2000 2/4/week/old One of [approximately equal to] 12 lambs milking breed fed artificial colostrum (snatched at lamb (960/00) birth to prevent transmission of maedi- visna virus
) that developed neurologic signs at [approximately equal to] 2 weeks of age, first weak in forelimbs, then hindlimbs, and by the second day, tremor and incoordination.
When they applied the LearnCoil program to databases of sequences, the researchers found evidence of coiled coils in fusion proteins associated with a wide variety of disease-causing viruses, including the influenza virus, Moloney murine leukemia virus, HIV, simian immunodeficiency virus, and visna virus.
Kim, who was at MIT but is now at the Merck Research Laboratories in West Point, Pa., and his collaborators, synthesized and analyzed proteins of the visna virus. "The structures were exactly as predicted," Berger says.
The Frederick group used a computer program to compare HTLV-III proteins with proteins from EIAV; from visna virus, a lentivirus that attacks sheep; and from two leukemia viruses, bovine leukemia virus (BLV) and HTLV-I.
Narayan worked with Gonda, Gallo and others to show the visna virus similarity.
"We have not yet infected the sheep with the visna virus because three animals are just not enough to work with.
However, antibodies normally produced by vaccines against the visna virus have not been effective.
The visna virus is transmitted at birth or through nursing or contact with saliva.
Like HIV in humans, animal viruses such as feline immunodeficiency virus (FIV) in cats, visna virus in sheep and simian immunodeficiency virus (SIV) in monkeys primarily infect cells of the immune system such as T cells and macrophages.
In animals, viral relatives of HIV with long and variable latency periods, such as visna virus in sheep, cause central nervous system damage even after the production of antibodies (NIAID, 1995).