The effect of pegylated granulocyte colony stimulating factor therapy against experimental mastitis in lactating Holsteins

Authors: POWELL, ELLIS - Oak Ridge Institute For Science And Education (ORISE); Reinhardt, Timothy; Casas, Eduardo; Lippolis, John

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2018
Publication Date: 9/1/2018
Citation: Powell, E.J., Reinhardt, T.A., Casas, E., Lippolis, J.D. 2018. The effect of pegylated granulocyte colony-stimulating factor treatment prior to experimental mastitis in lactating Holsteins. Journal of Dairy Science. 101(9):8182-8193. https://doi.org/10.3168/jds.2018-14550.
DOI: https://doi.org/10.3168/jds.2018-14550

Interpretive Summary: Mastitis disease is defined as the inflammation of the mammary gland and can affect all lactating animals. Mastitis can result from various bacterial infections including E. coli. In particular, mastitis is of great health and economic concern to the dairy industry, where an infection can result in discomfort and damage to the animal, as well as a loss of safe, consumable milk. Preventing and treating mastitis is thus critically important to the dairy cow industry. One developing therapy option is to treat the cows with a cell signalling protein (cytokine) designed to activate the immune cells most important in fighting mastitis-causing bacteria. Five cows were treated with two injections of a cytokine, and six cows were used as untreated controls. All eleven cows were challenged with E. coli to produce a mastitis infection. Data was collected regarding the cow's milk production, feed consumption, blood cell profile, and the presence of bacteria and immune cells in the milk. Our goals were to examine the effects of the cytokine therapy and learn more about the mechanism of immune system response to mastitis. The cows that had been treated with the cytokine produced more milk, had a higher feed consumption, had less bacteria in their milk, and had a more activated immune system compared to untreated cows. These findings are important in the development of mastitis prevention and treatment therapies.

Technical Abstract: Mastitis continues to lead health and economic concerns for the dairy industry. Better understanding of dairy cattle's response to pathogens is important for development of next-generation antibiotic alternatives. Neutrophils are the first-acting, most prominent, cellular defense against mastitis causing pathogens. This makes neutrophil activation and expansion obvious candidates for targeted therapeutics. One such treatment includes the cytokine granulocyte colony-stimulating factor (G-CSF). The G-CSF cytokine targets neutrophil regulation, and has been well associated with neutrophilia. A two-injection treatment of a pegylated form of G-CSF (PEG-gCSF) has been shown to significantly decrease naturally-occurring cases of mastitis compared to untreated control cows. However, PEG-gCSF had not been evaluated in response to an experimental mastitis challenge. In this study, we challenged 11 mid-lactation Holsteins with ~400 cfu Escherichia coli P4 by intramammary infusion. Five cows received subcutaneous injections of PEG-gCSF 14 days and 7 days prior to disease challenge, six cows remained untreated. To evaluate the response to PEG-gCSF, we measured complete blood counts (CBCs), somatic cell counts (SCCs), bacterial counts, milk yield, and feed intake data from 20 days prior to disease challenge, through day 11 post challenge including relevant 6 and 12 hour intervals immediately post infection. PEG-gCSF treated cattle had significantly increased circulating levels of neutrophils and lymphocytes after each PEG-gCSF injection, as well as following mastitis challenge. Treated cows had significantly lower bacterial counts in the 48 hours post infection, but did not differ in SCCs pre or post infection compared to control cows. In addition, control cattle had greater decreases in milk yield post challenge and similarly, had reduced feed intake post challenge compared to PEG-gCSF treated cows. Collectively, PEG-gCSF treatment resulted in reduced disease severity. This data suggests the utilization of gCSF as a potential antibiotic alternative to mastitis treatment and prevention and supports neutrophil focused therapies as an important facet of mastitis disease protection.