in day care centers and nursing homes?
Definition
norovirus
Term
What virus causes about 50% of acute gastroenteritis in infants and children under 2 years?
Definition
rotavirus
Term
Which viruses are fecal oral and cause GI symptoms of vomiting and diarrhea?
Definition
norovirus, rotavirus, astroviruses, and adenoviruses
Term
Which viruses have fecal oral transmission but cause disease at a secondary site?
Definition
enteroviruses (in the piconavirus family: poliovirus, Coxsackie virus, echovirus and enterovirus) and hepatitis A and E
Term
Give examples of chronic viral diseases.
Definition
HIV, hepatitis, HTLV-1 (hep B is a chronic disease while HIV and HTVL-1 are chronic with late disease)
Term
When was the last US case of small pox? When was the last naturally occurring case of small pox?
Definition
1949, 1977 in Somalia (certified eradication in Dec. 1979)
Term
What are the different types of zoonoses?
Definition
arboviruses (togaviruses [alpha], flaviviruses, bunyaviruses), pox viruses (orf, monkeypox), hantavirus (deer mouse), rabies (bats, raccoons, skunk dogs)
Term
How can West Nile be transmitted human to human?
Definition
transplanted organs, blood transfusions, breast milk, transplacental, occupational exposure
Term
T/F Most humans with West Nile develop no clinical symptoms.
Definition
true! only 20% develop disease (west nile fever)
Term
What are the symptoms of west nile?
Definition
range from febrile headache to aseptic meningitis to encephalitis
Term
T/F Humans are the primary host for West Nile virus.
Definition
False, birds are the primary host, humans are only incidental hosts
Term
What is SARS?
Definition
characterization of a novel coronavirus associated with severe acute respiratory syndrome
Term
What are the best methods for controlling viruses?
Definition
prophylaxis is best, vaccines, universal precautions, education
Term
Name common live attenuated virus vaccines.
Definition
MMR, varicella-zoster, yellow fever
Term
Name common killed or inactivated vaccines.
Definition
IPV [salk], influenza A and B, hepatitis A, and rabies
Term
T/F Recombinant/subunit vaccines are considered live vaccines.
Definition
false
Term
Name the type of vaccine and the target population for hep a vaccine.
Definition
nonliving
travelers, or persons living in high risk areas
Term
Name the type of vaccine and target population for hep b vaccine.
Definition
non-living (recombinant)
universal childhood (healthcare workers)
Term
What type of vaccine and what is the target population for influenza A and B vaccines?
Definition
1)non-living and 2) live
elderly, at risk population, others, medical personnel
Term
What is the type of vaccine and the target population for japanese encephalitis virus?
Definition
non-living
travelers to endemic regions
Term
What is the type of vaccine and target population for measles?
Definition
live
universal childhood
Term
What is the type of vaccine and target population for mumps?
Definition
live
universal childhood
Term
What is the type of vaccine and target population for poliovirus [salk]?
Definition
nonliving
universal childhood
Term
What is the type of vaccine and target population for rabies (preexposure, HDCV)?
Definition
non-living
veterinarians, high risk persons
Term
What is the type of vaccine and target population for rubella?
Definition
live
universal childhood
Term
What is the type of vaccine and target population for varicella?
Definition
live
universal childhood
Term
What is the type of vaccine and target population for yellow fever?
Definition
live
travelers to endemic regions
Term
What is RotaTeq?
Definition
new vaccine for rotavirus
live, oral pentavalent vaccine that contains 5 reassortant rotaviruses
3 doses given to infants @ 2,4,6 months
Term
What type of vaccine is gardasil?
Definition
vaccine for cervical cancer via HPV infection
noninfectious viral like particles with capsid proteins of HPV types 6, 11, 16, 18. 3 doses IM to girls 11-12 yrs before sexual activity
Term
What type of vaccine is zostavax?
Definition
for shingles, live attenuated vaccine for adults > 60 yrs
Term
T/F Use of the Sabin poliovirus has been replaced by the attenuated salk vaccine.
Definition
true
Term
What type of vaccine is the smallpox vaccine?
Definition
live vaccine given intradermally to select first line defense personnel
Term
What are lytic infections?
Definition
viral infections that kill the cell via a number of different mechanisms such as apoptosis
Term
What does it mean for a virus to cause a persistent infection?
Definition
when it does not cause cell death and may be chronic, latent recurrent or transforming. Must be able to limit its cytolytic effects, maintain its genome within host cells and avoid elimination by the host's immune system
Term
Which viruses inhibit cellular protein synthesis?
Definition
polioviruses, herpes simplex, pox viruses, toagaviruses
Term
Which viruses inhibit or degrade DNA?
Definition
herpes viruses
Term
Which viruses use syncytia to harm host cells?
Definition
herpes simplex, HIV, varicella zoster, paramyxoviruses
Term
Which viruses cause inclusion bodies in the host cell?
Definition
rabies, adenovirus, poxvirus, reovirus, CMV
Term
What is a syncytia?
Definition
a mass of cytoplasm containing several nuclei. The expression of cell surface glycoproteins of some viruses like HIV, herpes, and RSV (a paramyxovirus) can trigger the fusion of neighboring cells into multinucleated giant cells called syncytia
Term
Negri bodies are characteristic of what infection?
Definition
rabies virus in the CNS
Term
What is a viral quasispecies?
Definition
a heterogenous group of sequences clustering around a consensus (aka viral swarm)
Term
Where would you take a specimen from if your patient had a maculopapular rash?
Definition
throat, stool, or rectal swabs (I know it doesn't make sense but its on the powerpoint)
Term
Where do you collect biological specimens from if your patient has a virus causes CNS illness (encephalitis and meningitis)?
Definition
stool, tissue, saliva, brain biopsy, CSF
Term
What are the visible, cytopathic effects of viral infection?
Definition
rounding/detachment, syncytia, shrinkage, increased refractility, aggregation, loss of adherence, cell lysis/death
Term
What is hemagglutination?
Definition
when viruses contain proteins that bind to erythrocytes can cause an easily visualized and quick indicator of viral presence
Term
What are the criteria for diagnosing primary infection via serology?
Definition
4 fold or more increase in titer of IgG or total antibody between acute and convalescent sera, presence of IgM, seroconversion, and a single high titer of IgG (or total antibody)-very unreliable
Term
For which types of viruses would serology NOT be a useful diagnostic tool and why?
Definition
most respiratory and diarrheal viruses produce clinical disease before the appearance of antibodies
Term
How do you detect antibodies via serology?
Definition
ELISA
Term
How do you diagnose a viral illness via direct examination?
Definition
visualization by EM, histologically via inclusion bodies, viral antigens, viral nucleic acid
Term
What labratory method is used for detection of viral genomes?
Definition
PCR
Term
Which viruses are FDA approved for in vitro nucleic acid amplification and detection?
Definition
HIV, HCV, and west nile
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