Engineering Disease Resistant Cattle

Challenges and prospects for the establishment of embryonic stem cell lines of domesticated ungulates

Embryonic stem (ES) cell lines provide an invaluable research tool for genetic engineering, developmental biology and disease models. These cells can be maintained indefinitely in culture and yet maintain competence to produce all the cells within a fetus. While mouse ES cell lines were first established over two decades ago and primate ES cells in the 1990 s, validated ES cell lines have yet to be established in ungulates. Why competent, pluripotent ES cells can be established from certain strains of mice and from primates, and not from cows, sheep, goats or pigs is an on-going topic of interest to animal reproduction scientists. The identification of appropriate stem cell markers, functional cytokine pathways, and key pluripotency-maintaining factors along with the release of more comprehensive bovine and porcine genomes, provide encouragement for establishment of ungulate ES cell lines in the near future.

The cell lysis activity of the Streptococcus agalactiae bacteriophage B30 endolysin relies on the cysteine, histidine-dependent amidohydrolase/peptidase domain

The Streptococcus agalactiae bacteriophage B30 endolysin contains three domains: cysteine, histidine-dependent amidohydrolase/peptidase (CHAP), Acm glycosidase, and the SH3b cell wall binding domain. Truncations and point mutations indicated that the Acm domain requires the SH3b domain for activity, while the CHAP domain is responsible for nearly all the cell lysis activity.

Peptidoglycan hydrolase fusions maintain their parental specificities

The increased incidence of bacterial antibiotic resistance has led to a renewed search for novel antimicrobials. Avoiding the use of broad-range antimicrobials through the use of specific peptidoglycan hydrolases (endolysins) might reduce the incidence of antibiotic-resistant pathogens worldwide. Staphylococcus aureus and Streptococcus agalactiae are human pathogens and also cause mastitis in dairy cattle. The ultimate goal of this work is to create transgenic cattle that are resistant to mastitis through the expression of an antimicrobial protein(s) in their milk. Toward this end, two novel antimicrobials were produced. The (i) full-length and (ii) 182-amino-acid, C-terminally truncated S. agalactiae bacteriophage B30 endolysins were fused to the mature lysostaphin protein of Staphylococcus simulans. Both fusions display lytic specificity for streptococcal pathogens and S. aureus. The full lytic ability of the truncated B30 protein also suggests that the SH3b domain at the C terminus is dispensable. The fusions are active in a milk-like environment. They are also active against some lactic acid bacteria used to make cheese and yogurt, but their lytic activity is destroyed by pasteurization (63 degrees C for 30 min). Immunohistochemical studies indicated that the fusion proteins can be expressed in cultured mammalian cells with no obvious deleterious effects on the cells, making it a strong candidate for use in future transgenic mice and cattle. Since the fusion peptidoglycan hydrolase also kills multiple human pathogens, it also may prove useful as a highly selective, multipathogen-targeting antimicrobial agent that could potentially reduce the use of broad-range antibiotics in fighting clinical infections.