Interaction between chronically HIV-infected promonocytic cells and human umbilical vein endothelial cells: role of proinflammatory cytokines and chemokines in viral expression modulation

HIV type 1 expression was significantly up-regulated in chronically infecte d promonocytic cell line (U1) co-cultured with human umbilical vein endothe lial cells (HUVEC). Virus replication, evaluated as supernatant p24 release , was higher when U1 were co-cultured with IL-1 beta-activated HUVEC than w ith unstimulated HUVEC. When non-adherent U1 were removed from co-cultures, the remaining U1 cells adherent to the endothelial monolayer still showed enhanced HIV replication in comparison with an equal number of U1 cultured alone. While addition of adhesion molecule blocking antibodies (anti-interc ellular adhesion molecule-1 (ICAM-1), -vascular cell adhesion molecule-1 (V CAM-1), -CD18 and -very late antigen-4 (VLA-4)) strongly inhibited adherenc e of U1 cells to endothelial monolayers, such treatment resulted in only a partial reduction in p24 release. Furthermore, HIV replication in U1 cells was enhanced on culture in HUVEC-conditioned media. Such data suggest that soluble mediators secreted by endothelial monolayers may modulate HIV-1 exp ression. Indeed, addition of cytokine and chemokine antagonists to both U1/ HUVEC co-cultures and to U1 cultured in HUVEC-conditioned media clearly dow n-regulated p24 release. Anti-IL-6, anti-tumour necrosis factor-alpha (TNF- alpha) and, particularly, anti-MCP-1 MoAbs reduced p24 release, while anti- IL-8 polyclonal antiserum and IL-1 receptor antagonist (IL-1Ra) had no sign ificant effect. Thus, the interaction between HUVEC and infected monocytic cells up-regulates HIV-1 replication predominantly through production of en dothelium-derived soluble factors including MCP-1, TNF-alpha and IL-6. This phenomenon may influence the passage of HIV-1 from latency to productive r eplication and enhance virus spreading during physiological and/or patholog ical contact of monocytes with endothelium.