NOTE: Final report date changed to 09/30/2024 per T. Sirmons/HRP JSC (Ed., 4/29/24)

NOTE: End date changed to 10/1/2023 per T. Sirmons/HRP JSC (Ed., 2/23/23)

NOTE: End date changed to 10/1/2022 per L. Singh/HRP JSC (Ed., 4/8/21)

The results were very encouraging. We we found a significant decrease in the viral shedding (both EBV and HSV1) in subjects after prophylactic administration of Valtrex as compared to placebo during the winterover at the South Pole station as well as MuMurdo station. A 21-fold decrease in average EBV viral load (copies/ml saliva) was observed in the treatment group (antiviral acyclovir administration) than the placebo group at both stations. South Pole Station had a 280-fold decrease, while McMurdo Station had a 4-fold decrease in viral load. For HSV-1, the reduction was 5-fold at both stations. When parsing out each location, South Pole had a 3-fold increase in viral load and McMurdo had an 8.5-fold decrease, respectively. Interestingly, there was no VZV shedding in the saliva of expeditioners from both groups, so the effect of Valacyclovir on VZV reactivation and shedding cannot be inferred in this case. These. As viral reactivation is related with robust immune system of the host, it would be very critical to identify the immune status of these individual with and without antiviral intervention. Unfortunately, we could not study any of the immune markers in this study except for a limited panel of saliva cytokines (specifically 13) due to sampling constraints for this specific study, as well as budgetary and time concerns [Omnibus is one year proposal]. Our laboratory has previously determined both plasma and saliva cytokine alterations in ISS astronauts.

A total of 1046 saliva samples were analyzed from 32 subjects enrolled in the Varicella Zoster Virus (VZV) Antivirals in Antarctica study. Nominally, five (5) passive drool saliva samples were collected at the beginning of every month for 6 (McMurdo) or 8 (South Pole) months. All samples were stored frozen until batch processing. In the already published paper, these samples were then thawed, aliquoted, and processed for viral (EBV, HSV1, and VZV) DNA by real-time polymerase chain reaction (PCR), stress hormone (cortisol, DHEA, and alpha-amylase), and cytokine analysis. The extra supernatant from these samples were refrozen and saved for this augment. The remaining saliva supernatant was used to analyze salivary C-reactive protein (CRP) and IgA, IgG1, IgG2, IgG3, IgG4, and IgM.

Summary of Results:

Nearly every sample was analyzed, but some samples were not analyzed due to too little volume resulting from previous use of the supernatant. In total, 624/625 for placebo and 420/429 for valacyclovir were able to be analyzed for this augment. CRP (pg/mL) was significantly less in the valacyclovir group (660 ± 36) compared to placebo (1472 ± 39) throughout the mission (p < 0.0001). This significance was observed similarly at both the South Pole and McMurdo stations. Significantly less CRP was observed between groups at every monthly timepoint except October (South Pole only). When parsing out the stations, however, South Pole did not begin to have a significant separation between the groups until May, which carried over all the way to September. March and April were not significant, but the valacyclovir group still had less CRP than the placebo group in both months. CRP was significantly less for valacyclovir at every month for McMurdo.

No significant difference was observed in IgA (ng/mL) between the groups (placebo 3666 ± 120 vs. valacyclovir 3689 ± 126; p = 0.8948). With combined data from both stations, IgA was significantly increased in the valacyclovir group as compared to placebo in March (placebo 2968 ± 217 vs. valacyclovir 4167 ± 337). Interestingly, IgA was significantly less at the South Pole station (p < 0.05) but significantly more at the McMurdo station (p < 0.0001). IgA was significantly less for valacyclovir in September at the South Pole station but was significantly increased at McMurdo in both March and July.

No significant difference was observed in IgM (ng/mL) between the groups when combining both station data either overall or separated by month. South Pole station, however, showed a significant reduction in IgM overall (placebo 2019 ± 100 vs. valacyclovir 1603 ± 101; p < 0.01). When separating out by each month and looking at placebo longitudinally, there was a significant increase in IgM in September compared to both March and April. No significant differences were seen at the McMurdo station.

IgG1 (ng/mL) was significantly less in the valacyclovir group (6469 ± 410) compared to placebo (8780 ± 411) throughout the mission (p < 0.0001). This result was exclusively driven by the McMurdo station and not South Pole. No significant difference was observed in IgG2 (ng/mL) between the groups (placebo 26311 ± 1396 vs. valacyclovir 23348 ± 1186; p = 0.1085). Interestingly, IgG2 was significantly more at the South Pole station (p < 0.05), but significantly less at the McMurdo station (p < 0.001). No significant difference was observed at any given month throughout the campaign. IgG3 (ng/mL) was significantly less in the valacyclovir group (171.9 ± 6.417) compared to placebo (190.7 ± 5.825) throughout the mission (p < 0.05). No differences were seen at either station or at any given month. IgG4 (ng/mL) was significantly less in the valacyclovir group (380.2 ± 10.25) compared to placebo (446.4 ± 9.137) throughout the mission (p < 0.0001). This result was mostly driven by both McMurdo (difference between means -61.35 ± 12.41; p < 0.0001) and South Pole (difference between means -51.69 ± 20.36; p < 0.05). However, it must be noted that most of the data (65%) for the IgG4 analyte was outside the range of the detection limit of the assay (673 above, 2 below, 371 within). When removing these data points outside the range, there was basically no change between the groups.

NOTE: End date changed to 10/1/2022 per L. Singh/HRP JSC (Ed., 4/8/21)

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.

Reactivation and shedding of herpes viruses such as Epstein-Barr virus (EBV), herpes simplex virus 1 (HSV1), varicella zoster virus (VZV), and cytomegalovirus (CMV) increase in astronauts during spaceflight as compared to their preflight and postflight levels. These potential reactivation events increase the risk of associated clinical conditions like herpes zoster, chronic neuropathic pain, vision loss, stroke, cognitive impairment, and cold sores. Furthermore, continued viral shedding for a longer period after space travel may increase the risk of transmitting the virus to crew contacts who are uninfected with the virus – including, but not limited to, the immunocompromised or to newborn infants. Thus, it is essential to develop spaceflight countermeasures to prevent reactivation of these herpes viruses, ensuring the health of the crewmembers and their contacts upon return. One such countermeasure is prophylactic administration of an antiviral drug (valacyclovir) against the alpha herpesviruses (VZV, HSV-1). To determine the effectiveness of this countermeasure using a large population, we studied shedding of EBV, VZV and HSV-1 in Antarctic expeditioners (who have been reported to have similar viral shedding patterns in their saliva during winter-over as astronauts during long spaceflights). Countermeasure efficacy of this antiviral drug was determined by 3 major parameters, including viral load, physiological stress biomarkers (cortisol, DHEA, and amylase) and immune markers (inflammatory cytokines) during the winter-over in the saliva of expeditioners with and without administration of this drug. Thirty-two volunteers from two Antarctic stations (McMurdo and South Pole) participated in this study. Subjects were randomly assigned to either treatment group (valacyclovir HCl: 1 g/day), or placebo group (oyster Calcium 500mg/day). EBV and HSV-1 viral shedding was significantly reduced in the treatment group versus the placebo group by >24 fold (EBV) and >5 fold (HSV1) over the course of winter-over period. No VZV shedding was seen in any of the subjects. 50% of the placebo saliva samples had measurable viral DNA (either EBV, HSV1, or both) compared to 19% of the treatment group. There was no significant change in the Cortisol to DHEA ratio or alpha amylase, indicating physiological stress was similar between the groups. No difference was detected in salivary cytokines except IL-10, which was significantly lower in the treatment group than the placebo group. These data indicate that valacyclovir (1g/day) is a safe and successful intervention to reduce herpes virus reactivations and shedding in individuals subjected to extreme environments and stressors.

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.