Virology--structures, genetics, vaccines, viral genomes, viral replication, viral envelopes

Question 1

name the structures of a naked virus with a icosahedral capsule

Answer 1

• capsid
• nucleic acid

Question 2

name the structures of a enveloped virus with icosahedral capsid

Answer 2

• surface protein
• lipid bilayer
• capsid
• nucleic acid

Question 3

name the structures of an enveloped virus with helical capsid

Answer 3

• surface protein
• lipid bilayer
• hilical nucleocapsid with integrated RNA

Question 4

explain recombination

Answer 4

• exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology

Question 5

explain reassortment

Answer 5

• when viruses with segmented genomes (ie. influenza virus) exchange genetic material
  
  • example: novel H1N1 influenza A pandemic emerged via complex viral reassortment of genes from human, swine, and avian viruses
  • has potential to cause antigenic shift

Question 6

explain complementation

Answer 6

• 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
  
  • example: hepatitis D virus requires the presence of replicating hepatitis B virus to supply HBsAg, the envelope protein for HDV

Question 7

explain phenotypic mixing

Answer 7

• occurs with simultaneous infection of a cell with 2 viruses
• genome of virus A can be partially or completely coated (forming pseudovirion) with the surface proteins of virus B
• type B protein coat determines the tropism (infectivity) of the hybrid virus
• however, the progeny from this infection have a type A coat that is encoded by its type A genetic material

Question 8

live attenuated vaccines–mechanism

Answer 8

• induce humoral and cell mediated immunitybut have reverted to virulence on rare occasions
• no booster needed for live attenuated virus

Question 9

which vaccines are LIVE attenuated vaccines?

Answer 9

• smallpx
• yellow fever
• rotavirus
• chickenpox (VZV)
• Sabin polio virus
• Influenza (intranasal)
  
  • “Live! One night only! See small yellow rotating chickens get vaccinated with SabinandMMR!It’sincredible!”

Question 10

live vaccines and immunocompromised patients

Answer 10

• dangerous to give live vaccines to immunocompromised patients
  
  • close contacts may be vaccinated with live vaccines (except live polio or influenza)

Question 11

MMR vaccine

Answer 11

• measles, mumps, rubella
• live attenuated vaccine that can be given to HIV + patients who do not show signs of immunodeficiency

Question 12

killed vaccines–mechanism

Answer 12

• killed/inactivated vaccines induce only humoral immunity but are stable

Question 13

which vaccines are Killed vaccines?

Answer 13

• Rabies
• Influenza (injected)
• Salk Polio
• HAV
  
  • “SalK = Killed”
  • “RIP Always”

Question 14

which vaccines are subunit vaccines?

Answer 14

• HBV (antigen = HBsAg)
• HPV (types 6, 11, 16, and 18)

Question 15

which DNA viruses are double stranded?

Answer 15

• all DNA viruses are double stranded
  
  • EXCEPT Parvoviridae
    
    • “all are dsDNA (like our cells), except “part-of-a-virus” (parvovirus) is ssDNA”

Question 16

which DNA viruses are linear?

Answer 16

• all are linear except papilloma-, polyoma-, and hepadnaviruses (circular)

Question 17

which RNA viruses are single stranded?

which RNA viruses are + stranded?

Answer 17

• all RNA viruses except Reoviridae are ssRNA
• • stranded RNA viruses:
    
    • “I went to a retro (retrovirus) toga (togavirus) party, where I drank flavored (flavivirus) Corona (coronavirus) and ate hippie (hepevirus) California (calicivirus) pickles (picornavirus).”
      
      • retrovirus
      • togavirus
      • flavivirus
      • coronavirus
      • hepevirus
      • calicivirus

Question 18

naked viral genome infectivity

Answer 18

• purified nucleic acids of most dsDNA (except poxviruses and HBV) and + strand ssRNA (= mRNA) viruses are infectious.
• naked nucleic acids of - strand ssRNA and dsRNA viruses are not infectious
  
  • they require polymerases contained in the complete virus

Question 19

DNA viruses–viral replication

Answer 19

• all replicate in the nucleus
  
  • except poxvirus

Question 20

RNA viruses–viral replication

Answer 20

• all replicate in the cytoplasm
  
  • except influenza virus and retroviruses

Question 21

name the naked (nonenveloped) viruses

Answer 21

• Papillomavirus
• Adenovirus
• Parvovirus
• Polyomavirus
• Calicivirus
• Picornavirus
• Reovirus
• Hepevirus
  
  • “Give PAPP smears and CPR to a naked hippie”

Question 22

which of the naked (nonenveloped) viruses are DNA?

Answer 22

• PAPP
  
  • ​Papillomavirus
  • Adenovirus
  • Parvovirus
  • Polyomavirus

Question 23

which of the naked (nonenveloped) viruses are RNA?

Answer 23

• CPR and hip
  
  • ​Calicivirus
  • Picornavirus
  • Reovirus
  • hepevirus