Influence of antiorthostatic suspension on resistance to murine Listeria monocytogenes infection

Abstract

The present study was designed to evaluate the influence of antiorthostatic suspension, a ground-based modeling system employed to simulate certain aspects of weightlessness that occur during space flight, on the capacity of mice to resist infection with the facultative intracellular bacterial pathogen Listeria monocytogenes. Female BDF1 mice were suspended by the tail in the orthostatic or antiorthostatic position and were infected with a sublethal dose of virulent L. monocytogenes at various times during the suspension. It was found that suspension did not influence the kinetics of bacterial growth in vivo if the infection was started concurrently with the suspension. However, mice that were antiorthostatically suspended 2, 4, or 7 days before the onset of infection exhibited an enhanced capacity to eliminate the challenge infection. Suspending mice on day 2 of the infection did not alter the kinetics of bacterial growth. Finally, the enhancement of resistance to the primary Listeria infection was accompanied by failure of the mice to generate long-term protective immunological memory to the challenge organism. Collectively, these results indicate that the stress of antiorthostatic suspension can influence the capacity of mice to resist bacterial infection.

Active hexose correlated compound enhances the immune function of mice in the hindlimb-unloading model of spaceflight conditions

“…Development of countermeasures to prevent those changes has become a critical issue to ensure the safety of space travelers. It has been shown that hindlimb unloading, a ground-based rodent model of spaceflight conditions, alters the immune response (14,24,29,30,45) and compromises resistance to infection (4,8,17,29,30). We have also shown that AHCC can be used as a countermeasure to reduce the effects of hindlimb-unloading conditions (5).…”

“…Exposure to hindlimb-unloading conditions induces muscle and bone loss and a fluid shift to the head, which are similar to changes induced in that area by spaceflight (20,(33)(34)(35)(36). The immune system is one of the important regulatory mechanisms affected by spaceflight (15, 23, 26, 40 -44, 46) and has been shown to be dramatically affected in groundbased models (14,24,29,30,45).…”

Antiorthostatic Suspension Stimulates Profiles of Macrophage Activation in Mice

“…Tail-suspended mice were housed individually in suspension cages similar to those described by Wronski and Morey-Holton [16] as we have described previously [17,18]. For suspension in the antiorthostatic position, total mechanical unloading of the hindlimbs occurred, while the forelimbs were allowed to make contact with the floor of the cage to facilitate movement.…”

“…Previously, we demonstrated that virulent L. monocytogenes injected into BDF1 mice suspended in the antiorthostatic orientation for 2-4 days could not be detected in target organs 24 h after infection [17,18]. Concomitant with the enhanced rate of clearance, antiorthostatically suspended mice failed to generate protective immunological memory against the challenge organism [18].…”

“…We have previously studied the influence of antiorthostatic suspension on the capacity of BDF1 mice to resist infection with virulent Listeria monocytogenes [17,18]. Protective immunity to intracellular bacterial pathogens, such as L. monocytogenes, is mediated by the interactions between antigen-specific T lymphocytes and infected macrophages [19,20].…”