Virus Structure and Classification

What is a Virus?

•A virus is genetic information packaged for delivery into a cell.

What do viruses contain ?

they can contain both RNA or DNA (one or the other, but its only one of them)

What do viruses depend on

•depend on living cells;

New virions are assembled from

components rather than produced by binary fission.

What is the definition of Virus

The biological entity across its full replication cycle

• this is the whole thing

What is the defition of virion

The extracellular infectious particle.

• this is everything outside

What is the defintion of Delivery

Recognizes a susceptible cell and releases the genome at the correct site.

What is the defintion of cargo

May carry enzymes the next cell cannot supply quickly enough.

For every virus we ask ourselves these questions?

• What is it made of?

• How does it enter the susceptible host cell?

• Where does it replicate, and which cells does it damage?

• How does this damage manifest in the animal?

• Where can we interrupt infection or transmission?

What is a genome

DNA or RNA that encodes the viral program.

What is a capsid

Protein shell built from repeating subunits.

What is Nucleocapsid:

Genome plus associated capsid proteins.

What is an Envelope:

Host-derived lipid bilayer containing viral surface proteins.

What is the matrix proteins

connect the nucleocapsid and envelope in many enveloped viruses.

What is a tegument

a protein-rich layer between the capsid and envelope, characteristic of herpesviruses.

What are the characteristics of a viral genome

• can be DNA or RNA

• Single stranded or double stranded

• for ssRNA virus (-,+, or both)

• linear or circular

• one or multiple segments

What is the viral genome for Canine enteric coronavirus (CECoV)

+ single-stranded RNA

What is the viral genome for Canine parvovirus (CPV)

single-stranded DNA.

What does the genome type help us to predict?

helps predict the replication strategy and likely cellular location, with important exceptions.

What is the function of capsid

Protect the genome, deliver it, and sometimes bind receptors

What are the major capsid symmetry patterns:

• helical

• icsahedral

• complex

What kind of capsid symmetry pattern is Canine enteric coronavirus (CECoV)

•A helical nucleocapsid

What kind of capsid symmetry pattern is Canine parvovirus (CPV)

•A small, rigid icosahedral capsid

All known animal viruses with helical nucleocapsid are

enveloped

Describe the envelope of Canine enteric coronavirus (CECoV)

host-derived lipid membrane with viral spike proteins.

Describe the envelope of Canine parvovirus (CPV)

absent; the protein capsid is exposed.

Describe the outer layer of the enveloped viruses

Lipid envelope with viral glycoproteins

Describe the outer layer of the non-enveloped viruses

Protein capsid is the outermost layer

Describe the environmental stability of non-enveloped viruses

Often more environmentally stable

Describe the environmental stability of enveloped viruses

Usually lower

Describe the Drying/Soap of enveloped viruses

Often susceptible

Describe the Drying/Soap of non-enveloped viruses

Often more tolerant

Describe the Disinfection of enveloped viruses

Many labeled products are effective

Describe the Disinfection of non-enveloped viruses

Use a product proven effective for that virus

What is the defintion of Fragile respiratory virus:

Collect early from the active mucosal site and place the sample in an appropriate transport medium.

What is the defintion of Durable enteric virus:

Feces or an intestinal sample may contain high genome loads after clinical onset.

What is the defintion of Cell-associated virus:

Whole blood or affected tissue may outperform serum.

How are viruses classified

1. Structural classification

2. Host range

3. Clinical classification

What is the structural classification

enveloped versus non-enveloped; icosahedral, helical, or complex capsids; virion size and shape.

What is the Host range

Animal versus plant; the species they infect (canine, bovine, feline,...).

What do we mean about clinical classification for viruses

- Grouping viruses by the syndrome they cause, such as enteric, respiratory, neurologic, or multisystemic disease.

- Practical ways of grouping viruses, not formal classifications

- It doesn’t necessarily reflect evolutionary relationships.

What is the Baltimore classficiation ?

•Seven groups: Organize viruses by genome type and gene-expression strategy.

What is an example of Group I

Herpesvirus

The genetic material for Group 1 is what ?

dsDNA

What is an example of Group II

parvovirus

What is the genetic material of Group II viruses

+ssDNA

What is an example of Group III viruses

rotaviruses

What kind of genetic material is Group III

dsRNA

What is an example of Group IV viruses

coronaviruses

What is the genetic material of Group IV viruses

+ssRNA

What is an example of Group V

Influenza

What is the genetic material of Group V viruses

-ssRNA

What is an example of Group VI viruses

FLV

What is the genetic material of Group VI viruses

+ssRNA (with reverse transcriptase)

What is an example of Group VII viruses

Duck Hepatitis B vius

What is the genetic material of Group VII

dsDNA-RT