S.M Lecture 4

Question 1

Parovoviridae Family, 6 genera divided between 2 subfamiles. Name the two sub families.

Answer 1

• Parvovirinae - vertebrate hosts
• Densovirinae - arthropod hosts

Question 2

Name the genus, type species and host organisms of the Parvovirinae sub family

Answer 2

• Parvovirus - Mice minute virus - vertebrates
• Erythrovirus - B19 virus - vertebrates
• Dependovirus - Adeno-associated virus 2 - vertebrates

Question 3

Name the genus, type species and host organisms of the Densovirinae sub family

Answer 3

• Densovirus - Jumonia coenia densovirus - invertebrates
• Iteravirus - Bombym mori densovirus - invertebrates
• Contravirus - Aedes aegypti densovirus - invertebrates

Question 4

What is another name for the B19 virus?

Answer 4

erythema infectiosum or fifth disease

Question 5

What group of people are more susceptible to the B19 virus?

Answer 5

More common in children than adults
About 20% of children and adults who get infected with this virus will not have any symptoms

Question 6

Signs and Symptoms of B19 virus

Answer 6

• mild and nonspecific, fever, runny nose and headache
• Rash on face and body (slapped cheek rash)
• Painful or swollen joints (polyarthyopathy syndrome)

Question 7

Transmission of B19 Virus

Answer 7

• B19 transmission through polyarthropathy respiratory secretions (such as saliva, sputum, or nasal mucus) when an infected person coughs or sneezes.
• Likely not contagious after rash

Question 8

Tropism of Human B19 virus

tropism refers to the ability of a virus to infect specific types of cells or tissues in a host organism.

Answer 8

• human erythroid progenitor cells & foetal liver cells

Question 9

Characteristics of the Human B19 virus

Answer 9

• Icosahedral Capsid
• Nonenveloped
• ss DNA (linear) nonsegmented
• 25nm diameter
• consist only of protein (50%) + DNA (50%)
• 2 capsid proteins, VP1-2. 60 capsomeres. VP2 (95%) and VP1 (5%)

Question 10

What is the purpose of the capsid proteins on B19 Virus ?

Answer 10

The capsid confers considerable stability on the virions , which are resistant to inactivation by pH, solvents or high temperatures (1h @ 50 ° C).

Question 11

B19 V genome organisation

Answer 11

Linear ss DNA genome (Generally ve, sometimes +)
5kb, flanked by terminal (TR) repeats (hairpins)

see slide 14

Question 12

B19V gene expression

Answer 12

• B19 is difficult to grow in culture (erythrocyte progenitor cells required)
• Poorly understood
• Little known of its biology

Question 13

What is hydrops fetalis?

Answer 13

B19 infection in pregnancy is also associated with miscarriage, although the probability of this appears to be low (<10%). Hydrops fetalis

Question 14

Reticulocytopenia

Answer 14

• Loss of rbc due to infection of reiculocytes
• Aplastic crisis leads to AIDS and sickle cell anaemia

Question 15

Is there a treatment to B19?

Answer 15

• No treatment, but Intravenous immunoglobin therapy
• No vaccine

Question 16

What group is Herpesviridae?

Answer 16

• Baltimore group I

Question 17

Name the subfamililies of herpesviridae

Answer 17

• Alpha herpesviruses (e.g. Human herpesvirus simplex (Cold sores); HHV (HHV)– 1 or Herpes 2 (genital herpes); HHV3 or Varicella or Herpes zoster virus (Chickenpox/shingles)
• Beta herpesviruses (e.g. HHV5 or Human Cytomegalovirus)
• Gamma herpesviruses (HHV 4 or Epstein Barr Virus)

Question 18

Latency

Answer 18

quiescent state of viral infection with minimal effect on cell function

Question 19

Characteristic of HHV1

Answer 19

• Complex and large (200nm)
• Lipid envelop (10 proteins, gB, gN)
• Tegument (15 proteins)
• Icosahedral nucleocapsid
• Linear ds DNA genome
• Nonlytic (budding) gB binds to extracellular matrix proteins HHV 1 is pantropic

Question 20

HHV1 Genome organisation

Answer 20

Linear ds DNA genome 126kb Unique long (U L ) region,
26kb Unique short (U s flanked by terminal (TR) or internal (IR) inverted repeats >84 ORFs (Ori;3)

Question 21

How is HHV1-Disease transmitted?

Answer 21

Exchange body fluids (saliva).

Question 22

How is HHV1-Disease treated?

Answer 22

Acyclovir

Question 23

Primary Infection HHV-1 Disease

Answer 23

• Inapparent or Mouth ulcers (Mucosal), whitlow (skin), or rare more serious forms
• HHV1 establishes a persistent infection (not cleared by the immune system).
• After 1st infection in buccal mucosa, HHV travels via nerve cells to trigeminal ganglion where it remains 1 latent
• In some people it reactivates (UV, other infection, stress etc)

Question 24

Reactivated infection of HHV-1 Disease

Answer 24

Cold sores uveitis/keratitis (rare) Immunosuppressed (renal transplant) large necrotic lesions of face.

Question 25

HHV-1 Latency

Answer 25

1. Virus binds to extracellular matric 2. Tegument proteins corrupt cell function, viral core (capsid) goes to nucleus 3. DNA circualizes and transcribes LAT mRNA and small number LAT proteins

Question 26

Where does HSV establish latent infection?

Answer 26

* HSV establishes latent infection in neurons; neurons do not divide, which allows the viral genome to avoid complete replication in order for the virus to remain in the neuron for the lifetime of the cell