Náttúrufræðingurinn - 2015, Blaðsíða 44

Náttúrufræðingurinn
44
Lokaorð
Þegar veirur sem ræktuðust frá al-
næmissjúklingum laust eftir 1980
voru skoðaðar í rafeindasmásjá
komu í ljós veiruagnir sem líktust
RNA-æxlisveirum og mynduðust á
sama hátt við knappskot frá frumu-
himnu sýktra frumna. Þetta benti til
að alnæmisveiran væri retroveira.
Það var staðfest þegar öfugumriti
fannst í veiruögnunum.1 Raðgrein-
ing á erfðaefni sýndi meiri skyld-
leika við mæði-visnuveiru en við
æxlisveirur. Alnæmisveirunni HIV
var því skipað í undirflokk lenti-
veira,49,50 enda olli hún ekki æxlis-
vexti í sýktum einstaklingum. Áður
en rannsóknir á alnæmisveirunni
hófust voru það einkum dýra-
læknar og lítill hópur áhugasamra
veirufræðinga sem lögðu stund á
rannsóknir á lentiveirum. Þær þóttu
nokkuð sérstakar, ekki síst vegna
þeirra sérkennilegu hæggengu
sjúkdóma sem þær ollu í dýrum.
Eftir að alnæmisveiran fannst varð
hún fljótlega best þekkt af öllum
veirum og sú sem flestar rannsóknir
beindust að, og varð hún ímynd
lentiveira. Áður höfðu sjúkdómar
sem lentiveirur ollu einkum valdið
sauðfjárbændum áhyggjum vegna
fjárfellis og annars tjóns. Hliðstæður
hæggengur og banvænn smitsjúk-
dómur af völdum lentiveiru ógn-
aði nú sjálfu mannkyninu. Það er
athyglisvert að þær rannsóknir sem
leiddu til þess að alnæmisveiran var
greind sem lentiveira eru hliðstæðar
fyrstu rannsóknum á visnuveiru,
eins og lýst er í þessari grein.
Summary
Maedi and visna and the origin
of lentivirus research
Maedi, a slowly progressing pneumonia
of sheep, and a central nervous system
disease called visna were brought to
Iceland in 1933 by imported sheep of
Karakul breed. They were transmissible
in sheep with an incubation time of 2–3
years. Based on his studies of visna and
maedi, Björn Sigurðsson formulated the
concept of slow infections in 1954. Visna
virus was isolated in tissue culture from
sheep brain in 1957 and maedi virus was
isolated the following year from sheep
lungs. Both viruses caused similar cyto-
pathic effect and electron microscope
studies showed identical spherical parti-
cles, which were formed by budding
from the cell membrane. Further studies
confirmed that maedi and visna are
caused by the same virus, named maedi-
visna virus (MVV). Electron microscope
studies suggested that MVV was related
to RNA tumor viruses of animals, oncor-
naviruses.This was later supported by
the finding that MVV is an RNA virus
and confirmed when reverse tran-
scriptase was found in MVV, which was
therefore classified as a retrovirus to-
gether with the oncornaviruses. In 1975
MVV was placed in a subgroup of retro-
viruses named lentiviruses, which cause
cytopathic effect in vitro and slowly pro-
gressing inflammatory disease in ani-
mals, but are non-oncogenic. In the early
1980s, the causative agent of AIDS was
found to be a non-oncogenic retrovirus
and was classified as a lentivirus. Thus,
human immunodeficiency virus HIV
became the first lentivirus causing a
slow infection in humans.
Þakkir
Höfundur þakkar Tilraunastöð Háskóla Íslands í Meinafræði á Keldum
fyrir leyfi til að birta gamlar myndir frá Keldum.
Greinin er tileinkuð íslensku sauðkindinni.
Heimildir
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