This study evaluated the safety of meat from genetically modified sheep overexpressing TLR4 compared to meat from wild-type sheep in a 90-day feeding study using Sprague-Dawley rats. Meat samples from GM and wild-type sheep were analyzed for composition. Rats were fed diets supplemented with 3.75%, 7.5%, or 15% GM or wild-type sheep meat powder. Results showed no differences in body weight, blood parameters, organ weights, or histopathology between rats fed GM versus wild-type meat. The study concluded that meat from GM sheep overexpressing TLR4 showed no adverse or toxic effects compared to wild-type sheep meat.

1. A 90-Day Toxicology Study of
Meat from
Genetically Modified Sheep
Overexpressing
TLR4 in Sprague-Dawley Rats
BY:
Ling Lian1 et al.
April 13, 2015

2. • TLR 4 is a toll-like receptor which is responsible for activating the
innate immune system. It is most well-known for recognizing
lipopolysaccharide (LPS), a component of Gram-negative bacteria.

3. Introduction
• The present study is part of a Chinese research project . The project is
designed to develop scientific methodologies for assessing the safety
of GM sheep meat.
• The objective of the 90-day feeding study in Sprague- Dawley rats was
to evaluate the safety of meat from GM sheep overexpressing TLR4 in
an animal model, specifically when compared with wild-type (WT)
sheep meat.
• Prior to the 90-day feeding study, a sample each of minced meat
from GM sheep and WT sheep were subjected to a comprehensive
analysis as the compositional data could provide the general
information necessary to explain any possible effects that would be
observed in our study.

4. Materials and Methods
Production and screening of GM sheep : TLR4 gene (GU461886)
was derived from sheep and cloned by laboratory . Genetically
modified sheep were produced through microinjection and identified
by PCR and Southern blot.
• Southern blot analysis is a procedure for identifying specific
sequences of DNA, in which fragments separated on a gel are
transferred directly to a second medium on which test may be carried
out.
• The polymerase chain reaction (PCR) is a technology used to
generating thousands to millions of copies of a particular DNA
sequence.

5. Sothern blot method

6. The polymerase chain reaction (PCR)

7. • Composition analysis of meat and rat diet : After removing the
head, limbs, and entrails, as well as excessive fat from the sheep
carcass, the remaining meat was minced and measured.
• Based on the results of the compositional analysis, the rodent diets
were supplemented with 3.75%, 7.5% or 15% (wt/wt) meat powder
of GM and WT sheep, respectively, which met the required standard.
Additionally, a meat-free commercial diet (CD) was used as the
negative control

8. • RAT HOUSING :One hundred-forty weaning Sprague-Dawley rats
with a body weight of 150–200 g and around 5 weeks of age were
obtained from the Peking Animal Center (Beijing, China).
• The animal room temperature was maintained at 22±3°C, relative
humidity was held at 30–70%.

9. Observation and examination of rats
• Hematology and blood biochemistry : On day 90 of the study, blood
samples were obtained from the orbital sinus of the rats under
anesthesia. Samples were collected for hematology and placed in
tubes containing heparin.
• Samples collected for blood biochemistry were centrifuged, after
which the supernatants were collected for evaluation.

10. • A complete gross necropsy was conducted by visual inspection on all
of the rats at the end of the study. Selected organs were trimmed and
relative weights (as a percentage of the final body weight) were
determined for brain, heart, kidney, liver, lung, spleen, thymus, testes
and ovaries. Paired organs were weighed together.
• A histopathological examination of tissue sections was conducted at a
thickness of 2–5 μm and stained with hematoxylin and eosin.

11. Results
• Compositional analysis of meat :The rodent diet formulations
included 3.75%, 7.5% or 15% (wt/wt) meat powder met the nutrient
specifications for rodents as per the diet
• Body weight : The mean weekly body weights for male and female rats
in both the GM sheep meat groups and the WT sheep meat groups were
similar.
• Hematology and blood biochemistry :No differences were observed
inmost of the blood parameters between the GM and WT groups. There
were some differences, however, between the CD and WT groups, and
between the CD and GM groups.

12. • Organ weight and histopathology :
The mean relative weights of organs in the GM meat groups were similar to
those found in the WT meat groups. No differences were observed between
the GM and WT groups.
• There were no remarkable gross pathological alterations in any of the
animals during the necropsy, nor were there any alterations in the
histopathological examination related to the different diets.
• No abnormalities were observed in the brain, heart, thymus, lung and
stomach. As these were normal physiological changes, the injuries or
diseases to these tissue sections could not be considered harmful or were
not caused by consuming GM meat.

13. Conclusion
• The current 90-day toxicology study indicated that the meat of GM
sheep overexpressing TLR4 had no adverse or toxic effects on
Sprague-Dawley rats in comparison with WT sheep meat.

14. References
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Production of transgenic rabbits,
sheep and pigs by microinjection. Nature. 1985; 315: 680–683. PMID: 3892305
2. Murray JD, Nancarrow CD, Marshall JT, Hazelton IG, Ward KA. Production of
transgenic merino sheep
by microinjection of ovine metallothionein-ovine growth hormone fusion genes.
Reprod Fertil Dev.
1989; 1: 147–155. PMID: 2552507
3. Huang YJ, Huang Y, Baldassarre H, Wang B, Lazaris A, Leduc M, et al.
Recombinant human butyrylcholinesterase
from milk of transgenic animals to protect against organophosphate poisoning.
Proc
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