Charles Stephensen, Ph.D.

Acting Center Director, Research Leader

Adjunct Professor, UC Davis Department of Nutrition

Office: (530) 752-9266

Email address: charles.stephensen@usda.gov

Google Scholar page

Research Interests

The Stephensen lab is focused on (1) the effect of vitamin A on immune function, including response to immunization; (2) the effect of diet on the intestinal microbiota and, in turn, the effect of the microbiota on systemic immunity (e.g., response to vaccination), immune activation (e.g., of specific leukocyte populations, such as T cells) and inflammation; (3) the effect of vitamin D on immune function and inflammation, as well as on bone health during immune activation (e.g., during HIV infection); and (4) the effect of diet on lung health and pulmonary inflammation

Stephensen Lab Themes

Assessing the Impact of Diet on Inflammation in Healthy and Obese Adults in a Cross-Sectional Phenotyping Study and a Longitudinal Intervention Trial (in-house appropriated funds): This project funds a component of the WHNRC Nutritional Phenotyping Study (ClinicalTrials.gov Identifier: NCT02367287), a multi-investigator study involving research scientists from both the Immunity and Disease Prevention and Obesity and Metabolism Research Units at the WHNRC. Dr. Stephensen is coordinating the study with Dr. Brian Bennet. The principal goal for Dr. Stephensen’s lab is to determine if diet quality and specific nutrient composition are associated with intestinal bacterial community composition and, in turn, to determine whether bacterial taxa are associated with systemic immune activation and inflammation. This work is being conducted with Dr. Mary Kable and Dr. Danielle Lemay of the Immunity and Disease Prevention Research Unit.

Newborn Vitamin A Supplements, Gut Microbiota and Vaccine Response at 15-18m in Bangladeshi Infants (Thrasher Research Fund): The purpose of this study is to examine the effect of vitamin A supplementation on composition of the intestinal microbiota and, in turn, to examine the association of the intestinal microbiota, particularly the genus Bifidobacterium, on the response to early childhood vaccines. The study will include measures of T-cell and antibody responses to vaccines. The vaccines are given early in infancy and the responses are assessed in early infancy and at 2 y of age. Stool microbiota composition is measured at the same time points. Research collaborators include Dr. S.M. Ahmad, International Centre for Diarrhoeal Disease Research, Bangladesh, and Dr. David A. Mills of the Departments of Food Science & Technology at the University of California at Davis.

Immunology Component of Lao Zinc Trial at Khon Kaen University (Micronutrient Initiative and Mathile Institute): The purpose of this study is to examine the effect of zinc supplementation on immune function. The study will include measures of T-cell immunity and production of cytokines by activated leukocytes. The overall study principal investigator is Dr. Sonja Hess of the Department of Nutrition, University of California, Davis, and the principal collaborator on the immunology component is Dr. Ganjana Lertmemongkolcha of Khon Kaen University, Thailand.

Additional current collaborations:

Effects of vitamin D supplementation during HIV infection in the Adolescent Trials Network (National Institutes of Health): Two studies with the ATN Network (ATN063 and ATN109) examined the effect of vitamin D supplementation on minimizing loss of bone mineral density in HIV infected youth taking antiretroviral therapy including tenofovir. One study (ATN117) has examined the association of vitamin D status with preventive use of antiretroviral therapy containing tenofovir on men at risk of HIV infection. Laboratory work was carried out at the WHNRC. The principal collaborators on these studies included Dr. Peter Havens, Medical College of Wisconsin, Dr. Kathleen Mulligan, University of California, San Francisco, and Dr. Craig Wilson, University of Alabama at Birmingham.