Medical Virology Exam 3 Prep

Is Parvoviridae naked or enveloped

Naked

Is parvoviridae single or double stranded

single stranded linear (-)

Parvoviridae replication strategy

Requires host cells and replicates in the nucleus

Is parvoviridae a big or small virus

small 5kb

Poxviridae replication cycle

1. Attachment

2. Transport of DNA to nucleus (entire capsid and genome enter)

3. Transcription of viral genes into mRNA; splicing may occur

4. Translation of mRNA into proteins (viral proteins transported back to nucleus)

5. Replication of the DNA genome

6. Assembly in nucleus or cytoplasm, and release

How do poxviridae attatch?

They attach to specific cell surface receptors that determine host range and tissue tropism.

Binding occurs via the capsid proteins

Receptor-mediated endocytosis

How do poxviridae transport?

Intact capsid enters the nucleus through nuclear pores since they’re so small

How many genes does a poxviridae have and what are they?

2, NS or REP and CP or VP

What is the NS gene good for?

They are needed to target and assist the process of:

• Site specific binding

• Site specific endonuclease

• Helicase

What is the VP/CP gene good for?

Gene used to form capsid later in translation.

Where does translation occur for parvoviridae and what is it translated by?

In the cytoplasm, translated by host ribosomes.

Pathogenisis of parvoviridae (What phase does it infect, how does it replicate, and what does it cause?)

1. Must infect actively dividing cells (S phase) because they need host DNA pol to replicate

2. Replicated in rapidly dividing lymphoid tissue cells

3. Causes viremia

Parvoviridae succeptible cells

Intestinal —> diarrhea, hemorrhage, dehydration

Bone marrow —> leukopenia, immunosuppression

Fetal Tissue —> abortion, fetal death, stillbirth

Myocardial cells —> myocarditis

Whats the most sensitive test for parvoviridae

PCR

AAV (Dependoparvovirus)

Needs a helper; used for gene therapies

Parvovirus B19

Childhood illness; pathogenesis leads to anemia complications

Feline Parvo; clinical signs, transmission

Resilient, causes fever & anorexia & vomiting & diarrhea. transmitted fecal/orally

What is the classification criteria of the poxvirus family?

Complex, enveloped, ds linear (linked)

What are the properties of Pox

dsDNA(+) and big around 130-280kb in genome size

What is the baltimore classification of Pox

Group 1

Where does Pox replicate?

In the cytoplasm

Structure: what are the two forms? (POX)

Intracellular Mature Vius (IMV) and Extracellular Enveloped Virus (EEV)

What does the IMV have (POX)

A lipid surface membrane (enveloped)

What does the EEV have? (POX)

An extra lipid membrane with extra surface glycoproteins

Whats a characteristic of the terminal ends of the DNA for Pox

Ends are covalently closed making a circular single molecule, protecting from exonuclease, assists with initiation of DNA replication, encode virulence factors.

Pox replication: how does it prime?

It primes with hairpin loops

What does pox replicate as?

Concatemers that are later cut into genome size pieces

Pox virus replication cycle:

1. Entry

2. Transcription cascade: Early mRNA

3. Uncoating

4. DNA replication

5. Transcription cascade: Intermediate mRNA

6. Transcription cascade: Later mRNA

7. Translation

8. Assembly

9. Concatemer resolution

10. DNA packaging

11. Maturation

12. Golgi wrapping

13. Exit

Who’s transcription machinery does Pox use?

Its own

How many forms of small pox are there and what are they?

2 forms: Variola Major 20-50% mortality and Minor 1% mortality.

Whats small pox contagiousness? And when is it contagious

High Ro of 5-7, after the onset of the rash

How is small pox transmitted

Transmission through respiratory, direct contact, fomite, or vertical

Small pox zoonosis and how long does the immunity last

Strictly humans, life long immunity

Why was small pox the first disease to be fully eradicated

1. Specifically human disease

2. No subclinical cases

3. Good vaccine with efficient production in different countries

4. International effort

5. Wealthier countries had interest in helping less developed countries