title: Endogenous CCL2 neutralization restricts HIV-1 replication in primary human macrophages by inhibiting viral DNA accumulation.
abstract: BACKGROUND
  Macrophages are key targets of HIV-1 infection. We have previously described that the expression of CC chemokine ligand 2 (CCL2) increases during monocyte differentiation to macrophages and it is further up-modulated by HIV-1 exposure. Moreover, CCL2 acts as an autocrine factor that promotes viral replication in infected macrophages. In this study, we dissected the molecular mechanisms by which CCL2 neutralization inhibits HIV-1 replication in monocyte-derived macrophages (MDM), and the potential involvement of the innate restriction factors protein sterile alpha motif (SAM) histidine/aspartic acid (HD) domain containing 1 (SAMHD1) and apolipoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3 (APOBEC3) family members.
  
  
  RESULTS
  CCL2 neutralization potently reduced the number of p24 Gag+ cells during the course of either productive or single cycle infection with HIV-1. In contrast, CCL2 blocking did not modify entry of HIV-1 based Virus Like Particles, thus demonstrating that the restriction involves post-entry steps of the viral life cycle. Notably, the accumulation of viral DNA, both total, integrated and 2-LTR circles, was strongly impaired by neutralization of CCL2. Looking for correlates of HIV-1 DNA accumulation inhibition, we found that the antiviral effect of CCL2 neutralization was independent of the modulation of SAMHD1 expression or function. Conversely, a strong and selective induction of APOBEC3A expression, to levels comparable to those of freshly isolated monocytes, was associated with the inhibition of HIV-1 replication mediated by CCL2 blocking. Interestingly, the CCL2 neutralization mediated increase of APOBEC3A expression was type I IFN independent. Moreover, the transcriptome analysis of the effect of CCL2 blocking on global gene expression revealed that the neutralization of this chemokine resulted in the upmodulation of additional genes involved in the defence response to viruses.
  
  
  CONCLUSIONS
  Neutralization of endogenous CCL2 determines a profound restriction of HIV-1 replication in primary MDM affecting post-entry steps of the viral life cycle with a mechanism independent of SAMHD1. In addition, CCL2 blocking is associated with induction of APOBEC3A expression, thus unravelling a novel mechanism which might contribute to regulate the expression of innate intracellular viral antagonists in vivo. Thus, our study may potentially lead to the development of new therapeutic strategies for enhancing innate cellular defences against HIV-1 and protecting macrophages from infection.
authors.forename: Michela
authors.initials: M
authors.lastname: Sabbatucci
authors.forename: Daniela Angela
authors.initials: DA
authors.lastname: Covino
authors.forename: Cristina
authors.initials: C
authors.lastname: Purificato
authors.forename: Alessandra
authors.initials: A
authors.lastname: Mallano
authors.forename: Maurizio
authors.initials: M
authors.lastname: Federico
authors.forename: Jing
authors.initials: J
authors.lastname: Lu
authors.forename: Arturo Ottavio
authors.initials: AO
authors.lastname: Rinaldi
authors.forename: Matteo
authors.initials: M
authors.lastname: Pellegrini
authors.forename: Roberta
authors.initials: R
authors.lastname: Bona
authors.forename: Zuleika
authors.initials: Z
authors.lastname: Michelini
authors.forename: Andrea
authors.initials: A
authors.lastname: Cara
authors.forename: Stefano
authors.initials: S
authors.lastname: Vella
authors.forename: Sandra
authors.initials: S
authors.lastname: Gessani
authors.forename: Mauro
authors.initials: M
authors.lastname: Andreotti
authors.affiliation: Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Rome, Italy. laura.fantuzzi@iss.it.
authors.forename: Laura
authors.initials: L
authors.lastname: Fantuzzi
mesh_terms: D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors* / Q000276:immunology; D003564:Cytidine Deaminase / Q000037:antagonists & inhibitors / Q000235:genetics; D004279:DNA, Viral / Q000378:metabolism*; D015870:Gene Expression; D020869:Gene Expression Profiling; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D008264:Macrophages / Q000821:virology*; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D000076106:SAM Domain and HD Domain-Containing Protein 1; D053586:Virus Internalization; D014779:Virus Replication
chemical_list: C111835:CCL2 protein, human; D018932:Chemokine CCL2; D004279:DNA, Viral; D011506:Proteins; D000076106:SAM Domain and HD Domain-Containing Protein 1; C484280:SAMHD1 protein, human; C121399:APOBEC3A protein, human; D003564:Cytidine Deaminase; D020559:Monomeric GTP-Binding Proteins