About the Authors
Biological Defense Research Directorate, Naval Medical Research Center, Silver Spring, Maryland, United States of America
United States Army Medical Research Institute for Infectious Diseases, Fort Detrick, Maryland, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: KABL CAW TDR. Performed the experiments: KABL MJT KMW AB NMEN SML. Analyzed the data: KABL AA AM TNB SS CAW TDR. Wrote the paper: KABL SS TDR.