Human lysozyme expressed in the mammary gland of transgenic dairy goats can inhibit the growth of bacteria that cause mastitis and the cold-spoilage of milk

High-Pressure Processing of Human Milk: A Balance between Microbial Inactivation and Bioactive Protein Preservation

BACKGROUND

Donor human milk banks use Holder pasteurization (HoP; 62.5°C, 30 min) to reduce pathogens in donor human milk, but this process damages some bioactive milk proteins.

OBJECTIVES

We aimed to determine minimal parameters for high-pressure processing (HPP) to achieve >5-log reductions of relevant bacteria in human milk and how these parameters affect an array of bioactive proteins.

METHODS

Pooled raw human milk inoculated with relevant pathogens (Enterococcus faecium, Staphylococcus aureus, Listeria monocytogenes, Cronobacter sakazakii) or microbial quality indicators (Bacillus subtilis and Paenibacillus spp. spores) at 7 log CFU/mL was processed at 300-500 MPa at 16-19°C (due to adiabatic heating) for 1-9 min. Surviving microbes were enumerated using standard plate counting methods. For raw milk, and HPP-treated and HoP-treated milk, the immunoreactivity of an array of bioactive proteins was assessed via ELISA and the activity of bile salt-stimulated lipase (BSSL) was determined via a colorimetric substrate assay.

RESULTS

Treatment at 500 MPa for 9 min resulted in >5-log reductions of all vegetative bacteria, but <1-log reduction in B. subtilis and Paenibacillus spores. HoP decreased immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin G, lactoferrin, elastase and polymeric immunoglobulin receptor (PIGR) concentrations, and BSSL activity. The treatment at 500 MPa for 9 min preserved more IgA, IgM, elastase, lactoferrin, PIGR, and BSSL than HoP. HoP and HPP treatments up to 500 MPa for 9 min caused no losses in osteopontin, lysozyme, α-lactalbumin and vascular endothelial growth factor.

CONCLUSION

Compared with HoP, HPP at 500 MPa for 9 min provides >5-log reduction of tested vegetative neonatal pathogens with improved retention of IgA, IgM, lactoferrin, elastase, PIGR, and BSSL in human milk.

Microbiological Quality of Raw Donkey Milk from Serbia and Its Antibacterial Properties at Pre-Cooling Temperature

The aim of this study was to examine the microbiological quality of raw donkey milk of an indigenous Serbian breed as well as the changes in the microbial populations during storage at 4 °C. In addition, antibacterial activity of donkey milk against E. coli, L. monocytogenes and S. aureus at 15 °C as well as the content of the two main antibacterial proteins lysozyme and lactoferrin were investigated. Microbiological examination of 137 individual milk samples collected over a period of 21 months showed good microbiological quality since foodborne pathogens such as Salmonella spp. and L. monocytogenes were not detected in any of the analyzed samples, while the number of E. coli, Enterobacteriaceae, total coliform bacteria, sulfite-reducing Clostridia and aerobic sporogenic bacteria was below the limit of quantification (<1 cfu mL^-1). During the six-days storage at 4 °C, total bacterial counts and the counts of lactic acid bacteria remained at the initial level while pathogenic bacteria were not detected. The strongest antibacterial activity of the tested milk was observed against E. coli, while S. aureus was the least sensitive to milk antibacterial compounds. Although further research is needed to fully elucidate the antibacterial mechanism and synergistic activity of different compounds in donkey milk, the high content lysozyme (2.63 ± 0.03 g L^-1) and lactoferrin (15.48 mg L^-1) observed in tested milk could contribute to its strong antibacterial activity and extension of the storage period during which it can be safely consumed.

Towards progressive regulatory approaches for agricultural applications of animal biotechnology

Traditional breeding techniques, applied incrementally over thousands of years, have yielded huge benefits in the characteristics of agricultural animals. This is a result of significant, measurable changes to the genomes of those animal species and breeds. Genome editing techniques may now be applied to achieve targeted DNA sequence alterations, with the potential to affect traits of interest to production of agricultural animals in just one generation. New opportunities arise to improve characteristics difficult to achieve or not amenable to traditional breeding, including disease resistance, and traits that can improve animal welfare, reduce environmental impact, or mitigate impacts of climate change. Countries and supranational institutions are in the process of defining regulatory approaches for genome edited animals and can benefit from sharing approaches and experiences to institute progressive policies in which regulatory oversight is scaled to the particular level of risk involved. To facilitate information sharing and discussion on animal biotechnology, an international community of researchers, developers, breeders, regulators, and communicators recently held a series of seven virtual workshop sessions on applications of biotechnology for animal agriculture, food and environmental safety assessment, regulatory approaches, and market and consumer acceptance. In this report, we summarize the topics presented in the workshop sessions, as well as discussions coming out of the breakout sessions. This is framed within the context of past and recent scientific and regulatory developments. This is a pivotal moment for determination of regulatory approaches and establishment of trust across the innovation through-chain, from researchers, developers, regulators, breeders, farmers through to consumers.

Intestinal Dysbiosis in the Infant and the Future of Lacto-Engineering to Shape the Developing Intestinal Microbiome

PURPOSE

The goal of this study was to review the role of human milk in shaping the infant intestinal microbiota and the potential of human milk bioactive molecules to reverse trends of increasing intestinal dysbiosis and dysbiosis-associated diseases.

METHODS

This narrative review was based on recent and historic literature.

FINDINGS

Human milk immunoglobulins, oligosaccharides, lactoferrin, lysozyme, milk fat globule membranes, and bile salt-stimulating lipase are complex multifunctional bioactive molecules that, among other important functions, shape the composition of the infant intestinal microbiota.

IMPLICATIONS

The co-evolution of human milk components and human milk-consuming commensal anaerobes many thousands of years ago resulted in a stable low-diversity infant microbiota. Over the past century, the introduction of antibiotics and modern hygiene practices plus changes in the care of newborns have led to significant alterations in the intestinal microbiota, with associated increases in risk of dysbiosis-associated disease. A better understanding of mechanisms by which human milk shapes the intestinal microbiota of the infant during a vulnerable period of development of the immune system is needed to alter the current trajectory and decrease intestinal dysbiosis and associated diseases.

Genetically modified animals for use in biopharmacology: from research to production

Introduction: In this review, the analysis of technologies for obtaining biologically active proteins from various sources is carried out, and the comparative analysis of technologies for creating producers of biologically active proteins is presented. Special attention is paid to genetically modified animals as bioreactors for the pharmaceutical industry of a new type. The necessity of improving the technology of development transgenic rabbit producers and creating a platform solution for the production of biological products is substantiated.

The advantages of using TrB for the production of recombinant proteins: The main advantages of using TrB are the low cost of obtaining valuable complex therapeutic human proteins in readily accessible fluids, their greater safety relative to proteins isolated directly from human blood, and the greater safety of the activity of the native protein.

The advantages of the mammary gland as a system for the expression of recombinant proteins: The mammary gland is the organ of choice for the expression of valuable recombinant proteins because milk is easy to collect in large volumes.

Methods for obtaining transgenic animals: The modern understanding of the regulation of gene expression and the discovery of new tools for gene editing can increase the efficiency of creating bioreactors for animals and help to obtain high concentrations of the target protein.

The advantages of using rabbits as bioreactors producing recombinant proteins in milk: The rabbit is a relatively small animal with a short duration of gestation, puberty and optimal size, capable of producing up to 5 liters of milk per year per female, receiving up to 300 grams of the target protein.

Improvement of Disease Resistance in Livestock: Application of Immunogenomics and CRISPR/Cas9 Technology

Disease occurrence adversely affects livestock production and animal welfare, and have an impact on both human health and public perception of food-animals production. Combined efforts from farmers, animal scientists, and veterinarians have been continuing to explore the effective disease control approaches for the production of safe animal-originated food. Implementing the immunogenomics, along with genome editing technology, has been considering as the key approach for safe food-animal production through the improvement of the host genetic resistance. Next-generation sequencing, as a cutting-edge technique, enables the production of high throughput transcriptomic and genomic profiles resulted from host-pathogen interactions. Immunogenomics combine the transcriptomic and genomic data that links to host resistance to disease, and predict the potential candidate genes and their genomic locations. Genome editing, which involves insertion, deletion, or modification of one or more genes in the DNA sequence, is advancing rapidly and may be poised to become a commercial reality faster than it has thought. The clustered regulatory interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) [CRISPR/Cas9] system has recently emerged as a powerful tool for genome editing in agricultural food production including livestock disease management. CRISPR/Cas9 mediated insertion of NRAMP1 gene for producing tuberculosis resistant cattle, and deletion of CD163 gene for producing porcine reproductive and respiratory syndrome (PRRS) resistant pigs are two groundbreaking applications of genome editing in livestock. In this review, we have highlighted the technological advances of livestock immunogenomics and the principles and scopes of application of CRISPR/Cas9-mediated targeted genome editing in animal breeding for disease resistance.

Genetic Engineering of Livestock: The Opportunity Cost of Regulatory Delay

Genetically engineered (GE) livestock were first reported in 1985, and yet only a single GE food animal, the fast-growing AquAdvantage salmon, has been commercialized. There are myriad interconnected reasons for the slow progress in this once-promising field, including technical issues, the structure of livestock industries, lack of public research funding and investment, regulatory obstacles, and concern about public opinion. This review focuses on GE livestock that have been produced and documents the difficulties that researchers and developers have encountered en route. Additionally, the costs associated with delayed commercialization of GE livestock were modeled using three case studies: GE mastitis-resistant dairy cattle, genome-edited porcine reproductive and respiratory syndrome virus-resistant pigs, and the AquAdvantage salmon. Delays of 5 or 10 years in the commercialization of GE livestock beyond the normative 10-year GE product evaluation period were associated with billions of dollars in opportunity costs and reduced global food security.

Disease resistance for different livestock species

This chapter deals with progress in disease resistance for the livestock population species-wise and describes the progress that occurred globally. Certain genes were identified for mastitis resistance and the strategies for genomic control of mastitis are discussed. Gene-edited tuberculosis-resistant cattle were developed for the first time with CRISPR/Cas 9 technology with NRAMP gene insert. Similarly studies are in progress for the development of trypanosomiasis-resistant cattle at ILRI. Genomic insights were discussed for disease resistance for goat against gastrointestinal nematode infestation, coccidiosis, peste des petits ruminants, and scrapie. Similarly genomic resistance was also discussed for sheep, discussing the mechanism of disease resistance with MHC, antibody and T cell response, cytokines, and receptors. Genes identified for bacterial diarrhoeal resistance as K88, F18 (an intestinal receptor) for resistance to bacterial infection in pig. Gene-edited pigs were developed against porcine reproductive and respiratory syndrome and transmissible gastroenteritis caused by corona virus using CRISPR/Cas9 technology. Insights on the omics technologies developed and studied were discussed for livestock species. Genomic control on various diseases of poultry is discussed as salmonellosis, avian influenza, Marek’s disease, Newcastle disease with advanced genomic and allied techniques for its control as RNA interference, flow cytometry, quantitative polymerase chain reaction, transcriptomics, etc. A new concept on natural antibodies was discussed.

Functional evaluation of a monotreme-specific antimicrobial protein, EchAMP, against experimentally induced mastitis in transgenic mice

EchAMP, the tenth most abundant transcript expressed in the mammary gland of echidna, has in vitro broad-spectrum antibacterial effects. However, the effects of EchAMP on mastitis, a condition where inflammation is triggered following mammary gland infection, has not been investigated. To investigate the impact of EchAMP against mastitis, EchAMP transgenic mice were generated. In antibacterial assays, the whey fractions of milk from transgenic mice significantly reduced growth of Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa compared with whey fractions from wildtype mice. Furthermore, a mastitis model created by infecting mammary gland with these four bacterial strains displayed a significant reduction in bacterial load in transgenic mice injected with S. aureus and B. subtilis. On further confirmation, histomorphologic analysis showed absence of necrosis and cell infiltration in the mammary glands of transgenic mice. To understand the role of EchAMP against inflammation, we employed an LPS-injected mastitis mouse model. LPS is known to induce phopshorylation of NF-κB and MAPK pathways, which in turn activate downstream proinflammatory signaling mediators, to promote inflammation. In LPS-treated EchAMP transgenic mice, phosphorylation levels of NF-κB, p38 and ERK1/2 were significantly downregulated. Furthermore, in mammary gland of transgenic mice, there was a significant downregulation of mRNA levels of proinflammatory cytokines, namely TNF-α, IL-6 and IL-1β. Taken together, these data suggest that EchAMP has an antiinflammatory response and is effective against S. aureus and B. subtilis. We suggest that EchAMP may be a potential prophylactic protein against mastitis in dairy animals by expressing this gene in their mammary gland.

Proposed U.S. regulation of gene-edited food animals is not fit for purpose

Dietary DNA is generally regarded as safe to consume, and is a routine ingredient of food obtained from any living organism. Millions of naturally-occurring DNA variations are observed when comparing the genomic sequence of any two healthy individuals of a given species. Breeders routinely select desired traits resulting from this DNA variation to develop new cultivars and varieties of food plants and animals. Regulatory agencies do not evaluate these new varieties prior to commercial release. Gene editing tools now allow plant and animal breeders to precisely introduce useful genetic variation into agricultural breeding programs. The U.S. Department of Agriculture (USDA) announced that it has no plans to place additional regulations on gene-edited plants that could otherwise have been developed through traditional breeding prior to commercialization. However, the U.S. Food and Drug Administration (FDA) has proposed mandatory premarket new animal drug regulatory evaluation for all food animals whose genomes have been intentionally altered using modern molecular technologies including gene editing technologies. This runs counter to U.S. biotechnology policy that regulatory oversight should be triggered by unreasonable risk, and not by the fact that an organism has been modified by a particular process or technique. Breeder intention is not associated with product risk. Harmonizing the regulations associated with gene editing in food species is imperative to allow both plant and animal breeders access to gene editing tools to introduce useful sustainability traits like disease resistance, climate adaptability, and food quality attributes into U.S. agricultural breeding programs.

Dietary Lysozyme Alters Sow's Gut Microbiota, Serum Immunity and Milk Metabolite Profile

The aim of current study was to determine variations in sow's gut microbiota, serum immunity, and milk metabolite profile mediated by lysozyme supplementation. Twenty-four pregnant sows were assigned to a control group without supplementation and two treatments with 0.5 kg/t and 1.0 kg/t lysozyme provided in formula feed for 21 days (n = 8 per treatment). Microbiota analysis and metagenomic predictions were based on 16s RNA high-throughput sequencing. Milk metabolome was assessed by untargeted liquid chromatography tandem mass spectrometry. Serum biochemical indicators and immunoglobulins were also determined. Gut microbial diversity of sows receiving 1.0 kg/t lysozyme treatment was significantly reduced after the trial. Spirochaetes, Euryarchaeota, and Actinobacteria significantly increased while Firmicutes showed a remarkable reduction in 1.0 kg/t group compared with control. Lysozyme addition rebuilt sow's gut microbiota to beneficial composition identified by reduced richness of Escherichia coli and increased abundance of Lactobacillus amylovorus. Accordingly, microbial metabolic functions including pyrimidine metabolism, purine metabolism, and amino acid related enzymes were significantly up-regulated in 1.0 kg/t group. Microbial metabolic phenotypes like the richness of Gram-positive bacteria and oxidative stress tolerance were also significantly reduced by lysozyme treatment. Serum alanine transaminase (ALT) activity and IgA levels were significantly down-regulated in the 1.0 kg/t group compared with control, but IgM levels showed a significantly increase in 1.0 kg/t group. Milk metabolites such as L-glutamine, creatine, and L-arginine showed significantly dose-dependent changes after treatment. Overall, lysozyme supplementation could effectively improve the composition, metabolic functions, and phenotypes of sow's gut microbiota and it also benefit sows with better serum immunity and milk composition. This research could provide theoretical support for further application of lysozyme in promoting animal gut health and prevent pathogenic infections in livestock production.

Livestock 2.0 - genome editing for fitter, healthier, and more productive farmed animals

The human population is growing, and as a result we need to produce more food whilst reducing the impact of farming on the environment. Selective breeding and genomic selection have had a transformational impact on livestock productivity, and now transgenic and genome-editing technologies offer exciting opportunities for the production of fitter, healthier and more-productive livestock. Here, we review recent progress in the application of genome editing to farmed animal species and discuss the potential impact on our ability to produce food.

Production of hypoallergenic milk from DNA-free beta-lactoglobulin (BLG) gene knockout cow using zinc-finger nucleases mRNA

The whey protein β-lactoglobulin (BLG) is a major milk allergen which is absent in human milk. Here, we for the first time generated DNA-free BLG bi-allelic knockout cow by zinc-finger nuclease (ZFNs) mRNA and produced BLG-free milk. According to the allergenicity evaluation of BLG-free milk, we found it can trigger lower allergic reaction of Balb/c mice including the rectal temperature drop and the allergen-specific immunoglobulin IgE production; BLG free-milk was easily digested by pepsin at 2 min, while BLG in control milk was still not completely digested after 60 min, and the binding of IgE from cow's milk allergy (CMA) patients to BLG free-milk was significantly lower than that to the control milk. Meanwhile, the genome sequencing revealed that our animal is free of off-target events. Importantly, editing animal genomes without introducing foreign DNA into cells may alleviate regulatory concerns related to foods produced by genome edited animals. Finally, the ZFNs-mediated targeting in cow could be transmitted through the germline by breeding. These findings will open up unlimited possibilities of modifying milk composition to make it more suitable for human health and also improve the functional properties of milk.

A 100-Year Review: Advances in goat milk research

In the century of research chronicled between 1917 and 2017, dairy goats have gone from simply serving as surrogates to cows to serving as transgenic carriers of human enzymes. Goat milk has been an important part of human nutrition for millennia, in part because of the greater similarity of goat milk to human milk, softer curd formation, higher proportion of small milk fat globules, and different allergenic properties compared with cow milk; however, key nutritional deficiencies limit its suitability for infants. Great attention has been given not only to protein differences between goat and cow milk, but also to fat and enzyme differences, and their effect on the physical and sensory properties of goat milk and milk products. Physiological differences between the species necessitate different techniques for analysis of somatic cell counts, which are naturally higher in goat milk. The high value of goat milk throughout the world has generated a need for a variety of techniques to detect adulteration of goat milk products with cow milk. Advances in all of these areas have been largely documented in the Journal of Dairy Science (JDS), and this review summarizes such advances.

Expression of recombinant human lysozyme in bacterial artificial chromosome transgenic mice promotes the growth of Bifidobacterium and inhibits the growth of Salmonella in the intestine

Targeted gene modification is a novel intervention strategy to increase disease resistance more quickly than traditional animal breeding. Human lysozyme, a natural, non-specific immune factor, participates in innate immunity, exerts a wide range of antimicrobial activities against pathogens, and has immuneregulatory effects. Therefore, it is a candidate gene for improved disease resistance in animals. In this study, we successfully generated a transgenic mouse model by microinjecting a modified bacterial artificial chromosome containing a recombinant human lysozyme (rhLZ) gene into the pronuclei of fertilized mouse embryos. rhLZ was expressed in serum, liver, spleen, lung, kidney, stomach, small intestine, and large intestine but not in milk. rhLZ protein concentrations in the serum of transgenic mice ranged from 2.09 to 2.60 mg/l. To examine the effect of rhLZ on intestinal microbiota, total aerobes, total anaerobes, Clostridium, Enterococcus, Streptococcus, Salmonella, Escherichia coli, Staphylococcus, Bifidobacterium, and Lactobacillus were measured in the intestines of transgenic and wild type mice. Results showed that Bifidobacteria were significantly increased (p < 0.001), whereas Salmonella were significantly decreased (p < 0.001) in transgenic mice compared to wild type mice. Our study suggests that rhLZ expression is a potential strategy to increase animal disease resistance.

Genome editing for disease resistance in livestock

One of the major burdens on the livestock industry is loss of animals and decrease in production efficiency due to disease. Advances in sequencing technology and genome-editing techniques provide the unique opportunity to generate animals with improved traits. In this review we discuss the techniques currently applied to genetic manipulation of livestock species and the efforts in making animals disease resistant or resilient.

Young Pigs Consuming Lysozyme Transgenic Goat Milk Are Protected from Clinical Symptoms of Enterotoxigenic Escherichia coli Infection

Background: Diarrheal diseases in infancy and childhood are responsible for substantial morbidity and mortality in developing nations. Lysozyme, an antimicrobial component of human milk, is thought to play a role in establishing a healthy intestinal microbiota and immune system. Consumption of breast milk has been shown to prevent intestinal infections and is a recommended treatment for infants with diarrhea.Objective: This study aimed to examine the ability of lysozyme-rich goat milk to prevent intestinal infection.Methods: Six-week-old Hampshire-Yorkshire pigs were assigned to treatment groups balanced for weight, sex, and litter and were fed milk from nontransgenic control goats (GM group) or human lysozyme transgenic goats (hLZM group) for 2 wk before they were challenged with porcine-specific enterotoxigenic Escherichia coli (ETEC). Fecal consistency, complete blood counts, intestinal histology, and microbial populations were evaluated.Results: Pigs in the hLZM group had less severe diarrhea than did GM pigs at 24 and 48 h after ETEC infection (P = 0.01 and 0.05, respectively), indicating a less severe clinical disease state. Relative to baseline, postmilk hLZM pigs had 19.9% and 137% enrichment in fecal Bacteroidetes (P = 0.028) and Paraprevotellaceae (P = 0.003), respectively, and a 93.8% reduction in Enterobacteriaceae (P = 0.007), whereas GM pigs had a 60.9% decrease in Lactobacillales (P = 0.003) and an 83.3% enrichment in Burkholderiales (P = 0.010). After ETEC infection, hLZM pigs tended to have lower amounts (68.7% less) of fecal Enterobacteriaceae than did GM pigs (P = 0.058). There were 83.1% fewer bacteria translocated into the mesenteric lymph nodes of hLZM pigs than into those of GM pigs (P = 0.039), and hLZM pigs had 34% lower mucin 1 and 61% higher tumor necrosis factor-α expression in the ileum than did GM pigs (P = 0.046 and 0.034, respectively).Conclusion: Results of this study indicate that human lysozyme milk consumption before and during ETEC infection has a positive effect on clinical disease, intestinal mucosa, and gut microbiota in young pigs.

Genome editing and genetic engineering in livestock for advancing agricultural and biomedical applications

Genetic modification of livestock has a longstanding and successful history, starting with domestication several thousand years ago. Modern animal breeding strategies predominantly based on marker-assisted and genomic selection, artificial insemination, and embryo transfer have led to significant improvement in the performance of domestic animals, and are the basis for regular supply of high quality animal derived food. However, the current strategy of breeding animals over multiple generations to introduce novel traits is not realistic in responding to the unprecedented challenges such as changing climate, pandemic diseases, and feeding an anticipated 3 billion increase in global population in the next three decades. Consequently, sophisticated genetic modifications that allow for seamless introgression of novel alleles or traits and introduction of precise modifications without affecting the overall genetic merit of the animal are required for addressing these pressing challenges. The requirement for precise modifications is especially important in the context of modeling human diseases for the development of therapeutic interventions. The animal science community envisions the genome editors as essential tools in addressing these critical priorities in agriculture and biomedicine, and for advancing livestock genetic engineering for agriculture, biomedical as well as "dual purpose" applications.

Expression of recombinant human lysozyme in transgenic chicken promotes the growth of Bifidobacterium in the intestine and improves postnatal growth of chicken

Lysozyme is one kind of antimicrobial proteins and often used as feed additive which can defend against pathogenic bacteria and enhance immune function of animals. In this study, we have injected the lentiviral vector expressing recombinant human lysozyme (rhLZ) gene into the blastoderm of chicken embryo to investigate the effect of recombinant human lysozyme on postnatal intestinal microbiota distribution and growth performance of chicken. Successfully, we generated 194 transgenic chickens identified by Southern blot with a positive transgenic rate of 24%. The average concentration of rhLZ was 29.90 ± 6.50 μg/mL in the egg white. Lysozyme in egg white of transgenic chickens had a significantly higher antibacterial activity than those of non-transgenic chickens by lysoplate assay (P < 0.05). The feces of transgenic and non-transgenic chickens were collected and five types of bacteria (Lactobacillus, Salmonella, Bifidobacterium, Staphylococcus aureus and Escherichia coli) were isolated and cultured to detect the impact of rhLZ on gut microbiota. Among the five bacteria, the number of Bifidobacterium in the intestine of those transgenic was significantly increased (P < 0.05). Moreover, the growth traits of the transgenic and non-transgenic chickens were analyzed. It was found that the 6-week shank length, 6-week weight and 18-week weight of transgenic chickens were significantly increased than that of non-transgenic chickens. The results demonstrated that rhLZ-transgenic chicken could promote the growth of Bifidobacterium in the intestine and improve the postnatal growth of chicken.

Large-scale production of functional human lysozyme from marker-free transgenic cloned cows

Human lysozyme is an important natural non-specific immune protein that is highly expressed in breast milk and participates in the immune response of infants against bacterial and viral infections. Considering the medicinal value and market demand for human lysozyme, an animal model for large-scale production of recombinant human lysozyme (rhLZ) is needed. In this study, we generated transgenic cloned cows with the marker-free vector pBAC-hLF-hLZ, which was shown to efficiently express rhLZ in cow milk. Seven transgenic cloned cows, identified by polymerase chain reaction, Southern blot, and western blot analyses, produced rhLZ in milk at concentrations of up to 3149.19 ± 24.80 mg/L. The purified rhLZ had a similar molecular weight and enzymatic activity as wild-type human lysozyme possessed the same C-terminal and N-terminal amino acid sequences. The preliminary results from the milk yield and milk compositions from a naturally lactating transgenic cloned cow 0906 were also tested. These results provide a solid foundation for the large-scale production of rhLZ in the future.

Pluripotent stem cells and livestock genetic engineering. Transgenic Res. 2016;25:289-306. [PMID: 26894405 DOI: 10.1007/s11248-016-9929-5]

The unlimited proliferative ability and capacity to contribute to germline chimeras make pluripotent embryonic stem cells (ESCs) perfect candidates for complex genetic engineering. The utility of ESCs is best exemplified by the numerous genetic models that have been developed in mice, for which such cells are readily available. However, the traditional systems for mouse genetic engineering may not be practical for livestock species, as it requires several generations of mating and selection in order to establish homozygous founders. Nevertheless, the self-renewal and pluripotent characteristics of ESCs could provide advantages for livestock genetic engineering such as ease of genetic manipulation and improved efficiency of cloning by nuclear transplantation. These advantages have resulted in many attempts to isolate livestock ESCs, yet it has been generally concluded that the culture conditions tested so far are not supportive of livestock ESCs self-renewal and proliferation. In contrast, there are numerous reports of derivation of livestock induced pluripotent stem cells (iPSCs), with demonstrated capacity for long term proliferation and in vivo pluripotency, as indicated by teratoma formation assay. However, to what extent these iPSCs represent fully reprogrammed PSCs remains controversial, as most livestock iPSCs depend on continuous expression of reprogramming factors. Moreover, germline chimerism has not been robustly demonstrated, with only one successful report with very low efficiency. Therefore, even 34 years after derivation of mouse ESCs and their extensive use in the generation of genetic models, the livestock genetic engineering field can stand to gain enormously from continued investigations into the derivation and application of ESCs and iPSCs.

Genetically engineering milk

It has been thirty years since the first genetically engineered animal with altered milk composition was reported. During the intervening years, the world population has increased from 5bn to 7bn people. An increasing demand for protein in the human diet has followed this population expansion, putting huge stress on the food supply chain. Many solutions to the grand challenge of food security for all have been proposed and are currently under investigation and study. Amongst these, genetics still has an important role to play, aiming to continually enable the selection of livestock with enhanced traits. Part of the geneticist's tool box is the technology of genetic engineering. In this Invited Review, we indicate that this technology has come a long way, we focus on the genetic engineering of dairy animals and we argue that the new strategies for precision breeding demand proper evaluation as to how they could contribute to the essential increases in agricultural productivity our society must achieve.

Lactation and Intestinal Microbiota: How Early Diet Shapes the Infant Gut

Breast milk is a multifunctional biofluid that provides nutrients along with highly diverse non-nutritive bioactive components such as antibodies, glycans, bacteria, and immunomodulatory proteins. Research over the past decade has confirmed the essential role of breast milk bioactives in the establishment a healthy intestinal microbiota within the infant. The intestinal microbiota of an exclusively breastfed baby is dominated by several species of Bifidobacteria - the most influential member of which is Bifidobacterium longum subspecies infantis (B. infantis) - and is referred to as the milk-oriented microbiome (MOM). MOM is associated with reduced risk of infection in infancy as well as a reduced risk of certain chronic illnesses in adulthood. Establishment and persistence of MOM is dependent on the selective digestion of complex sugar structures in breast milk that are otherwise indigestible to the infant by B. infantis and its relatives. This review focuses primarily on the influence of breast milk glycans and glycosylated proteins on the development of the intestinal microbiome, and how maternal phenotype may influence the development of MOM providing a framework to understand how variation in diet shapes a protective intestinal microbiome.

Production of human lactoferrin and lysozyme in the milk of transgenic dairy animals: past, present, and future

Genetic engineering, which was first developed in the 1980s, allows for specific additions to animals' genomes that are not possible through conventional breeding. Using genetic engineering to improve agricultural animals was first suggested when the technology was in the early stages of development by Palmiter et al. (Nature 300:611-615, 1982). One of the first agricultural applications identified was generating transgenic dairy animals that could produce altered or novel proteins in their milk. Human milk contains high levels of antimicrobial proteins that are found in low concentrations in the milk of ruminants, including the antimicrobial proteins lactoferrin and lysozyme. Lactoferrin and lysozyme are both part of the innate immune system and are secreted in tears, mucus, and throughout the gastrointestinal (GI) tract. Due to their antimicrobial properties and abundance in human milk, multiple lines of transgenic dairy animals that produce either human lactoferrin or human lysozyme have been developed. The focus of this review is to catalogue the different lines of genetically engineered dairy animals that produce either recombinant lactoferrin or lysozyme that have been generated over the years as well as compare the wealth of research that has been done on the in vitro and in vivo effects of the milk they produce. While recent advances including the development of CRISPRs and TALENs have removed many of the technical barriers to predictable and efficient genetic engineering in agricultural species, there are still many political and regulatory hurdles before genetic engineering can be used in agriculture. It is important to consider the substantial amount of work that has been done thus far on well established lines of genetically engineered animals evaluating both the animals themselves and the products they yield to identify the most effective path forward for future research and acceptance of this technology.

Production of transgenic-cloned pigs expressing large quantities of recombinant human lysozyme in milk

Human lysozyme is a natural non-specific immune factor in human milk that plays an important role in the defense of breastfed infants against pathogen infection. Although lysozyme is abundant in human milk, there is only trace quantities in pig milk. Here, we successfully generated transgenic cloned pigs with the expression vector pBAC-hLF-hLZ-Neo and their first generation hybrids (F1). The highest concentration of recombinant human lysozyme (rhLZ) with in vitro bioactivity was 2759.6 ± 265.0 mg/L in the milk of F0 sows. Compared with wild-type milk, rhLZ milk inhibited growth of Escherichia coli K88 during the exponential growth phase. Moreover, rhLZ in milk from transgenic sows was directly absorbed by the intestine of piglets with no observable anaphylactic reaction. Our strategy may provide a powerful tool for large-scale production of this important human protein in pigs to improve resistance to pathogen infection.

Expression of recombinant human lysozyme in egg whites of transgenic hens

Chicken egg lysozyme (cLY) is an enzyme with 129 amino acid (AA) residue enzyme. This enzyme is present not only in chicken egg white but also in mucosal secretions such as saliva and tears. The antibacterial properties of egg white can be attributed to the presence of lysozyme, which is used as an anti-cancer drug and for the treatment of human immunodeficiency virus (HIV) infection. In this study, we constructed a lentiviral vector containing a synthetic cLY signal peptide and a 447 bp synthetic human lysozyme (hLY) cDNA sequence driven by an oviduct-specific ovalbumin promoter, and microinjected into the subgerminal cavity of stage X chick embryos to generate transgenic chicken. The transgene inserted in the chicken chromosomes directs the synthesis and secretion of hLY which has three times higher specific activity than cLY. Three G₁ transgenic chickens were identified, the only female of which expressed recombinant human lysozyme (rhLY) at 57.66 ± 4.10 μg/ml in the egg white and the G₂ transgenic hens of the G₁ transgenic cock A011 expressed rhLY at 48.72 ± 1.54 μg/ml. This experiment demonstrated that transgenic hens with stable oviduct-specific expression of recombinant human lysozyme proteins can be created by microinjection of lentiviral vectors. The results of this research could be contribute to the technological development using transgenic hens as a cost-effective alternative to other mammalian systems, such as cow, sheep and goats, for the production of therapeutic proteins and other applications.

Modification of Animal Products for Fat and Other Characteristics

This chapter includes information about modification of animal products using biotechnology and the importance of different modifications on the natural composition. The species considered for modified products include beef and dairy cattle, sheep, goats, poultry, and a wide variety of fishes. Moreover, the discussion includes the importance of animal food, nongenetically engineered animal modified food products, genetically engineered animal modified food items primarily for meat, milk, or egg and genetically engineered animal food along the transgenic approach for animal welfare. Modern biotechnology can improve productivity, consistency, and quality of alter animal food, fiber, and medical products. The transgenic technology is potentially valuable to alter characters of economic importance in a rapid and precise way. The food safety issue related to genetic engineering is also included in this chapter. The harm of such modified food and transgenic strategy should also be understood by the reader along with its advantages. In this context, transgenic approaches in animal biotechnology are under discussion that ranges from animal food production to their adverse effects.

Inducible expression of enhanced green fluorescent protein by interleukin-1α, interleukin-1β and Toll-like receptor 2 promoters in goat mammary epithelial cells in response to bacterial challenges

The development of a bacteria-inducible expression system has several advantages compared with persistent expression of anti-bacterial proteins in milk to prevent and treat mastitis. The present study determined whether mastitis responsive promoters could regulate enhanced green fluorescent protein (EGFP) expression in goat mammary epithelial cells (GMECs) in response to challenges with Escherichia coli, Staphylococcus aureus or Streptococcus agalactiae. The level of expression of interleukin (IL)-1α was significantly increased in GMECs challenged with E. coli, S. aureus or S. agalactiae compared with untreated GMECs. IL-1β was induced by E. coli and S. aureus, while Toll-like receptor 2 (TLR2) was induced by E. coli only. GMECs were transfected with IL-1α, IL-1β and TLR2 promoter-EGFP reporter gene lentiviral expression vectors and the levels of expression of EGFP were measured by flow cytometry and Western blot analysis after bacterial challenge. EGFP expression driven by the IL-1α and IL-1β promoters was higher in GMECs challenged with E. coli, S. aureus or S. agalactiae than in untreated GMECs. There were no differences in EGFP expression driven by the TLR2 promoter between GMECs challenged with S. aureus or S. agalactiae and untreated GMECs, but EGFP expression was significantly increased in GMECs challenged with E. coli. Overall, these results indicate that the promoters of some bacteria-inducible genes can regulate EGFP expression in GMECs in response to bacterial challenges. This bacteria-inducible expression strategy could be used for production of mastitis resistant animals by regulating the expression of anti-bacterial proteins in the mammary gland.

Construction and in vivo evaluation of a mammary gland-specific expression vector for human lysozyme

A mammary gland-specific expression vector p205C3 was constructed with the 5'- and 3'-flanking regions of β-lactoglobulin gene and the first intron of β-casein gene of Chinese dairy goat as regulatory sequences. Human lysozyme (hLYZ) cDNA from mammary gland was cloned into p205C3 and the recombinant vector was used to generate transgenic mice by microinjection. Based on the lysoplate assay, four female offspring of one male founder were detected expressing recombinant hLYZ in their milk at the levels of 5-200 mg/l, and the expressed protein had the same molecular weight as that of normal hLYZ. Besides mammary glands, ectopic expressions were also found in the spleens and the small intestines of the transgenic mice. Among the offspring, the female transgenic mice maintained and expressed the transgene stably with a highest expression level of 750 mg/l. Therefore, p205C3 could be used to develop animal mammary gland bioreactors expressing hLYZ.

Genetically engineered livestock: ethical use for food and medical models

Recent advances in the production of genetically engineered (GE) livestock have resulted in a variety of new transgenic animals with desirable production and composition changes. GE animals have been generated to improve growth efficiency, food composition, and disease resistance in domesticated livestock species. GE animals are also used to produce pharmaceuticals and as medical models for human diseases. The potential use of these food animals for human consumption has prompted an intense debate about food safety and animal welfare concerns with the GE approach. Additionally, public perception and ethical concerns about their use have caused delays in establishing a clear and efficient regulatory approval process. Ethically, there are far-reaching implications of not using genetically engineered livestock, at a detriment to both producers and consumers, as use of this technology can improve both human and animal health and welfare.

Analysis of raw goat milk microbiota: impact of stage of lactation and lysozyme on microbial diversity

To protect infants from infection, human milk contains high levels of the enzyme lysozyme, unlike the milk of dairy animals. We have genetically engineered goats to express human lysozyme (hLZ milk) in their milk at 68% the amount found in human milk to help extend this protection. This study looked at the effect of hLZ on bacteria in raw milk over time. As the microbial diversity of goats' milk has yet to be investigated in depth using next-generation sequencing (NGS) technologies, we applied NGS and clone library sequencing (CLS) to determine the microbiota of raw goat milk (WT milk) and hLZ milk at early, mid and late lactation. Overall, in WT milk, the bacterial populations in milk at early and mid lactation were similar to each other with a shift occurring at late lactation. Both methods found Proteobacteria as the dominant bacteria at early and mid lactation, while Actinobacteria surged at late lactation. These changes were related to decreases in Pseudomonas and increases in Micrococcus. The bacterial populations in hLZ milk were similar to WT milk at early and mid lactation with the only significant differences occurring at late lactation with the elevation of Bacillaceae, Alicyclobacillaceae, Clostridiaceae and Halomonadaceae.

High-level recombinant human lysozyme expressed in milk of transgenic pigs can inhibit the growth of Escherichia coli in the duodenum and influence intestinal morphology of sucking pigs

Lysozyme is often used as a feed additive and acts as an antimicrobial protein that enhances immune function and defends against pathogenic bacteria in pigs. In this study, we genetically added recombinant human lysozyme (rhLZ) to sow milk by somatic cell nuclear transfer and investigated whether the presence of recombinant human lysozyme can influence intestinal microbiota and morphology in sucking pigs. We generated transgenic cloned pigs and the first-generation hybrids (F1) produced high levels of rhLZ in milk. The average concentration of rhLZ was 116.34 ± 24.46 mg/L in the milk of F1 sows, which was 1500-fold higher than that of the native pig lysozyme. In vitro, it was demonstrated that rhLZ in milk of transgenic pigs had enzyme levels at 92,272 ± 26,413 U/mL. In a feeding experiment, a total of 40 newborn piglets were nursed by four transgenic sows and four sibling non-transgenic sows (F1), with five piglets per gilt. The piglets were allowed to nurse for 21 days and the sow milk was the only source of nutrition for the piglets. All piglets were slaughtered on postnatal day 22. Six types of bacteria were cultured and analyzed to detect the impact of rhLZ on gut microbiota. The number of Escherichia coli in the duodenum of piglets reared by transgenic sows was significantly decreased (p<0.001) and their villus height to crypt depth ratio in the intestine were increased due to the significant decrease of crypt depth in the duodenum, jejunum, and ileum (p<0.001). Together, we successfully generated rhLZ transgenic cloned pigs and elevated lysozyme level in nuring piglets. The results of the feeding experiments demonstrated that rhLZ-enhanced milk can inhibit the growth of E. coli in the duodenum and positively influence intestinal morphology without adversely affecting weight gain or piglet growth.

Consumption of transgenic milk containing the antimicrobials lactoferrin and lysozyme separately and in conjunction by 6-week-old pigs improves intestinal and systemic health

Lactoferrin and lysozyme are antimicrobial and immunomodulatory proteins produced in high quantities in human milk that aid in gastrointestinal (GI) health and have beneficial effects when supplemented separately and in conjunction in human and animal diets. Ruminants produce low levels of lactoferrin and lysozyme; however, there are genetically engineered cattle and goats that respectively secrete recombinant human lactoferrin (rhLF-milk), and human lysozyme (hLZ-milk) in their milk. Effects of consumption of rhLF-milk, hLZ-milk and a combination of rhLF-and hLZ-milk were tested on young pigs as an animal model for the GI tract of children. Compared with control milk-fed pigs, pigs fed a combination of rhLF and hLZ (rhLF+hLZ) milk had a significantly deeper intestinal crypts and a thinner lamina propria layer. Pigs fed hLZ-milk, rhLF-milk and rhLF+hLZ had significantly reduced mean corpuscular volume (MCV) and red blood cells (RBCs) were significantly increased in pigs fed hLZ-milk and rhLF-milk and tended to be increased in rhLF+hLZ-fed pigs, indicating more mature RBCs. These results support previous research demonstrating that pigs fed milk containing rhLF or hLZ had decreased intestinal inflammation, and suggest that in some parameters the combination of lactoferrin and lysozyme have additive effects, in contrast to the synergistic effects reported when utilising in-vitro models.

Assessing unintended effects of a mammary-specific transgene at the whole animal level in host and non-target animals

Risk assessment in transgenic plants is intrinsically different than that for transgenic animals; however both require the verification of proper transgene function and in conjunction, an estimate of any unintended effects caused by expression of the transgene. This work was designed to gather data regarding methodologies to detect pleiotropic effects at the whole animal level using a line of transgenic goats that produce the antimicrobial protein human lysozyme (hLZ) in their milk with the goal of using the milk to treat childhood diarrhea. Metabolomics was used to determine the serum metabolite profile of both the host (lactating does) and non-target organism (kid goats raised on control or hLZ milk) prior to weaning (60 days), at weaning (90 days) and 1 month post-weaning (120 days). In addition, intestinal histology of the kid goats was also carried out. Histological analysis of intestinal segments of the pre-weaning group revealed significantly wider duodenal villi (p = 0.014) and significantly longer villi (p = 0.028) and deeper crypts (p = 0.030) in the ileum of kid goats consuming hLZ milk. Serum metabolomics was capable of detecting differences over time but revealed no significant differences in metabolites between control and hLZ fed kids after correction for false discovery rate. Serum metabolomics of control or hLZ lactating does showed only one significant difference in an unknown metabolite (q = 0.0422). The results as a whole indicate that consumption of hLZ milk results in positive or insignificant intestinal morphology and metabolic changes. This work contributes to the establishment of the safety and durability of the hLZ mammary-specific transgene.

Anti-bacterial activity of recombinant human β-defensin-3 secreted in the milk of transgenic goats produced by somatic cell nuclear transfer

The present study was conducted to determine whether recombinant human β-defensin-3 (rHBD3) in the milk of transgenic goats has an anti-bacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Streptococcus agalactiae (S. agalactiae) that could cause mastitis. A HBD3 mammary-specific expression vector was transfected by electroporation into goat fetal fibroblasts which were used to produce fourteen healthy transgenic goats by somatic cell nuclear transfer. The expression level of rHBD3 in the milk of the six transgenic goats ranged from 98 to 121 µg/ml at 15 days of lactation, and was maintained at 90–111 µg/ml during the following 2 months. Milk samples from transgenic goats showed an obvious inhibitory activity against E. coli, S. aureus and S. agalactiae in vitro. The minimal inhibitory concentrations of rHBD3 in milk against E. coli, S. aureus and S. agalactiae were 9.5–10.5, 21.8–23.0 and 17.3–18.5 µg/mL, respectively, which was similar to those of the HBD3 standard (P>0.05). The in vivo anti-bacterial activities of rHBD3 in milk were examined by intramammary infusion of viable bacterial inoculums. We observed that 9/10 and 8/10 glands of non-transgenic goats infused with S. aureus and E. coli became infected. The mean numbers of viable bacteria went up to 2.9×10³ and 95.4×10³ CFU/ml at 48 h after infusion, respectively; the mean somatic cell counts (SCC) in infected glands reached up to 260.4×10⁵ and 622.2×10⁵ cells/ml, which were significantly higher than the SCC in uninfected goat glands. In contrast, no bacteria was presented in glands of transgenic goats and PBS-infused controls, and the SSC did not significantly change throughout the period. Moreover, the compositions and protein profiles of milk from transgenic and non-transgenic goats were identical. The present study demonstrated that HBD3 were an effective anti-bacterial protein to enhance the mastitis resistance of dairy animals.

A site-specific recombinase-based method to produce antibiotic selectable marker free transgenic cattle

Antibiotic selectable marker genes have been widely used to generate transgenic animals. Once transgenic animals have been obtained, the selectable marker is no longer necessary but raises public concerns regarding biological safety. The aim of this study was to prepare competent antibiotic selectable marker free transgenic cells for somatic cell nuclear transfer (SCNT). PhiC31 intergrase was used to insert a transgene cassette into a "safe harbor" in the bovine genome. Then, Cre recombinase was employed to excise the selectable marker under the monitoring of a fluorescent double reporter. By visually tracking the phenotypic switch from red to green fluorescence, antibiotic selectable marker free cells were easily detected and sorted by fluorescence-activated cell sorting. For safety, we used phiC31 mRNA and cell-permeant Cre protein in this study. When used as donor nuclei for SCNT, these safe harbor integrated marker-free transgenic cells supported a similar developmental competence of SCNT embryos compared with that of non-transgenic cells. After embryo transfer, antibiotic selectable marker free transgenic cattle were generated and anti-bacterial recombinant human β-defensin-3 in milk was detected during their lactation period. Thus, this approach offers a rapid and safe alternative to produce antibiotic selectable marker free transgenic farm animals, thereby making it a valuable tool to promote the healthy development and welfare of transgenic farm animals.

Consuming transgenic goats' milk containing the antimicrobial protein lysozyme helps resolve diarrhea in young pigs

Childhood diarrhea is a significant problem in many developing countries and E. coli is a main causative agent of diarrhea in young children. Lysozyme is an antimicrobial protein highly expressed in human milk, but not ruminant milk, and is thought to help protect breastfeeding children against diarrheal diseases. We hypothesized that consumption of milk from transgenic goats which produce human lysozyme (hLZ-milk) in their milk would accelerate recovery from bacterial-induced diarrhea. Young pigs were used as a model for children and infected with enterotoxigenic E. coli. Once clinical signs of diarrhea developed, pigs were fed hLZ-milk or non-transgenic control goat milk three times a day for two days. Clinical observations and complete blood counts (CBC) were performed. Animals were euthanized and samples collected to assess differences in histology, cytokine expression and bacterial translocation into the mesenteric lymph node. Pigs consuming hLZ-milk recovered from clinical signs of infection faster than pigs consuming control milk, with significantly improved fecal consistency (p = 0.0190) and activity level (p = 0.0350). The CBC analysis showed circulating monocytes (p = 0.0413), neutrophils (p = 0.0219), and lymphocytes (p = 0.0222) returned faster to pre-infection proportions in hLZ-milk fed pigs, while control-fed pigs had significantly higher hematocrit (p = 0.027), indicating continuing dehydration. In the ileum, pigs fed hLZ-milk had significantly lower expression of pro-inflammatory cytokine IL-8 (p = 0.0271), longer intestinal villi (p<0.0001), deeper crypts (p = 0.0053), and a thinner lamina propria (p = 0.0004). These data demonstrate that consumption of hLZ-milk helped pigs recover from infection faster, making hLZ-milk an effective treatment of E. coli-induced diarrhea.

Dissecting the role of milk components on gut microbiota composition

The composition of human milk is tailored to contribute to the development of the gastrointestinal (GI) tract of newborns and infants. Importantly, human milk contains the antimicrobial compounds lysozyme and lactoferrin that are thought to contribute to the formation of a health-promoting microbiota. As these protective factors are lacking in the milk of dairy animals, we genetically engineered goats expressing human lysozyme in their milk and have recently reported a new animal model to dissect out the role of milk components on gut microbiota formation. Using the pig as a more human-relevant animal model, we demonstrated that consumption of lysozyme-rich milk enriched the abundance of bacteria associated with GI health and decreased those associated with disease, much like human milk. This work demonstrated that the pig is a valid animal model for gut microbiome studies on the effects of dietary components on microbiota composition, host-microbe interactions and state of the intestine.

Production of cloned embryos from caprine mammary epithelial cells expressing recombinant human β-defensin-3

Transgenic animals that express antimicrobial agents in their milk can inhibit bacterial pathogens that cause mastitis. Our objective was to produce human β-defensin-3 (HBD3) transgenic embryos by nuclear transfer using goat mammary epithelial cells (GMECs) as donor cells. Three GMEC lines (GMEC1, GMEC2, and GMEC3) were transfected with a HBD3 mammary-specific expression vector by electroporation. There was a difference (P < 0.05) in the rate of geneticin-resistant colony formation among cell lines GMEC1, GMEC2, and GMEC3 (39 and 47 vs. 19 colonies per 3 × 10(6) cells, respectively). After inducing expression, the mRNA and protein of HBD3 were detected by reverse transcription polymerase chain reaction and Western blot analysis in transgenic cells. Transgenic clonal cells expressing HBD3 were used as donor cells to investigate development of cloned embryos. There were no significant differences in rates of cleavage or blastocyst formation of cloned embryos from transgenic (GMEC1T2 and GMEC2T3) and nontransgenic (GMEC1 and GMEC2) GMECs (72.3 ± 5.0%, 69.5 ± 2.3%, 61.8 ± 4.8%, and 70.0 ± 2%; and 16.8 ± 0.5%, 17.5 ± 0.7%, 16.7 ± 0.9%, and 17.5 ± 0.6%, respectively). However, the fusion rate, cleavage rate, and blastocyst formation rate of cloned embryos from a transgenic clonal cell line (GMEC2T6, 50.7 ± 2.1%, 55.5 ± 2.0%, and 11.1 ± 0.6%) were lower than those of other groups (P < 0.05). We concluded that genetic modification of GMECs might not influence the in vitro development of cloned embryos, but that some of the transgenic clonal cells were not suitable for nuclear transfer to produce transgenic goats, because of low developmental rates. However, transgenic GMECs expressing HBD3 might be used as donor cells for producing transgenic goats that express increased concentrations of β-defensins in their milk.

Transgenic sheep generated by lentiviral vectors: safety and integration analysis of surrogates and their offspring

The safety of HIV-1 based vectors was evaluated during the production of transgenic sheep. Vectors were introduced into the perivitelline space of in vivo derived one-cell sheep embryos by microinjection then transferred into the oviducts of recipient females. At 60-70 days of gestation, a portion of the recipients were euthanized and tissues collected from both surrogates and fetuses. Other ewes were allowed to carry lambs to term. Inadvertent transfer of vector from offspring to surrogates was evaluated in 330 blood and tissue samples collected from 57 ewes that served as embryo recipients. Excluding uterine contents, none of the samples tested positive for vector, indicating that that the vector did not cross the fetal maternal interface and infect surrogate ewes. Evaluating ewes, fetuses and lambs for replication competent lentivirus (RCL); 84 serum samples analyzed for HIV-1 capsid by ELISA and over 600 blood and tissue samples analyzed by quantitative PCR for the VSV-G envelopes revealed no evidence of RCL. Results of these experiments provide further evidence as to the safety of HIV-1 based vectors in animal and human applications.

Endolysins as antimicrobials

Peptidoglycan (PG) is the major structural component of the bacterial cell wall. Bacteria have autolytic PG hydrolases that allow the cell to grow and divide. A well-studied group of PG hydrolase enzymes are the bacteriophage endolysins. Endolysins are PG-degrading proteins that allow the phage to escape from the bacterial cell during the phage lytic cycle. The endolysins, when purified and exposed to PG externally, can cause "lysis from without." Numerous publications have described how this phenomenon can be used therapeutically as an effective antimicrobial against certain pathogens. Endolysins have a characteristic modular structure, often with multiple lytic and/or cell wall-binding domains (CBDs). They degrade the PG with glycosidase, amidase, endopeptidase, or lytic transglycosylase activities and have been shown to be synergistic with fellow PG hydrolases or a range of other antimicrobials. Due to the coevolution of phage and host, it is thought they are much less likely to invoke resistance. Endolysin engineering has opened a range of new applications for these proteins from food safety to environmental decontamination to more effective antimicrobials that are believed refractory to resistance development. To put phage endolysin work in a broader context, this chapter includes relevant studies of other well-characterized PG hydrolase antimicrobials.

Goat milk with and without increased concentrations of lysozyme improves repair of intestinal cell damage induced by enteroaggregative Escherichia coli

BACKGROUND

Enteroaggregative Escherichia coli (EAEC) causes diarrhea, malnutrition and poor growth in children. Human breast milk decreases disease-causing bacteria by supplying nutrients and antimicrobial factors such as lysozyme. Goat milk with and without human lysozyme (HLZ) may improve the repair of intestinal barrier function damage induced by EAEC. This work investigates the effect of the milks on intestinal barrier function repair, bacterial adherence in Caco-2 and HEp-2 cells, intestinal cell proliferation, migration, viability and apoptosis in IEC-6 cells in the absence or presence of EAEC.

METHODS

Rat intestinal epithelial cells (IEC-6, ATCC, Rockville, MD) were used for proliferation, migration and viability assays and human colon adenocarcinoma (Caco-2, ATCC, Rockville, MD) and human larynx carcinoma (HEp-2, ATCC, Rockville, MD) cells were used for bacterial adhesion assays. Goats expressing HLZ in their milk were generated and express HLZ in milk at concentration of 270 μg/ml. Cells were incubated with pasteurized milk from either transgenic goats expressing HLZ or non-transgenic control goats in the presence and absence of EAEC strain 042 (O44:H18).

RESULTS

Cellular proliferation was significantly greater in the presence of both HLZ transgenic and control goat milk compared to cells with no milk. Cellular migration was significantly decreased in the presence of EAEC alone but was restored in the presence of milk. Milk from HLZ transgenic goats had significantly more migration compared to control milk. Both milks significantly reduced EAEC adhesion to Caco-2 cells and transgenic milk resulted in less colonization than control milk using a HEp-2 assay. Both milks had significantly increased cellular viability as well as less apoptosis in both the absence and presence of EAEC.

CONCLUSIONS

These data demonstrated that goat milk is able to repair intestinal barrier function damage induced by EAEC and that goat milk with a higher concentration of lysozyme offers additional protection.