Haemophilus influenzae porin contributes to signaling of the inflammatory cascade in rat brain

In the present study we observed that the Haemophilus influenzae type b (Hi b) porin, among the different surface bacterial components, is involved in the pathophysiology of bacterial meningitis. This study demonstrates that i noculation of Hib porin into the fourth cerebral ventricle causes the simul taneous expression of interleukin-1 alpha (IL-1 alpha), tumor necrosis fact or alpha (TNF-alpha), and macrophage inflammatory protein 2 (MIP-2) at 6 h after inoculation. At 24 h, the expression of MIP-2 decreases while the exp ression of IL-1 alpha and TNF-alpha increases. The mRNA expression of IL-1 alpha, TNF-alpha, and MIP-2 is correlated with injury to the blood-brain ba rrier as demonstrated by the appearance of serum proteins and leukocytes in cerebrospinal fluid and by the increase in brain water content.