Differential activation of CC chemokine receptors by AOP-RANTES

RANTES (regulated on activation normal T cell expressed) has been found at elevated levels in biological fluids from patients with a wide range of all ergic and autoimmune diseases and is able to attract several subtypes of le ukocytes including eosinophils and monocytes into inflamed tissue. Amino-te rminal modifications of RANTES produce receptor antagonists which are candi dates for blocking this cellular recruitment. Met-RANTES has been shown to modulate inflammation in vivo, while AOP-RANTES is a potent inhibitor of R5 human immunodeficiency virus type 1 (HIV-1) strains and has been shown to down-modulate CCR5 and prevent recycling of the receptor. We have studied t he effect of AOP-RANTES in eosinophil activation and have found that it is able to efficiently elicit eosinophil effector functions through CCR3, as m easured by the release of reactive oxygen species and calcium mobilization, whereas Met-RANTES is inactive in these assays. AOP-RANTES is found to inh ibit CCR3-mediated HIV-1 infection with moderate potency, in contrast to it s potent inhibition of CCR5-mediated HIV-1 infection. Furthermore, we have investigated the abilities of these modified proteins to down-modulate CCR1 and CCR3 from the surface of monocytes and eosinophils. We show here that AOP-RANTES is much less effective than RANTES in down-modulation of CCR1. S urprisingly, recycling of CCR1 was minimal after incubation with RANTES whi le there was complete recycling with AOP-RANTES. In the case of CCR3, no si gnificant difference was found between RANTES and AOP-RANTES in down-modula tion and recycling. It therefore appears that trafficking of RANTES recepto rs follows different patterns, which opens up potential new targets for the rapeutic intervention.