Harlan D. Caldwell, Ph.D.

Senior Investigator

Chlamydia Pathogenesis Section


4 Memorial Drive, Room 228B
Bethesda, MD 20814



Research Topics

Chlamydia are important human pathogens that cause blinding trachoma and sexually transmitted disease for which vaccines are needed. The focus of our research is to identify chlamydial virulence factors that function in the pathobiology of chlamydial host-cell interactions and evasion of host immunity. We use in vitro and in vivo models of chlamydial infection together with comparative genomics, transcriptomics, proteomics, modern cell biology, and immunology to accomplish these goals. This information is being used to design novel subunit and live-attenuated vaccines for the prevention of human chlamydial diseases.


Dr. Caldwell received his Ph.D. in pathobiology from the University of Washington in 1976. After completing a senior research fellowship in the Department of Medicine at the University of Washington in 1978, Dr. Caldwell joined the faculty of the University of California, San Francisco, as an assistant professor of microbiology and immunology. In 1980, he was recruited to the National Institutes of Health (NIH) as a tenure-track investigator in the Laboratory of Microbial Structure and Function. He became a tenured investigator in 1986 and chief of the Laboratory of Intracellular Parasites in 1990. He is a recipient of the NIH Director’s Award, NIH Merit Award, and PHS Superior Service Award. He was appointed to the NIH Senior Biomedical Research Service in 1997. Dr. Caldwell is a member of the editorial board of Infection and Immunity and a fellow of the American Academy of Microbiology. He is an internationally recognized leader in the fields of chlamydial pathogenesis and immunology.

Selected Publications

  1. Lei L, Yang C, Patton MJ, Smelkinson M, Dorward D, Ma L, Karanovic U, Firdous S, McClarty G, Caldwell HD. A Chlamydial Plasmid-Dependent Secretion System for the Delivery of Virulence Factors to the Host Cytosol. mBio. 2021;12(3):e0117921.
  2. Yang C, Starr T, Song L, Carlson JH, Sturdevant GL, Beare PA, Whitmire WM, Caldwell HD. Chlamydial Lytic Exit from Host Cells Is Plasmid Regulated. mBio. 2015;6(6):e01648-15.
  3. Kari L, Goheen MM, Randall LB, Taylor LD, Carlson JH, Whitmire WM, Virok D, Rajaram K, Endresz V, McClarty G, Nelson DE, Caldwell HD. Generation of targeted Chlamydia trachomatis null mutants. Proc Natl Acad Sci U S A. 2011;108(17):7189-93.
  4. Yang C, Kari L, Lei L, Carlson JH, Ma L, Couch CE, Whitmire WM, Bock K, Moore I, Bonner C, McClarty G, Caldwell HD. Chlamydia trachomatis Plasmid Gene Protein 3 Is Essential for the Establishment of Persistent Infection and Associated Immunopathology. mBio. 2020;11(4).
  5. Kari L, Whitmire WM, Olivares-Zavaleta N, Goheen MM, Taylor LD, Carlson JH, Sturdevant GL, Lu C, Bakios LE, Randall LB, Parnell MJ, Zhong G, Caldwell HD. A live-attenuated chlamydial vaccine protects against trachoma in nonhuman primates. J Exp Med. 2011;208(11):2217-23.

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This page was last updated on Tuesday, July 20, 2021