8. Host-Pathogen Interactions

Lecture 8 - virus pathogenesis, effects on host cells, host response to viral infection

Pathogenicity

The ability of a virus to cause disease in the host.

Pathogen

A virus that causes disease is a ___________.

pathogenesis

The manner/mechanisms of development of a disease.

virulence

Quantitative or relative measure of the degree of pathogenicity of the infecting virus.

Avirulent

Not virulent.

true

(TRUE/FALSE): Virulence is not an absolute property of a virus.

false

(TRUE/FALSE): Virulence is an absolute property of a virus.

tug-of-war

Virulence is the outcome of a game of ____________ between the virus and host with contributions from the environment and co-infections.

virulence

____________ is the outcome of a game of tug-of-war between the virus and host with contributions from the environment and co-infections.

LD50

The dose of the virus required to cause death in 50% of animals.

ID50

The dose of virus that will infect 50% of the experimental group.

virulence

ID50 and LD50 are quantitative methods of measuring _______________.

ID50 and LD50 are ______________ methods of measuring virulence.

lower

The (LOWER/HIGHER) the ID50, the more virulent the organism.

lower

The (LOWER/HIGHER) the LD50, the more virulent the organism.

less

The higher the LD50, the (LESS/MORE) virulent the organism.

relatively

Virus virulence can be assessed quantitatively or _____________.

A

Virus A as an LD50 value of 20. Virus B has an LD50 value of 50. Virus (A/B) is more virulent.

exposure without infection

Of the possible virus-host interaction outcomes, the best outcome for the host is __________ ________ __________.

death

Of the possible virus-host interaction outcomes, the worst outcome for the host is ____________.

cannot

A virus (CAN/CANNOT) penetrate intact skin.

skin

_________ defenses against viral infection

* dense outer layer of keratin
* low pH
* presence of fatty acids
* bacterial flora
* dryness
* components of the immune system

keratin

Skin defenses against viral infection

* dense outer layer of ___________
* low pH
* presence of fatty acids
* bacterial flora
* dryness
* components of the immune system

low

Skin defenses against viral infection

* dense outer layer of keratin
* ____ pH
* presence of fatty acids


* bacterial flora
* dryness
* components of the immune system

fatty acids

Skin defenses against viral infection

* dense outer layer of keratin
* low pH
* presence of ________ _______
* bacterial flora
* dryness
* components of the immune system

bacterial

Skin defenses against viral infection

* dense outer layer of keratin
* low pH
* presence of fatty acids
* ______________ flora
* dryness
* components of the immune system

dryness

Skin defenses against viral infection

* dense outer layer of keratin
* low pH
* presence of fatty acids
* bacterial flora
* __________
* components of the immune system

immune system

Skin defenses against viral infection

* dense outer layer of keratin
* low pH
* presence of fatty acids
* bacterial flora
* dryness
* components of the _________ ___________

cuts

Viruses can enter the skin of a host through

* _______
* bites of arthropods
* bites of infected animals
* contaminated objects

arthropods

Viruses can enter the skin of a host through

* cuts
* bites of ___________
* bites of infected animals
* contaminated objects

infected animals

Viruses can enter the skin of a host through

* cuts
* bites of arthropods
* bites of ________ _______
* contaminated objects

contaminated objects

Viruses can enter the skin of a host through

* cuts
* bites of arthropods
* bites of infected animals
* ___________ __________

mucus membrane

_________ __________ defenses against viral infections

* IgA
* Virucidal proteins

IgA

Mucus membrane defenses against viral infections

* _____
* Virucidal proteins

virucidal proteins

Mucus membrane defenses against viral infections

* IgA
* ________ _________

gastrointestinal tract

____________ ____________ defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

mucus membrane

Gastrointestinal tract defenses against viral infections

* _________ __________ of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

acidity, alkalinity

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* _________ of the stomach
* _________ of the intestines
* mucus layer
* lipolytic bile
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

mucus layer

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* ______ ______
* lipolytic bile
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

lipolytic

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* _____________ bile
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

bile

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic _______
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

proteolytic

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* __________ pancreatic enzymes
* Defensins
* IgA
* Scavenging macrophages

pancreatic enzymes

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* proteolytic _________ ________
* Defensins
* IgA
* Scavenging macrophages

defensins

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* proteolytic pancreatic enzymes
* __________
* IgA
* Scavenging macrophages

IgA

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* proteolytic pancreatic enzymes
* Defensins
* _____
* Scavenging macrophages

macrophages

Gastrointestinal tract defenses against viral infections

* mucus membrane of oral cavity and esophagus
* acidity of the stomach
* alkalinity of the intestines
* mucus layer
* lipolytic bile
* proteolytic pancreatic enzymes
* Defensins
* IgA
* Scavenging ________________

mucociliary

Respiratory tract defenses against viral infections

* ____________ blanket
* alveolar macrophages
* NALT
* BALT
* temperature gradient

alveolar

Respiratory tract defenses against viral infections

* mucociliary blanket
* ________ macrophages
* NALT
* BALT
* temperature gradient

NALT

Respiratory tract defenses against viral infections

* mucociliary blanket
* alveolar macrophages
* _____
* BALT
* temperature gradient

BALT

Respiratory tract defenses against viral infections

* mucociliary blanket
* alveolar macrophages
* NALT
* _____
* temperature gradient

temperature gradient

Respiratory tract defenses against viral infections

* mucociliary blanket
* alveolar macrophages
* NALT
* BALT
* _________ _________

viremia

Presence of virus in the blood

disseminated infection

Infection spreads beyond the primary site of infection.

systemic infection

Infection affect a number of organs or tissues.

apical

Directional shedding of viruses from the infected epithelium is critical to subepithelial spread. (APICAL/BASOLATERAL) spread facilitates virus dispersal.

basolateral

Directional shedding of viruses from the infected epithelium is critical to subepithelial spread. (APICAL/BASOLATERAL) spread gives access to underlying tissue, facilitating systemic spread.

primary viremia

The initial entry of virus into the blood after infection.

secondary viremia

Re-entry of the virus into the blood circulation after replicating in major organs.

active viremia

Release of virion from the initial site of replication into the blood stream.

passive viremia

Direct inoculation of virus into host blood stream without initial replication elsewhere in the host.

short duration

In the bloodstream, the virus can be free in the plasma, resulting in ________ _______ viremia, or cell-associated, resulting often in prolonged viremia.

prolonged

In the bloodstream, the virus can be free in the plasma, resulting in short duration viremia, or cell-associated, resulting often in ____________ viremia.

prolonged

In ______________ viremia, the virus multiplies in monocytes or lymphocytes.

false

(TRUE/FALSE): Mosquito bites can transmit viruses directly into the blood. This is active viremia.

true

(TRUE/FALSE): Mosquito bites can transmit viruses directly into the blood. This is passive viremia.

trafficking monocyte

Viruses can travel from the bloodstream into tissues via

* fenestrations
* ____________ __________ transport
* transcytosis
* vesicles
* replication in endothelial cells

epithelial

Viruses can spread through the body via

* ___________ surfaces
* subepithelial invasion and lymphatics
* blood
* nerves

subepithelial

Viruses can spread through the body via

* epithelial surfaces
* _______________ invasion and lymphatics


* blood
* nerves

lymphatics

Viruses can spread through the body via

* epithelial surfaces
* subepithelial invasion and _____________
* blood
* nerves

blood

Viruses can spread through the body via

* epithelial surfaces
* subepithelial invasion and lymphatics
* _______
* nerves

nerves

Viruses can spread through the body via

* epithelial surfaces
* subepithelial invasion and lymphatics
* blood
* _________

neurotropic virus

Virus that can infect neural cells

neuroinvasive viruse

Virus that enters the CNS after infection of a peripheral site.

neurovirulent virus

Virus that causes disease of the nervous tissue, manifesting by neurological symptoms and often death.

false

(TRUE/FALSE): A neurotropic virus can be either neuroinvasive or neurovirulent, never both.

false

(TRUE/FALSE): A neuroinvasive virus is always highly neurovirulent.

true

(TRUE/FALSE): A neuroinvasive virus is not always highly neurovirulent.

high neuroinvasiveness

A virus that readily enters the CNS shows (HIGH/LOW) (NEUROINVASIVENESS/NEUROVIRULENCE).

low neuroinvasiveness

A virus that readily enters the PNS, but rarely the CNS shows (HIGH/LOW) (NEUROINVASIVENESS/NEUROVIRULENCE).

high neurovirulence

A virus that causes severe consequences upon entering the CNS shows (HIGH/LOW) (NEUROINVASIVENESS/NEUROVIRULENCE).

low neurovirulence

A virus that causes minor neuro diz upon entering the CNS shows (HIGH/LOW) (NEUROINVASIVENESS/NEUROVIRULENCE).

retrograde

A virus travels in the opposite direction of the nerve impulse flow demonstrates (RETROGRADE/ANTEROGRADE) spread.

anterograde

A virus travels in the same direction of the nerve impulse flow demonstrates (RETROGRADE/ANTEROGRADE) spread.

retrograde

A virus travels in that invades axon terminals and spreads to the cell body or dendrites before cross-synapsing to reach the next axon terminal demonstrates (RETROGRADE/ANTEROGRADE) spread.

anterograde

A virus travels in that invades dendrites or cell bodies and spreads to the axon before cross-synapsing to reach the next dendrite or cell body demonstrates (RETROGRADE/ANTEROGRADE) spread.

true

(TRUE/FALSE): viruses can reach the CNS via olfactory routes.

true

(TRUE/FALSE): viruses can reach the CNS via the BBB.

anterograde

A neurotropic virus traveling from the nasal cavity to the CNS demonstrates (RETROGRADE/ANTEROGRADE) spread.

BBB

A neurotropic virus can pass the _______ utilizing

* TNF - increasing permeability of the endothelial cells
* MMP - breaking down endothelial cell junctions
* Trojan horse - using monocytes

TNF

A neurotropic virus can pass the BBB utilizing

* _____ - increasing permeability of the endothelial cells
* MMP - breaking down endothelial cell junctions
* Trojan horse - using monocytes

permeability

A neurotropic virus can pass the BBB utilizing

* TNF - increasing __________ of the endothelial cells
* MMP - breaking down endothelial cell junctions
* Trojan horse - using monocytes

MMP

A neurotropic virus can pass the BBB utilizing

* TNF - increasing permeability of the endothelial cells
* _____ - breaking down endothelial cell junctions
* Trojan horse - using monocytes

junctions

A neurotropic virus can pass the BBB utilizing

* TNF - increasing permeability of the endothelial cells
* MMP - breaking down endothelial cell __________
* Trojan horse - using monocytes

monocytes

A neurotropic virus can pass the BBB utilizing

* TNF - increasing permeability of the endothelial cells
* MMP - breaking down endothelial cell junctions
* Trojan horse - using __________

portal of entry

Localized acute infections: site of pathology

short

Localized acute infections: incubation period

no

Localized acute infections: viremia?

variable

Localized acute infections: duration

very important

Localized acute infections: role of secretory IgA

distant sites

Systemic acute infections: site of pathology