Acta Astronautica 60 (2007) 247 – 253 www.elsevier.com/locate/actaastro Predictors of immune function in space flight  William T. Shearer a , ∗ , Shaojie Zhang b , James M. Reuben c , Bang-Ning Lee c , Janet S. Butel b a Department of Pediatrics, Section of Allergy and Immunology, Texas Children’s Hospital, 6621 Fannin Street (MC: FC330.01), Houston, TX 77030, USA b Department of Molecular Virology and Microbiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA c Department of Hematopathology, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, USA Available online 19 October 2006 Abstract Of all of the environmental conditions of space flight that might have an adverse effect upon human immunity and the incidence of infection, space radiation stands out as the single-most important threat. As important as this would be on humans engaged in long and deep space flight, it obviously is not possible to plan Earth-bound radiation and infection studies in humans. Therefore, we propose to develop a murine model that could predict the adverse effects of space flight radiation and reactivation of latent virus infection for humans. Recent observations on the effects of gamma and latent virus infection demonstrate latent virus reactivation and loss of T cell mediated immune responses in a murine model. We conclude that using this small animal method of quantitating the amounts of radiation and latent virus infection and resulting alterations in immune responses, it may be possible to predict the degree of immunosuppression in interplanetary space travel for humans. Moreover, this model could be extended to include other space flight conditions, such as microgravity, sleep deprivation, and isolation, to obtain a more complete assessment of space flight risks for humans. © 2006 Elsevier Ltd. All rights reserved. Keywords: Space flight; Radiation; Polyoma virus infection; T lymphocytes; Interferon-gamma; Latent virus reactivation  Supported by National Aeronautics and Space Administration Cooperative Agreement NCC 9-58 (project numbers IIH00202, IIH00204, and IIH00403) through the National Space Biomedical Research Institute. The subject of this article was presented in part at the 15th International Academy of Aeronautics Humans in Space Symposium (Helmut H. Hinghofer-Szalkay, Rupert Gerzer, Organiz- ers): The Immune System, (G. Sonnenfeld, Chair), May 24, 2005, in Graz, Austria. ∗ Corresponding author. Tel.: +1 832 824 1274; fax: +1 832 825 7131. E-mail address: wtsheare@TexasChildrensHospital.org (W.T. Shearer). 0094-5765/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2006.08.005 1. Radiation and latent viruses: risk factors for space travel Predicting immune function in space flight must be one of the most important long-term goals of preparing for interplanetary travel, because of the immune sys- tem’s unique capability of preserving life free of infec- tion and cancer [1]. Because of the numerous restraints of previous and present modes of space flight, it has been important to utilize several models of space flight using both animal and human subjects, each designed to test hypotheses of the effects of space travel on im- mune responses [2–5]. Because of these studies and information derived from non-space medical research,