Abstract: Objective To explore the role of CD44 in monocyte adhesion to human brain microvascular endothelial cells
(HBMECs) and monocyte migration across an in vitro model of blood-brain barrier (BBB) infected by Cryptococcus neoformans
(Cn). Methods An in vitro blood-brain barrier model was constructed using a transwell chamber covered with a HBMEC
monolayer. The wild-type strain of Cn B4500FO2, TYCC645#32 strain with CPS1 gene deletion and PCIP strain with CPS1
complementation were chosen to infect the monolayer HBMECs. THP-1 cells were added to the upper chamber of transwell,
and the relative migration rate was determined by counting the number of the cells entering the lower chambers. The
inhibitory effects of anti-CD44 monoclonal antibody and the CD44 inhibitor bikunin were examined on THP-1 binding to and
migration across HBMECs. Results Cn infection of the HBMECs caused markedly enhanced THP-1 cell adhesion and
migration across the monolyers (P<0.01) dependent on Cn concentration and exposure time. Addition of anti-CD44
monoclonal antibody and bikunin significantly lowered THP-1 adhesion and migration rates in the BBB model with
Cn-infected HBMECs (P<0.01) with a dose dependence of the antibody (within 0-1 μg) and inhibitor (within 0-20 nmol/L). Both
THP-1 adhesion rate and migration rate were lowered in the BBB model infected with CPS1 gene-deleted Cn but increased in
the model infected with the complemented strain compared with those in the wild-type strain-infected model. Conclusion In
the in vitro BBB model, CD44 expressed on HBMECs may play an essential role in monocyte adhesion to and migration across
the BBB. The capsular hyaluronic acid may mediate Cn-induced monocyte adhesion and migration.