Viral Pathogenesis (Dr. West)

Front 1

What two factors play a role in viral pathogenesis?

Back 1

VIRUS REPLICATION coupled with the impact of the IMMUNE RESPONSE to the infection.

Front 2

What do acute viruses seek to accomplish within their host?

Back 2

1. Propagation
2. Transmission

(Just get in there, do some replicating, and then get out)

Front 3

What do CHRONIC viruses seek to accomplish within their host?

Back 3

They seek the establishment of a chronic but sub-clinical state (maintenance) that can, at some point, facilitate transmission.

Front 4

T or F.

Disease often results as much from the immune response as from the pathogen's intrinsic virulence.

Back 4

TRUE!

Ex: immune responses can result in jaundice or encephalitis.

Front 5

What are the 4 major pathogenetic pathways induced by viral infection?

Back 5

1. Acute infection
2. Chronic infection
3. Persistent infection
4. Transformation

Front 6

Which pathogenetic pathway is followed by resolution and temporary or lifetime immunity?

Back 6

Acute infection
(Rhinovirus, Hepatitis A)

Front 7

Which pathogenetic pathway is characterized by periods of latency and recrudescence (a new outbreak)?

Back 7

Chronic infection
(Herpes)

Front 8

Which pathogenetic pathway does not involve periods of virologic latency?
(Virus replication is detectable for life of the organism!)

Back 8

Persistent infection
(chronic infection with clinical latency but no virologic latency)
(HIV-1, HCV)

Front 9

Which pathogenetic pathway results in virus-induced tumors?

Back 9

Transformation
(EBV, HTLV-1, HCV, HPV)

Front 10

The common cold (rhinovirus) is an example of what type of infection?

Back 10

Acute infection

Front 11

Varicella Zoster Virus (causes chickenpox and shingles) is an example of what kind of infection?

Back 11

Latent infection
(After first infection, virus is not demonstrable for a number of years)

Front 12

Herpes Simplex Virus is an example of what type of infection?

Back 12

Persistent (Chronic) infection
(recrudescent episodic)

Front 13

Hepatitis B and HTLV are examples of what type of infection?

Back 13

Viral transformation:
Chronic infection with late disease
(over the course of many years, Hep B can result in cirrhosis and hepatocellular carcinoma, and HTLV can result in leukemia)

Front 14

What are the 5 steps in viral pathogenesis?

Back 14

1. ENTRY and primary replication
2. Viral DISSEMINATION and tissue TROPISM.
3. CELLULAR INJURY and clinical illness (direct and indirect effects)
4. Virus SHEDDING and host-host SPREAD)
5. Host IMMUNE RESPONSE and recovery from infection

Front 15

In general, where do most viruses enter a host?

Back 15

Through mucosal surfaces.

Front 16

T or F.

An initial round of replication often occurs at the site of entry.

Back 16

TRUE!

Front 17

T or F.

Acute and Chronic viruses always disseminate.

Back 17

FALSE!

Many acute and some chronic viruses never disseminate.

Front 18

What is the #1 most common route of entry for viruses?

Back 18

RESPIRATORY route
(mucosal surfaces)

Ex: Influenza, measles, mumps, rubella

Front 19

What is the 2nd most common route of entry for viruses?

Back 19

Alimentary route
(mucosal)

Ex: Rotavirus, polio, herpes simplex

Front 20

Besides the respiratory and alimentary routes, name 2 other primary routes of entry and replication.

Back 20

1. Genitourinary tract (mucosal)
(ex: Herpes, HIV, HPV)
2. Ocular (mucosal)
(ex: Herpes, Adenovirus)

Front 21

T or F.

An initial round of replication often occurs at the site of entry.

Back 21

TRUE!

Front 22

T or F.

Acute and Chronic viruses always disseminate.

Back 22

FALSE!

Many acute and some chronic viruses never disseminate.

Front 23

What is the #1 most common route of entry for viruses?

Back 23

RESPIRATORY route
(mucosal surfaces)

Ex: Influenza, measles, mumps, rubella

Front 24

What is the 2nd most common route of entry for viruses?

Back 24

Alimentary route
(mucosal)

Ex: Rotavirus, poilio, herpes simplex

Front 25

Besides the respiratory and alimentary routes, name other primary routes of entry through mucosal tissue.

Back 25

1. Genitourinary tract (mucosal)
(ex: Herpes, HIV, HPV)
2. Ocular (mucosal)
(ex: Herpes, Adenovirus)

Front 26

Name 2 non-mucosal routes of entry for viruses.

Back 26

1. Skin-- via trauma, injection, or bites
2. Blood-borne-- viruses enter via injection/transfusion or through abrasions in skin or mucus membranes.

Front 27

What is the most common mechanism of subject-caregiver or caregiver-subject transmission?

Back 27

Parenteral or iatrogenic exposure.

Front 28

Describe how the epithelial cells in the respiratory system act as barrier to infection?

Back 28

Ciliated epithelial cells sweep clean dust and germs trapped in mucus secreted by "goblet cells"

Front 29

How do viruses generally enter through the alimentary system?

Back 29

Fecal-oral contamination
(gross)

Front 30

Which secretory immunoglobulin is found in mucosal secretions and can opsonize or neutralize digested viruses?

Back 30

IgA

Front 31

Where does disease often manifest relative to the primary route of entry?

Back 31

Disease usually manifests at a site DISTANT from the primary route of entry

Front 32

What factors dictate tissue tropism?

Back 32

1. *Presence of receptors for the virus
2. To a lesser extent, the metabolic or differentiation state of the target

(Tissue tropism is a term most often used in virology to define the cells and tissues of a host which support growth of a particular virus)

Front 33

What 4 factors can determine the virulence of a virus?

Back 33

1. Factors that PROMOTE REPLICATION capacity (replicases, receptor-binding proteins)
2. Factors that DEFEAT OR INTERFERE w/ host defenses (virokines, Ag presentation interference)
3. Factors that PROMOTE SPREAD within or among hosts (inflammatory mediators, histamine inducers)
4. Gene products that are DIRECTLY TOXIC (enterotoxins, neurotoxins)

Front 34

T or F.

The age of an individual does not affect a virus's ability to infect.

Back 34

FALSE.

How old the individual is affects virulence.

Front 35

T or F

The route of introduction affects a virus's ability to infect a host.

Back 35

TRUE!

Front 36

T or F.

The host's genetics do not affect a virus's ability to infect.

Back 36

FALSE

Genetics contribute to a host's resistance or susceptibility to a particular virus.

Front 37

T or F.

The strain of the virus (genotype/phenotype) of the infecting strain affects a virus's virulence.

Back 37

TRUE!

Front 38

T or F.

The host's immune paramaters (immunocompetence) can affect a virus's ability to infect.

Back 38

TRUE!

Front 39

T or F

Genetic relatedness between viruses often has nothing to do with pathogenesis.

Back 39

TRUE!

Receptor trophism plays more of a role in phathogenesis than the genetic relatedness. So, the receptors throughout body tissues will determine how the virus disseminates and where it propagates

Front 40

What type of immunity protects against virus-infected cells?

Back 40

Cell mediated immunity
(CD8+ T cells)

Front 41

What type of immunity protects against reinfection, provides elimination of intact virus particles, and prevents infection of a cell?

Back 41

Humoral immunity

Front 42

Which antibody is important for infections of the respiratory or GI tract?

Back 42

IgA

Front 43

What kind of host defense mechanism may result in symptoms?

Back 43

Inflammation
(Caused by IL-1, IL-6, TNF chemokines)

Front 44

How can viruses like Herpes, VZV in neural tissue evade the immune response?

Back 44

The virus hides in a site (neural tissue) not accessible to the immune system.

Front 45

How do viruses like EBV and HIV evade the immune system for so long, resulting in clinical latency?

Back 45

They restrict viral gene expression, resulting in minimal production of viral proteins.

Front 46

How do viruses like HIV and Influenza utilize their surface glycoproteins to evade the immune system?

Back 46

Antigenic variation--
virus rapidly evolves and mutates

Front 47

How do viruses like Herpes, HIV, Poxviridae, and EBV evade T-cell recognition?

Back 47

They suppress MHC I, MHC II, and/or adhesion molecules

Front 48

How do viruses interfere with the function of cytokines in order to evade the immune system?

Back 48

They can:
1. Inhibit TNF-a or Type I interferons (IFN-a/B)
2. Produce IL-10 homologues (downregulates cytokine production)
3. Express cytokine receptor analogs (to catch and "use up" cytokines)

Front 49

How can viruses evade the immune system by escaping interferons?

Back 49

1. IL-10 induction
2. Secretion of scavenging IFN receptors
3. Blocking IFN-stimulated genes

Front 50

The primary determinant of viral tropism is....?

Back 50

The presence or absense of cellular receptors

Front 51

***The most common portal for viral entry in to humans?

Back 51

RESPIRATORY TRACT