These findings will indicate if valacyclovir treatment will reduce or stop viral reactivation and its shedding in saliva. This will enhance the selection and vetting of potential countermeasures to address clinical risks associated with reduced immune function. This will improve crew health care on International Space Station (ISS) missions, and will further enable exploration-class missions.

Background and Significance: In a recent collaborative study with Dr. Alexander Chouker (European Space Agency-ESA physician researcher), 19 subjects at Concordia Station in Antarctica were examined during overwintering for their latent viral reactivation and shedding patterns in their saliva samples collected each month for before, during, and after winter-over period. VZV DNA was found by real time polymerase assay in 10 out of 19 subjects (52%) with most of the shedding occurring during the study than before or afterwards. This is about the same rate of VZV shedding as we have found in astronauts during short and long duration spaceflights (50-65%). This data provide the motivation for this proposal, i.e., that wintering over in Antarctica is an excellent analog to spaceflight for studying the efficacy of a countermeasure against viral shedding. More specifically, we can study the effect of antiviral agents (e.g., valacyclovir) during an Antarctica winterover and apply lessons learned to upcoming spaceflight missions. This might allow us to prevent viral shedding in astronauts and thus reduce the risk of contaminating the internal environment of the spacecraft with infectious viruses, as well as decreasing their risk of associated VZV diseases including zoster, chronic neuropathic pain, vision loss, stroke and cognitive impairment.

Hypothesis: Prophylactic administration of valacyclovir (1 gram daily) to Antarctic expeditioners will significantly reduce salivary shedding of VZV compared to placebo controls. Measures of stress and immune dysregulation should remain unaltered. To test this hypothesis, we will treat 20 expeditioners with daily valacyclovir and another 20 with placebo and measure VZV DNA (as well as other herpesviruses) before, during, and after the expedition.

Study Population

* General description of the study population: Antarctica expeditioners

* Target number of non-astronaut participants: Total 40: 20 experimental, 20 Placebo

Saliva samples

* About 900 human saliva samples (2 ml each) were collected in total throughout the winter season at McMurdo and 500 samples were collected from South Pole.

* Samples were maintained at -80°C during shipping and received in the Immunology and Virology Lab of Johnson Space Center.

Future plan: A detailed inventory of the samples collected from both McMurdo and South Pole will be done and a plan will be drawn to process these samples as described in the original proposal.

These findings will indicate if valacyclovir treatment will reduce or stop viral reactivation and its shedding in saliva. This will enhance the selection and vetting of potential countermeasures to address clinical risks associated with reduced immune function. This will improve crew health care on International Space Station (ISS) missions, and will further enable exploration-class missions.