retroviruses Flashcards
retroviral replication
- replicate via dna intermediate
- 2x stranded dna = integrated into host dna mediated by viral integrate, from this integrated ds dna have viral replication from and production of new viral proteins and new virions released from virally infected cells
types retroviruses
- oncogenic retroviruses (alpha, death, and beta retroviruses)
- complex retroviruses (lentiviruses)
oncogenic retroviruses general featreus
tumors
important oncogenic retroviruses
- feline leukemia virus
- avian leukosis virus
- bovine leukemia virus
complex retroviruses general features
immunodeficiency
complex retroviruses important
- feline immunodeficiency virus
- equine infectious anemia virus
- ovine progressive pneumonia virus
- caprine arthritis- encephalomyelitis virus
retroviruses primarily important in who
cats
retroviruses structure
- two copies single stranded rna (pos sense)
- capsid
- envelope
- 30 copies reverse transcriptase packed into viron
retrovirus reverse transcriptase
- convert genomic rna into provirus
- released upon entry into cell
retrovirus structure
- simple retroviruses
- complex retrovirses
simple retrovirus structure
- gag, pol, env genes
gag genes encode what
group antigens (structural specific)
pol genes encode what
encode viral enzymes
env genes encode what
encode for envelope
complex retroviruses genes
additional genes that regulate replication and gene expression plus gag, pol, env
retroviruses key features
- undergo mutation and recomb
retroviruses and host genome
- integrate into host genome
- endogenous / replication defective retrovirses
- (in)activate host genes near site of integration
endogenous/ replication defective retroviruses
- live in host genome
- no replication
- no dx
- mo transmission
- can recombine with exogenous retroviruses if cell gets infected -> highly virulent sarcoma viruses
(in)activation host genes effect
- oncogenic retroviruses do this, if near tumor suppressor or oncogene can allow virus to -> tumors
retrovirus transmission
- inefficient
- not spread easily form animal to animal requires prolonged contact
oncogenic retroviruses affect who
- infect and transform cells in all classes vertebrates
- best known in cats, ruminants, chickens, and fish
oncogenic retorvirus tumor production mechanisms
- insertional mutagenesis
- capture of cell oncogene
- retroviral oncogenic gene
clinical signs oncogenic retrovirus
- depend on site of tumor
oncogenic retroviruses insertional mutagenesis
- virus integrates into host genome -> viral promotor -> infleunce expression host genes at that site ->
- if cell oncogene activation -> transofrmaiton
- if cell tumor suppression gene disruption -> loss suppressor control -> transoformation (rare)
oncogenic retrovirus tumor onset speed
very slow
oncogenic retroviruses capture of cellular oncogenes
virus captures cell oncogene and puts in own genome -> replace one of its own genes with cell oncogene -> replication defective virus bc lacking all genes needed for replication
how does replication defective virus repliacte
need to be in cell co infected with intact retrovirus (helper or replication competent virus) -> recombination -> deficient virus use enzyme from competent virus to start replicating -> sarcoma virus bc replication deficient virus has cell oncogene
oncogenic retroviruses capture cell oncogene tumor arising speed
- arise v quickly
oncogenic retroviruses cell oncogene capture nature
- rare in nature bc not transmitted bc so fatal
retroviral oncogene
- genes of certain retroviruses are themselves oncogenic
- beta and delta retroviruses, not important to vet med
feline leukemia virus virus type
- gamma retrovirus
- simple retrovurs
feline leukemia virus effects who
cat
feline leukemia virus found where how prevalent
- worldwide
- common (dec bc vac and better diagnostics)
feline leukemia virus syndromes
- tumors (lymphoma)
- leukemia
- bone marrow suppression (immunodeficiency, anemia)
most common infectious cause of death in cats
feline leukemia virus
pathogenesis feline leukemia virus
- primary oro-nasal infection -> localized virus replication in epithelium and pharyngeal lymphoid tissues -> various outcomes (depends on age, immune status, viral dose):
- abortive
- regressive
- progressive
- focal
abortive infection feline leukemia virus
- immune system kicks in -> abortive infection no viremia no dx (not abortion just not viremic)
regressive infection feline leukemia virus
- immune system does not kick in -> regressive infeciton w/ transient viremia, no dx
progressive infection feline leukemia virus
- immune system does not kick in -> progressive infection w. replication in salivary gland and urogenital mucosa -> virus sheds in saliva and urine
- persistently viremic animals, dx
focal infection feline leukemia virus
atypical
feline leukemia virus diff ages
- 100% neonatal kittens become persistently infected (90% develop tumors)
- 15-30% cats > 4 moths become persistently infected (10-15% develop tumors)
feline leukemia virus transmission
- direct contact w/ saliva of persistently infected cat (must be prolonged contact)
- vertical transmission via placenta and milk