Lecture 14: retroviruses Flashcards
Are retroviruses enveloped or non-enveloped, + sense ssRNA or - sense ssRNA
enveloped, +sense ssRNA
what are the 3 major genes that encode for general structure of retroviruses
- Env gene
- Gag gene
- Pol gene
what does env gene do
envelope glycoprotein
Encodes for
1. Surface glycoproteins- bind to host cell receptor
2. Transmembrane glycoproteins: mediate membrane fusion
what does gag gene do
encodes for
1. Nucleocapsid
2. Capsid
3. Matrix
what does pol gene do
enzymes
Encode for
1. Reverse transcriptase: RNA—> RNA
2. Integrase: integrate pro viral DNA into host genome
3. Protease: cleave polypeptide into functional proteins
what is retrovirus life cycle
- Attachment of envelope glycoproteins to host cell receptor
- Fusion
- Reverse transcription of ssRNA to DNA
- Integration of pro viral DNA into host cell chromosome
- Viral replication and protein synthesis
- Assembly of nucleocapsid and insert glycoproteins into host membrane
- Release of virions by budding from plasma membrane
what is main target of retroviruses
immune cells
what are the 3 ways retroviruses can result in cancer
- Capture and transfer of a host cell proto-oncogene
- Insertional mutagenesis
- Encoding of proteins that are directly oncogenic to infected cells
how does capture and transfer of host cell proto-oncogene work
- Incorporates host proto-oncogene into viral genome forming viral oncogene
- Infection of another host cell results in transformation
how does insertional mutagenesis work
- Pro viral insertion near host proto-oncogene may disrupt regulation= conversion of host proto-oncogene to oncogene
What is the important structure in FeLV that we detect antigen for in flow by assay
p27 capsid protein
what viral subtype of FeLV is only transmitted between animals
FeLV-A
how do other subtypes of FeLV arise
mutations and recombination events
FeLV-T arises from mutations in FeLV-A and causes what
infects and destroys T cells, leading to lymphoid depletion and immunodeficiency
what is most common mode of transmission for FeLV
saliva, grooming, feeding, bites
what are some signs of FeLv
Fever, diarrhea, weight loss, anorexia, pale gums, poor coat condition, enlarged LN, leukopenia, anemia, recurrent secondary infections, neurlogical
what cancers are most commonly associated with FeLV
lymphomas/leukemias
what is pathogenesis of FeLV
- Virus replicates in local lymphoid tissue, often oropharynx
- Virus infected WBC’s enter blood= primary viremia (bone marrow)
- Secondary viremia leading to infection of endothelial cells that can allow for viral replication and shedding
what are the 3 outcomes of FeLv infection
- Abortive infection
- Regressive infection
- Progressive infection
what happens in abortive infection of FeLV
- Effective immune response
- Elimination of virus
what happens in regressive infection of FeLV
- Effective immune response- virus contained after systemic spread
- Generally aviremic
- Remains latent can reactivate if immune system declines
what happens in progressive infection with FeLV
- Ineffective immune response
- Viral replication and viral spread- persistent viremia
- Clinical disease- often fatal
t of f: most cats infected with FeLV will eventually develop a progressive infection
False
what are some FeLV associated diseases
- Cancers
- Myelosuppression
- Secondary infections
- Other disorders
