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CAE: The Mystery Lady

Research ongoing

By Alice Hall

Her identity is concealed by the code name 4g2. Very few people know who she is, but I think I have a clue. I’m guessing, but it’s an educated guess. I won’t reveal her hidden identity, but I can tell you she is an angular black-agouti Nubian with an excellent mammary. She was born in January, 1998, and she died in January, 2005 somewhere in Southern California. That’s a short life span, but it’s typical of dairy goats that test positive for CAEV (Caprine Arthritis Encephalitis Virus), although a few have lived twice that time. She started donating blood to the caprine research at USC before she was a year old, and she became their most valued donor. The last two years of her life were spent in a special holding herd for the USC research, and her blood was collected every month.

Doe 4g2 was special because she tested positive for CAEV-63 and HIV-IIIBr, but not for HIV-IIIbm. Now I won’t pretend to know what all that means, but it made her valuable for the research, and her tag came up a couple dozen times in the last published paper. Incidentally, that paper, from which this is taken, is available on line at www.elsevier.com/locate/yviro (type the name of the virus in the search bar). Simila research is being done in Mexico.

Doe 4g2 was one of 46 Central and Southern California CAEV positive goats from 20 herds whose blood was drawn regularly for the CAEV/HIV crossover research. Of the 46 positive goats, 21 tested positive for interaction with HIV, but only eight were positive for interaction with the HIV protein. In other words, some CAEV positive goats make “cross-reactive antibodies” against HIV.

Among the CAEV positive goat herds, 24 CAEV negative goats were found in their positive environments and among all positive herd mates. One such negative goat, however, was positive for interaction with HIV. Wish we could find those immune goats for our breeding programs, as it’s been my experience that most negative goats, when introduced to a CAEV- positive environment, will contract CAEV within three years, even without direct exposure to “body fluids” other than breeding.

Both CAEV and HIV are lentiviruses. The prefix lenti possibly relates to lenticular, meaning resembling a lens. Lentiviruses display a wide variety of symptoms in their specific hosts. They share complex genetic structures, and they are very diverse, especially in their envelope genes. The envelope protein of CAEV is gp135, and the HIV envelope protein is gp120. Although the two viruses are not particularly alike, they do have a few similarities: they both possess five variable regions and short motifs, and they are both heavily glycosylated. The envelope proteins intercede for viral entry into target cells.

This research has demonstrated that “some goats possess gp135 (CAEV)-specific antibodies which cross-react with gp120 from several HIV strains, provided the protein is expressed in insect cells.” (Virology)

Peripheral mononuclear cells from goat 4g2 were co-cultured with goat synovial (joint) membrane cells. The virus was amplified for 14 days at room temperature and isolated by super centrifugation.

A conclusion drawn from the results of these experiments is that “several CAEV-infected goats possess (CAEV) antibodies which interact (cross-react) with (HIV) from several viral strains, (this is an unexpected and intriguing finding) provided the protein is expressed in insect, not mammalian, cells.” In other words, the lab work has to go through an insect transfer stage to obtain the results looked for and needed, showing that the 4g2 goat antibodies are carbohydrate dependent. Specifically, the 4g2 goat generated envelope specific (CAEV) antibodies that cross-reacted with the (HIV) IIIB protein.

Experiments are ongoing to determine if the CAEV recognition of HIV is cross-reaction or molecular mimicry. Speaking as a layman, I hope, now that mystery goat 4g2 is gone, others will be found to take her place. I also hope that some positive vaccination trials come from this research. I’m sure if researchers put their minds to it, a vaccine against CAEV could also be developed. Now wouldn’t that be something to celebrate!

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