February 1, 2017

expert reaction to CRISPR cows with TB resistance

Scientists publishing in Genome Biology report that they have produced cloned cattle with increased resistance to bovine TB. The researchers used the genome editing tool CRISPR/Cas9 to alter the genetic code of the cattle.

Prof. Alan Archibald FRSE, Head of Genetics and Genomics at The Roslin Institute, University of Edinburgh, said:

“I was not convinced that this was an important paper.  Resistance and tolerance are different; to be resistant an organism should not get infected whilst if tolerant an organism could be infected but its performance would not suffer greatly.  I was not convinced that the authors had demonstrated that the edited calves were resistant – there was no pathology reported for the edited or control animals.

“The authors had shown some evidence of differences in response to infection, but views on the interpretation of some of the assays differ.

“Tb is a problem in the UK dairy sector and is controlled in the UK by culling.  Animals that show positive skin tests are culled; the skin test provides some evidence that the animal has been infected, so cattle that are genome edited to be tolerant would be just as likely to be culled.

“Susceptibility to Tb is now included in genomic breeding values in the UK following research at Roslin.  Genome editing in farmed animal species has merit in the context of food security, and genome editing to create disease resistant animals is a good thing.”

Prof. Ian McConnell, Emeritus Professor of Veterinary Science at the University of Cambridge, said:

“TB in cattle is a bacterial infectious disease affecting many different organ systems. Infection and disease is a complex process involving different components of the immune system in immunity and resistance. For example major cell surface proteins such as the  tissue type as well as other cells and molecules  of the immune/ inflammatory axis all play a role in TB resistance and disease process.

“Although the NRAMP or resistant gene described in this paper is an important gene in terms of conferring resistance in the target cells in in vitro systems–in vivo it is a different story. I doubt if resistance in vivo is solely at the level of NRAMP in macrophages.

“Although it is a thorough and novel paper on using gene technology in transgenic cattle at this stage I doubt if the research will have any application to prevention of TB in cattle using transgenic technology.”

* ‘Single Cas9 nickase induced generation of NRAMP1 knockin cattle with reduced offtarget effects’ by Yuanpeng Gao et al. published in Genome Biology on Wednesday 1 February 2017, which is also when the embargo will lift. 

Declared interests

None declared