The research, published in PLoS One, claims to be the first study to result in the production of a herd of cloned transgenic cattle expressing recombinant human lysozyme (rHLZ) in their milk.
Lysozyme, a bactericidal protein that protects human infants from microbial infections, is highly expressed in human milk but is found in only trace amounts in cow milk. The researchers said that the new transgenic milk may allow for the transfer of the nutritional aspects of human lysozyme in human milk to bovine milk.
“Our study not only describes transgenic cattle whose milk offers the similar nutritional benefits as human milk but also reports techniques that could be further refined for production of active human lysozyme on a large scale,” said the authors, led by Professor Ning Li, at the China Agricultural University, China.
“This approach could provide an inexpensive and industrial-scale method for the purification of rHLZ … In addition, we have shown that the enzymatic properties and physicochemical characteristics of rHLZ were identical to those of [human lysozyme (HLZ)],” they added.
Human lysozyme is widely distributed in human tissues and body fluids (tears, saliva, milk) and it plays important roles as a non-specific immune factor and anti-inflammatory factor.
Prof Li and colleagues said that the benefits of lysozyme present in breast milk include improving immunity and preventing infection in infants.
“It increases the levels of beneficial intestinal microflora and strengthens disease resistance in infants. These effects are believed to occur through the lysis of certain potentially damaging Gram-positive bacteria and a few Gram-negative bacteria in the gastrointestinal tract of breast-fed babies,” explained Li and co-workers.
The researchers explained that in human milk, the content of lysozyme ranges from 3 to 3000 micrograms per millilitre, with a ‘typical concentration’ of between 200–400 micrograms per ml.However, bovine milk typically contains only 0.05–0.22 micrograms per ml of lysozyme.
“There is great potential for using transgenic technology to improve the quality of cow milk,” said the authors.
“Purified recombinant human lysozyme showed the same physicochemical properties, such as molecular mass and bacterial lysis, as its natural counterpart … Moreover, both recombinant and natural lysozyme had similar conditions for reactivity as well as for pH and temperature stability during in vitro simulations,” said the authors.
The Chinese researchers added that the composition of transgenic and non-transgenic milk, including levels of lactose, total protein, total fat, and total solids were not found to significantly differ.
“In our study, rHLZ purified from transgenic milk had the same optimal temperature and was equally thermostable as HLZ. We conclude that post-processing procedures will have only minor effects on rHLZ activity,” added Li and colleagues.
In response to recent mainstream media coverage of the study, Mike Brady, campaigns and networking coordinator, for Baby Milk Action attempted to put the findings of the study into context.
He said that any suggestion of GM cows producing 'human breast milk' is misleading.
“Scientists are actually claiming they have found a way to produce three components missing from current formulas and change fat and protein levels,” he explained.
“Every time we see these types of headlines it reinforces the fact that formula currently on the market is not the same as breast milk and scientists are still seeking ways to reduce its shortcoming,” said Brady
“Baby Milk Action is working for the composition of formula to be improved for those babies who are not breastfed and it will be interesting to see if the missing components that these scientists claim to be able to produce can be proven to be beneficial and safe if included in a formula,” he added.
Source: PLoS ONE
Published online ahead of print, do: 10.1371/journal.pone.0017593
“Characterization of Bioactive Recombinant Human Lysozyme Expressed in Milk of Cloned Transgenic Cattle”
Authors: B. Yang, J. Wang, B. Tang, Y. Liu,C. Guo, P. Yang, et al