The extracellular envelope glycoprotein (gpl35) of
maedi-visna virus interacts with cellular receptor molecules
and is the major target of neutralising antisera in vivo.
Antigenic drift of gpl35 may have an important role in viral
In order to begin to investigate the roles of different
regions of gpl35, yeast and bacterial expression systems were
used to generate recombinant protein and gpl35 was expressed
as 3 overlapping fragments. There have been no published
reports of expression of recombinant gpl35 proteins.
By using the proteins to screen sera from infected
sheep it was shown that sheep vary in the regions of gpl35 to
which they mount an antibody response detectable in this
system. At least 3 epitopes on gpl35 are recognised by sera
from infected sheep.
The recombinant proteins were used to investigate
interactions of gpl35 with cellular molecules, and as
immunogens to raise gpl35-specific sera. Possible future
experiments using these reagents are suggested.
gpl35 fragments derived from different viral stocks of
the British isolate of maedi-visna virus were sequenced, to
obtain a preliminary estimate of the extent of the
variability of the gene. The data suggested the presence of
both relatively conserved and variable regions in gpl35.