Phenotypic and functional activation of monocytes in HIV-1 infection: interactions with neural cells.

To investigate mechanisms that facilitate transendothelial migration of HIV-infected leukocytes and their interactions with neural tissues early in the disease, we studied peripheral blood from Centers for Disease Control class A patients. Patients' monocytes displayed increased quantities of the adhesion molecules CD11a, CD11b, and very late antigen 4 (VLA-4). Expression of these correlated directly with the numbers of monocytes that migrated through confluent endothelium. These ligands also mediated leukocyte interactions with cultured human neural cell lines. Although patients' cells bound in greater numbers, there was no evidence of target cell injury. To evaluate the direct effect of HIV-1 on monocyte neuroadhesion, we compared infected with uninfected monocytoid (U-937,THP-1) and T lymphoblastoid (MT-4) cell lines. HIV infection increased the neuroadhesiveness of monocytoid lines only. By using lines with more than 95% HIV-infected cells, we demonstrated that HIV-1 gp120 participates with lymphocyte function-associated antigen 1 and VLA-4 to mediate monocyte-neural cell interactions.