DNA Viruses: Parvovirus Flashcards
(12 cards)
List the criteria used to classify viruses Q
P1. Host types
2. Disease syndrome
3. Viral structure & symmetry
4. Nucleic acid types (Genome)
5. mRNA production mechanism
6. Modern taxonomy (Phylogenetic)
What is Baltimores classification? Q
What is it based on?
Classification based on
the Nucleic Acid types
m-RNA production mechanism
Classification into six groups/families
ds-DNA viruses
ss-DNA viruses
ds- RNA viruses
ss-RNA viruses with positive strands(+ve polarity)
ss-RNA viruses with negative strands(-ve polarity)
ss-RNA viruses associated with the enzyme reverse transcriptase.
What are the MEDICAL IMPORTANT double stranded DNA VIRUSES? And how can they be classified?
Poxviridae
Herpesviridae
Hepadnaviridae
Adenoviridae
Papovaviridae
DNA viruses can be classified as:
Enveloped viruses
Non-enveloped viruses
MCQ what is the origin of the name Parvovirus
Identified by Cossart & co. (1974) while evaluating HBV surface Ag
Its name originated from the coding of serum specimen from which it was detected (Panel B, No 19)
What are the Unique Properties of Parvoviruses?
Smallest DNA virus (Both capsid diameter & genome size: 18-6nm diameter)
Icosahedral
Non-enveloped
ssDNA, 4000-6000 bases
Has predilection for erythroid progenitor cells
Causes various disease in various animals:
distemper in cats,
enteric disease in dogs,
fatal cardiac infection in puppies
B19 is the only member that cause infections in humans
Has only one serotype
Highly resistant to inactivation
Resistant at 53OC for 30 minutes
Stable at pH 3-9
Inactivated by:
Formalin
Propiolactone
Oxidizing agents
Codes for many proteins
Encoded proteins Incudes:
3 structural proteins
1 major non-structural protein
Many smaller proteins
What is the Classification of parvoviruses?
What is Dependovirus and Adenosatellite virus?
Consist of 3 Genera: Erythrovirus, Parvovirus & Dependovirus
Dependovirus are:
1. Poxviruses
2. Defective viruses
3. Replicate only in the presence of helper virus (Adenoviruses) aka: Adeno-associated viruses,
Adenosatellite virus
1. Do cause infection alone
2. Do not alter the one caused by the helper virus
Transmission of parvovirus
Aerosol droplet,
Fecal–oral route
Direct inoculation of conjunctivas by fingers
Vertical transmission during birth
Percutaneous inoculation with blood contaminated items
Transfusion of blood & blood related products
The Infected is contagious from 24-48 hours before prodrome to rash appearance
What is the pathogenesis of parvovirus?
Tropism for:
RBC precursors
Endothelial cells of blood vessels
Predilection for mitotic cells
Infects rapidly dividing RBC precursors in the bone marrow, foetal liver & erythroid leukemic cells
Destroys infected cells leading to anaemia
Infected blood vessel endothelial cells leads to Erythema infectiosum
Viral replication occurs in the nucleus of the infected cells
Viral ssDNA has hairpin loops at both ends to simulate dsDNA areas
Cellular DNA polymerase takes the advantage of the simulated dsDNA areas for synthesis of viral genome
Cellular RNA polymerase synthesizes viral mRNA from the dsDNA intermediate & then viral capsid
This is followed by assembly & subsequently viral death
Production of RBC stops approximately 1wk after infection
Flu-like illness
Develops due to large viraemia
Viruses are shed in oral & respiratory secretions
Viraemia then wins due to the production of specific Ig to B19
Rash & Arthralgia
occurs in the second stage of the disease
believed to be immunologically mediated
coincides with the disappearance of viraemia
and appearance of IgM & IgG (Ab mediated immunity)
and finally, formation of immune complexes
role of Cell mediated immunity in the disease is unknown
Q difference between primary and secondary viremia
Primary after contact, it enters the blood and then other organs into the GIT then the lymph nodes
Secondary after contact and enter the lymph nodes and multiplies, and then enters the blood
Q Clinical syndrome associated with parvovirus
- Flu-like illness
- Erythema infectiosum (5th Disease): common in children
- Infection in pregnant women
- Chronic B19 infection
Diagnosis
Serology
+ve IgG & IgM is diagnostic in B19 Erythema infectiosum in children
+ve IgG & IgM within 7 days-4 months of pregnancy constitute risk to foetus
IgG alone in serum suggest past infection
Can be done using ELISA, RIA & IFA
PCR
done on blood sample
+ve test suggest viraemia
Management
Treatment
Not available at present
Prevention & Control
No specific measure available at present
Vaccine development ongoing (Phase 1 Clinical trial)
