About the Authors

Anke M. Mulder

mulder@nanoimagingservices.com (AMM); qinjianzhao@gmail.com (QZ)

Affiliation Department of Research & Development, NanoImaging Services, La Jolla, California, United States of America

Bridget Carragher

Affiliation Department of Research & Development, NanoImaging Services, La Jolla, California, United States of America

Victoria Towne

Affiliation Merck Manufacturing Division, Vaccine Manufacturing Science and Commercialization, West Point, Pennsylvania, United States of America

Yuan Meng

Affiliation Vaccine Analytical R&D, Merck Research Laboratories, West Point, Pennsylvania, United States of America

Yang Wang

Current address: Sino Biologicals, Inc., Beijing, China

Affiliation Vaccine Analytical R&D, Merck Research Laboratories, West Point, Pennsylvania, United States of America

Lance Dieter

Affiliation Vaccine Bioprocess R&D, Merck Research Laboratories, West Point, Pennsylvania, United States of America

Clinton S. Potter

Affiliation Department of Research & Development, NanoImaging Services, La Jolla, California, United States of America

Michael W. Washabaugh

Current address: MedImmune, Gaithersburg, Maryland, United States of America

Affiliation Vaccine Analytical R&D, Merck Research Laboratories, West Point, Pennsylvania, United States of America

Robert D. Sitrin

Current address: SitrinSolutions, LLC, Lafayette Hill, Pennsylvania, United States of America

Affiliation Merck Manufacturing Division, Vaccine Manufacturing Science and Commercialization, West Point, Pennsylvania, United States of America

Qinjian Zhao

mulder@nanoimagingservices.com (AMM); qinjianzhao@gmail.com (QZ)

Current address: School of Public Health, Xiamen University, Xiamen, Fujian, China

Affiliation Vaccine Analytical R&D, Merck Research Laboratories, West Point, Pennsylvania, United States of America

Competing Interests

AMM, BC, and CSP are employed at NanoImaging Services, Inc. VT, YM, YW, LD, MWW, RDS, and QZ are employed by Merck & Co. CryoTEM imaging and 3D reconstruction was performed by the Department of Operations at NanoImaging Services, Inc. (www.nanoimagingservices.com) as a service paid for by Merck & Co (www.merck.com). There are no patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Author Contributions

Conceived and designed the experiments: QZ BC CP MW RS. Performed the experiments: LD QZ YW VT YM BC. Analyzed the data: AMM QZ BC. Wrote the paper: AMM QZ RS.