Plant-Grown Antibodies Save Monkeys from Ebola
Ebola virus causes a deadly hemorrhagic fever in humans and primates. There are no licensed vaccines or treatments, but several promising projects are in the works. For instance, isolating antibodies from macaques recuperating from an Ebola infection and transferring them to newly exposed macaques has shown to be protective up to 48 hours post-infection. Alternatively, antibodies have been produced in tissue culture using Chinese hamster ovary (CHO) cells.
The problem with both of these techniques is that they are not pragmatic, scalable or cost-effective. To solve this, scientists at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) genetically modified tobacco plants (transiently, not permanently) to produce antibodies against Ebola virus. They isolated the antibodies and administered them to rhesus macaques either 24 or 48 hours post-infection. (See figure.)
As shown above, control animals were given PBS (a saline solution) or an irrelevant control antibody (RAMP control). None of those animals survived. However, 67% of macaques given experimental antibodies 24 or 48 hours post-infection survived. (See chart below for details on each animal. S= survivor, NS = non-survivor.)
As shown, there were only 8 experimental animals. (Unlike mice, rhesus macaques are expensive and difficult to obtain. It is typical for such experiments to use very few animals.) Animal #4 was an irrelevant antibody control, and it died on day 7. Animal #8 was the saline control, and it died on day 7 as well. Animals #1, #2 and #3 were given experimental antibodies 24 hours post-infection. Two out of three survived. Animals #5, #6 and #7 were given antibodies 48 hours post-infection, and once again, two out of three survived.
Perhaps one day, genetically modified plants could be grown in Africa, near the source of Ebola outbreaks. This would allow relatively quick access to large amounts of antibodies which could then be administered to suffering people.
Source: Gene Garrard Olinger, Jr, James Pettitt, Do Kim, Cara Working, Ognian Bohorov, Barry Bratcher, Ernie Hiatt, Steven D. Hume, Ashley K. Johnson, Josh Morton, Michael Pauly, Kevin J. Whaley, Calli M. Lear, Julia E. Biggins, Corinne Scully, Lisa Hensley, and Larry Zeitlin. "Delayed treatment of Ebola virus infection with plant-derived monoclonal antibodies provides protection in rhesus macaques." PNAS October 15, 2012. doi: 10.1073/pnas.1213709109