Retroviridae - Delatretrovirus: Bovine Leukemia Virus Flashcards
True/False. Bovine leukemia virus is free in blood.
False.
This virus is associated with B lymphocytes, free virus is rarely or never found in blood.
What sequence is unique to BLV and is situated between the env gene and the 3’-LTR?
pX sequence
**NOT AN ONCOGENE!”
Which protein plays a central role in the leukemogenesis of BLV and is encoded in the pX region?
Tax protein
What are the primary target cells of BLV?
B lymphocytes that express IgM
Where is BLV enzootic?
Worldwide
(USA BLV prevalence in dairy cattle ranges from 10-50%)
What is the primary mode of transmission for BLV?
Blood transfusion from infected animal to susceptible animal (potential transfer of lymphocytes)
[OTHER: iatrogenic transmission, rectal palp, mechanical, vertical (in-utero), colostrum or milk containing infected lymphocytes]
Which protein activates replication of BLV and contributes to oncogenesis?
Tax protein
How is BLV thought to escape immune elimination?
By tightly controlling viral gene expression in vivo and promoting cell survival by inhibiting apoptosis
Which type of BLV infection is often asymptomatic but will sometimes cause flu-like signs?
Primary infection
Development of detectable levels of antibodies 4 to 12 weeks after exposure.
Which type of BLV infection is asymptomatic and seen in latent carriers of infection?
Persisent infection
This phase extends for several months/years and is characterized by an immune dysregulation (ex: overexpression of cytokines)
These animals are considered seropositive
What conditions will cattle develop when a persistent latent infection becomes active?
Persistent lymphocytosis (benign proliferation of B lymphocytes, weakness, 30-70% of infected cattle)
Tumor (lymphosarcoma, sudden death from hemorrhage of spleen, 5-10% of infected cattle)
Which alleles are present in cattle resistant to BLV?
BoLA-Aw 7 alleles
Which alleles are present in cattle susceptible to BLV?
BoLA-Aw12 alleles
What are the clinical signs for BLV?
Development of tumors (lymphosarcoma) in lymphoid organs, as well as other tissues
Enlarged superficial lympnodes
Lesions in digestive tract, heart, and nervous system involvment
(clinical signs can vary depending on the other tissues affected)
What is the cause of death with animals that develop lymphosarcoma?
Sudden death from the hemorrhage of the spleen
