Abstract

Background:

Approximately 4 million people worldwide are co-infected with chronic HBV (CHBV) and HIV due to shared transmission routes. The progression of CHBV to cirrhosis and hepatocellular carcinoma is accelerated by HIV coinfection compared to HBV mono-infection. The mechanisms underlying this accelerated natural history are not well characterized. HIV and its proteins, such as gp120, signal through CCR5 and CXCR4 on hepatocytes and hepatic stellate cells to promote cell growth and proliferation through hypoxia-inducible factor-1α (HIF-1α). We hypothesize that HIV and its proteins promote HBV-induced liver fibrosis in HIV/HBV coinfected cell culture models through HIF-1α and TGF-β1 signaling.

Methods: Infectious HBV viral particles (HBVvp) were purified from the HBV supernatant (HBVsup) of HepAD38 cells. HIV NL4-3 strains viral particles (HIVvp) were isolated from HIV-infected U937 macrophage supernatant (HIVsup). The HBVvp, HBVsup, HIVvp or HIVsup were directly incubated (or infected) with LX-2 stellate cells, U937, and HBV-infected NTCP-HepG2 cells in mono or 3D spheroid coculture models. Cells were incubated with recombinant HIV proteins including gp120. HBV subgenomic constructs were transfected into NTCP HepG2 cells. We also evaluated the effects of inhibitors of HIF-1α and HIV gp120 in the HBV carrier mouse that were generated by hydrodynamic injection of pAAV/HBV1.2 plasmid though the tail vein into wild-type C57BL/6. The HIV/HBV replication, HIF-1α, and fibrotic gene expressions were monitored by qRT-PCR, ELISA, Western blot, and immunostaining.

Results: HIV and HIV gp120, through engagement with CCR5 and CXCR4 coreceptors, activate AKT and ERK signaling and subsequently upregulate HIF-1α to increase HBV-induced TGF-β1 and profibrogenic gene expression in hepatocytes, HSCs and in the HBV carrier mouse. HIV gp120 exacerbates HBV X protein overexpression-induced HIF-1α expression and liver fibrogenesis through the TGF-β1 induced SMAD signaling pathway. Of note, HIF-1α siRNA transfection or the small molecule HIF-1a inhibitor acriflavine blocked HIV, HBV and the TGF-β1-induced fibrogenic response. HIV-induced upregulation of HIF-1α and profibrotic genes was abrogated by CCR5/CXCR4 inhibition.

Conclusion: HIV and gp120 exacerbate HBV-induced liver fibrogenesis through upregulation of the HIF-1α and TGF-β1 pathway through CCR5/CXCR4. HIF-1α may be a novel target for antifibrotic therapeutic development in HBV/HIV coinfection.