Stowaway Viruses May Imperil Space Voyagers

The University of Texas Medical Branch at GalvestonPublic Affairs Office301 University Boulevard, Suite 3.102Galveston, Texas 77555-0144(409) 772-2618 / (800) 228-1841www.utmb.edu

FOR RELEASE: November 21, 2001

CONTACT: Jim Kelly, science writer(409) 772-8791[email protected]

Raymond P. Stowe, Ph.D, assistant professor of pathology [email protected]

EMBARGOED UNTIL NOVEMBER 21, 2001

Scientists measure space-stress activation of stowaway viruses Microbes may menace Mars explorers and others

GALVESTON, Texas -- Every time astronauts blast off for outer space, they carry tiny stowaways with them -- viruses that have been latent in their bodies since childhood. These viruses, typically including Epstein-Barr, herpes simplex and varicella zoster (which causes chicken pox in children) exist in almost everyone, but they have a special significance for astronauts, whose immune systems are weakened by the unique stresses of spaceflight. Unchecked by the body's usually strong defenses, the viruses can reactivate, possibly posing serious health problems for space travelers.

Now, researchers from the University of Texas Medical Branch at Galveston and NASA's Johnson Space Center (JSC) have published a study relating spaceflight-induced stress to the reactivation of one of the most troubling of these agents: Epstein-Barr virus, which is linked to lymphoma, chronic fatigue, and infectious mononucleosis. In the November / December 2001 issue of Psychosomatic Medicine, UTMB's Raymond Stowe and Alan Barrett and JSC's Duane Pierson draw on data gathered before and after a series of space shuttle flights between 1997 and 1999 to connect significant decreases in astronauts' cellular immunity and simultaneous increases in Epstein-Barr activity with rises in the stress hormones epinephrine and norepinephrine.

The goal, according to lead author Stowe, was both to test the impact of spaceflight stress on the cellular immune system --the most important arm of the overall immune system when it comes to fighting viruses -- and shed light on the crew-health implications of Epstein-Barr reactivation. "This virus poses a constant challenge to the immune system, so you can measure this virus and infer back that the immune system is not doing quite the job that it did before they went up into space," Stowe says. "The health significance comes into play when you ask what happens on interplanetary missions such as one to Mars, where you're gone for two years. The question is, when you throw in the factors of stress, decreased immune functions and added radiation, will this cause one of these lymphomas or cancers on these longer missions?"

To determine the degree to which spaceflight weakens the cellular immune system and opens the way for Epstein-Barr proliferation, the researchers took blood samples from 28 astronauts (23 men and five women) ten days before launch, within four hours after landing, and three days after landing. They then tested the samples for two different antibodies: those for Epstein-Barr nuclear antigen (EBNA), which indirectly measures virus-specific cellular immunity, and those for Epstein-Barr viral capsid antigen (VCA), which reflects reactivation (virus production).

Comparing these results with earlier measurements obtained from the astronauts' annual medical exams, the scientists noted a decline in EBNA antibodies and an increase in VCA antibodies in twelve of the 28 test subjects, results they related to falling cellular immunity and rising Epstein-Barr virus replication. Both trends could be seen in the samples taken ten days before liftoff -- a period of highly stressful last-minute training -- but both were magnified in samples taken upon the astronauts' return. At the same time, urine samples collected ten days before launch and just after landing indicated that the twelve astronauts evidencing Epstein-Barr reactivation also had by far the highest levels of epinephrine and norepinephrine -- hormones associated with physical and psychological stresses.

For the space traveler, Stowe points out, those stresses are quite different from the ones experienced on Earth. Weightlessness, in particular, has no Earthbound equivalent, and life aboard a spacecraft combines other challenges -- confinement, the sudden high-G-force accelerations of launch and landing, and the anxiety that goes with any complicated mission in a dangerous environment -- in ways that have never been seen before. "Space is a unique environment that causes some unique responses," Stowe says. "Our research shows that immune responses and the reactivation of latent viruses do occur, and they're clearly known from other models to have health implications. While there have been no health issues from these viruses on the shuttle flights, such flights are short -- typically only five or sixteen days. But when we think about long-term spaceflights, these changes in the body's ability to defend against viruses may have negative implications for human health and survival."

Stowe, Barrett, and Pierson's paper, titled "Elevated Stress Hormone Levels Relate to Epstein-Barr Virus Reactivation in Astronauts," appears in the November / December 2001 Psychosomatic Medicine, Volume 63, Issue 6.

--UTMB--