In a triple world first, researchers at Texas A & M University have successfully cloned a calf using enetic material from a dead bull which had been frozen for 15 years, and which had been preselected on the basis of its natural resistance to the major diseases – a trait now displayed by the cloned individual.

Eighty-six Squared is a lusty three month-old Angus bull calf that is not only a dead ringer of his genetic donor, bull 86, in looks and temperament, but has his "daddy’s" macrophages that make mince-meat out of Brucella abortus, Mycobacterium bovis and Salmonella Dublin in in vitro killing tests.

The cloning of the placid bull calf represents 21 years of intensive breeding, selection and resistance testing by researchers under the guidance of project founder and immunogeneticist, Professor Joe Templeton. Along with his long-time friend and colleague, veterinarian Dr Gary Adams, he had this idea about breeding cattle that were naturally resistant to major diseases and would, therefore, require less vaccination, less medication and would help cattle farmers worldwide.
Professor Templeton explained in a drawl as wide as Texas itself, that he had been interested in natural resistance since being told as a child about his uncle who, in World War I, failed to succumb to the Spanish Flu – even after being locked in the barracks to nurse 1500 men in his regiment with the killer disease.

And in testimony that necessity is often the mother of invention, the calf that now proudly carries the gene Natural Resistance-Associated Macrophage Protein 1, or NRAMP 1 for short, came into being after human error nearly wiped the project.

After exhaustive breeding trials using cattle of different breeds from brucellosis-free, isolated areas of Texas and Montana, Angus bull 86 was identified as naturally resistant. The future of the project looked very rosy and when bull 86 died in 1997, at the grand age of 17 years, enough semen had been frozen for posterity.

But near-disaster struck when a technician in a hurry to get away for Christmas accidentally turned off the freezer. When the poor sap remembered, Professor Templeton said all that was left of 86’s semen was "a big congealed mess".

It would have been enough to make even big Texans weep. But not to be deterred, the two intrepid researchers, along with reproductive biologist, Dr M Westhusan, and Koreantrained veterinarian, Dr T Shin, set about trying to use the dead sperm to impregnate ova using in vitro sperm head injection techniques.

This was not going particularly well when Dr.Shin said, in a classic understatement, that it might be nice to try to clone bull 86. In a fortuitous stroke of luck, Professor Templeton remembered that cells grown from a piece of the bull’s ear had been stored since 1985 and could supply the fibroblasts needed to provide a plentiful source of DNA.

In 1998, the cloning program began and on only the second attempt, the triple-resistant 86 Squared was born. However, there are still a few hurdles to go before Professor Templeton’s dream is realised and the resistant cattle will be available on the market. Eighty-six Squared is a nuclear clone and not theoretically an exact clone (his mitochondrial DNA, involved in energy production and ageing, came from the ovum which had its DNA removed to make way for bull 86’s). The team wants to make sure their "super calf" ages normally and, most importantly, when he is about 10
months old, he will be challenged in vivo with the three bacterial pathogens.

Already, plans are afoot to produce whole animal transgenic cattle that will contain the resistant form of the NRAMP 1 gene (this has already been successfully inserted into cells) and the cloning program is also continuing.

Professor Templeton said the advantages of producing cattle resistant to Brucella, TB and Salmonella were just the beginning and that capitalising on the genetic material of cattle naturally resistant to other pathogens such as parasites, viruses and even, hopefully, prions will allow more profitable and environmentally safer cattle raising ventures, especially in Third World countries. Naturally resistant cattle could also enjoy higher levels of animal welfare, as less human intervention was required to raise them.

by Jeni Hood (Complements of The Veterinarian, Feb 2001).