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51 Cards in this Set

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How RNA viruses differ from DNA viruses.
1. 3x more prevalent.
2. Tremendous genetic variability b/c no proof-reading or editing function.
3. Small genomes to limit error rate.
4. Short replication cycles.
+RNA undergo genetic ______ while -RNA undergo genetic ________.
genetic recombination
genetic reassorment.
5 strategies used by RNA viruses to overcome the lack of space for genetic info.
1. Overlapping genes.
2. Read-thru (override termination codon & develop fusion protein).
3. Frame shift (ribosome stalls & then shifts to different frame)
4. Slicing
5. Polyprotein
4 characteristics of +RNA viruses.
1. Mostly nonsegmented.
2. Genome serves as mRNA.
3. Codes for polyproteins.
4. Genetic recombination.
Name 5 +RNA viruses and indicate whether naked or enveloped.
1. Picornaviridae (naked)
2. Caliciviridae (naked)
3. Togaviridae (Enveloped)
4. Flaviviradae (Enveloped)
5. Coronaviridae (Enveloped)
Name 6 -RNA viruses and indicate whether enveloped or naked.
All -RNA viruses are naked.
1. Filo
2. Rhabdo
3. Bunya
4. Orthomyxo
5. Paramyxo
6. Arena
5 Char of -RNA viruses.
1. Enveloped.
2. Either single or segmented genome.
3. Carry RNA dependent RNA polymerase with them.
4. NEVER makes polyproteins.
5. Genetic reassortment.
Name 4 viruses of the Picornaviradae family.
1. Enteroviruses.
2. Rhinoviruses.
3. Hepatoviruses.
4. Parechoviruses.
6 diseases caused by enteroviruses.
1. poliomyelitis.
2. aseptic meningitis
3. myocarditis
4. Juvenile onset diabetes.
5. Hand-Foot-Mouth disease
6. Hemorhhagic conjunctivitis.
Name 2 responses of CNS to viral infection.
1. ^ lymphocytes & monocytes
2. ^ proteins, but CSF remains clear.
Char. of poliovirus.
Family: Picornaviradae; Species: Enterovirus.
Destroys motor neurons (flaccid paralysis).
Oral-fecal route.
1:1000 enter CNS; others are asymptomatic.
Virus grows in gut.
Summer peak of infections.
2 types of viruses for polio.
1. Salk inactivated. Used in US.
2. Sabin attenuated life(oral). Used globally. Some healthy pts will get polio and some IMC will get PV dissemination.
Also, oral form assoc with highly neuroviulent emergent strains.
How does influenza differ from other RNA viruses?
Influenza goes to the nucleus for transcription/translation.
Name 2 viruses of the Togaviridae family.
1. Rubella
2. Alpha virus (E & W encephalitis)
Char. of Rubella.
Togaviridae
+RNA
Enveloped
Trans: respiratory
Severe birth defects if infection during early pregnancy.
6 members of Flaviviradae family.
1. Tick-borne encephalitis.
2. St. Louis Encephalitis.
3. West File virus.
4. Yellow Fever
5. Dengue
6. Hepatitis C
Char of Yellow fever.
1. Member of Flaviviradae family.
2. vector = aedes agypti mosquito; hu-hu in epidemic.
3. Major target is liver.
4. Can cause hemorrhaging fever, nausea, vomiting, abrupt chills, hig fever.
5. 20-50% fatility in serious infections.
6. Vaccine.
Char of Dengue Fever.
1. Member of Flaviviridae.
2. Mostly asia/south america.
3. Ranges from asymptomatic to dengue fever to dengue hemorraghic fever.
4. Transmitted by A. aegypti.
5. Dengue Type II causes minor headache. With subsequent infection with Type I, pt may die.
4 Viruses that cause hepatitis.
1. Hep A-E and G.
2. Yellow fever.
3. Epstein Barr.
4. CMV.
Disease caused by Coronaviridae.
SARS.
List 5 viruses found in the Paramyxoviridae.
1. Parainfluenza.
2. Mumps.
3. Measles
4. Respiratory syncytial virus.
5. Human Metapneumovirus (Netherlands)
Name 2 viruses in the Rhabdoviridae family.
1. Rabies
2. VSV
Name 2 viruses in the Filoviridae family.
1. Ebola
2. Marburg
Name 1 virus in the Orthomyxoviridae family.
Influenza.
Name 1 virus in Bunyaviridae family.
Hanta.
Name 1 virus in the Arenaviridae family.
Lassa Fever.
Char of measles.
Family Paramyxoviridae.
Infection occurs in resp. tract; replication in lymphoid tissue. 1 viremia disseminates virus. Replication in reticuloendothelial system. 2 viremia spread to surfaces of body.
Human is only reservoir.
Spread by direct contact.
Immune suppresion leads to secondary infection.
Subacute Sclerosing Panencephalitis: rare, but lethal; occurs in 1:1000.
Char of mumps.
Family Paramyxoviridae.
Trans: respiratory route.
Infectious pd: 3 days before to 9 days after symptom onset
Incubation: 16-18 days
Symp: fever, headache, muscle aches, fatigue, anorexia, swelling of parotid salivary glands.
Char. of Respiratory Syncytial Virus.
Family Paramyxoviridae.
Leading cause of pneumonia in infants worldwide.
Infection begins in URT; spreads to LRT in 1/3 of primary infections.
Incomplete immunity after infection.
Very serious in IMC.
Char. of Rabies virus.
Family Rhabdoviridae.
Replication in muscle; entrance into CNS at NMJ. Retrograde axonal transport.
Incubation pd: 30-80 days.
Post-exposure vaccine possible.
Why does influenza go to the nucleus/
mRNAs are spliced in the nucleus to different reading frames.
Does + or -RNA viruses make polyproteins?
+ (mono) poly
- (segmented) NEVER polys
Describe pathophysiology of influenza.
Enter respiratory tract via aerosols ..Infection of superficial cells of U/L RT...Viral replication...Cell Death...Local symptoms due to cell death/inflammatory response.
INcubation period for influenza.
1-4 days, but viral shedding begins 1 day before symptom onset.
Influenza symptoms:
Abrupt onset fever, chills, headache, myalgia, arthralgia dry cough, sore throat, rhinitis, weakness. Kids may have diarrhea/vomiting.
4 possible complications of influenza.
1. otitis media
2. Primary influenza pneumonia.
3. Secondary bacterial pneumonia.
4. Reye's syndrome.
Why can viral influenza predispose to secondary bacterial pneumonia?
1. Enhanced bacterial adherence due to exposure of BM & cryptic receptors.
2. ^ mucinous secretions, edema, fibrin obstruct small airways & provide favorable conditions for bacterial growth in lungs.
3. Decreased ciliary function.
4. Induction of apoptosis in alveolar macrophages.
What is antigenic shift?
Cell is dually infected with a hu-adapted virus and a non-human adapted subtype. Because influenza is a segmented genome, it can reassort so that novel viruses are produced.
Describe reservoirs for influenza.
Aquatic birds are natural hosts for Type A flu. Virus replicates in respiratory & GI tracts. passed to domestic birds where it is pathogen. Then to swine (antigenic shift) to humans.
Why can influenza rarely be transmitted from bird directly to human?
Receptor speciificity.
Avian siayl-galactosyl residues with alpha 2,3 linkage.
Human have 2,6 linkage.
Swine has both types in about equal numbers.
What is antigenic drift?
gradual accumulation of mutations. In influenza, it may allow hemagglutinin to escape neutralizing Ab. Epidemic strains involve changes in 3 or more of the 5 antigenic determinates.
Describe the role of hemaglutinnin and neuraminidase molecules in the biolog of influenza.
These are envelope proteins.
Hemaglutinnin - attachment & penetration of envelope w/cell membrane. Require proteolytic activation. Binds to sialic acid.

Neuraminidase - cleaves sialic acid to release progeny from injected cells. No sialic acid on infected cell, so virus binds to neighboring cells.
Describe key structural components of influenza virus.
ss -RNA segmented virus
2 envelope proteins: 1. Hemagglutinin (attachment/penetration) and 2. Neuraminidase (progeny release from infected cell)
Other proteins
1. M2 (passive ion channel that allows H+ into virus; functions in uncoating/maturation)
2. M1 - matrix protein (assembly)
3. NEP - nuclear export protein.
4.Nucleoprotein (NP) - determines type-speciric antigen.
5. Polymerase proteins (PA1,PB2,PB1)-pre-made for transcription/translation.
How did SARS b/c adapted to humans?
Receptor is ACE2.A 4 aa difference in the binding domain of the spike glycoprotein b/w palm civet & human caused >1000 increase in binding affinity for human ACE2.
Symptoms of SARS.
Fever, malaise, lymphopenia, thrombocytopenia, subpleural consolidation.
What does amantadine block in the influenza virus?
Amantadine
Why does influenza replicate in the nucleus?
It requires nuclear functions for replication.
How does the influenza virus inhibit host protein synthesis?
Makes NS1 protein which blocks PKR activation. PKR normally phosphor. eIF-2alpha.
What does PB1-F2 protein viral protein do?
Sensitizes cells to TNF-alpha-induced apoptosis, especially monocytes.
What vaccines are available for influenza?
1. Whole inactivated virus vaccine grown in embryonated eggs(70-90% effective, except in those >65, then 30-70%)
2. Live, attenuated (mutations with PB1, PB2, NP genes; less effective)
INfluenza chemoprophylaxis agents.
Amantadine & rimantadine: effective against type A; blocks M2 ion channel.
70-90% effective in reducing severity & duration. Only amantadine can be used in children.

Zanamivir & oseltamivir (neuramidase inhibitors; acts on both type Aand B)