Arch Virol (1997) 142: 1563±1575
Expression of the SU glycoprotein of maedi visna virus
P. Carter and R. G. Dalziel
Department of Veterinary Pathology, University of Edinburgh, Summerhall,
Accepted March 26, 1997
Summary. The envelope glycoprotein, gp 135, of the ovine lentivirus maedi
visna virus is the main target for a speci®c antibody response in vivo, however,
little is known about the speci®c regions of gp 135 which elicit this response.
Research on the function of gp 135 has been hampered by the lack of reagents
to study such structure/function relationships. We have used a baculovirus
expression system to express gp 135 lacking the viral signal sequence. This
recombinant protein is glycosylated and recognised by immune sera from
clinically affected animals.
Maedi visna virus (MVV) is the prototype virus of the family Lentiviridae other
members of which include human immunode®ciency virus (HIV), feline
immunode®ciency virus (FIV) and equine infectious anaemia virus (EIAV).
MVV infection in sheep results in the development of chronic pneumonitis 
and/or a progressive demyelinating disease  either of which may become
manifest years after the initial infection. In some cases chronic mastitis or
arthritis [15, 21] may also be apparent. In contrast to HIV which infects
lymphocytes and cells of the monocyte/macrophage
lineage, MVV infection in vivo is limited to monocyte/macrophages with a
possible involvement of cells in the CNS .
Following experimental infection of sheep a low level of MVV speci®c
antibody (Ab) is produced one to two weeks post infection, however, it is not
until approximately six months post-infection that neutralising Ab can be
demonstrated . The component of the MVV virion to which neutralising Abs
are directed is the envelope glycoprotein. The envelope precursor protein is
cleaved post-translationally to yield a membrane associated gp 46 non-
covalently linked to gp 135, which is exposed on the virion surface. Despite