684 Mechanism of CD16+ Monocyte Trafficking in HIV-associated Dementia: Role of FKN in CD16+ Monocyte Recruitment and MMP-9 Induction P. Ancuta*1, R. Rao2, A. Moses3, A. Mehle1, A. Wurcel4, D. Stone4, F. W. Luscinskas2, D. Gabuzda1 1Dana-Farber Cancer Inst, Boston, MA; 2Vascular Res Div, Brigham and Women's Hosp and Harvard Med Sch, Boston, MA; 3Vaccine and Gene Therapy Inst, Oregon Hlth Sci Univ, Beaverton; and 4Lemuel Shattuck Hosp, Jamaica Plain, MA
Background: The percentage of circulating CD16+ monocytes (Mo) is dramatically increased in patients (pts) with HIV-associated dementia (HAD). Furthermore, perivascular CD16+ monocytes/macrophages are a major reservoir of virus in the CNS. In this study, we investigated mechanisms of CD16+ Mo trafficking that may increase HIV entry into the brain and contribute to neurologic injury in HAD.
Methods: PBMC isolated from fresh blood of HIV- individuals and HAD patients (pts) were triple stained with anti-CD14, anti-CD16, and a large panel of mAbs and analyzed by FACS to phenotypically characterize Mo subsets. Total Mo isolated by negative selection were stained with anti-CD16, and CD16-/CD16+ Mo subsets were assessed for their ability to undergo transwell/transendothelial migration in response to MCP-1, MIP-1a, SDF-1a, and FKN and firm adhesion to TNF-a/IFN-g-stimulated or FKN-expressing endothelial cells (EC) under flow conditions. CD16-/CD16+ Mo isolated by negative/positive selection were co-cultured with resting, TNF-a/IFN-g-stimulated or FKN-expressing EC for 48 h and MMP-9 levels in the supernatants were detected by ELISA.
Results: In HIV- individuals, CD16+ Mo express high CX3CR1 and CXCR4 and low CCR1 and CCR2 levels, and migrate in response to FKN and SDF-1a but not MIP-1a and MCP-1. Despite low expression of CD62L, CD16+ Mo undergo firm arrest on TNF-a/IFN-g-stimulated or FKN-expressing EC under flow conditions. CD16+ Mo, but not CD16- Mo, produce high MMP-9 levels when co-cultured with TNF-a/IFN-g stimulated or FKN-expressing EC. In HAD pts, the expression of CCR1, CCR2, CXCR4, and CX3CR1 on CD16+ Mo was similar to that detected in HIV- individuals. However, we found a significantly lower expression of CCR1, CCR2, and CD62L on CD16- Mo in HAD pts compared to HIV- individuals.
Conclusions: These results suggest that FKN and SDF-1a play an important role in recruitment of CD16+ Mo into peripheral tissues. This finding together with previous studies which showed increased expression of FKN and SDF-1a in the CNS of HAD pts suggest that CD16+ Mo can migrate into the CNS and contribute to neurologic injury in HAD. The high levels of MMP-9 produced by CD16+ Mo after interaction with EC may affect the integrity of the blood-brain barrier, particularly in HAD pts where the number of circulating CD16+ Mo is dramatically increased.
