L24: Retroviridae 1 (Romero) Flashcards
Name 2 subfamilies of retroviridae
Orthoretrovirinae
Spumaretrovirinae
name 6 classes of viruses within subfamily orthoretrovirinae and a virus in each class
alpharetrovirus (avian leukosis/sarcoma complex)
betaretrovirus (ovine pulmonary adenomatosis)
gammaretrovirus (feline leukemia virus)
deltaretrovirus (bovine leukosis virus)
lentivirus (caprine arthritis encephalitis)
epsilonretrovirus (Walleye dermal sarcoma)
Structure of retroviruses
- ss+RNA genome
- enveloped (released via budding)
Feline leukemia caused by what virus?
Feline leukemia virus (a gammaretrovirus in subfamily orthoretrovirinae)
Feline leukemia virus transmission
- horizontal and vertical
- kittens, males, older cats more susceptible
- shed in body fluids
FeLV pathogenesis
- initial replication in oral/pharyngeal lymphoid tissue, then systemic spread via lymphocytes, monocytes
- infection life-long, but infection prevalence low
- are multiple strains of FeLV
FeLV virulence is determined by:
changes to SU glycoprotein
FeLV-A vs. B vs. C
FeLV-A: minimally pathogenic
FeLV-B: linked to thymus lymphosarcoma, lymphoid tumors
FeLV-C: assoc. with severe aplastic anemia
Assoc. CS of FeLV
- anisocoria
- protein deposits in anterior uvea
- lymphadenopathy
path. assoc. with FeLV infection
- lymphomas
- myeloproliferative diseases, anemia
- immunopathologic disease
- fibrosarcoma
types of FeLV-associated lymphosarcomas
multicentric (lymphoid and non-lymphoid)
thymic (kittens)
alimentary (older cats; affects lymphoid tissues of GIT)
unclassified (non-lymphoid tissue, skin, eyes, CNS)
FeLV-associated myeloproliferative diseases and anemia
Erythremic myelosis (targets erythroid progenitor cell)
Granulocytic leukemia (targets granulocytic myeloid progenitor cell)
Erythroleukemia (targets erythroid and granulocytic myeloid precursors)
Myelofibrosis (proliferation of fibroblasts)
2 types of FeLV-associated immunopathologic disease
1) Immune-complex mediated
2) Immunodeficiency: chronic stomatitis, gingivitis, non-healing skin lesions, infertility, fetal deaths, abortions, etc.
FeLV-associated fibrosarcomas
- usually seen as solitary tumors in old cats
- can occur in kittens from recombinant feline sarcoma virus after infection with FeLV
- can occur after SC or IM immunization with inactivated adjuvanted vaccines (NOT virus-related)
Dx of FeLV
- Ag detection (snap test)
- PCR to detect FeLV PROVIRUS
- immunofluorescence prone to false positives
- vaccine doesn’t interfere with FeLV Ag tests
FeLV immunity, prevention, control
- test and segregte infected cats
- vaccine does NOT protect against infection, only progressive infection and dz
- vax of infected cats useless
cause of Avian lymphoid leukosis
-caused by exogenous RNA tumor virus within Retroviridae
transmission of Avian lymphoid leukosis virus
- exogenous viruses: vertical and horizontal
- endogenous: genetically by both rooster and hen; not oncogenic
pathogenesis of avian lymphoid leukosis
- originate by transformation of lymphoid cells within bursa of Fabricius
- gross tumors follow microscopic lesions at about 16 wks
- May involve viscera, but NO nerve involvement
T/F: will never see nerve lesions in tumors of lymphoid cells**
T
dz syndromes induced in chickens by alpharetroviruses and tissue effected in each
Alpharetrovirus (target cells) Lymphoid leukosis (lymphoblasts) Osteopetrosis (Osteoblasts) Nephroblastoma (Renal cells) Erythroblastosis (Erythroblasts) Hemangioma (Capillary endothelium) Myeloblastosis (Myeloblasts) Myelocytomatosis (Myelocytes) Sarcoma (various mesenchymal cells)
tumors caused by replication-competent avian retroviruses
lymphoid leukosis
osteopetrosis (diaphysis thickens)
renal tumors
tumors caused by replication-defective avian retroviruses
erythroblastosis myeloblastosis myelocytomatosis hemangioma sarcomas
erythroblastosis char. by:
severe anemia, liver, spleen, kidneys enlarged and dark red
dx of avian lymphoid leukosis
- tumor cells in bursa of Fabricius react with antiserum
- RT-PCR of tumor RNA and sequencing
- absence of Marek’s MEQ gene in tumors
- no infiltration of nerves with lymphoid cells
control of Avian lymphoid leukosis***
- ERADICATION of exogenous lymphoid leukosis virus from breeders or genetic stocks
- NO VACCINE!
- sanitation, biosecurity
Ovine Pulmonry Adenomatosis (Jaagsiekte) chars.
- dz of adult sheep
- leads to wasting and severe resp. distress
- worldwide
- reportable in some U.S. states
- high incidence in Peru
- caused by a BETARETROVIRUS
CS of Ovine Pulmonary Adenomatosis (Jaagsiekte)
- long incubation period after infection with severe losses
- progressive dyspnea, anorexia, caquexia
- resp. failure –> death
transmission/path. of Ovine Pulmonary Adenomatosis
- trans. in aerosolized lung fluids (facilitated by close confinement)
- transforms differentiated lung epithelial cells (PNEUMOCYTES) –> epithelial proliferation –> nodular lesions
- active replication restricted to broncholveolar epithelial cells!**
- tumors correspond to adenoma or adenocarcinoma
- mets uncommonly
Dx of Ovine Pulmonary adenomatosis
- infected animals don’t develop circulating Ab (lack of response possibly due to immunological tolerance triggered by closely related endogenous retroviruses (endJSRVs))**
- JSRV proviral DNA sequences detected by PCR or in colostrum/milk from infected and/or clinically ill ewes
Control of Ovine Pulmonary Adenomatosis
- NO vaccines available**
- strict biosecurity and immediate removal of sick sheep as soon as CS appear**
- don’t keep lambs of affected ewes as replacement stock
most important management strategy in reducing Jaagsiekte’s losses
rear sheep in single age groups
