Virology - parvovirus, adenovirus, poxvirus, herpesvirus Flashcards
Is parvovirus enveloped?
No - stable in environment
What type of symmetry does parvovirus nucleocapsid have?
Icosahedral
What is the surface of a parvovirus like?
Rugged
What is the classification of parvovirus?
Linear single stranded DNA
Can be either positive or negative sense
Class 2
What does parvovirus need to replicate?
Host cell proteins from dividing cells
What does the open reading frame on the 3’ end of the parvovirus genome encode for?
Non-structural proteins (NS)- for DNA transcription and replication
What does the open reading frame on the 5’ end of the parvovirus genome encode for?
Structural proteins (VP)- form the capsid
What does parvovirus NS1 do?
Unzips DNA (helicase) for viral DNA replication
What does parvovirus NS 2 do?
Regulates viral gene expression
Which is less frequent out of the parvovirus structural proteins - VP1 or VP2?
VP1
How is the parvovirus genome replicated?
ssDNA made into dsDNA
Then mRNA is made to make viral proteins
And new ssDNA is made to be packaged into virions
Where does parvovirus DNA replication occur? In what kind of cells?
In the nucleus
Dividing cells
What does parvovirus not have?
DNA polymerase
What receptor does canine parvovirus use to enter cells?
Transferrin receptor
What age does canine parvovirus affect?
All ages, less than 6 months the worst
How is canine parvovirus transmitted/infection?
Ingestion or inhalation via direct or indirect contact
Where in the body does parvovirus infect?
Replicates in lymph nodes via naso and oropharynx
Then to where cells rapidly divide (bone marrow and intestine crypts of villi) via blood stream
Also heart of young dogs
What are the clinical symptoms of canine parvovirus?
Diarrhoea due to blunting of villi
Haemorrhage in severe cases
Immunosuppression
How is canine parvovirus diagnosed?
Virus in faecal samples
Haemagglutination
PCR
Antigen ELISA
Can you vaccinate against canine parvovirus?
Yes
Vaccination also provides maternal antibodies so puppies more protected
What does porcine parvovirus infection cause in pigs?
Reproductive failure - stillbirths, mummification, infertility, embryo death
Where is porcine parvovirus infection mostly found?
Foetuses - lots of dividing cells
Before 60 days old - no immune system
How is porcine parvovirus infection transmitted?
Transplacentally
How is porcine parvovirus infection controlled?
Vaccination of gilts (young female pigs)
What classification is adenovirus?
Single linear double stranded DNA
Group 1
Is adenovirus enveloped?
No
What symmetry does adenovirus have?
Icosahedral
What is unique to the adenovirus capsid?
Has a fibre - attaches the virus to host cells and is a haemagglutinin
What is the adenovirus capsid made up of?
Hexons and pentons
What does the adenovirus genome have on each end?
An inverted terminal repeat
What do the adenovirus early region genes do?
Regulate transcription
What is the role of the adenovirus late region genes?
Structural
What is the promotor region for the late region of the adenovirus genome called?
Major late promoter
What does adenovirus use for transcription of their genome?
Its own viral DdDp - copies genome
Host DdRp - makes mRNA to produce viral proteins
Where does adenovirus replication occur?
In the nucleus - needs hosts DdRp which is found in the nucleus
Which form of adenovirus is infectious and why?
Mature virions - contain the entire genome and have proteolytically processed capsid proteins
What does adenovirus E proteins do?
Cause immune evasion
What can you use to diagnose adenovirus infections?
Haemagglutination inhibition assay
What severe disease is caused by adenovirus in dogs?
Canine adenovirus 1 - causes canine hepatitis
How is canine adenovirus 1 transmitted?
Ingestion of infected bodily fluids eg. urine, faeces or saliva
What age of dogs are affected by canine adenovirus 1? What severity?
All ages
More severe in puppies
Subclinical infection is common
What are the three syndromes of canine adenovirus 1?
Peracute disease - dead without a sign
Acute disease
Mild disease - partial immunity, vaccine
What are the symptoms of acute disease?
Fever, thirst, vomiting and diarrhoea etc.
Blue eye in 25% of affected dogs - bilateral corneal opacity
Why does blue eye form in canine adenovirus 1 infections?
Virus forms immune complexes with antibodies in the eye, causes inflammation
What milder disease is caused by adenovirus in dogs ?
Canine adenovirus 2 - localised respiratory disease, kennel cough
Can you vaccinate against canine adenovirus?
Yes - canine adenovirus 2 vaccine is used to vaccinate against both 1 and 2
What classification is poxvirus?
Linear double stranded DNA
Group 1
Where does poxvirus replicate?
In the cytoplasm
Does poxvirus have an envelope?
No - stable in environment in dry conditions
What shape are poxviruses?
Brick shaped
How many layers does a pox virus have? What are they?
4 layers Core Core wall Inner membrane Outer membrane
What does poxvirus have on its outer membrane?
Short surface tubules
What shape is the poxvirus core?
Egg timer - lateral bodies squash middle together
How are poxvirus virions released from the host cell?
Budding
What shape is the parapoxvirus?
Ovoid shaped
What are found at the ends of the poxvirus genome?
Inverted terminal repeats
What do inverted terminal repeats do?
Join DNA strands together by crosslinking them
Where are the genes that code for the structural proteins found on the poxvirus genome?
In the centre
Where does poxvirus replicate?
In the cytoplasm - minimally dependent on host cell
What is the main feature of the poxvirus genome?
Very big, codes for lots of (100+) proteins eg. DdDp and immune modulating (affecting) proteins
What are viroreceptors?
Cell receptors that are altered by poxvirus so they are not anchored to the cell membrane, get secreted
What are virokines?
Secreted viral proteins made by poxvirus which resemble host cytokines but are not functional
How are poxviruses transmitted?
Skin abrasions
Aerosol
Contaminated environment
Biting arthropods
What transmits swinepox?
Pig/hog louse (haematopinis suis)
How can poxviruses affect a wide range of different species?
They dont rely on specific cellular receptors to enter cells, instead they use host molecules
How does the vaccinia poxvirus attach to cells?
Viral outer membrane proteins bind to host cell glycosaminoglycans
What are the 3 stages of poxvirus replication?
Early, intermediate and late
How are each stage of poxvirus protein encoded?
By the genes from the stage before eg. intermediate gene transcription factors are encoded by early genes
What is a characteristic of cells which are infected with poxvirus?
Host cell has intra-cytoplasmic inclusion bodies - stain red
What are the flat red spots on skin from a poxvirus infection called?
Macules
What are the raised red spots on skin from a poxvirus infection called?
Papules
What are papules that are filled with with fluid/pus called?
Vesicles/pustules (3/4 weeks to develop
What are examples of poxvirus?
Vaccinia virus
Orf
Where is vaccinia virus found?
Not seen in Europe since smallpox vaccination ceased - vaccinia used as a human vaccine for smallpox
Outbreaks still in India
Where are the lesions found in cowpox and buffalopox virus?
Mild form - udders and teats Severe form (only in buffalopox) - generalised lesions
How is cowpox spread?
In rodents - mice and voles
Cows lie on grass and udder comes in contact with rodent droppings
What is feline cowpox like?
More severe - single lesion, necrotising dermatitis for 6-8 weeks
What is the other name for orf?
Contagious ecthyma
Where does orf affect?
Mucocutaneous junctions of the muzzle and lips
What does orf affect?
Young lambs and kids
How can you prevent orf?
Vaccination - live attenuated
Of ewes before lambing
How is orf vaccine administered?
Scratch application to skin - scarification
What are examples of parapoxviruses?
Pseudocowpox virus
Bovine papular stomatitis
What is pseudocowpox virus?
Less severe than cowpox
Affects udder and teats of cows
How is pseudocowpox transmitted?
Horizontally through milking teat cups and hands, suckling and flies
What is papular stomatitis?
Less severe than orf
Affects mouth, muzzle and nostrils
What classification is herpesvirus?
Linear double stranded DNA
Group 1
Does herpesvirus have an envelope?
Yes
What type of herpesvirus is cold sores?
Herpes simplex virus 1 (HSV1)
What type of herpes virus is genital herpes?
HSV2
What type of herpes virus is chickenpox?
Varicella zoster
What are the 3 subfamilies of herpesvirus?
Alpha herpesvirinae
Beta herpesvirinae
Gamma herpesvirinae
What are the characteristics of alpha herpesviruses?
Short replication cycle (<24hrs)
Wide host range
Rapid destruction of cultured cells
Latent infections in neurones
What are the characteristics of beta herpesviruses?
Long replication cycle (>24hrs)
Narrow host range
Slow destruction of cultured cells
Infected cells contain cytoplasmic and nuclear inclusions
Latent infection in lymph and secretory cells
What are the characteristics of beta herpesviruses?
Narrow host range Lymphotropic Latent in lymphocytes Linked to oncogenic transformation of lymphocytes Cytolytic Infects epithelial cells and fibroblasts
What are the three distinct structures of a herpes virus?
Envelope
Capsid
Tegument
How does herpes virus replicate its genome?
Uses a host DdRp RNA polymerase to create mRNA to make proteins for new virions
Uses a viral DdDp to copy its genome
What happens to herpesvirus genome when it enters the host cell nucleus?
It binds at its ends to form a circle
How do herpesviruses enter cells?
Most bind to glycosaminoglycans
Some bind to receptors
What part of herpesviruses are released into the cytoplasm?
The tegument and nucleocapsid
Where does transcription of herpesvirus occur?
All in the nucleus - none in the cytoplasm
How are herpesviruses packaged and matured after replication?
By budding through the nuclear membrane to envelop the nucleocapsid and then be in vacuoles in the cytoplasm
How does herpesvirus remain latent in cells?
Stay in host cell nucleus as circular viral genome or by integrating the genome into a host chromosome
How does the immune system protect against herpesvirus?
Neutralising antibodies ad antibody dependent cellular cytotoxicity
IFN-a limits virus spread
Cytotoxic T cells clears active infection
How does herpesvirus evade the immune system?
Viral proteins not expressed on cell surface
Blocks and destroys MHC
Secretes virokines
What diseases does bovine herpes virus 1 cause?
Bovine rhinotracheitis and pustular vulvovaginitis
What are the symptoms of bovine rhinotracheitis (bovine herpes virus 1)?
Fever
Serous nasal discharge
Tissue necrosis - secondary infections, death
Conjunctivitis
What are the symptoms of pustular vulvovaginitis (bovine herpes virus 1)?
Affects cows uterus, oviducts, ovaries and vulva
Tail held away from vulva
Fever and depression
How long does pustular vulvovaginitis (bovine herpes virus 1) last?
Acute stage - 4-5 days
Heals by 10-14 days
Where does bovine herpes virus 1 remain latent?
Sciatic and trigeminal ganglia
How is bovine herpes virus 1 diagnosed?
Swabs, ELISA, PCR
How is bovine herpes virus 1 prevented?
Vaccination - used extensively, reduces severity of disease
What diseases does bovine herpes virus 2 cause?
Mammillitus
Pseudo-lumpy skin disease
Where does mammillitus affect?
Teats and udder
How is mammillitus transmitted?
Serous exudate from lesions
Suckling, direct, indirect
How is pseudo-lumpy skin disease transmitted?
Biting insects
How is BHV2 infection diagnosed?
Cultured in bovine cells, electron microscope
PCR
