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Microimm 2500 > (V) 25: Viral Pathogenesis > Flashcards

(V) 25: Viral Pathogenesis Flashcards

1
Q

Why is skin not a good host?

A

B/c it is mostly DEAD SKIN
- viruses need something alive for ribosomes to work

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2
Q

Inapparent infections

A

able to transmit even though host does not know they are infected

  • no major symptoms but immune system is activated
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3
Q

Flaviridae

A

ex. West Nile Virus
- INAPPARENT infection

(+) ssRNA - ready to go WITH ENVELOPE

  • spread my mosquitoes
  • 1st North American case 1999 in NYC
  • almost caused cancellation of US Open Tennis Tourney –> instead sprayed insecticide
  • CDC was mystified b/c they couldn’t test for a virus they didn’t have in their collection

80% of infected ppl do NOT have symptoms

transmitted IN blood –> could be passed through transfusion (blood donation)

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4
Q

How did West Nile Virus make it to North America?

A

Likely originated in Israel (closest match to virus in NYC)

discovered through using physical measurement - SEQUENCING
- make primer sequences/oligonucleotides from small bit of viral genome then amplify w/ PCR

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5
Q

First virus known to cause disease in humans

A

Yellow Fever Virus

  • Reed Commission: US soldiers becoming sick in Cuba

Dr. Lazear inoculated Dr. Caroll with an infected mosquito
- inject virus in human –> virus can kill human –> virus can induce pathogenesis

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6
Q

Viral pathogenesis

A

To produce a disease

TWO ARMS
1. effects of viral replication on HOST
2. effects of HOST RESPONSE on virus and host

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7
Q

Viral pathogenesis steps

A
  1. virus enters cell and loses its shell
  2. virus exposes nucleic acid
  3. virus uses host ribosome machinery to make viral proteins
  4. assembly
  5. leave and infect next cell

need a susceptible AND permissive cell
also need the “right #” of virus particles - no set #

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8
Q

Fenner experiment

A

unfortunate pathogenesis of mousepox

mousepox was injected into the footpad
- host response = swelling at sit of inoculation
- after viremia: host response = replication in skin = rash (viremia)

  1. invasion of skin and multiplication in susceptible + permissive cells
  2. multiplication in lymph node
  3. primary viremia
  4. multiplication + necrosis in spleen and liver
  5. secondary viremia
  6. swelling of foot - primary lesion
  7. early rash: Papules
  8. severe rash: Ulceration
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9
Q

Viremia

A

presence of virions in the blood

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10
Q

Primary viremia

A

progeny virions released in blood after initial replication at site of entry

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11
Q

Secondary viremia

A

delayed appearance of virions in the blood

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12
Q

Viral entry points

A
  • conjunctiva (via outer surface of eyes)

following are lined w/ mucosal cells:
- respiratory
- alimentary
- urogenital

viruses enter via mucosal linings of respirator, alimentary and urogenital tracts - lots of susceptible + permissive cells

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13
Q

Skin

A

Epidermis (outer layer) = DEAD CELLS
- violates “host requirement”

skin can be broken by insects and viruses may enter via blood (ex. WNV)
- virus gains access to vascularized DERMIS

virions will be INACTIVATED by:
- acidic (pH= 5.5) on skim surface
- anti-viral peptides
- dryness

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14
Q

How are virions inactivated on the skin?

A
  • ACIDIC skin surface (pH = 5.5)
  • anti-viral PEPTIDES
  • DRYNESS
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15
Q

Respiratory tract viruses

A
  • lots of surface area for viruses to find susceptible + permissive cells
  • viruses often enter in form of AEROSOLIZED droplets or through SALIVA CONTACT
  • mucous layer production = mucus removes intruders

Ex. Rhinovirus (common cold), influenza virus

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16
Q

Alimentary tract viruses

A
  • can “COME DOWN” with food
  • must survive HARSH acidic environments
  • can get absorbed by small intestine

upper alimentary tract: acidic pH, proteases, bile detergents (Ex. Reoviruses - viruses that cause gastroenteritis)

lower alimentary tract (anus): virus does not have to withstand harsh environment of upper alimentary tract (Ex. HIV - entry via anal intercourse)

17
Q

Reoviruses

A

Non-enveloped, ONION-like genome, dsRNA

onion-like genome = has to go through many layers
- layers protect genome from harsh environment of upper alimentary tract

18
Q

Lower alimentary tract

A

Anus

less acidic

Ex. HIV

19
Q

Urogenital tract

A

Mucus and pH protection (especially low pH in vagina)

Abrasions during sexual activity will create tears and allow viral entry (ex. losing low pH of vagina)

Ex. Retrovirus (HIV) and HPV

20
Q

Conjunctival entry

A
  • eyes are covered by layers of cell (conjunctiva)
  • blinking is a defense mechanisms
  • certain types of ADENOVIRUSES can infect conjunctiva
  • cornea is partially covered by conjunctiva
21
Q

Virus Shedding

A

Release of virions form infected individual

Transmission - viral population will survive if many infections in series occur in a host population

22
Q

Methods of Virus Shedding

A
  • aerosol secretions: coughing, talking, sneezing
  • feces
  • blood
  • milk (breastfeeding)
  • urine, semen
  • skin lesion (ex. herpes infected skin lesions transmits virus during close contact - think wrestling)
23
Q

Virus Shedding and Envelopes

A

Enveloped viruses are more fragile = easier to KILL
- mostly AEROSOL transmission
- sensitive to low pH

Non-enveloped: withstand a LOT including LOW pH
- mostly transmitted in RESPIRATORY, FECAL-ORAL route
- also transmitted via FOMITES (objects contaminated by virus)

24
Q

Modes of transmission

A
  • iatrogenic
  • nosocomial
  • vertical
  • germline
  • horizontal
25
Q

Iatrogenic transmission

A

Health care WORKER infects a patient

26
Q

Nosocomial transmission

A

Patient infected while in a HOSPITAL
- could be due to fomites

27
Q

Vertical transmission

A

PARENT TO OFFSPRING
- through childbirth or breastfeeding

28
Q

Germline transmission

A

genomic transfer
- through chromosomal segregation

29
Q

Horizontal transmission

A

NONE of the others

  • transmission btwn two same or different species

MOST COMMON MODE OF TRANSMISSION

30
Q

Picornaviridae Hep A

A

(+) RNA

entry: alimentary tract

  • spreads to liver causing JAUNDICE
  • virus incubates for 30 days
  • in later 90s, every February, 10-40% of residents in Puglia, Italy develop Hep A
  • residents eat RAW shellfish that live in contaminated water/sewage on NYE
  • humans that are Hep A positive poop in water - virus shedding in FECES into shellfish habitat

Microimm 2500 (29 decks)

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