My research focuses on studying the impact of expressing antimicrobials in the mammary gland of dairy animals. Transgenic goats expressing lysozyme in their milk are being investigated as a means to improve human health with work being conducted in three main areas including 1) characterization of the antimicrobial nature of lysozyme-rich milk both in vitro and in vivo; 2) impact of consuming milk at the level of the intestine; 3) the characterization of the health and well-being of transgenic animals. The overall goal of this work is the translation of the use of lysozyme milk as a treatment or preventative agent to fight diarrheal and other intestinal illnesses. In addition, studies on the relationship between casein genotypes and milk quality are being carried out in goats.
1) Characterization of lysozyme-rich milk
Lysozyme is present in the tears, saliva and milk of all mammals as part of the natural defense system against pathogenic bacteria. Lysozyme acts as a bacteriostatic agent by cleaving a specific link the cell wall of bacteria. The antimicrobial nature of the milk from lysozyme transgenic goats is being characterized by investigating the susceptibility of bacterial isolates important to animal health (mastitis-causing bacteria) and human health (diarrhea-causing bacteria) to the milk itself. The bacterial diversity of milk from lysozyme transgenic and control goats is being defined using molecular techniques (Illumina-based next-generation sequencing) and the manufacture and shelf-life of dairy products made from lysozyme-rich milk are also being investigated.
2) Impact of lysozyme milk consumption at the level of the intestine
Human milk contains the antimicrobial compounds lysozyme and lactoferrin at much higher levels than the milk of dairy animals. These compounds are thought play a key role in the establishment of a healthy gut microbiota in breast-fed infants. We hypothesize that milk our transgenic goats that express human lysozyme at 68% the level found in human milk will be capable of modulating gut microbiota in a fashion similar to human milk to result in a healthier intestinal epithelium. We are using the milk as a research tool to investigate the consequences of gut microbiota modulation on overall health and the resistance to disease and with the goal of translating this work into a preventative or treatment agent for diarrheal illnesses. We have established a novel, more human-relevant model consisting of young pigs with and without E. coli-induced diarrhea with which to assess the ability of milk consumption in general as well as consumption of lysozyme-rich milk to influence the state of the intestine. We are investigating 1) changes in gut microbiota using Illumina-based next-generation sequencing, 2) changes in gut architecture using histology and 3) changes in immune response by looking at intestinal cytokine expression using qPCR and the distribution of immune cells in the intestine using immunohistochemistry. In addition, RNA-seq is being used to identify global changes in gene expression in the intestine in response to milk treatment.
3) Health and well-being of transgenic animals
Transgenic livestock of several species have been generated with the intent to benefit animal agriculture. In addition to investigating the desired impact of the transgene, transgenic animals must also be studied to ensure that the presence of the transgene and transgene product are not in any way detrimental to the transgenic animals themselves. We have been investigating general traits such as the reproduction, growth, lactation and behavior of the lysozyme line of transgenic dairy goats to generate information on the safety and well-being of genetically engineered animals. In addition, identification of any off-target effects on the host (lactating does) and non-target organisms (growing goats) will be investigated at the whole animal level by conducting metabolite and microbial profiling. Data along this line will be useful to regulators and the general public in assessing the safety of genetically engineered animals.
4) Relationship between casein genotypes and milk production in goats
The as1-casein genotype of a goat can have a profound impact on the amount of milk a goat makes as well as the protein content of the milk. Depending on the allele they carry, goats can make a high (3.6 g/L), medium (1.6 g/L), low (0.6 g/L) or null amount of as1-casein in their milk. This can have a large impact if the milk is to be used for cheese-making. We developed a genotyping scheme and found a high proportion of the low-expressing alleles in a representative sample of the American dairy goat population. Production records will be used to correlate with genotype to determine if there would be an advantage to selecting goats with certain genotypes. Selective breeding can then be carried out to result in the desired milk composition.