Induction of the antiviral factors APOBEC3A and RSAD2 upon CCL2 neutralization in primary human macrophages involves NF-kB, JAK/STAT, and gp130 signaling.

Abstract

The CC chemokine ligand 2 (CCL2)/CC chemokine receptor 2 axis plays key roles in the pathogenesis of human immunodeficiency virus type 1 (HIV-1) infection. We previously reported that exposure of monocyte-derived macrophages (MDMs) to CCL2 neutralizing antibody (αCCL2 Ab) restricted HIV-1 replication at post-entry steps of the viral life cycle. This effect was associated with induction of transcripts coding for innate antiviral proteins, amongst which apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3A (APOBEC3A) and radical S-adenosyl methionine domain containing 2 (RSAD2). This study aimed at identifying the signaling pathways involved in induction of these factors by CCL2 blocking in MDMs. Through a combination of pharmacologic inhibition, quantitative RT-PCR, western blotting, and confocal laser-scanning microscopy, we demonstrated that CCL2 neutralization activates the canonical NF-kB and JAK/STAT pathways, as assessed by time-dependent phosphorylation of IkB, STAT1, and STAT3 and p65 nuclear translocation. Furthermore, pharmacologic inhibition of I kappa B kinase and JAKs strongly reduced APOBEC3A and RSAD2 transcript accumulation elicited by αCCL2 Ab treatment. Interestingly, exposure of MDMs to αCCL2 Ab resulted in induction of IL-6 family cytokines, and interfering with glycoprotein 130, the common signal-transducing receptor subunit shared by these cytokines, inhibited APOBEC3A and RSAD2 up-regulation triggered by CCL2 neutralization. These results provide novel insights into the signal transduction pathways underlying the activation of innate responses triggered by CCL2 neutralization in macrophages. Since this response was found to be associated with protective antiviral effects, the new findings may help design innovative therapeutic approaches targeting CCL2 to strengthen host innate immunity.