The drug being credited with potentially saving the lives of two American missionaries infected with the deadly Ebola virus was produced in Owensboro.

The serum wasn't manufactured but grown — in a greenhouse full of genetically modified tobacco plants.

Kentucky BioProcessing, acquired by Reynolds American in January, conducts contract research and development for San Diego-based Mapp Biopharmaceutical, said David Howard, spokesman for RAI Ser vices, a subsidiary of Reynolds American.

"In the last week, Kentucky BioProcessing complied with a request from Emory University and Samaritan's Purse to provide a very limited amount (of the compound) to Emory, and KPB has done that," Howard said.

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CNN and NBC News reported Monday that ZMapp had been given to Dr. Kent Brantly and Nancy Writebol, who have been described as showing significant improvement.

The experimental drug apparently had never been tested on humans.

In 2007, Mapp, working under contract for the U.S. Department of Defense and other federal agencies, engaged KBP to develop a process to manufacture a compound designed to be a post-exposure treatment for Ebola virus.

That compound was MB-003 or ZMapp, a cocktail of antibodies that has proven to be the most effective treatment so far in fighting off the Ebola virus.

In a study published last year, scientists at the U.S. Army Medical Research Institute of Infectious Diseases reported that 43 percent of infected nonhuman primates recovered after receiving the treatment intravenously 104 to 120 hours after infection — after symptoms developed.

"Mapp Biopharmaceutical has the structure of this protein to battle the Ebola. And KPB is building that protein," Howard said.

In Owensboro, tobacco plants are "infected" with the protein, he said, and then they reproduce it "like a photocopier."

The desired proteins are extracted from the plants and purified into a serum.

Scientists have long known that tobacco readily picks up genes inserted into it. The Owensboro facility uses that ability to quickly and inexpensively produce large volumes of a compound within weeks.

KBP also has been selected for work on some of the biggest health threats on the planet, including H1N1 vaccine production, an anti-rabies antibody, norovirus or the "cruise ship virus," HIV prevention, parvovirus, and HPV vaccine.

ZMapp, the drug used on the American Ebola victims, has not been approved in the United States or other countries, Howard said, but the Owensboro facility had begun ramping up production for anticipated drug approval testing protocols this year.

That process might be accelerated now.

"KBP is working closely with Mapp and other agencies to increase production, but that process will take several months," Howard said.