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No—not on the evidence reported so far. Researchers used RNA interference (RNAi) to lower activity of the bovine PRNP gene in cells and in one calf, but the calf study did not test whether the animal resisted BSE infection. Its reduction in prion-protein levels was also much smaller than its reduction in PRNP messenger RNA.
What RNAi changes—and what it does not prove
The bovine PRNP gene encodes cellular prion protein, PrPC, which is relevant to prion propagation. RNAi uses short, sequence-matched RNAs to reduce a target messenger RNA. It is an expression knockdown: it aims to reduce the gene’s RNA output rather than remove or rewrite the gene itself.
That distinction matters when interpreting results. A lower PRNP transcript measurement is not the same as an equally large reduction in PrPC protein, and neither measurement alone demonstrates resistance to infection.
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Cell-culture work in 2007
Sutou and colleagues tested bovine PRNP-targeting siRNA designs in cultured cells, varying the promoter or vector, target site and siRNA length. Under the conditions they tested, a 21-nucleotide sequence produced the strongest knockdown. The study described its findings as “a basis for further studies in vivo”—not as evidence that cattle were resistant to BSE. Read the 2007 study.
#1 Best Overall
The RNAi calf reported in 2011
A later study combined RNAi with somatic cell nuclear transfer (SCNT) to produce a calf with reduced PRNP expression. Researchers transferred 42 reconstructed embryos to 11 recipients. Only embryos made with the tRNA-promoter vector established pregnancies; the report describes four aborted fetuses, one stillbirth and one live-born calf.
The calf was killed for analysis at 20 days old. In sampled nervous tissues, its average PRNP transcript level was 35% of the control calf’s level, while measured PrPC protein averaged 86% of control. These are measurements from that particular experiment, not estimates of disease resistance or performance in a population. The authors concluded that RNAi reduced PRNP mRNA but that the reduction in PrPC was insufficient under those conditions. The calf was not shown to have undergone a live BSE challenge. Read the 2011 calf study.
Rank #2
RNAi, PRNP knockout and CRISPR are different approaches
| Approach | What it does | Evidence reported in the cited cattle studies | What the result does not establish |
|---|---|---|---|
| RNAi knockdown | Targets PRNP RNA to reduce gene expression. | Knockdown in cultured cells in 2007; one calf studied to 20 days in 2011, with transcript levels averaging 35% and PrPC averaging 86% of control. | Resistance to BSE infection or the effect of long-term knockdown. |
| PRNP knockout | Disrupts or removes the gene, rather than reducing its RNA through RNAi. | A 2007 study characterized knockout cattle as clinically, physiologically, histopathologically, immunologically and reproductively normal through over 20 months. Brain homogenates resisted prion propagation in vitro. | Resistance of live cattle to BSE challenge; the reported homogenate result was an in-vitro finding. |
| CRISPR-Cas9 model | Uses genome editing to target PRNP; it is not RNAi. | A 2025 study reported transgenic cattle expressing Cas9 and a guide RNA targeting PRNP, with transmission to F1 cattle. The paper describes the F1 animals as a BSE-resistance model and reports that they were growing and healthy at the reported age. | A live-animal BSE challenge result; the cited findings do not report one. |
The studies used different interventions, animals and endpoints, so they are not head-to-head tests and cannot be used to rank the approaches under a common protocol. Read the 2007 knockout study and the 2025 Cas9 study.
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What would demonstrate BSE resistance?
Reduced gene expression or protein levels are biological measurements, not proof of protection from disease. Likewise, resistance of brain homogenates to prion propagation in a laboratory assay is not the same as showing that live cattle resist infection after exposure. The evidence described in these studies does not establish that RNAi cattle resist BSE in a live-animal challenge.
A USDA National Agricultural Library project description says that a portion of the cattle in the proposed work would be challenged with infectious BSE or bovine scrapie to assess resistance. That language describes planned work in the project record; it is not evidence that the challenge was completed or that resistance was demonstrated. See the project description.
Quick Recap
What can be concluded about engineered BSE-resistant cattle?
- RNAi has reduced bovine PRNP expression in cell culture and in one reported calf.
- In that calf, transcript reduction was substantially greater than the measured reduction in PrPC, and the animal was analyzed at 20 days old.
- Neither the RNAi calf findings nor the cited knockout and CRISPR model findings establish resistance to BSE infection in live cattle.
- The cited evidence does not establish regulatory approval or commercial availability of BSE-resistant cattle.
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