Anti-CD11b monoclonal antibody suppresses brain dissemination of Cryptococcus neoformans in mice

To elucidate the role of the β2 integrin family of adhesion molecules in the disseminated infection of Cryptococcus neoformans from the lung to the central nervous system, we examined the effects of monoclonal antibodies (mAbs) against CD11a, CD11b, CD11c and CD18 on the number of live microorganisms in both the lung and brain of mice three weeks after intratracheal infection. Administration of anti-CD11b mAb partially, but reproducibly, reduced the fungal loads in the brain in three independent experiments, while the lung loads were not affected. In addition, the same treatment significantly decreased the number of live microorganisms in the blood. In sharp contrast, the brain loads one week after intravenous injection with C. neoformans were not affected by treatment with anti-CD11b mAb. Finally, administration of mAb against other adhesion molecules (CD11a, CD11c or CD18) failed to affect the fungal loads in the brain as well as in the lung three weeks after intratracheal instillation, except for anti-CD18 mAb which rather increased the brain loads. Our results suggested that CD11b might be involved at least in part in the process of fungal dissemination from lung to brain, although the significance of other β2 integrin family adhesion molecules remains to be substantiated.