OXFORD, Miss. – Wherever U.S. troops are deployed, they must guard not only against their country’s human foes but also whatever Mother Nature throws at them from her well-stocked arsenal.
Her weapons include a barrage of blood-feeding arthropods – mosquitoes, lice, sand flies, ticks, mites, stable flies and bed bugs – and the diseases they transmit. Among the chief threats are malaria, yellow fever, typhus, dengue fever, encephalitis and leishmaniasis.
America’s war against these insect and disease threats is being fought by a squad of unlikely soldiers serving in the Deployed War-Fighter Protection, or DWFP, research program under the leadership of the Armed Forces Pest Management Board, or AFPMB. Its mission is to provide an arsenal of new weapons to U.S. troops, so they can protect or defend themselves from insect and disease attacks.
Some of the most productive soldiers in this “war on bugs” are scientists in the Thad Cochran Research Center at the University of Mississippi, home to the university’s National Center for Natural Products Research, or NCNPR, and the Natural Products Utilization Research Unit, or NPURU, of the U.S. Department of Agriculture-Agricultural Research Service, or USDA-ARS.
Scientists in this facility have discovered and developed several new insecticides and repellents by studying the region’s folk remedies or by investigating plants used for centuries as medicines or insect deterrents elsewhere in the world.
Discovery of callicarpenal, which repels mosquitoes and ticks, was prompted by a story about a Mississippi farmer crushing leaves of American beautyberry (Callicarpa americana) and putting them under the harnesses of his draft animals to deter pests. Discovery of an entire class of new mosquito-repelling compounds occurred after NPURU chemist Charles Cantrell learned that people in Africa and India burn oil from seeds of the physic nut plant (Jatropha curcas) in lamps to keep insects out of their homes.
Cantrell extracted smoke from J. curcas, analyzed its chemical constituents and found that triglycerides were among the compounds responsible for its mosquito-deterring effects.
“What our forefathers used that worked can’t be ignored,” said NCNPR assistant director Ikhlas Khan. “We need to use the technology available today to figure out why they worked and use that knowledge to create things that work even better.”
Another compound was found by NPURU chemist Kumudini Meepagala in fungi growing on leaves in her Oxford flowerbed. A scientist at another USDA-ARS lab in Gainesville, Fla., sprayed the compound on mosquitoes and found that they quickly died.
“Sometimes we go to rainforests or faraway places to get plant material from which to isolate compounds, but sometimes you find them in your own backyard,” she said. “A lot of metabolites produced by plant pathogenic fungi have not been tested for mosquitocides or repellents. This is something we just recently began exploring.”
With the help of another scientist at the Gainesville lab, Meepagala found yet another novel compound, a chromene derivative, in leaves of a member of the Rutaceae family, to which citrus fruits belong.
“This compound has no odor and is viscous (oily) and colorless, which makes it suitable for applications to clothes and skin,” Meepagala said. “Plus, this compound lasts six days, while DEET (the ‘gold standard’ of repellents) lasts only two days.”
After discovering the derivative’s mosquito-repelling activity, Meepagala and her colleagues made more than 50 chemical variations of the compound before arriving at the one they are patenting. In the process, they learned the compound is also active against termites.
“We are now looking for partners willing to help us bring it to the market,” she said.
“The Department of Defense is particularly excited about the potential of Dr. Meepagala’s efforts and the promising products she and her team are developing aimed at reducing the risk of vector-borne diseases to our U.S. military personnel,” said U.S. Army Lt. Col. Jason Richardson, DWFP program manager and AFPMB research liaison officer.
The university has a unique facility in which to scale up production of compounds found or being developed by scientists such as Meepagala, Cantrell and others: a 3,400-square-foot Proof-of-Concept and Commercialization Center in the Innovation Hub of Insight Park, UM’s research park.
“The center was designed to meet the area’s long-standing, unmet need for a facility in which to scale up production of synthetic compounds and to extract natural compounds from biomass at a pilot scale,” said Walt Chambliss, director of UM’s Division of Technology Management. “Our intent is that the facility be used not only to support the War-Fighter project but also other critical projects across the country funded by the Department of Defense, USDA, National Institutes of Health and others.”
The inability to scale up production of promising lead compounds through either synthesis or extraction is what limits commercialization of many pharmaceutical and agrochemical discoveries funded by the federal government.
“That’s why we approached USDA and DOD about partnering with us on this facility, and they were very supportive,” Chambliss said. “In fact, the USDA listed the partnership with UM at Insight Park as one of its top initiatives in response to President Obama’s call for accelerated commercialization of discoveries from university and government laboratories.”
In addition to those compounds discovered by NPURU’s and NCNPR’s foot soldiers in the war on bugs, a compound that may be processed in the center is isolongifolenone, which was discovered in another USDA-ARS lab in Beltsville, Md. Scientists there also developed a method to synthesize the compound, which repels mosquitoes and ticks, from pine oil feedstock, but the process uses a metal and an organic solvent, which are of concern to the Environmental Protection Agency.
“USDA approached us about coming up with a safer and greener way to produce this compound,” said NCNPR senior scientist Amar Chittiboyina, a synthetic and medicinal chemist.
Chittiboyina led the Oxford lab’s offensive to devise a method to make large-scale production of the compound environmentally safe and economically feasible. The oxidative method he and his collaborators developed employs a nontoxic catalyst and solvent, which eliminate the EPA’s concerns, and begins with raw material available in bulk, which makes the process cheaper.
Chittiboyina and his colleagues have made a few grams of isolongifolenone using the method and are exploring ways to improve the process and make it even more cost-effective. The next step in getting the promising repellent to market “is producing it on a semi-industrial scale,” he said.
Whether such naturally derived products come from plants, fungi or other natural materials, they are discovered by bioactivity-guided fractionation. In the process, scientists isolate the materials’ chemical constituents and test them for desired biological activity.
Some of those constituents are tested for insecticidal, biting-deterrent and repellent activity at UM’s biological field station by entomologist and NCNPR senior research scientist Abbas Ali. Since 2009, he has screened 1,450 natural products for larvicidal activity and 1,225 for biting-deterrent activity.
“He’s a wizard with all that stuff,” said NPURU research leader Steve Duke.
While Duke’s team is focusing on ways to prevent soldiers, sailors, airmen and marines from getting bit by a horde of blood-sucking arthropods, NCNPR scientists are targeting diseases the arthropods transmit. In their sights are the parasites that cause malaria, which kills more than 1 million people each year.
“Our work has opened the way for developing safer drugs that kill the liver and blood transmission stages of the parasite,” said NCNPR director Larry Walker. “These forms are hard to kill.”
They also are working to improve primaquine, which has for 50 years been used to treat and prevent relapsing malaria. Primaquine causes side effects in some people (those with a certain enzyme deficiency), and malaria parasites have become immune to the drug.
“We’re trying to make it better, safer and more effective,” Walker said. “We’re also working on other drugs in hopes of developing one that is safe and effective.”
The lead compound for one of those drugs, which UM has patented and licensed to a company for development, also exhibits activity against leishmaniasis and a type of pneumonia common among patients with immune deficiencies.
To expedite getting the results of their 20 years of malaria research into the hands of the people who need it most, Walker and his colleagues are collaborating with the Walter Reed Army Institute of Research in Silver Spring, Md., the National Institute of Allergy and Infectious Diseases, Cumberland Emerging Technologies (a subsidiary of Nashville-based Cumberland Pharmaceuticals), Medicines for Malaria Venture in Geneva, Switzerland, and faculty members at Mahidol University in Bangkok, Thailand, as well as the scientists involved in the DWFP research program.
The university has twice hosted the DWFP team’s annual review meeting, which is attended by not only USDA-ARS and DOD brass but also many of the foot soldiers conducting DWFP research.
“The leadership of Dr. Walker and Dr. Duke, combined with NPURU’s dedicated team of scientists in developing new products to reduce the impact of biting arthropods is a definite win for the Department of Defense,” said U.S. Navy Capt. Mark Beavers, AFPMB director.
“The military is very interested in all the research we’re doing here, and companies are interested in finding natural alternatives to DEET and picardin,” Duke said. “Both of these are synthetic and work well, but people want something more natural and green.”
As a result of DWFP research in Oxford and labs elsewhere, people may one day be able to walk into a store and buy candles that really do repel mosquitoes from their homes, patios and campsites.
“We took the best compounds from several plants and put them together to generate candles that really work,” Duke said.
Some of those compounds may also end up in the traps, foggers, sprays, factory-treated uniforms and other items placed directly in the hands of U.S. troops, so they can go hand-to-hand with Mother Nature around the world.
“We have a very synergistic relationship between USDA and NCNPR researchers here, as well as DOD and USDA labs elsewhere,” Duke said. “This means that all the pieces are coming together to achieve something really important.”
“We have seen steady progress in the usefulness and, especially, safety of insecticides since the discovery of DDT in 1939,” said Daniel A. Strickman, USDA-ARS national program leader for Veterinary, Medical and Urban Entomology and a retired U.S. Army colonel. “The next generation of improvements may come from the wide variety of natural products examined by the Oxford laboratory in cooperation with the University of Mississippi.”
UM’s National Center for Natural Products Research was created to bring together an alliance of academia, government and industry to integrate research, development and commercialization of useful natural products. USDA-ARS’s Natural Products Research Utilization Unit was created to develop more benign pest management tools and to improve the nutraceutical value of crops. For more than 15 years, NCNPR and NPURU have shared facilities and collaborated on discovery and development of natural products. That collaboration has already resulted in several jointly owned patents and one commercial product.