SM L4

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)

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

3 large subfamilies:
Alpha herpesviruses (e.g. Human herpesvirus (HHV)-1 or Herpes
simplex (Cold sores); HHV-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 envelope (10 proteins, gB, gN)
Tegument (15 proteins)
Icosahedral nucleocapsid
Linear ds DNA genome
Non-lytic (budding)
gB binds to extracellular matrix proteins
HHV-1 is pantropic (but is sometimes
described as neurotropic)

Question 20

HHV1 Genome organisation

Answer 20

126kb Unique long (UL) region, 26kb Unique short (Us) region
TRL UL Us TRs
IRL IRs
flanked by terminal (TR) or internal (IR) inverted repeats
>84 ORFs (Ori;3)

Question 21

How is HHV1-Disease transmitted?

Answer 21

Transmission: 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
HHV-1 establishes a persistent infection (not cleared by the immune
system).
After 1o
infection in buccal mucosa, HHV-1 travels via nerve cells to
trigeminal ganglion where it remains 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.29

Question 25

HHV-1 Latency

Answer 25

1. Virus (gB) binds to
   extracellular
   matrix
   HHV-1 Latency
   2 Tegument proteins corrupt
   cell function, Viral core
   (capsid) goes to nucleus.
2. DNA circularizes and
   transcribes LAT
   mRNA and small
   number LAT
   proteins
   LAT
   proteins
   Function
   unknown
   LAT=Latency
   associated
   transcript
   Latent neurone only becomes
   permissive on “stress signal”
   leading to reactivation

Question 26

Where does HSV establish latent infection?

Answer 26

Latent infections
established in
nondividing neurons,
excluded from some
immune surveillance