IL-27 Reduces Cell-Surface LDLR in Human Macrophages and Restricts VSV-G-Pseudotyped HIV infection

The low-density lipoprotein receptor (LDLR) is a major cellular receptor for vesicular stomatitis virus glycoprotein (VSV-G), which is widely used to pseudotyped virus vectors. A replication incompetent VSV-G-pseudotyped HIV (VSV-G-HIVLuc) has been used in HIV infection studies. Although IL-27-polarized macrophages induce multiple antiviral genes and resist replication-competent HIV infection, their impact on VSV-GHIVLuc infection has not been studied. Here, we evaluated the role of IL-27 polarization on VSV-G-HIVLuc infection. Infection was monitored by luciferase activity. Cell-surface LDLR was analyzed by flow cytometry. LDLR transcripts and protein expression were quantified by qRT-PCR and Western blotting, respectively. Viral binding was assessed by measuring cell-associated p24 antigen, while post-entry events were evaluated by quantifying late reverse-transcription products. VSV-G-HIVLuc infection in IL-27-polarized M-CSF-induced macrophages (27M-Mac) and IL-27-polarized GM-CSFinduced macrophages (27GM-Mac) was reduced to 5.8{+/-}0.4% and 5.9{+/-}2.1%, respectively (both p<0.0001), compared to unpolarized macrophages. 27M-Mac and 27GM-Mac reduced cell-surface LDLR to 38.3{+/-}2.6% (p<0.01) and 31.4{+/-}3.2% (p<0.01). Western blotting showed that total LDLR protein decreased to 48{+/-}0.8% in 27M-Mac (p<0.01), whereas 27GM-Mac showed no significant change. However, LDLR transcripts increased approximately 1.6-1.9-fold following IL-27 treatment in both macrophage types (p<0.01). Viral binding to 27M-Mac decreased modestly, while binding to 27GM-Mac decreased significantly to 67.5 {+/-} 7.5% of that to GM-Mac (p<0.05, n=3). In contrast, late reverse-transcription products decreased to 23{+/-}2.1% (p<0.0001) and 44{+/-}1.5% (p<0.0001). These findings demonstrate that IL-27 downregulates cell-surface LDLR expression in macrophages despite increasing LDLR transcript abundance, suggesting that IL-27 restricts VSV-G-pseudotyped Lentiviral infection through both receptor-associated and additional post-entry mechanisms.