SM L4 Flashcards
Parovoviridae Family, 6 genera divided between 2 subfamiles. Name the two sub families.
Parvovirinae - vertebrate hosts
Densovirinae - arthropod hosts
Name the genus, type species and host organisms of the Parvovirinae sub family
Parvovirus - Mice minute virus - vertebrates
Erythrovirus - B19 virus - vertebrates
Dependovirus - Adeno-associated virus 2 - vertebrates
Name the genus, type species and host organisms of the Densovirinae sub family
Densovirus - Jumonia coenia densovirus - invertebrates
Iteravirus - Bombym mori densovirus - invertebrates
Contravirus - Aedes aegypti densovirus - invertebrates
What is another name for the B19 virus?
erythema infectiosum or fifth disease
What group of people are more susceptible to the B19 virus?
More common in children than adults
About 20% of children and adults who get infected with this virus will not have any symptoms
Signs and Symptoms of B19 virus
mild and nonspecific, fever, runny nose and headache
Rash on face and body (slapped cheek rash)
Painful or swollen joints (polyarthyopathy syndrome)
Transmission of B19 Virus
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
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
human erythroid progenitor cells & foetal liver cells
Characteristics of the Human B19 virus
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%)
What is the purpose of the capsid proteins on B19 Virus ?
The capsid confers considerable stability on the virions , which are resistant to inactivation by pH, solvents or high temperatures (1h @ 50 ° C).
B19 V genome organisation
Linear ss DNA genome (Generally ve, sometimes +)
5kb, flanked by terminal (TR) repeats (hairpins)
B19V gene expression
B19 is difficult to grow in culture (erythrocyte progenitor cells required)
Poorly understood
Little known of its biology
What is hydrops fetalis?
B19 infection in pregnancy is also associated with miscarriage, although the probability of this appears to be low (<10%). Hydrops fetalis
Reticulocytopenia
Loss of rbc due to infection of reiculocytes
Aplastic crisis leads to AIDS and sickle cell anaemia
Is there a treatment to B19?
No treatment, but Intravenous immunoglobin therapy
No vaccine
What group is Herpesviridae?
Baltimore group I
Name the subfamililies of herpesviridae
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)
Latency
quiescent state of viral infection with minimal effect
on cell function
Characteristic of HHV1
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)
HHV1 Genome organisation
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)
How is HHV1-Disease transmitted?
Transmission: Exchange body fluids (saliva).
How is HHV1-Disease treated?
Acyclovir
Primary Infection HHV-1 Disease
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)
Reactivated infection of HHV-1 Disease
Cold sores
uveitis/keratitis (rare)
Immunosuppressed (renal transplant) large necrotic lesions of face.29
HHV-1 Latency
- Virus (gB) binds to
extracellular
matrix
HHV-1 Latency
2 Tegument proteins corrupt
cell function, Viral core
(capsid) goes to nucleus. - 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
Where does HSV establish latent infection?
Latent infections
established in
nondividing neurons,
excluded from some
immune surveillance
