Replication kinetics of the chimeric viruses derived from two different compartments differed in cell lines expressing the single co-receptors CCR5 or CXCR4.
In the U87 cell line expressing CD4 and CCR5, viruses with envelopes derived from both the kidney (Fig. 1b) and blood replicated (Fig. 1c). The CCR5-specific antibody 2D7 and the small molecule antagonist TAK-779 inhibited replication of the kidney-derived viruses in U87-CD4-CCR5, confirming the use of CCR5 by these envelopes (Fig. 1b). Infection of the same cells with blood-derived viruses was completely inhibited by TAK-779 but not by 2D7 antibody at a dose of 20 μg/ml (Fig. 1c). Using a control R5 virus (BAL), anti-CCR5 antibody (2D7) completely abolished infection (data not shown).
In contrast, only the kidney-derived viruses replicated in the U87-CD4-CXCR4 cell line (Fig. 1d). The anti-CXCR4 antibody 12G5 and small molecule antagonist AMD3100 inhibited replication of kidney-derived viruses by 85–99% (Fig. 1d) as well as the control X4 virus III-B (data not shown).
Three kidney and one blood-derived viruses also productively infected the U87-CD4-CCR3 cell line (data not shown) whereas two kidney-derived viruses utilized BONZO/STRL33 and BOB/GPR15 in GHOST cell lines expressing these co-receptors (data not shown).
All chimeric viruses replicated in the HPT-1 cell line (data not shown). The latter had detectable CD4 and CXCR4 messenger RNA as well as mRNA for some of the minor co-receptors (CCR9, BONZO/STRL33, APJ, GPR1, and ChemR23) by reverse transcriptase–polymerase chain reaction (data not shown) but no detectable CCR5 mRNA. In view of the fact that the blood isolates showed only an R5 phenotype, these viruses most likely utilized one of the alternative co-receptors for entry to the HPT-1 cell line.
In this study, we analysed the phenotype of HIV-1 envelopes simultaneously derived from renal epithelium and PBMC. HIV-1 envelopes from isolates derived from renal epithelium were dual tropic (R5X4) and were able to utilize a number of alternative co-receptors. In contrast, envelopes simultaneously derived from PBMC were R5 tropic with a heterogeneous pattern of co-receptor utilization. There was a clear distinction in co-receptor utilization between the kidney and the blood-derived envelopes.
The role of alternative co-receptors in HIV-1 entry in the kidney is unclear. We found that three kidney-derived envelopes could use CCR3 and two of them could use GPR15 and BONZO/STRL33. Interestingly, we did find BONZO/STRL33 mRNA in HPT-1 cells, consistent with earlier reports of its presence in the kidney . In addition, we detected mRNA expression of CXCR4, GPR1 and APJ in HPT-1 cells.
In conclusion, this study demonstrates that HIV-1 quasispecies in the kidney are phenotypically distinct from those in the blood, as indicated by the differential use of co-receptors, consistent with renal compartmentalization. Furthermore, the use of CXCR4 by these isolates and the presence of CXCR4 on the renal epithelial cell line suggests that entry might be mediated via this co-receptor.
Further studies on HIV-1 variants from the kidney may shed more light on HIV-1 pathogenesis and compartmentalization.
The following reagents were obtained through the AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: U87MG cells from Dr Bruce Chesebro, U87-CD4 cells from Drs Hongkui and D. Litman, and GHOST cells from Dr Vineet, N. KewalRamani and Dr D. Litman.
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