LEGIONELLA PNEUMOPHILA-INDUCED VISUAL LEARNING IMPAIRMENT REVERSED BYANTI-INTERLEUKIN-1-BETA

Infecting mice with the opportunistic intracellular pathogen Legionell a pneumophila markedly inhibited place learning of infected C57BL/6 mi ce as determined by the Morris water maze test. Mice infected with L. pneumophila evinced much less ability to learn the position of a hidde n platform than did normal noninfected mice, which quickly learned the location of the hidden platform and escaped from the cool water of th e pool with increasing efficiency. However, infected mice treated with anti-interleukin-1 (anti-IL-1) neutralizing antibody learned the task with about the same efficiency as the controls. When the animals were tested 1 week after learning, control animals remembered the task wel l and were able to escape with near maximal efficacy. On the other han d, L. pneumophila-infected mice performed as poorly after the 1 week r est as during the training period, indicating that infection blocked l earning and not merely performance. Mice infected with L. pneumophila and given the antibody treatment were found to be indistinguishable fr om controls in that they remembered the task and escaped with good eff iciency. Thus, the results of this study suggest that the pro-inflamma tory cytokine, IL-1 beta, is involved, at least partly, in the attenua tion of spatial navigational learning in mice infected acutely with a sublethal concentration of L. pneumophila. These results, therefore, s uggest that cognitive impairment of L. pneumophila-infected mice may b e related to the cytokine II-1 beta and, furthermore, that cytokines m ay be related to learning and memory changes experienced by individual s suffering acute bacterial infections.