Viruses Flashcards
recombination
exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology
reassortment
when virsuses with segmented genomes (inflenza) exchange segments. high-frequency recombination. cause of worldwide influenza pandemics
complementation
when 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein. the nonmutated virus “complements” the mutated one by making a functional protein that serves both viruses
phenotypic mixing
occurs with simultaneous infection of a cell with 2 viruses. genome A can be partially or completely coated with surface proteins from B. therefore virus A can infect a new type of cell, although its progeny will not be able to
live attenuated vaccines
- humoral and cell mediated immunity
- boosters not needed
- ex: smallpox, yellow fever, chicken pox, sabin polio virus, MMR, influenza (intranasal)
killed vaccines
- produce only humoral immunity
- rabies, influenza, salk polio, and HAV
recombinant vaccines
- HBV, HPV
DNA viral genomes
- all dsDNA except parvoviridae
- all are linear except papilloma, polyoma and hepadnaviruses (circular)
RNA viral genomes
all are ssRNA excpet reoviridae
- positive stranded RNA viruses: I went to a retro(virus) toga(virus) party, where I drank flavored (flavivirus) corona(virus) and ate hippy (hepevirus) california (calicivirus) pickles (picornavirus)
which naked genomes are infectious?
dsDNA and + sense ssRNA (dsRNA and -ve sense ssRNA are not)
naked viruses
I gave PAPP smears and CPR to a naked Heppy
- DNA: papilloma, adenovirus, parvovirus, polyomavirus
- RNA: calicivirus, picornavirus, reovirus, hepevirus
theres something weird about all the “P” DNA viruses
- pox - not icosahedral, replicates outside the nucleus
- polyoma and papilloma - circular DNA
- parvo - single stranded DNA
HSV-1
gingivostomatitis, keratoconjunctivitis, temporal lobe encephalitis, herpes labalis
- latent infection in the trigeminal ganglia
- transmitted via respiratory secretions, saliva
- intranuclear inclusions seen on oral scrapings
HSV-2
- herpes genitalis, neonatal herpes
- latent in the sacral ganglia
- transmitted by sexual contact, perinatally
VZV
HHV-3
- chickenpox, shingles, encephalitis, pneumonia
- latent in the dorsal root or trigeminal ganglia
- most common complication of shingles is post-herpetic neuralgia
- transmitted by respiratory secretions
EBV
HHV-4
- mono (feer, HSmegaly, pharyngitis, lymphadenopathy - esp post cervical nodes)
- transmitted via respiratory secretions and saliva
- infects B cells by binding to CD21 on B cells and nasopharyngeal epithelial cells
- atypical lymphocytes (abundant pale blue cytoplasm with basophilic rim) seen on PBS - reactive cytotoxic T cells
- assoc with Hodgkin lymphoma, endemic burkitt lyphoma, nasopharyngeal carcinoma
CMV
HHV-5
- congenital infection, mono with negative monospo, pneumonia, retinitis
- “owl eye” inclusions
- latent mononuclear cells
- transmitted congenitally and via transfusion, sex, saliva, urine, transplant
HHV-6
roseola - high fevers for several days that can cause seizures, followed by diffuse maculopapular rash
- transmitted by saliva
HHV-8
Kaposi sarcoma, neoplasm of endothelial cells
- seen in HIV/AIDS, transplants
- dark/violaceous flat and nodular skin lesions representing endothelial growhts
- can also affect GI tract and lungs
- transmitted by sexual contact
HSV identification
- viral culture for skin/genitalia
- CSF PCR for encephalitis
- Tzank smear - multinucleated giant cells
- infected cells also have a intranuclear Cowdry A inclusions
Hepadnavirus
Hep B - not a retrovirus but has a reverse transcriptase
- enveloped, partially DS DNA and circular
Adenovirus
- no envelope, DS and linear
- febrile pharyngitis, acute hemorrhagic cystitis, pneumonia, pink eye
parvovirus
- ssDNA, not enveloped, linear
- aplastic crises in sickle cell pts, 5th disease, hydrops fetalis, pure RBC aplasia/rhematoid arthritis-like disease in adults
papillomavirus
- dsDNA, not enveloped, circular
- HPV warnts (1,2,6,11), CIN, cervical cancer (16, 18)
polyomavirus
- dsDNA, not enveloped, circular
- JC virus - PML
- BK virus - transplant patients, affects the kidney
poxvirus
- dsDNA, enveloped, linear, replicates outside the nucleus, not icosahedral
- smallpox, cowpox (“milkmaid blisters”), and molluscum contagiosum
reoviruses
- no envelope, dsRNA, icosahedral capsid
- coltivirus - Colorado tick fever
- rotavirus - #1 cause of fatal diarrhea in kids
picornaviruses
- no envelope, + ssRNA, icosahedral capsid
- PERCH: poliovirus, echovirus (aseptic meningitis), rhinovirus, coxsackievirus* (aseptic meningitis, herpangina, HFM, myocarditis, pericarditis), HAV
- 1 large polypeptide that is cleaved by proteases into functional viral proteins
- aseptic meningitis
- are all enteroviruses (fecal-oral), except rhinovirus
hepevirus
- no envelope, + ssRNA, icosahedral capsid
- HEV
caliciviruses
- no envelope, + ssRNA, icosahedral capsid
- norovirus - viral gastroenteritis
flavivirus
- enveloped, + ssRNA, icosahedral capsid
- HCV, yellow fever, dengue, St. louis encephalitis, West Nile virus
togaviruses
- enveloped, + ssRNA, icosahedral
- rubella, eastern and western equine encephalitis
retroviruses
- enveloped, + ssRNA
- HTLV - T cell leukemia (icosahedral)
- HIV (complex and conical) - AIDS
coronaviruses
- enveloped, + ssRNA, helical capsid
- common cold and SARS
orthomyxoviruses
- enveloped, - ssRNA, helical capsid
- influenza
paramyxoviruses
- enveloped, - ssRNA, nonsegmented, helical capsid
- PaRaMyxovirus
- parainfluenza (croup), RSV (bronchiolitis) {{Rx - ribavarin}}, Measles, Mumps
- all contain surface F (fusion) protein, which causes resp epi cells to fuse –> multinucleated cells
- palivizumab prevents RSV pneumonia
Rhabdoviruses
- enveloped, -ssRNA, helical capsid
- rabies
filoviruses
- enveloped, - ssRNA, helical capsid
- ebola/marburg hemorrhagic fever - often fatal!
arenaviruses
- enveloped, -ssRNA circular (2 segments), helical capsid
- LCMV - lymphocytic choriomeningitis virus
- lassa fever encephalitis - spread by mice
bunyaviruses
- enveloped, -ssRNA circular (3 segments), helical capsid
- california encephalitis, sandlfy/Rift valley fevers, crimean-congo hemorrhagic fever, hantavirus - hemorrhagic fever, pneumonia
delta virus
- enveloped, - ssRNA circular, uncertain capsid
- HDV - “defective” without HBV coinfection
segmented viruses
BOAR
- bunyavirus, orthomyxoviruses, arenaviruses, reoviruses
rhinovirus
- picornavirus, nonenveloped RNA virus
- cause of the common cold
- acid labile - destroyed in stomach, does not infect the GI tract like the enteroviruses
yellow fever virus
- flavivirus/arbovirus transmitted by Aedes mosquito
- virus has monkey and human reservoir
- high fever, black vomit, jaundice
rotavirus
- segmented RNA virus, the most important cause of infantile gastroenteritis
- day care centers and kindergartens
- villous destruction with atrophy leads to dec absorption of Na and loss of K
influenza viruses
- orthomyxoviruses, enveloped -ssRNA with 9 segment genome
- contain hemagglutinin (promotes viral entry) and neuraminidase (promotes progeny release)
- anti-hemagglutining IgA and IgG mediate immunity
genetic shift/antigenic shifts
causes pandemics
- reassortment of viral genome, segments undergo high-freq recombination
- ex: flu and swine flu recombination
genetic drigt
causes epidemics
- minor changes based on random mutation
rubella
- togavirus
- fever, postauricular adenopathy, arthralgias, fine rash
- blueberry muffin baby
measles virus
- paramyxovirus
- Koplik spots and descending maculopapular rash
- possible sequelae: SSPE, encephalitis, and giant cell pneumonia
mumps
- paramyxovirus
- parotidis, orchitis, aseptic meningitis
- may cause sterility
rabies virus
bullet shaped virus
- Negri bodies commonly found in Purkinje cells (cerebellum, hippocampus)
- travels to the CNS via retrograde motion
- more commonly from bat, racoon and skunk in the US
HBV
DNA hepadnavirus
- parenteral, sexual and maternal-fetal transmission
- dsDNA –> + ssRNA –> dsDNA
- incorporates into host genome
- acute infection - “serum sickness”: malaise, fever, skin rash, pruritis, lymphadenopathy, joint pain
HCV
DNA flavivirus
- has no 3’-5’ proofreading, so many errors are made during replication and many subspecies can coexist in one person)
HDV
RNA delta virus
- parenteral, sexual and MFM transmission
- dependent on HBV
HEVv
- RNA hepevirus
- fecal-oral
- high mort in preggos
HBsAg
- noninfective envelope glyoprotein –> spheres/tubules 22nm in diameter
- indicative of active Hep B infection
3 structural genes of HIV
- env (gp120 for attachment and gp41 for fusion/entry)
- gag - capsid protein
- pol - reverse trascriptase
HIV diagnosis
ELISA is sensitive, Western Blot is specific
- AIDS if < 200 CD4, AIDS-defining condition or CD % < 14%
prion diseases
- conversion of a normal (usually alpha helical) protein to a B-pleated form, cannot be degraded by proteases
- sporadic (CJD), inherited (Gerstmann-Staussler-Scheinker) or acquired (kuru)
