INFLUENCE OF ANTIORTHOSTATIC SUSPENSION ON RESISTANCE TO MURINE LISTERIA-MONOCYTOGENES INFECTION

The present study was designed to evaluate the influence of antiorthos tatic suspension, a ground-based modeling system employed to simulate certain aspects of weightlessness that occur during space flight, on t he capacity of mice to resist infection with the facultative intracell ular bacterial pathogen Listeria monocytogenes. Female BDF1 mice were suspended by the tail in the orthostatic or antiorthostatic position a nd 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 infecti on was started concurrently with the suspension. However, mice that we re antiorthostatically suspended 2, 4, or 7 days before the onset of i nfection exhibited an enhanced capacity to eliminate the challenge inf ection. Suspending mice on day 2 of the infection did not alter the ki netics 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 ant iorthostatic suspension can influence the capacity of mice to resist b acterial infection.