|dc.description.abstract||Jaagsiekte is a contagious cancer affecting the lungs of sheep.
Although the etiological agent is Jaagsiekte retrovirus (JSRV),
two other retroviruses viz South African maedi visna virus ( SA -
OMVV) and a novel Bovine retrovirus (BRV) have been associated
with or implicated in the jaagsiekte disease complex.
JSRV was sufficiently purified from lung rinse material using a
Freon extraction, Percoll density gradient centrifugation and
chranatography on a Sephacryl column, its polypeptide composition
was studied by gel electrophoresis and its morphology observed
electron microscopically. Monoclonal antibodies were made against
purified preparations of the virus. Two hybridomas were isolated
that produced MAbs which appear to be tumour cell specific. A
third hybridoma, called 4A1O, produces antibodies considered to
be viral specific. These MAbs have been used in the development of
JS specific immunoassays. A cross reaction between JSRV and a
polyclonal serum against Mason Pfizer monkey virus (MPMV) was
confirmed and used in a Western blot technique to identify,
monitor and differentiate JSRV from other viruses.
During the study of JSRV it became apparent that another retrovirus
was often present in JS infected lungs. This virus, referred
to as SA - OM1V I, is a novel South African isolate of maedi
visna virus (MVV). As SA - OM1V I has physicochemical characteristics
similar to JSRV, it was often found in purified JSRV preparations.
Being a retrovirus it is also detected by the reverse transcriptase assay which was the only method used to assay and
monitor for JSRV during the early stages of our work. Using a
Westen blot technique and sera against MVV and MPMV it was possible
to simultaneously detect and differentiate JSRV from SA -
OMVV I. A method was also developed whereby the two viruses could
be separated from each other during purification.
The information gained and techniques developed whilst studyiing
JSRV were also used to isolate and characterize BRV. This novel
virus originated from bovine cells that had been co-cultivated
with white blood cells from an ox suffering from malignant
catarrhal fever. Three out of four sheep inoculated with BRV
developed JS. It therefore had to be· ascertained whether this
virus was related to JSRV or not. The comparative study revealed
that BRV was biochemically and morphologically quite different
fran JSRV. Interestingly, it was shown that serum against MPMV
cross reacted with a 32 kd protein of BRV indicating a serological
relationship between JSRV, MPMV and BRV. The possible role of BRV
in the etiology of jaagsiekte remains to be elucidated.||en