SketchyMicro: Viruses Flashcards
Piconavirus: 3 main features
Piconaviruses:
- positive sense: meaning the RNA is directly translated into proteins
- RNA virus
- naked
3 main subgroups of piconaviruses
Piconaviruses: positive sense RNA viruses w/o capsules (naked)
ABC
- A for Hepatitis A
- B for birds = Enterovirus
- C for common cold = Rhinovirus
Main manifestation of the three classes of piconoviruses
(a) Hep A
(b) Enterovirus
(c) Rhinovirus
(a) Hep A => anicteric acute febrile self limited
(b) Enterovirus = MC cause of aspetic (aka nothing grows on gram stain b/c there’s no bacteria) meningitis
(c) Rhinovirus => common cold
MC cause of aspetic meningitis
Aspetic meningitis = viral meningities, MC cause = enterococcus species = poliovirus, coxsackie A and B, echovirus
Called aseptic b/c the gram stain doesn’t grow anything (b/c it’s viral not bacterial)
Where does the polio virus replicated?
(a) Duration of latency period
Polio virus replicated in Peyers patches of the GI tract
(a) Remains latent for about 2-3 weeks, then infects anterior horn cells of the spinal cord
Differentiate the 2 vaccines for poliomyelitis
- Salk = inactivated, killed vaccine given intramuscularly
- IM so bypass Peyer’s patches => mostly IgG not IgA - Sabin = oral live attenuated vaccine- gives both IgA and IgG but can shed in feces and revert to infectious strain
- rare but this is why we don’t use it in the US (we use Salk)
Where does the poliovirus infect to cause symptoms?
(a) Clinical presentation
(b) Cause of death
Poliovirus infects the anterior horn cells of the spinal cord
(a) Ascending asymmetric paralysis
(b) Paralysis rises to diaphragm => respiratory insufficiency
Compare and contrast coxsackie A and B viruses
Both coxsackie viruses are enteroviruses, which are picornaviruses = positive sense RNA naked viruses
A => hand-foot-mouth disease, red vesicular rash, and aseptic meningitis (like the other enteroviruses)
B => dilated cardiomyopathy and Devil’s grip
Name 3 rashes that involve the hands and feet
- Hand-foot-mouth disease = Cocksackie A
- Syphilis
- Rickettsia Ricketsia
Buzzwords
(a) Devil’s grip
(b) Child immigrant p/w descending rash and lymphadenopathy
(a) Cocksackie B caused syndrome of severe unilateral CP that makes it hard to breathe
(b) Rubella = German measles
Which of the picornaviruses is acid labile?
3 subgroups of picornaviruses = ABC
- A: Hepatitis A
- B: Birds = Enterococcus
- C: Common cold = rhinovirus
Rhinovirus is the only acid labile one of the three => can’t survive gastric acid => not fecal/oral transmitted, instead by fomites and respiratory droplets
While Hep A and enterococcus are acid stable => transmitted fecal/oral
What group of virus causes
(a) Rhinovirus
(b) Cruise ship diarrhea
(c) Dengue fever
Viral group
(a) Rhinovirus = picornavirus- positive sense RNA naked virus
(b) Cruise ship diarrhea = Norwalk virus = Calicivirus = ssRNA naked positive sense
(c) Dengue fever = flavivirus
What group of viruses causes
(a) Yellow fever
(b) Rubella
(c) Hepatitis A
Viral group
(a) Yellow fever = flavivirus
(b) Rubella (German measles) = togavirus
(c) Hepatitis A = picornavirus
What group of viruses causes
(a) West Nile Virus
(b) SARS
Viral group
(a) West nile = Flavivirus
(b) SARS = coronavirus
Explain why rhinovirus infects the location it does
Rhinovirus prefers cooler temps (33 C) as in colder than body temp, so likes the upper respiratory tract where air comes in and is colder
Why don’t we have a vaccine for the
(a) Common cold
(b) Hepatitis C
(a) Ummm b/c there’s literally 113 serotypes of rhinovirus- can’t cover for all of them
(b) Hep C envelop proteins have a ton of antigen variability b/c their virion encoded RNA polymerase lacks 3’ to 5’ exonuclease proofreading activity
MC mode of transmission of Hepatitis A
(a) Underdeveloped countries
(b) US
Hepatitis A
(a) Contaminated water in underdeveloped countries
(b) US- uncooked shellfish
Smoker suddenly develops aversion to smoking
Buzzword for Hepatitis A infection
Describe the clinical presentation of Hepatitis A
(a) Duration
Usually asymptomatic (esp in children), but can be acute febrile illness w/ RUQ pain and jaundice (jaundice esp in adults)
Lasts about 1 mo without a chronic state! No carrier/chronic state
Who gets the Hep A vaccine?
MSM, travel to endemic area, other chronic liver disease
Viral group
(a) Hepatitis A
(b) Hepatitis C
Viral group
a) Hepatitis A = picornavirus
(b) Hepatitis C = flavivirus (also Dengue, West Nile, Yellow fever
Break bone fever
Break bone fever = Dengue fever, infects bone marrow and can cause thrombocytopenia
Which flavivirus has a vaccine?
Live attenuated vaccine available for yellow fever
-not Dengue or West Nile Virus
Differentiate clinical presentation of Dengue vs. Yellow fever
Dengue fever- break bone fever (infects bone marrow) => thrombocytopenia, hemorrhagic fever, high risk renal failure
Yellow fever- jaundice, back ache, bloody diarrhea
Both by the same species of mosquito
Major complication of West Nile Virus
Meningitis!
Can also cause flaccid paralysis, seizure, coma
More likely to become chronic- hep B or C?
Hep C- like 60-80% become chronic
‘C for chronic’
For Hep B chronicity depends on age of primary infection- 90% chronic in infected as infant, while only 5-10% adult cases become chronic
Hepatitis C
(a) Acute presentation
(b) When does anti-HCV develop
(c) Chronic risk
Hep C = Flavivirus (positive sense, enveloped RNA virus)
(a) Acutely w/ jaundice, can have RUQ pain and elevated LFTs (ALT drops w/in 6 mo), then 60-80% progress to chronic
(b) anti-HCV develops after 2-3 months
(c) Chronic risk = cirrhosis and HCC
Chronic Hep C infection
(a) Histologically
(b) Serum finding
Chronic Hep C (develops in 60-80% of primary infections)
(a) See tons of lymphocytes in the portal tracts
(b) Serologically: Hep C RNA remains positive after 6 months
- also cryoglobulins = IgM that precipitate in cold temps (extremities)
What is cryoglobulinemia?
(a) Differentiate from cold agglutinin
Cryoglobulinemia = blood contains a lot of cryoglobulins = proteins (usually IgM against Fc of IgG) that precipitate at colder temps
(a) While cold agglutinins are precipitates of RBCs (not IgM)
Name 3 classes of disease commonly associated w/ cryoglobulinemia
Cryoglobulinemia = blood contains high concentration of cryoglubulins that precipitate at cold temps, usually IgM
- Multiple myeloma (makes sense b/c it’s a cancer of IgM producing cells)
- Hepatitis C
- AI d/o: RA, SLE
General overview of tx for Hep C
Hep C tx: need to genotype to determine exact regimen, but overall protease inhibitors, previously used ribavarin and interferon alpha
Classic clinical presentation of the most common togavirus
MC togavirus = Rubella = German measles
Classic presentation = immigrant child (aka not vaccinated) w/ descending rash (macpap rash beginning on face) and cervical and postauricular lymphadnopathy
Name the TORCHeS infections
TORCHeS infections = ones that cross the placenta and cause disease in newborn
Toxoplasma gondii Rubella CMV HIV, HSV Syphilis
Also includes Varicella, Parvovirus
Classic triad of congenital rubella
Congenital rubella = congenital blindness (cataracts), sensorineural deafness, patent ductus arteriosis
Also: ID, microcephaly, purpuric blueberry muffin rash
2 contraindications to the MMR vaccine
- Pregnancy
2. HIV w/ CD4 under 200, safe if over 200
Where in the cell do the picornaviruses replicated?
All RNA viruses, esp positive strand that just directly translate into proteins, replicate in the cytoplasm (not the nucleus!)
Classify the HIV virus
(a) Type of genetic material
(b) Diploid
(c) How makes proteins
HIV virus
(a) Technically positive sense RNA virus, but not directly translated into proteins
(b) Diploid b/c two molecules of viral RNA in each virion
(c) positive sense RNA reverse transcriptase into cDNA which is then incorporated into host genomes then made into proteins
Fxn of these 3 key HIV genes
(a) Gag
(b) Env
(c) Pol
HIV genes
(a) Gag codes for p24 protein = capsule for RNA strands
(b) Env codes for glycoproteins 41 (transmembrane protein) and 120 (outer protein)
(c) Pol codes for the reverse transcriptase
Describe the clinical features of the HIV prodrome stage
(a) Latent period?
HIV prodrome: flu or mono-like symptoms w/ cervical lymphadnopathy/fever 2/2 infection of first macrophages then CD4
(a) Latent period of virus replicating in the lymph nodes can last for up to 10 years
HIV increases risk for which malignancy?
HIV increases risk for large diffuse B cell lymphoma (MC type of Non-Hodgkin Lymphoma)
Name the two receptor proteins on CD4 cells used by HIV for access
CD4 cell receptor proteins that HIV binds to for access
Early in disease- CCR5 (hence CCR5 receptor inhibitors used as anti-HIV drug)
Later in disease- CXCR4
Differentiate how to diagnose HIV in adult vs. newborn
In adults: first ELISA to look for HIV Ab, if positive then confirm w/ Western blot
In newborn: will automatically have IgG of mother so ELISA is useless => dx w/ NAT (nucleic acid amplification testing) to look directly for the virus
Which HIV drug is used in pregnant F to prevent vertical transmission?
Zidovudine = NRTI (nucleotide reverse transcriptase inhibitor) aka nucleotide analog
Mechanism of
(a) Maraviroc
(b) Zidovudine
Mechanism
(a) Maraviroc = CCR5 receptor inhibitor
- inhibits the receptor used by HIV to infect CD4 cells
(b) Zidovudine = NRTI = nucleotide reverse transcriptase inhibitor = nucleotide analog
Name some negative sense RNA viruses
Negative sense RNA viruses
- Orthomyxovirus: influenza
- Paramyxovirus: Measles (rubeola), mumps, parainfluenza (croup)
- rhabdovirus: rabies
- filovirus: ebola
- Bunyavirus, arenavirus, reovirus
Name some positive sense RNA viruses
Positive sense RNA viruses
- Picornavirus: hep A, enterococcus, rhinovirus
- Flavivirus: hep C, West Nile, Dengue fever
- Togavirus: Rubella
- HIV/AIDS
Negative sense RNA viruses
(a) How many strands?
(b) Location of replication?
(c) Necessary for replication
Negative sense RNA viruses
(a) All are single stranded except reovirus (ds)
(b) All replicate inside the cytoplasm except orthomyxovirus
(c) Since negative sense they can’t be made directly into proteins => bring their own RNA polymerase
Name the 4 negative sense RNA viruses that form segments
‘BOAR’ mnemonic for segmented viruses- all of which are negative RNA viruses
Bunyavirus: 3 circular segments
Arenavirus: 2 segments
Orthomyxovirus (influenza): 8 segments
Reovirus: 11 segments
Differentiate antigenic drift and antigenic shift
Antigenic drift = point mutation that causes epidemics
ex: seasonal flu
Antigenic shift = gene reassortment (possible in ‘BOAR’ segmented viruses), much more dangerous, causes pandemics
ex: H1N1 swine flu
Mechanism of hemagluttinin
Hemagluttinin is a glycoprotein on viral membranes that bind salic acid reside on host cell membranes in upper respiratory tract and RBC
-called hemagluttinin b/c agglutinates BRC in vitro
So the strain of hemagluttinin determines which cells the virus can infect
-so H1, H2, and H3 are the strains that infect humans
What protein determines which organisms are infected by which influenza strains?
Hemagluttinin protein defines the tropism- hemagluttinin is the viral membrane glycoprotein that binds host membrane
Ex: H1, H2, H3 are the strains that can infect humans
Mechanism of M2 protein
M2 protein of influenza responsible for creating pH needed for viral encoding
Name the three virulence factors of influenza virus
3 virulence factors of influenza A
- Hemagluttinin- allows binding to host cell
- M2 protein- creates pH for viral encoding
- Neuraminidase- release of new virions out of host nucleus
Mechanism of the following against influenza virus
(a) Amantadine
(b) Oseltamivir
(a) Amantadine (but not used b/c of resistance) inhibits M2 protein that codes for the ion channel needed to make the right pH for viral replication
(b) Oseltamivir = inhibits neuraminiase (protein that cleaves sialic acid to release new virions from the nucleus), taken early (w/in 72 hrs) or else not helpful b/c virions already released
3 complications of influenza
(a) Pulm
(b) Aspirin
(c) Neurologic
Complications of influenza
(a) Pneumonia super infection, often staph aureus
(b) Give aspirin to a kid w/ influenza = risk of Reye syndrome = liver failure and encephalitis
(c) Can precipitate Guillain-Barre: ascending paralysis, albuminocytologic dissociation of CSF
4 syndromes caused by paramyxovirus
Paramyxovirus = negative sense ssRNA viruses, enveloped
- Measles (rubella): cough, coryza, conjunctivitis, Koplik spots, fever, rash starting on face
- Mumps- parotitis b/l, possible orchitis and meningitis
- RSV- bronchitis and pneumonia in infants
- Parainfluenza- croup/laryngotracheobronchtiis = seal like cough w/ inspiratory stridor
Prodrome syndrome of Rubeola
Rubeola = Measles = paramyxovirus = -sense ssRNA virus
4 Cs: cough, coryza (runny nose), conjunctivitis, Koplik spots
and fever
