Viral Pathogenesis

Question 1

How can viruses hold their own against the host?

Answer 1

Virulence/ immune evasion and rapid evolution (particularly RNA)

Question 2

How can hosts hold their own against viruses?

Answer 2

Defense mechanisms via immune system.

Question 3

Define viral pathogenesis

Answer 3

Dynamic process where virus and host factors contribute to disease outcomes.

Mechanistic study of how viruses and host responses cause cellular and tissue damage leading to clinical symptoms.

Question 4

How doe the site of infection contribute to the dissemination of virus in the host?

Answer 4

Cite of location often has to do with what kind of virus is caught. Mode of entry can give clues to what is there and how it will affect the host.

Question 5

What are the three types of viral tropism?

Answer 5

Cellular, tissue, and host.

Question 6

What viral factors will contribute to enhanced spread of a virus? What host factors do this?

Answer 6

Viral: many - immune evasion, trickery, etc.
Host: mislabelling, cytokines, apoptosis.

Question 7

What is dissemination? What must happen in order for dissemination to occur?

Answer 7

When an infection spreads beyond original site: local vs. systemic infections.
Physical and immune barriers much be breached.

Question 8

How can viruses promote spread in the epithelium?

Answer 8

Release virions directionally into basolateral surface.

Question 9

What is hematogenous spread?

Answer 9

When viral particles enter bloodstream.

Question 10

What is viremia?
What kinds of viremia are there?
Describe them.

Answer 10

When virions are detected in the blood.
Active, passive, primary, and secondary.
Active - produced by viral replication. Passive - Introduced to blood without replication. Primary - low titer when progeny released. Secondary - high titer with dissemination.

Question 11

Name a virus that can spread by nerve endings at primary infection.

Answer 11

Herpesvirus

Question 12

Name a virus that can enter the CNS via the blood.

Answer 12

HIV

Question 13

What is a neurotropic virus?
Neuroinvasive virus?
Neurovirulent virus?

Answer 13

Viruses that can infect neural cells (neurons and glia).
Viruses that can enter the CNS after peripheral infection.
Viruses causes disease in CNS with neurological manifestation.

Question 14

What are gene products of a virus that alter pathogenicity?

Answer 14

Number of virions, viral proteins for speed, impairment of virulence genes with no effect on cellular replication, toxic viral genes

Question 15

What are gene products of viruses that modify host’s anti-viral mechanisms?

Answer 15

Cell viral receptors, immune pathways, tissue remodeling/repair.

Question 16

Describe hantavirus in brief.

Answer 16

From mice
Hemorrhagic fever with renal failure.
1-10% mortality
Hantavirus pulmonary syndrome (HPS) >40% mortality.
-ssRNA bunyavirus

Question 17

How does hantavirus kill?

Answer 17

infects lungs with no cytopathic effect. Results in microvascular leakage

Question 18

What is the replication strategy of Hantavirus?

Answer 18

It is a segmented -ssRNA virus so it requires its own polymerase that it should encode.

Question 19

What is Dengue?

Answer 19

Zoonotic disease spread by Aedes egyptii mosquitoes with four serotypes, each causing worse infection response than the next if multiply infected by other types.

Question 20

Describe Dengue symptoms.

Answer 20

Hemorrhagic fever, shock syndrome, vascular leakage, headache, pain behind eyes, rashes, bleeding from nose and mouth, vomiting.

Question 21

Why are there ranges of symptoms for Dengue?

Answer 21

Dengue is caused by the parasite as well as the host’s response. If the host has low response there will be very little issue. Moderate gives fever and high response gives dengue hemorrhagic fever.

Question 22

What is ADE?

Answer 22

Antibody dependent enhancement is when the antibodies from one illness increase the odds or symptoms of other illnesses because they will amplify the response.

Question 23

To what does virulence refer?

Answer 23

The capacity of a virus to cause disease in an infected host. It is a quantitative statement about the ability or degree of pathogenesis in the host.

Question 24

How is Marburg virus transmitted?

Answer 24

It is spread by contact with bodily fluids and tissues of the infected. Can also occur by handling infected dead wild animals.

Question 25

Provide a brief description of the Marburg Virus.

Answer 25

Marburg is a -ssRNA that is filamentous and has diagnostic loops at the end of its tail looking like a lowercase letter ‘d’.

Question 26

Do humans contribute towards enhanced viral pathogenesis?

Answer 26

Yes. Via GM crops etc. sometimes viral sequences can lead to emergence of novel viruses. Virus resistant transgenic plants were developed in the 80s and they express viral sequences.

Question 27

What are PDR Techniques?

Answer 27

Pathogen-Derived Resistance Techniques.

Question 28

What do PDR techniques aim to do?

Answer 28

Limit plant pathogens, unintentional targeting of endogenous genes and non-target organisms. Risk of hetero-encapsidation, viral recombination, and transcomplementation.