L24: Retroviridae 1 (Romero)

Question 1

Name 2 subfamilies of retroviridae

Answer 1

Orthoretrovirinae

Spumaretrovirinae

Question 2

name 6 classes of viruses within subfamily orthoretrovirinae and a virus in each class

Answer 2

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)

Question 3

Structure of retroviruses

Answer 3

• ss+RNA genome

- enveloped (released via budding)

Question 4

Feline leukemia caused by what virus?

Answer 4

Feline leukemia virus (a gammaretrovirus in subfamily orthoretrovirinae)

Question 5

Feline leukemia virus transmission

Answer 5

• horizontal and vertical
• kittens, males, older cats more susceptible
• shed in body fluids

Question 6

FeLV pathogenesis

Answer 6

• 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

Question 7

FeLV virulence is determined by:

Answer 7

changes to SU glycoprotein

Question 8

FeLV-A vs. B vs. C

Answer 8

FeLV-A: minimally pathogenic
FeLV-B: linked to thymus lymphosarcoma, lymphoid tumors
FeLV-C: assoc. with severe aplastic anemia

Question 9

Assoc. CS of FeLV

Answer 9

• anisocoria
• protein deposits in anterior uvea
• lymphadenopathy

Question 10

path. assoc. with FeLV infection

Answer 10

• lymphomas
• myeloproliferative diseases, anemia
• immunopathologic disease
• fibrosarcoma

Question 11

types of FeLV-associated lymphosarcomas

Answer 11

multicentric (lymphoid and non-lymphoid)
thymic (kittens)
alimentary (older cats; affects lymphoid tissues of GIT)
unclassified (non-lymphoid tissue, skin, eyes, CNS)

Question 12

FeLV-associated myeloproliferative diseases and anemia

Answer 12

Erythremic myelosis (targets erythroid progenitor cell)
Granulocytic leukemia (targets granulocytic myeloid progenitor cell)
Erythroleukemia (targets erythroid and granulocytic myeloid precursors)
Myelofibrosis (proliferation of fibroblasts)

Question 13

2 types of FeLV-associated immunopathologic disease

Answer 13

1) Immune-complex mediated
2) Immunodeficiency: chronic stomatitis, gingivitis, non-healing skin lesions, infertility, fetal deaths, abortions, etc.

Question 14

FeLV-associated fibrosarcomas

Answer 14

• 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)

Question 15

Dx of FeLV

Answer 15

• Ag detection (snap test)
• PCR to detect FeLV PROVIRUS
• immunofluorescence prone to false positives
• vaccine doesn’t interfere with FeLV Ag tests

Question 16

FeLV immunity, prevention, control

Answer 16

• test and segregte infected cats
• vaccine does NOT protect against infection, only progressive infection and dz
• vax of infected cats useless

Question 17

cause of Avian lymphoid leukosis

Answer 17

-caused by exogenous RNA tumor virus within Retroviridae

Question 18

transmission of Avian lymphoid leukosis virus

Answer 18

• exogenous viruses: vertical and horizontal

- endogenous: genetically by both rooster and hen; not oncogenic

Question 19

pathogenesis of avian lymphoid leukosis

Answer 19

• 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

Question 20

T/F: will never see nerve lesions in tumors of lymphoid cells**

Answer 20

T

Question 21

dz syndromes induced in chickens by alpharetroviruses and tissue effected in each

Answer 21

Alpharetrovirus (target cells)
Lymphoid leukosis (lymphoblasts)
Osteopetrosis (Osteoblasts)
Nephroblastoma (Renal cells)
Erythroblastosis (Erythroblasts)
Hemangioma (Capillary endothelium)
Myeloblastosis (Myeloblasts)
Myelocytomatosis (Myelocytes)
Sarcoma (various mesenchymal cells)

Question 22

tumors caused by replication-competent avian retroviruses

Answer 22

lymphoid leukosis
osteopetrosis (diaphysis thickens)
renal tumors

Question 23

tumors caused by replication-defective avian retroviruses

Answer 23

erythroblastosis
myeloblastosis
myelocytomatosis
hemangioma
sarcomas

Question 24

erythroblastosis char. by:

Answer 24

severe anemia, liver, spleen, kidneys enlarged and dark red

Question 25

dx of avian lymphoid leukosis

Answer 25

- 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

Question 26

control of Avian lymphoid leukosis***

Answer 26

- ERADICATION of exogenous lymphoid leukosis virus from breeders or genetic stocks - NO VACCINE! - sanitation, biosecurity

Question 27

Ovine Pulmonry Adenomatosis (Jaagsiekte) chars.

Answer 27

- 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

Question 28

CS of Ovine Pulmonary Adenomatosis (Jaagsiekte)

Answer 28

- long incubation period after infection with severe losses - progressive dyspnea, anorexia, caquexia - resp. failure --> death

Question 29

transmission/path. of Ovine Pulmonary Adenomatosis

Answer 29

- 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

Question 30

Dx of Ovine Pulmonary adenomatosis

Answer 30

- 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

Question 31

Control of Ovine Pulmonary Adenomatosis

Answer 31

- 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

Question 32

most important management strategy in reducing Jaagsiekte's losses

Answer 32

rear sheep in single age groups