The term “shotgun proteomics” may sound like research conducted by scientists operating outside the law.

But molecular biologist John Lippolis is using it to close in on the dynamics of the dairy cow immune system. His work is resulting in the first close-up look at how immune system proteins help protect the cows and how bacterial proteins fight back.

“I want to be able to find something that dairy farmers will incorporate into their management practices,” Lippolis says. “They tend to be very cautious about adopting new practices unless there’s a clear benefit.”

Lippolis works at the Agricultural Research Service (ARS) Periparturient Diseases of Cattle Research Unit, part of the National Animal Disease Center in Ames, Iowa. He is using proteomics – the identification of the proteins that make up a cell – to identify and study neutrophils, the white blood cells that are a key part of the immune system.

When dairy cows develop mastitis, a bacterial infection that costs dairy producers some $2 billion every year, neutrophils are an essential part of the immune response. Lippolis identified proteins in bovine neutrophils and tracked how they change during infection.

Lippolis identified hundreds of neutrophil proteins. Nearly 35 percent were associated with basic cellular metabolic pathways, including most of the proteins involved in the production of cellular energy. Another 30 percent were involved in immune functions or in cell structure and mobility.

Lippolis then compared these newly identified neutrophil proteins in pregnant cows with those in cows that were in an immunosuppressive interlude after calving. Compared to the pregnant cows, he observed changes in the concentration of 40 proteins in the immunosuppressed cows.

Lippolis also compared neutrophils from periparturient cows – animals that had recently given birth and were in an immunosuppressive interlude – with neutrophils from cows that had been given the steroid dexamethasone to artificially suppress immune function. Although he found some similar changes in protein expression in both groups, there were also some significant differences between them.

All of these findings could guide Lippolis and other researchers in their search for ways to bolster bovine immune systems at the cellular level and may give researchers new paths to explore in developing antibiotic therapies to treat mastitis. Dairy farmers would welcome the new tools, and Lippolis would be able to fulfill his wish of helping improve their dairy production practices.  PD

—Excerpts from Agricultural Research Magazine, Vol. 56, No. 7

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