Lecture 2 Nonenveloped Viruses Flashcards
Describe the phylogeny of picornaviruses
See image
Consequences of genome type (RNA vs DNA) on:
mutation rate?
host range?
DNA virus have a more stable genome b/c DNA pol has proofreading activity
RNA viruses have much higher mutation rate; allows a great host range (i.e. they cross species barriers more easily); makes vaccines harder
What is an IRES and why does it matter?
IRES = internal ribosome entry site; allows for viral translation in the middle of mRNAs (Cap-independent translation of genes); allows the virus to shut off Cap-dependent translation of normal prots while ensuring its own will be translated
Why don’t rhinoviruses infect your gut?
labile at pH and also prefer cooler climes of the nasopharynx
Enterovirus 70
hemorrhagic conjunctivitis
Enterovirus 71
can cause HFMDz and CNS problems
Enterovirus 72
72 = Hep A
Common Cold (most common cause)
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = Picornaviridae; Genus = Enterovirus; Species = Human rhinovirus
Epidem = worldwide; worse in fall/winter; most common cause of infection in humans
Pathogen w/ s/sx = spread via aerosol AND indirectly via contaminated surfaces; prefer lower temps of nasopharynx; causes common cold (sneezing, nasal discharge, sore throat, cough, headache, maybe chills but few systemic sx), lasts 1 week; does NOT grow in low pH (i.e. highly labile at low pH)
Dx = clinically, but could technically dx from cell culture
Vaccines? = no, too many serotypes (>100)
Tx = not really, supportive/sx mgmt
Poliomyelitis
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = Picornaviridae; Genus = Eneterovirus; Species =
Epidem = eradicated from W hemisphere; still 1000-2000 cases/yr in: Afghanistan, India, Nigeria and Pakistan; epidemics used to occur in summer/fall; was assoc’d w/ development: both incr conc of poop + maybe hygiene hypothesis?
Pathogen w/ s/sx = fecal-oral route; 10-14 day incubation; only 1% develop sx
Four grades: 1) asymptomatic infection; 2) abortive (short course w/ h/a sore thr, n/v), 3) non-paralytic p-m (aseptic meningitis), 4) paralytic p-m
oropharynyx/small bowel—>bloodstream—>CNS (also retrograde axonal trans) perferring motor neurons in ant. horn of spinal cord + brain stem—>neuronal death —>paralysis (resp paralysis if also brain stem = “bulbar poliomyelitis”)
Dx = isolation (throat, stool, CSF)—>CPE—>specific anitsera; OR elev. Ab titer
Vaccines? = Salk (“IPV,” killed, given IM); Sabin (“OPV,” live-atten. given PO)
Tx = sx mgmt; resp. support; PT after
Coxsackie Viruses
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = Picornaviridae; Genus = Enterovirus
Epidem = daycare (b/c F-to-O and stable in environment)
Pathogen w/ s/sx = F-to-O
TYPE A: Skim/Muc-Memb tropic
Herpangina (fev, sore thr, pharyngeal lesions); Hand, foot and mouth dz; Asep meningitis; Paralytic disease (rare)
TYPE B: Viscerotropic
pleurodynia (unilateral intercostal pain; possible orchitis); myocarditis; aseptic menin; paralytic dz (rare); possibly: Type I DM, chronic fatigue?
Dx = isol/culture, elev [Ab] or PCR of CSF
Vaccines? = None
Tx = None
ECHO VIRUSES
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = picornaviridae; Genus = enteroviruses; Species = Enteric Cytopathic Human Orphan viruses
Epidem = worldwide; daycare, again b/c non-env and therefore stable in the environment
Pathogen w/ s/sx = F-to-O trans; leading cause of aseptic meningitis; broad spec of dzs e.g. multiple rashes
Dx = isolation/cuture; sero tests not useful b/c >32 serotypes to date (of 67 total in enterovirus genus!)
No vaccine; no tx
Other Enteroviruses
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = Picornavirus; Genus = Enteroviruses
Epidem = ?
Pathogen w/ s/sx =
EV 70 —> acute hemorrhagic (of bulbar) conjuctivitis
EV 71 —> H,F&M dz; leading cause of viral CNS dzs
EV 72 —> HAV
Dx = ?
No vaccines/tx
Rotaviruses
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = Reoviridae; Genus = Rotavirus
Epidem = Endemic worldwide; peaks in winter; most deaths in poorer countries; children
Pathogen w/ s/sx = F-to-O trans; 2-day inc then gastroenteritis (n/v + diarrhea); dehydration —> death
Dx = usually clinical; radioimmunoassay or ELISA from stool sample
Vaccines? = yes, two orals now: Rotarix is live monovalent for more common U.S. serotype; Rotateq reassortment of surface Ags from 5 human serotypes on a live bovine strain
Tx = No antiviral; WASH YO HANDS
Norwalk virus
Family = ?; Genus = ?
Epidem = ?
Pathogen w/ s/sx = ?
Dx = ?
Vaccines? = ?
Tx = ?
Family = Calciviridae; Genus = Norovirus
Epidem = cruise ships/nursing homes/camps, highly contagious; easily spread via food esp shell fish/salads
Pathogen w/ s/sx = F-to-O trans; gastroenteritis; incr susceptibility if O blood type
Dx = usu. clinical; PCR of stool available for Public health measures
Vaccines? = in development
Tx = none; hygiene, rehydration-
Picornavirus
Nucleic acid set-up?
Virion structure?
How does it multiply?
Examples?
(+)ssRNA
naked nucleocapsid (therefore icosohedral)
REPLICATION:
- Enters cell; rep occurs in cytosol
- Its +sense ssRNA genome serves as mRNA—> expressed as one big polypeptide
- cleaved forming viral prots + RNA-dep RNA pol
- RNA pol forms -sense RNA template which is then used to make more viral genomes
- assemble and make crystals in the cytosol
EXAMPLES: polio, coxsackie, ECHO, rhion, HAV
