Lecture 8: Attachment

Question 1

Why study viral attachment

Answer 1

-First step in dissecting how the interaction between the virus and the host cell lead to viral entry
-Understanding of these interactions suggest possible targets for anti-viral therapy
-First step in targeting viruses to specific cell types-gene therapy, viral therapies for cancer
-Aid in the development of small animal models

Question 2

Exceptions of viral receptors in fungi viruses

Answer 2

No extracellular phase

Question 3

Exceptions of viral receptors in plant viruses

Answer 3

Entry occurs via a mechanical mechanism

Question 4

Viral receptor function

Answer 4

Mediates specific binding of viral particle to the host cell

Question 5

Adhesion receptors

Answer 5

-Mediate attachment; binding is reversible
-These are not required, but help to concentrate virus at cell surface

Question 6

Entry receptors

Answer 6

Binding induces fusion or endocytosis; not reversible

Question 7

Host range

Answer 7

Host must express the surface molecules in order for virus binding and infection to occur

Question 8

Two topological surfaces

Answer 8

-Apical surface: Presented to outside
-Basal surface: Presented to inside
Viral infections are initiated at exposed apical surfaces

Question 9

Tissue tropism

Answer 9

Tissue must express the surface molecule in order for infection to occur

Question 10

Transcytosis

Answer 10

Passage of a virus or any other molecule through one cell so that it may access another

Question 11

Confirming that sialic acid is the receptor for influenza

Answer 11

1. Treating cells with neuraminidase destroys the ability of flu to bind to cells
2. Reintroduction of sialic acid restores binding
3. Carbohydrates containing sialic acid compete for virus binding

Question 11

Types of cell surface molecules used for viral attachment

Answer 11

1. Proteins
2. Carbohydrates
3. Lipid

Question 12

How we can determine the type of molecule being used for attachment

Answer 12

1. Proteins: Treat with protease
2. Carbohydrates: Treat with glycosidase
3. Lipid: Treat with lipases

Question 13

Technology allowing identification of viral receptors

Answer 13

1. Monoclonal antibodies
2. Molecular biology-ability to clone genes
3. Methods for introducing genes into viral genomes

Question 14

Susceptible vs Permissive cells

Answer 14

Susceptible: Has receptor that virus can recognize
Permissive: Has interval machinery/components that virus requires

Question 15

Different receptor binding sites on non-enveloped viruses

Answer 15

1. Protruding fibers-adenovirus
2. Loops: foot and mouth disease virus
3. Canyons: Rhinovirus

Question 16

Enveloped viruses

Answer 16

Attach to receptors via viral envelope glycoproteins