HIV associated nephropathy (HIVAN) afflicts an estimated 1–3 million people worldwide and is a major cause of morbidity and mortality. Murine transgenic models have demonstrated that expression of HIV-1 genes in kidney cells results in characteristic HIVAN pathology: collapsing FSGS and microcystic tubular disease. While we have gained significant understanding of the podocyte disease, less is known about the tubular epithelial responses to infection. HIV-1 vpr plays an important role in the FSGS of HIVAN particularly in association with nef expression in podocytes. In addition, Vpr is reported to exacerbate tubular pathology. Therefore, we explored the effect of vpr expression on renal tubular epithelial cell function. Proximal tubule epithelial cells (PTEC) were transduced in vitro using a pseudotyped lentivirus vector carrying HIV-1 vpr and control genes. HIV-1 vpr expression in cultured PTECs impaired cytokinesis causing cell enlargement and multinucleation. Because the in vitro phenotype was so profound, we re-examined the HIVAN murine model and human HIVAN biopsies to see if similar changes could be seen in vivo. Surprisingly, both the transgenic murine HIVAN model and human HIVAN biopsies showed abundant hypertrophic tubule cells consistent with the in vitro findings. The extent of the tubular cell hypertrophy was particularly impressive and represents a previously unappreciated aspect of the disease. Additionally, multinucleated tubular cells were identified in the murine HIVAN model and increased chromosome number was detected in tubular cells in HIVAN biopsies. This study provides evidence of a new clinical phenotype in HIVAN that may result from Vpr’s ability to impair cytokinesis.

Objective HIV-associated nephropathy is the most common cause of end stage renal disease in persons with HIV/AIDS and is characterized by focal glomerulosclerosis and dysregulated renal tubular epithelial cell (RTEC) proliferation and apoptosis. HIV-1 viral protein r (Vpr) has been implicated in HIV-induced RTEC apoptosis but the mechanisms of Vpr-induced RTEC apoptosis are unknown. The aim of this study was therefore to determine the mechanisms of Vpr-induced apoptosis in RTEC. Methods Apoptosis and caspase activation were analyzed in human RTEC cells (HK2) after transduction with Vpr-expressing and control lentiviral vectors. Bax and BID were inhibited with lentiviral shRNA, and ERK activation was blocked with the MEK1,2 inhibitor, U0126. Results Vpr induced apoptosis as indicated by caspase 3/7 activation, PARP-1 cleavage and mitochondrial injury. Vpr activated both caspases-8 and 9. Inhibition of Bax reduced Vpr-induced apoptosis, as reported in other cell types. Additionally, Vpr induced cleavage of BID to tBID and suppression of BID expression prevented Vpr-induced apoptosis. Since sustained ERK activation can activate caspase-8 in some cell types, we studied the role of ERK in Vpr-induced caspase-8 activation. Vpr induced sustained ERK activation in HK2 cells and incubation with U0126 reduced Vpr-induced caspase-8 activation, BID cleavage and apoptosis. We detected phosphorylated ERK in RTEC in HIVAN biopsy specimens by immunohistochemistry. Conclusions These studies delineate a novel pathway of Vpr-induced apoptosis in RTEC, which is mediated by sustained ERK activation, resulting in caspase 8-mediated cleavage of BID to tBID, thereby facilitating Bax-mediated mitochondrial injury and apoptosis.

We have constructed a prostate-specific lentiviral vector based on the promoter of the prostate-specific antigen (PSA). The PSA promoter-based lentiviral vector has been used to deliver the diphtheria toxin A (DTA) gene into prostate cancer cells, and has shown promising tissue-specific eradication of prostate cancer cells in cell culture. To evaluate the efficacy of eradicating human prostate cancer cells in vivo, we used human LNCaP prostate xenografts in nude mice as an animal model and found that with a single injection of the DTA lentiviral vector into LNCaP prostate tumors, approximately 75% of the tumors (from three experiments; conducted 9/11, 11/15 and 3/4) in the animals were completely eradicated. The DTA vector has also shown the ability to cause tumor regression in recurrent prostate tumors. Intravenous injection of the DTA lentiviral vector into nude mice elicited no pathogenic effects, suggesting that this prostate tissue-specific vector is safe for eradicating prostate cancer cells in vivo.

Summary HIV associated nephropathy (HIVAN) is a major cause of HIV related morbidity and mortality. Pathogenesis involves direct infection of the glomerular and tubular epithelial cells leading to characteristic pathology. Recently, we have shown that HIV-1 Vpr causes hypertrophy, hyperploidy, and apoptosis. Here we report that Vpr activates the DNA damage response resulting in the observed renal phenotype. Renal sections from the HIVAN transgenic mouse model and human biopsies both show an abundant DNA damage response.