Microbiology Lecture 4.71: Virus Characteristics

What do viruses evade?

Host immune system

What do viruses do in the body?

1. Kill host cells

2. Trigger destructive immune responses

What is the outcome of viral infections determined by?

1. Nature of virus

2. Host interaction

3. Host response

What is the best treatment for viruses?

Host Immune Response

Can the host immune response contribute to the pathogenesis of viral infections?

Yes

What helps prepare the immune system to defend against future viral infections?

Vaccination

What kind of agents are viruses?

Filterable

Are viruses intercellular or extracellular?

Obligate intracellular

Are viruses parasites?

Yes

Can viruses make energy or proteins independently?

No

What must viruses be to endure in nature?

Infectious

What must viruses do for processes not provided by the cell?

Encode processes

Do viral components self assemble?

Yes

What are the means of classifying viruses?

1. Structure

2. Biochemcial characteristics

3. Means of transmission

4. Host cell

5. Tissue or organ

What is the size range of viruses?

18nm to 300nm

What are nonenveloped viruses surrounded by?

Capsid

Are enveloped or nonenveloped viruses contained by humoral immunity alone?

Nonenveloped

What are capsids made of?

Proteins

Are capsids more stable than envelopes?

Yes

What releases capsids from the cell?

Lysis

What are the consequences of naked capsids?

1. Spread easily

2. Dries out to retain infectivity

3. Survides acidic conditions

What are the components of viral envelopes?

1. Membrane

2. Lipid

3. Protein

4. Glycoprotein

What do viral envelopes modify during replication?

Cell membrane

What are viral envelopes released by?

Budding and cell lysis

Must viral envelopes always be wet?

Yes

What do viral envelopes spread in?

1. Large droplets

2. Secretions

Do viral envelopes need cell lysis to spread?

No

What do viral envelopes need for protection and control?

1. Antibody

2. Cell-mediated immune response

Are DNA viruses transient?

No

Where do DNA viruses replicate?

Nucleus

Are RNA viruses transient?

Yes

Where do RNA viruses replicate?

Cytoplasm

Can cells replicate RNA?

No

What do positive strand RNA viruses serve as?

mRNA

Can negative strand RNA viruses be directly translated?

No

What must RNA viruses encode?

RNA dependent RNA polymerase

Where do the attachment region of influenza viruses bind to?

Salic Acid Domains

Which viral replication inhibitor binds to viral proteins before entering the cell?

Antibodies

Which viral replication inhibitor inhibits DNA synthesis?

Nucleoside analogues

Which viral replication inhibitor inhibits the assembly of virus from a polyprotein segment?

Protease Inhibitors

What do proteases do in viral assembly?

Cleave polyproteins into functional proteins