Jaagsiekte is a contagious lung tumour of
sheep in which two types of secretory epithelial cell in
the lower respiratory tract are transformed. These cells
are type II pneumocytes in the alveoli, and the cells of
Clara in the terminal bronchioles.
An efficient and reproducible technique is
described for the isolation of transformed SPA cells. It
includes three basic steps: Prolonged trypsinisation to
kill fibroblasts, magnetic removal of macrophages, and
adherence to remove the rapidly adherent cells. The
resultant preparations of lung cells were enriched to
96.6% type II pneumocytes.
Four cell lines were initiated from lungs of
sheep with pulmonary adenomatosis and two of the cell
lines have been continuously propagated in vitro for more
than 140 passages. The morphologic and cytogenetic
characteristics of these lines have been examined. The
cells are epithelial and demonstrate ultrastructural
features consistent with the tumour of origin. The lines
are aneuploid and contain a spectrum of cytogenetic marker
SPARV P25 was detected in all cell lines in
early passes, but was undetectable after 11th passage.
After 16 or 20 in vitro passages, three cell
lines grew in soft agar with low cloning efficiency.
However, the efficiency increased with higher passage
The effect of bromhexine HC1 and prednisolone
on the morphology and ultrastructure of SPA cell lines
( JS7 and JS8 ) was studied. Cells treated with
prednisolone lost their squamous epithelial shape and
assumed a fusiform swirling appearance. Coincident with
this change in morphology, the JS7 cells also lost the
characteristic cytoplasmic lamellar bodies but not apical
microvilli nor desmosomes.
Cells treated with bromhexine HC1 showed an
increase in the number and size of lamellar bodies, and
retained their squamous epithelial appearance.
When the cell lines were transplanted
subcutaneously in athymic nude mice, they induced palpable
fluid-filled, cyst-like tumours at the site of injection.
Tumour cells had a morphology similar to that of the
parent cells and the original adenomatosis lung tumour
cells of jaagsiekte, even though they had been through
many in vitro passages. Ultrastructural and cytogenetic
analysis of cell cultures derived from the nude mice
tumours showed these to possess only the sheep karyotype.
SPA was successfully reproduced in neonatal
lambs by intratracheal inoculation of passaged cells.
Macroscopic lesions of SPA were observed in lambs and
confirmed by histopathology and electron microscopy. Cell
cultures were established from the lungs of these lambs.
Replication of a retrovirus in these cultures was
demonstrated by the detection in the supernate of SPARV
P25. The presence of the retrovirus in the lung fluids
from these lambs was also demonstrated.
Thus for the first time permanent cell lines
that contain the SPARV are available and should
considerably facilitate further studies on this virus and
the tumour it causes.