Flashcards in FA - Micro - Virology Deck (246):
Viral genetics - Recombination?
Exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology.
Viral genetics - Reassortment?
When viruses with segmented genomes (e.g., influenza virus) exchange segments.
==> 2009 novel H1N1 influenza A pandemic ==> Complex reassortment of genes from HUMAN + SWINE + AVIAN viruses.
==> POTENTIAL FOR ANTIGENIC SHIFT.
Viral genetics - complementation?
When 1 OF 2 viruses that infect the cell has a mutation that results in a NON FUNCTIONAL PROTEIN.
==> The NON MUTATED virus "complements" the mutated one by making a functional protein that serves BOTH viruses.
Viral genetics - phenotypic mixing?
1. Occurs with SIMULTANEOUS infection of a cell with 2 VIRUSES.
2. Genome of virus A can be partially or completely coated (forming pseudovirion) with the surface proteins of virus B.
3. Type B protein coat determines the tropism (infectivity) of the hybrid virus.
4. The progeny from this infection have a type A coat that is encoded by its type A genetic material.
Live attenuated vaccines - mechanism?
Induce humoral AND cell-mediated immunity - have reverted to virulence on RARE occasions.
Killed/inactivate vaccines - mechanism?
Induce ONLY HUMORAL immunity but are stable.
Live attenuated vaccines - mention some?
2. Yellow fever
3. Chickenpox (VZV)
4. Sabin polio virus
6. Influenza (Intranasal)
Live attenuated vaccines - need a booster?
Killed vaccines - mention some?
2. Influenza (injected)
3. Salk Polio
4. HAV vaccines
Recombinant vaccines - 2 examples?
1. HBV (antigen= HBsAg)
2. HPV (types 6, 11, 16, 18).
All DNA viruses are ds, EXCEPT?
Parvo (Latin for small)
All DNA viruses are linear, EXCEPT?
All RNA viruses are ss, EXCEPT?
Reo (Repeato-virus ==> ds).
Positive-stranded RNA viruses?
Naked viral genome infectivity?
Purified nucleic acids of most dsDNA (EXCEPT pox and HBV) and +strand ssRNA --> INFECTIOUS.
NON infectious naked nucleic acids?
Naked nucleic acids of (-)strand ssRNA and dsRNA viruses are NOT infectious --> Require polymerases contained in the complete virion.
DNA viruses - viral replication?
ALL IN THE NUCLEUS (except POX).
RNA viruses - viral replication?
ALL in the CYTOPLASM - except INFLUENZA and RETRO.
Viral envelopes - Naked?
Generally, how do enveloped viruses acquire their envelopes?
From plasma membrane when they exit the from cell.
EXCEPT HERPESVIRUSES ==> Acquire envelopes from nuclear membrane.
General rule - ALL DNA viruses are?
1. HHAPPPPy --> Hepadna, Herpes, Adeno, Pox, Parvo, Polyoma, Papilloma.
3. LINEAR GENOMES
4. ICOSAHEDRAL --> except pox (complex)
5. NUCLEUS for replica --> except pox (carries OWN DNA-dependent RNA poly).
Herpesviruses - envelope?
Herpesviruses - DNA structure?
DS and linear.
HSV-1 - disease?
3. Herpes labialis.
4. Herpetic whitlow on finger.
5. Temporal lobe encephalitis.
HSV-2 - disease?
1. Herpes genitalis.
2. Neonatal herpes.
VZV (HHV-3) - disease?
VZV - vaccine?
EBV (HHV-4) - disease?
2. ENDEMIC Burkitt
4. Nasopharyngeal carcinoma.
CMV (HHV-5) - disease?
1. Mononucleosis (Monospot NEGATIVE) in IMMUNOCOMPETENT patients.
2. PNEUMONIA in transplant patients.
3. AIDS RETINITIS ("sightomegalovirus") ==> Hemorrhage + Cotton-wool exudates + Vision loss.
4. CONGENITAL CMV.
HHV-6 - disease?
Roseola - exanthem subitum ==> HIGH FEVER for several days that can cause SEIZURES, followed by diffuse macular rash.
HHV-7 - disease?
Less common cause of roseola.
HHV-8 - disease?
Kaposi ==> Neoplasm of ENDOTHELIAL cells.
1. In HIV/AIDS patients.
2. In transplant patients.
Hepadna - envelope?
Hepadna - DNA structure?
Partially ds and circular.
Hepadna - disease?
==> NOT A RETROVIRUS, BUT HAS REVERSE TRANSCRIPTASE.
HBV - vaccine?
Available - contains HBV surface antigen.
HBV - reverse transcriptase?
YES, even if it's not a retrovirus.
Adenovirus - envelope?
Adeno - DNA structure?
DS and linear.
Adeno - disease?
1. Febrile pharyngitis - sore throat.
2. Acute hemorrhagic cystitis.
4. Conjunctivitis - "pink eye".
Parvo - envelope?
Parvo - DNA structure?
ss and linear (-) --> smallest DNA virus.
Parvo - disease?
1. Aplastic crises in SCA.
2. "Slapped cheeks" in children - erythema infectiosum (5th disease).
3. RBC destruction in fetus --> hydrops fetalis and death.
4. PURE RED CELL APLASIA + RA-like symptoms in adults.
Polyomavirus - envelope?
Polyoma - DNA structure?
ds and circular.
Polyoma - name 2 viruses?
JC virus - disease?
Progressive multifocal leukoencephalopathy in HIV.
BK virus - disease?
Transplant patients, commonly targets KIDNEY. (BK for Bad Kidney).
Pox - envelope?
Pox - DNA structure?
DS and linear - largest DNA virus.
Pox - disease?
1. Smallpox - ERADICATED world wide by use of LIVE-ATTENUATED vaccine.
2. Cowpox ("milkmaid blisters")
3. MOLLUSCUM CONTAGIOSUM - Flesh-colored dome lesions with central umbilication.
HSV-1 - Diseases?
3. Temporal lobe encephalitis (MCC of sporadic encephalitis in the US)
4. Herpes labialis
5. Herpetic whitlow on finger.
HSV-1 - Latent where?
In the trigeminal ganglia.
HSV-1 - transmission?
1. Respiratory secretions
HSV-2 - disease?
1. Herpes genitalis
2. Neonatal herpes
==> Viral MENINGITIS is more common with HSV-2 than with HSV-1.
HSV-2 - Latent where?
In sacral ganglia.
HSV-2 - Transmission?
VZV - Diseases?
1. Varicella-zoster (chickenpox, shingles).
==> MC complication of shingles is POST-HERPETIC NEURALGIA.
VZV - Latent where?
Dorsal root or trigeminal ganglia.
VZV - MC complication?
Post herpetic neuralgia.
VZV - Transmission?
EBV - disease?
Mono - Features?
4. Lymphadenopathy --> especially POSTERIOR CERVICAL nodes.
EBV - transmission?
1. Respiratory secretions
EBV - Mechanism?
Infects B cells THROUGH CD21.
==> Atypical lymphocytes seen on peripheral blood smear infected B cells BUT rather REACTIVE CYTOTOXIC T CELLS.
EBV - Monospot?
Heterophile antibodies detected by agglutination of sheep or horse RBCs.
EBV - associations?
2. Endemic Burkitt
3. Nasopharyngeal carcinoma
CMV - Diseases?
1. Congenital infection
2. Mononucleosis (Monospot (-))
CMV - special feature?
Infected cells have characteristic "owl's eye" inclusions.
CMV - Latent where?
CMV - Transmission?
2. By transfusion
HHV-6 - disease?
ROSEOLA --> High fevers for several days that can cause seizures, followed by a diffuse macular rash.
1. Kaposi sarcoma - neoplasm of endothelial cells.
2. Dark/violaceous flat and nodular skin lesions representing endothelial growths.
3. Can ALSO affect GI/Lungs.
HHV-8 - target patients?
HHV-8 - transmission?
HSV - Identification?
1. Viral culture for skin/genitalia.
2. CSF PCR for herpes encephalitis.
3. Tzanck test (genital herpes) - a smear of an opened skin vesicle to detect multinucleated giant cells ==> COMMONLY SEEN IN HSV-1/HSV-2/VZV infections.
4. Infected cells also have intranuclear Cowdry A inclusions ==> HSV-1/2 + VZV.
Reo - envelope?
Reo - RNA structure?
Reo - Capsid symmetry?
Icosahedral - double.
Reo - Medical importance?
1. Coltivirus --> Colorado tick fever.
2. Rotavirus --> #1 cause of FATAL diarrhea in CHILDREN.
Pircorna - envelope?
Picorna - RNA structure?
Picorna - capsid symmetry?
Picorna - medical importance?
2. Echo --> ASEPTIC meningitis
3. Rhinovirus --> "common cold"
Picorna - Coxsackievirus?
1. ASEPTIC meningitis
2. Herpangina (mouth blisters, fever)
3. Hand, foot, and mouth disease
Hepevirus - Envelope?
Hepevirus - RNA structure?
Hepevirus - Capsid symmetry?
Hepevirus - Medical importance?
Calici - envelope?
Calici - RNA structure?
Calici - Capsid symmetry?
Calici - Medical importance?
Norovirus - Viral gastroenteritis.
Flavivirus - Envelope?
Flavi - RNA structure?
Flavivirus - capsid symmetry?
Flavivirus - Medical importance?
2. Yellow fever
4. St.Luis encephalitis
5. West Nile virus
==> ALL ARBO.
Toga - Envelope?
Toga - RNA structure?
Toga - Capsid symmetry?
Toga - Medical importance?
2. Eastern equine encephalitis = ARBO
3. Western equine encephalitis = ARBO.
Retroviruses - Envelope?
Retroviruses - RNA structures?
Retroviruses - Capsid symmetry?
Complex and conical (HIV)
Retroviruses - Medical importance?
1. Have reverse transcriptase
Corona - envelope?
Corona - RNA structure?
Corona - Capsid symmetry?
Corona - medical importance?
1. Coronavirus - "common cold".
3. MERS = Middle East Respiratory Syndrome.
Orthomyxo - envelope?
Orthomyxo - RNA structure?
SS(-) linear - 8 SEGMENTS.
Orthomyxo - Capsid symmetry?
Orthomyxo - Medical importance?
Paramyxo - Envelope?
Paramyxo - RNA structure?
SS(-) linear - NON SEGMENTED.
Paramyxo - Capsid symmetry?
Paramyxo - medical importance?
1. Parainfluenza - croup.
2. RSV - bronchiolitis in babies; Rx-Rivabirin.
3. Measles, Mumps
Rhabdo - envelope?
Rhabdo - RNA structure?
Rhabdo - capsid symmetry?
Rhabdo - medical importance?
Filo - envelope?
Filo - RNA structure?
Filo - capsid symmetry?
Filo - Medical importance?
Ebola/Marburg hemorrhagic fever --> often FATAL.
Arena - envelope?
Arena - RNA structure?
SS(+) OR SS(-) circular, 2 SEGMENTS.
Arena - Capsid symmetry?
Arena - Medical importance?
1. LCMV - Lymphocytic choriomeningitis virus.
2. Lassa fever encephalitis - spread by RODENTS.
Bunya - envelope?
Bunya - RNA structure?
SS(-) circular - 3 SEGMENTS.
Bunya - Capsid symmetry?
Bunya - medical importance?
1. California encephalitis = ARBO
2. Sandfly/Rift valley fevers = ARBO
3. Crimean-Congo hemorrhagic fever = ARBO
4. Hantavirus - hemorrhagic fever, pneumonia
1. California encephalitis
2. Sandfly/Rift valley fevers
3. Crimean-Congo hemorrhagic fever
Delta - envelope?
Delta - RNA structure?
Delta - Capsid symmetry?
Delta - Medical importance?
HDV is a "defective" virus that requires HBV to replicate.
Negative-stranded viruses - what must be done?
Must transcribe (-)strand to (+). Virion brings its own RNA-dependent RNA polymerase.
Negative-stranded viruses - Mention them.
ALL are RNA viruses:
Picorna - mention the viruses:
Picorna - Special features?
1. RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins.
2. Can cause aseptic (viral) meningitis (except rhinovirus and HAV).
3. ALL are ENTEROviruses (fecal-oral spread) except rhinovirus.
Rhinovirus - Serologic types?
Rhinovirus - acid labile?
YES ==> DOES NOT INFECT THE GI (unlike the other picornaviruses).
Yellow fever virus - what type of virus?
Flavivirus (also an Arbovirus).
Yellow fever virus - Transmission?
Yellow fever virus - reservoir?
Monkey or human.
Yellow fever virus - symptoms?
1. High fever
2. Black vomitus
Rotavirus - important feature?
Major cause of acute diarrhea in the US during winter - especially in day-care centers, kindergartens.
Rotavirus - pathogenic mechanism?
Villous destruction with atrophy leads to decrr. absorption of Na and loss of K.
Influenza virus - antigens?
1. Neuraminidase (promotes progeny virion release)
2. Hemagglutinin (promotes viral entry)
Influenza virus - 2 important features?
1. Risk for FATAL bacterial superinfection ==> S.aureus + S.pneumo + H.flu.
2. Rapid genetic changes.
Influenza virus - Reformulated vaccine (the flu shot)?
Containing viral strains most likely to appear during the flu season, due to virus' rapid genetic change.
Influenza virus - killed viral vaccine?
Most frequently used.
Influenza virus - live attenuated (temperature-sensitive mutant) vaccine?
Replicates in the nose BUT NOT IN THE LUNG ==> Administered intranasally.
Genetic shift/antigenic shifts?
Reassortment of viral genome segments undergo high-frequency recombination, such as when human flu A virus recombines with swine flu A virus.
Minor (antigenic drift) changes based on random mutation in hemagglutinin OR neuraminidase genes.
Rubella virus - what virus?
Another name for rubella?
German (3day) measles.
Rubella virus - disease features?
2. Post-auricular and other lymphadenopathy
4. Fine, confluent rash ==> Starts on face and spreads centrifugally to invovle trunk and extremities.
Mild disease in children but serious congenital disease (ToRCHeS).
Congenital rubella features?
Blueberry muffin appearance ==> DERMAL extramedullary hematopoiesis.
Seal-like barking cough.
Paramyxo (parainfluenza, mumps, measles, RSV) contain?
Fusion protein (F protein) --> Causes respiratory epithelial cells to fuse and form multinucleated cells.
Monoclonal antibody against F protein --> prevents pneumonia caused by RSV infection in premature infants.
Measles - Usual presentation:
1. Prodromal fever with COUGH + CORYZA + CONJUNCTIVITIS.
2. Then, Koplik spots on buccal mucosa.
3. Followed by 1-2 days later by maculopapular rash ==> Head towards toe.
Measles virus - Possible sequelae?
1. SSPE - subacute sclerosing panencephalitis, occurring YEARS later.
2. Encephalitis (1:2000).
3. Giant cell pneumonia (rarely, in immunosuppressed).
3C's of measles:
VitA used for what in malnourished children?
Can REDUCE MORTALITY + MORBIDITY from measles.
Rash of measles:
Discrete erythematous rash, presents late, and includes limbs (vs rubella) as it spreads downward.
Mumps virus - Diseases?
3. Aseptic meningitis
==> Can cause sterility especially AFTER puberty.
Rabies virus - characteristic shape?
Rabies virus - characteristic bodies?
Negri bodies (CYTOPLASMIC inclusions) --> Commonly found in Purkinje cells of cerebellum and in hippocampal neurons.
Rabies incubation period?
LONG - Weeks to months before symptom onset.
Rabies - Postexposure treatment?
Wound cleansing and vaccination +/- rabies immune globulin.
==> Example of PASSIVE-ACTIVE IMMUNITY.
Rabies - mechanism?
Travels to the CNS by migrating in a retrograde fashion up nerve axons ==> Binding to ACh RECEPTORS.
Rabies - Progression of disease?
Fever, malaise --> Agitation, photophobia, hydrophobia, hypersalivation --> Paralysis, coma --> Death.
Rabies - Transmission?
1. Bat bites
2. Raccoon bites
3. Skunk bites
than dog bites in US.
==> AEROSOL TRANSMISSION (eg bat caves) ALSO POSSIBLE.
HAV - Virus?
HAV - incubation?
Short - weeks.
HBV - Virus?
HBV - incubation?
LONG - months.
HCV - virus?
HDV - virus?
HDV - incubation?
Superinfection with HBV - Short.
Co-infection with HBV - Long.
HEV - virus?
Signs/symptoms of all hepatitis viruses:
1. Episodes of Fever
3. UP AST/ALT
Best test to detect active hep A?
Antibody to HBcAg:
IgM = acute/recent infection
IgG = prior exposure or chronic infection.
POSITIVE during window period.
A second different antigenic determinant in the HBV core.
--> Indicates active viral replication + HIGH TRANSMISSIBILITY.
Antibody to HBeAg - indicates low transmissibility.
Anti-HBc = IgM
Anti-HBc = IgM
Anti-HBc = IgG
Chronic HBV - High infectivity.
Chronic HBV - Low infectivity.
Anti-HBc = IgG
DIPLOID - 2 molecules of RNA.
HIV 3 structural genes?
Env, gag, pol
env protein formation?
Formed from cleavage of gp160 to form envelope glycoproteins.
Attachment to host CD4+ T cell.
Fusion and entry.
1. p24 CAPSID PROTEIN.
2. p17 MATRIX PROTEIN.
1. Reverse transcriptase
2. Aspartate protease
HIV binds which receptors on T cells?
HIV binds which receptors on macrophages?
Homozygous CCR5 mutation?
Heterozygous CCR5 mutation?
HIV diagnosis - which lab tests?
1. Presumptive diagnosis made with ELISA - sensitive, high false-positive rate and low threshold --> RULE OUT test.
2. (+) Results are then CONFIRMED with Western blot assay - specific, high false-negative rate and high threshold --> RULE IN test.
1. Under 2 hundred CD4/mm^3.
2. HIV (+) with AIDS-defining condition.
3. CD4 PERCENTAGE UNDER 14%.
ELISA/Western blot tests look for what?
1. Antibodies to viral proteins.
2. Often FALSE(-) in the first 2 MONTHS of HIV infection.
3. FALSE(+) initially in BABIES born to infected mothers --> Anti-gp120 crosses placenta.
Four stages of untreated infection:
1. Flu-like (acute)
2. Feeling fine (latent)
3. Falling count
4. Final crisis
Common diseases of HIV(+) - Systemic - Clinical presentation?
1. Low-grade fever
4. Tongue ulcer
Common diseases of HIV (+) - Systemic - Lab findings?
Oval yeast cells within macrophages, CD4<100cells/mm3.
Common diseases of HIV(+) - Systemic - Pathogen?
Histoplasma capsulatum (Causes only pulmonary symptoms in immunocompetent hosts).
Common diseases of HIV(+) - Dermatologic - Clinical presentation?
1. Fluffy white cottage-cheese lesions --> C.albicans
2. Hairy leukoplakia --> EBV.
3. Superficial vascular proliferation --> B.henselae
HIV (+) diseases - lab findings - Pseudohyphae, commonly oral if CD4<100?
C.albicans --> causes oral thrush and esophagitis.
HIV(+) diseases - findings - hairy leukoplakia often on LATERAL TONGUE?
Bartonella henselae causes?
HIV(+) disease - GI presentation?
Chronic, watery diarrhea - Cryptosporidium spp.
Cryptosporidium diarrhea - findings?
1. Acid-fast cysts seen in stool.
2. Especially when CD4<200cells/mm3.
HIV(+) diseases - T.gondii?
Abscesses --> many ring-enhancing lesions on imaging.
CD4 for T.gondii?
Directly associated with HIV - Must differentiate from other causes.
JC virus reactivation (cause of PML) --> Due to reactivation of latent virus.
Results in demyelination.
CD4 for JC reactivation?
C.neoformans meningitis in HIV(+) - Findings?
India ink stain reveals yeast with narrow-based budding and large capsule.
CD4 for C.neoformans?
HIV(+) CMV retinitis - findings?
Cotton-wool spots on fundoscopic exam and may also occur with esophagitis.
CD4 for CMV retinitis?
HIV(+) NHL (large cell type) ?
Often on oropharynx (Waldeyer ring) - May be associated with EBV.
HIV(+) primary CNS lymphoma?
1. Focal or multiple, differentiate from toxoplasmosis.
2. May be associated with EBV.
HPV - Often in anus (gays) or cervix.
HIV(+) superficial neoplastic proliferation of vasculature?
HHV-8 - Biopsy reveals LYMPHOCYTIC INFLAMMATION.
Do not confuse with bacillary angiomatosis caused by B.henselae (neutrophils).
HIV(+) interstitial pneumonia CMV?
Biopsy reveals cells with intranuclear (owl eye) inclusion bodies.
Invasive aspergillosis - HIV(+)?
Aspergillus fumigatus - Pleuritic pain, hemoptysis, infiltrates on imaging.
1. Especially when CD4<200.
2. Ground-glass appearance on imaging.
Pneumonia in HIV(+)?
1. Generally when CD4>200.
TB-like disease in HIV(+)?
1. Especially with CD4<50.
2. M.avium-intracellulare - also known as MAC.
Prion diseases - etiology?
Conversion of a normal (predominantly alpha-helical) protein termed prion protein (PrPc) to a β-pleated form (PrPsc), which is transmissible:
1. CNS-related tissue --> Iatrogenic CJD
2. Food contaminated by BSE-infected animal products (variant CJD)
PrPsc does what?
Resists PROTEASE DEGRADATION and facilitates the conversion of still more PrPc to PrPsc.
Accumulation of PrPsc results in what?
1. Spongiform encephalopathy