The Viruses: Host-Pathogen Interactions

Question 1

Viral Sources (3)

Answer 1

• Humans
• Environment
• Animals/Insects

Question 2

Human Reservoirs for Respiratory Viruses

Answer 2

• Coronavirus
• Influenza
• Parainfluenza
• RSV
• Rhinovirus

Question 3

Human Reservoirs for Mucosal Viruses Oral

Answer 3

• HSV
• CMV
• EBV

Question 4

Human Reservoirs for Mucosal Viruses Genital

Answer 4

• HBV, HCV
• HIV
• HSV
• HPV

Question 5

Environmental Viruses

Answer 5

Fecal-oral
-norovirus, rotavirus, Hep A
Fomites
-adenovirus

Question 6

Vector Borne Viruses

Answer 6

Mosquitoes
-West Nile
-Dengue
Animals
-Rabies
-LCMV

Question 7

Viral Factors Influencing Clinical Outcomes (5)

Answer 7

• viral inoculum
• virulence of virus
• efficiency of attachment to host cell
• ability to spread
• effect on cell (eg. cytopathic, transformative)

Question 8

Stages of Viral Infections (3)

Answer 8

Acute
Latent
Chronic

Question 9

Latent Ix

Answer 9

• no clinical presentation during latency
• can reactivate later
• dormancy
• eg. herpesviridae

Question 10

Chronic Ix

Answer 10

• slow progression of clinical disease

- eg. HIV

Question 11

Variability in viral populations due to (5)

Answer 11

• Large population
• Selective pressure
• Heterogeneity
• High mutability
• Genome structure

Question 12

RNA vs. DNA viruses mutability

Answer 12

-higher in RNA virus, RNA pol lacks proofreading abilities

Question 13

Quasispecies

Answer 13

• population of viruses infecting a host are not all exactly the same
• group of genetically similar viruses
• allows selective pressures (ie. antivirals) to select for resistance in the viral population

Question 14

Influenza

Answer 14

• ssRNA virus
• segmented genome
• surface proteins - hemagluttinin and neuraminidase

Question 15

Antigenic Drift

Answer 15

-mutations in genome cause slightly altered surface glycoproteins

Question 16

Antigenic Shift

Answer 16

-rearrangement of genome causes different pairings of H’s and N’s to come together

Question 17

Clinical Significance of Drift

Answer 17

• need for yearly vaccine

- antibodies from last year’s vaccines may not completely recognize this year’s strain

Question 18

Clinical Significance of Shift

Answer 18

• abrupt reassortment results in virus to which immune system has little to no protection
• rearrangement with H’s and N’s from animal hosts

Question 19

Spanish Influenza

Answer 19

• 1918

- H1N1, novel reassortment

Question 20

Bird Flu

Answer 20

• H5N1, H7N9

- poor pt to pt spread

Question 21

Neuraminidase Inhibitors

Answer 21

• influenza antivirals
• oseltamavir, zanamavir
• MOA: inhibit NA, prevents virus from cleaving sialic acid as it leaves cell, new viruses can’t be released
• covers A and B

Question 22

M2 Inhibitors

Answer 22

• influenza antiviral
• amantadine
• MOA: inhibits M2 ion channel, preventing acidification of vision which is necessary for uncoating

Question 23

Clinical Benefit of Influenza Antivirals

Answer 23

-if given within 24-48 hrs of symptom onset, reduce symptoms and recovery time

Question 24

Acyclovir and Valacyclovir

Answer 24

• phosphorylated by viral and cellular kinases to become triphosphate form where they can be integrated into growing nucleic acids, prevent chain elongation and disrupt viral replication
• used in HSV and VZV

Question 25

Gancyclovir

Answer 25

• only phosphorylated by cellular kinases to triphosphate form, prevents chain elongation and disrupts viral replication
• used in CMV