Candidate sulfonated and sulfated topical microbicides: comparison of anti-human immunodeficiency virus activities and mechanisms of action

Poly(styrene 4-sulfonate), cellulose sulfate, polymethylenehydroquinone, and PRO 2000 are sulfated or sulfonated polymers (SPs) under development as topical microbicides. They are presumed to work through similar mechanisms of action, although to date there has been no extensive comparison of their anti-human immunodeficiency virus activities. To determine whether any of these candidate microbicides offers a potential advantage, their in vitro activities, mechanisms of action, stabilities in biological secretions, and toxicities were compared. All four compounds were found to be active against X4, R5, and dualtropic primary isolates and against X4 and R5 laboratory-adapted strains in CD4+ T cells, macrophages, and single-coreceptor cell lines. Our single-cycle experiments using pseudotyped virus suggest that all four SPs function at the binding and entry stages of the viral life cycle but differ in degree of postentry effect. Surface plasmon resonance analyses demonstrate that SPs bind to X4 and R5 monomeric glycoprotein 120 with similar high binding affinities. When mixed with cervicovaginal lavage fluid, SPs maintain inhibitory activity at concentrations achievable in formulations.

HIV-1 Nef induces dedifferentiation of podocytes in vivo: a characteristic feature of HIVAN

OBJECTIVE

To determine the specific role of Nef in the pathogenesis of HIV-associated nephropathy.

DESIGN

Podocytes are highly differentiated non-dividing cells in the normal glomerulus, however, they undergo dedifferentiation and acquire a proliferative phenotype in HIVAN patients, in HIV-transgenic mice and if infected by HIV-1 in vitro. These changes are accompanied by loss of the maturation markers synaptopodin and WT1, and expression of the proliferation marker Ki-67. Previously, we mapped the gene responsible for these changes in vitro to HIV-1 Nef. To determine the role of Nef in vivo, we developed a transgenic mouse model in which Nef was exclusively expressed in podocytes.

METHODS

Transgenic mice were generated using a construct in which Nef expression was blocked by a floxed lacZ intervening gene. When crossed with another transgenic mice expressing Cre under the Podocin promoter (a podocyte specific gene), the intervening lacZ gene was removed activating the expression of Nef in podocytes. The in vivo expression profiles of the Nef, the proliferation marker Ki-67, the differentiation markers synaptopodin and WT1, and phospho-Stat3, were determined by immunohistochemistry.

RESULTS

Podocyte-specific expression of Nef induced loss of synaptopodin and WT1, and expression of Ki-67 in podocytes. Furthermore, Nef activated expression of phospho-Stat3, one of the downstream signaling pathways for cell proliferation.

CONCLUSIONS

We conclude that Nef induces the early molecular changes in podocytes that are essential for the dedifferentiation and proliferation of podocytes in HIVAN pathogenesis. These data provide the first clear molecular evidence that Nef alters the podocyte phenotype in vivo.

Cervicovaginal secretions contribute to innate resistance to herpes simplex virus infection

Defining and preserving the innate antiviral activity found in cervicovaginal secretions is critical. Cervicovaginal lavage (CVL) samples were obtained from 20 healthy women and evaluated for anti-herpes simplex virus (HSV) activity. CVL samples reduced HSV-2 yields by 23-fold (median), and the anti-HSV activity of CVL samples correlated with the concentration of human neutrophil peptides (HNP)-1-3. Both CVL samples and HNP-1-3 interacted with virus and prevented entry after binding. Substantially less protective activity was observed in CVL samples obtained from 20 human immunodeficiency virus--infected subjects, but the addition of CVL samples from healthy subjects enhanced the antiviral activity. The significance of the innate activity was further demonstrated by showing that CVL samples prevented murine genital herpes. Fourteen of 15 mice were protected from genital herpes if they were challenged with HSV-2 pretreated with CVL samples from healthy subjects. In contrast, all 15 mice challenged with untreated HSV-2 died. These findings are evidence that cervicovaginal secretions contribute to innate resistance to HSV-2 and identify defensins as contributors to this activity.

HIV-1 extrachromosomal 2-LTR circular DNA is long-lived in human macrophages

HIV-1 extrachromosomal 2-LTR circles (cc2LTR) are rapidly lost in dividing cell populations and, therefore, might be interpreted as representing new infection and ongoing viral replication. However, recent work demonstrated that cc2LTR persist in infected, growth-arrested T cell lines beyond their predicted half-life as previously determined in dividing cell populations. In this study, the evaluation of the stability of cc2LTR was extended to include primary human macrophages, a natural, non-dividing target of HIV-1. By quantitative real-time PCR, cc2LTR were found to persist out to 21 days post-infection in macrophages infected with both integrase competent and integrase- defective, recombinant HIV-1, whereas in activated CD4(+) T lymphocytes, they rapidly decreased over time. This persistence was associated with persistent, low level expression of the indicator gene, luciferase. These data suggest that the presence of HIV-1 cc2LTR in the PBMC of HIV-1-infected patients on suppressive HAART could be due either to ongoing generation of newly infected dividing cells, or persistence of circles in non-dividing cell populations where they appear to be stable. Furthermore, exrachromosomal circular DNA in this cell population could be a source of persisent viral protein expression.

Highly active antiretroviral therapy and the epidemic of HIV+ end-stage renal disease

The rise in the number of patients with HIV-associated nephropathy and HIV-infection with end-stage renal disease (HIV+ ESRD) continues to be a substantial concern for the ESRD program. In order to assess the impact of highly active antiretroviral therapy (HAART) on the progression of patients with AIDS to the development of ESRD and to project the prevalence of HIV+ ESRD through 2020, a mathematical model of the dynamics of HIV+ infection in the ESRD population was developed. Epidemiologic data on AIDS and HIV+ ESRD among black individuals in the United States were obtained since 1991 from the Centers for Disease Control and Prevention and US Renal Data System, respectively. The model was constructed to predict the prevalence of HIV+ ESRD incorporating the current rate of growth in AIDS prevalence. Two possible trends were considered: linear AIDS growth and exponential AIDS growth. The likely effectiveness of HAART in slowing progression to HIV+ ESRD was estimated from the best fit of the model to the data after 1995, when HAART was introduced. The model was then used to evaluate recent data and to project the prevalence of HIV+ ESRD through 2020. The model suggested that HAART has reduced the rate of progression from AIDS to HIV+ ESRD by 38%. The model projected an increase in HIV+ ESRD prevalence in the future as a result of the increase in the AIDS population among black individuals. This increase was predicted even assuming a 95% reduction in the progression from AIDS to HIV+ ESRD. Despite the potential benefit of HAART, the prevalence of HIV+ ESRD in the United States is expected to rise in the future as a result of the expansion of the AIDS population among black individuals. It is concluded that prevention of progression to ESRD should focus on early antiretroviral treatment of HIV-infected patients who have evidence of HIV-associated nephropathy.

Dual role of alpha-defensin-1 in anti-HIV-1 innate immunity

Alpha-defensins are abundant antimicrobial peptides in polymorphonuclear leukocytes and play an important role in innate immunity. We have previously shown that alpha-defensin-1 can inhibit HIV-1 replication following viral entry. Here we examined the molecular mechanism(s) of alpha-defensin-1-mediated HIV-1 inhibition. Alpha-defensin-1 had a direct effect on HIV-1 virions at a low MOI in the absence of serum. The direct effect on HIV-1 virions was abolished by the presence of serum or an increase in virus particles. Studying the kinetics of the HIV life cycle revealed that alpha-defensin-1 inhibited steps following reverse transcription and integration. Analysis of PKC phosphorylation in primary CD4+ T cells in response to alpha-defensin-1 indicated that alpha-defensin-1 inhibited PKC activity. Pretreatment of infected CD4+ T cells with a PKC activator, bryostatin 1, partially reversed alpha-defensin-1-mediated HIV inhibition. Like alpha-defensin-1, the PKC isoform-selective inhibitor Go6976 blocked HIV-1 infection in a dose-dependent manner. Furthermore, kinetic studies and analysis of HIV-1 products indicated that alpha-defensin-1 and Go6976 blocked HIV-1 infection at similar stages in its life cycle, including nuclear import and transcription. Taken together, our studies demonstrate that, in the absence of serum, alpha-defensin-1 may act directly on the virus, but, in the presence of serum, its effects are on the cell, where it inhibits HIV-1 replication. At least 1 of the cellular effects associated with HIV inhibition is interference with PKC signaling in primary CD4+ T cells. Studying the complex function of alpha-defensin-1 in innate immunity against HIV has implications for prevention as well as therapeutics.

Dual role of alpha-defensin-1 in anti-HIV-1 innate immunity

Alpha-defensins are abundant antimicrobial peptides in polymorphonuclear leukocytes and play an important role in innate immunity. We have previously shown that alpha-defensin-1 can inhibit HIV-1 replication following viral entry. Here we examined the molecular mechanism(s) of alpha-defensin-1-mediated HIV-1 inhibition. Alpha-defensin-1 had a direct effect on HIV-1 virions at a low MOI in the absence of serum. The direct effect on HIV-1 virions was abolished by the presence of serum or an increase in virus particles. Studying the kinetics of the HIV life cycle revealed that alpha-defensin-1 inhibited steps following reverse transcription and integration. Analysis of PKC phosphorylation in primary CD4+ T cells in response to alpha-defensin-1 indicated that alpha-defensin-1 inhibited PKC activity. Pretreatment of infected CD4+ T cells with a PKC activator, bryostatin 1, partially reversed alpha-defensin-1-mediated HIV inhibition. Like alpha-defensin-1, the PKC isoform-selective inhibitor Go6976 blocked HIV-1 infection in a dose-dependent manner. Furthermore, kinetic studies and analysis of HIV-1 products indicated that alpha-defensin-1 and Go6976 blocked HIV-1 infection at similar stages in its life cycle, including nuclear import and transcription. Taken together, our studies demonstrate that, in the absence of serum, alpha-defensin-1 may act directly on the virus, but, in the presence of serum, its effects are on the cell, where it inhibits HIV-1 replication. At least 1 of the cellular effects associated with HIV inhibition is interference with PKC signaling in primary CD4+ T cells. Studying the complex function of alpha-defensin-1 in innate immunity against HIV has implications for prevention as well as therapeutics.

Nef expressed from human immunodeficiency virus type 1 extrachromosomal DNA downregulates CD4 on primary CD4+ T lymphocytes: implications for integrase inhibitors

Recently developed integrase inhibitors targeting the HIV-1 integrase (IN) protein block integration of HIV DNA in the target cell, preventing subsequent virus replication. In the absence of integration, viral DNA is shunted towards the formation of extrachromosomal DNA (E-DNA). Although HIV-1 E-DNA does not support productive replication, it is transcriptionally active and produces viral proteins. However, the significance of E-DNA in virus replication and pathogenesis is poorly understood. In this study, the functional activity of the HIV-1 Nef protein expressed in the absence of viral integration was analysed. Using both a recombinant HIV-1 IN defective virus and a diketo acid IN inhibitor, evidence was provided showing that Nef expressed from E-DNA downregulates CD4 surface expression on primary CD4(+) T lymphocytes. These results suggest that proteins expressed in the absence of integration may have potential clinical consequences, an issue that should be further explored with the introduction of IN inhibitors.

Persulfated molecular umbrellas as anti-HIV and anti-HSV agents

A series of persulfated molecular umbrellas have been synthesized from putrescine, spermidine, spermine, lysine, and cholic acid (1a, 2a, 3a, 4a, and 5a) and their anti-HIV and anti-HSV activities determined. Despite it size, the most active of these conjugates (5a) was able to cross phospholipid bilayers made from 1-palmitoyl-2-oleyol-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG). The unique combination of anti-viral activity, an ability to cross hydrophobic barriers, a lack of cytotoxicity, and a simple three-step synthesis from biogenic starting material suggests that 5a and related conjugates may be exploitable as a novel class of anti-viral agents for systemic and topical applications.

Novel integrase-defective lentiviral episomal vectors for gene transfer

High levels of circular viral extrachromosomal DNA (E-DNA) are normally produced after infection with integration-competent and -incompetent lentiviruses. Although E-DNA has been shown to be transcriptionally active, it lasts for only a short time in replicating cells. Here, we report an integrase (IN)-defective lentiviral episomal vector in which insertion of the simian virus 40 (SV40) promoter, containing the origin of replication (ori), is associated with long-term expression and persistence of E-DNA in the presence of SV40 large T antigen (TAg) from 293T cells. 293 and 293T cell lines transduced with IN-competent lentiviral vectors expressing green fluorescent protein (GFP) or luciferase from the cytomegalovirus (CMV) or SV40 promoter gave similar levels of transduction and expression. In contrast, only transient reporter expression occurred when using the CMV IN-defective control vector in both 293 and 293T cells. However, reporter gene expression was maintained for more than 8 weeks in 293T, but not 293, cells transduced with the IN-defective lentiviral vector containing the SV40-ori promoter. Polymerase chain reaction for two-long terminal repeat (2LTR) extrachromosomal circular forms, a marker of lentiviral E-DNA, and fluorescence in situ hybridization analysis confirmed the persistence and episomal nature of circular E-DNA up to 60 days after transduction. Taken together, these results indicate that insertion of the SV40-ori promoter in a lentiviral vector contributes to long-term expression by promoting episomal replication when TAg is provided in trans. Lentiviral episomal vectors may serve as specific tools for therapeutic approaches to diseases, particularly those associated with episomal replication of DNA viruses including papillomaviruses, polyomaviruses, and herpesviruses.

Nef stimulates proliferation of glomerular podocytes through activation of Src-dependent Stat3 and MAPK1,2 pathways

In collapsing focal segmental glomerulosclerosis (FSGS) of HIV-associated nephropathy (HIVAN), podocytes exhibit a high proliferation rate and loss of differentiation markers. We have found previously that the nef gene of HIV-1 is responsible for these changes. Here, we investigated the signaling pathways induced by Nef and its role in the pathogenesis of HIVAN. Using conditionally immortalized podocytes after differentiation, we found that infection of podocytes with nef increased Src kinase activity and signal transducer and activator of transcription 3 (Stat3) phosphorylation and activated the Ras-c-Raf-MAPK1,2 pathway. A dominant negative mutant of Src abolished the Nef effect, whereas inhibition of MAPK1,2 or dominant negative Stat3 reduced Nef effects partially. Reducing the expression of Nef with small interference RNA reversed the Nef effect. Mutation of Nef in the PxxP or R105R106 motifs diminished Nef signaling and the phenotypic changes in podocytes. Both phospho-MAPK1,2 and phospho-Stat3 staining increased in podocytes of kidneys from HIV-1 transgenic mice compared with their littermates and in podocytes of kidneys from HIVAN patients compared with HIV patients with non-HIVAN kidney diseases or non-HIV patients with idiopathic FSGS, classic FSGS, or minimal-change disease. These data suggest that Nef-induced activation of Stat3 and Ras-MAPK1,2 via Src-dependent pathways is responsible for podocyte proliferation and dedifferentiation, a characteristic finding in collapsing FSGS of HIVAN.

Candidate topical microbicides bind herpes simplex virus glycoprotein B and prevent viral entry and cell-to-cell spread

Topical microbicides designed to prevent acquisition of sexually transmitted infections are urgently needed. Nonoxynol-9, the only commercially available spermicide, damages epithelium and may enhance human immunodeficiency virus transmission. The observation that herpes simplex virus (HSV) and human immunodeficiency virus bind heparan sulfate provided the rationale for the development of sulfated or sulfonated polymers as topical agents. Although several of the polymers have advanced to clinical trials, the spectrum and mechanism of anti-HSV activity and the effects on soluble mediators of inflammation have not been evaluated. The present studies address these gaps. The results indicate that PRO 2000, polystyrene sulfonate, cellulose sulfate, and polymethylenehydroquinone sulfonate inhibit HSV infection 10,000-fold and are active against clinical isolates, including an acyclovir-resistant variant. The compounds formed stable complexes with glycoprotein B and inhibit viral binding, entry, and cell-to-cell spread. The effects may be long lasting due to the high affinity and stability of the sulfated compound-virus complex, as evidenced by surface plasmon resonance studies. The candidate microbicides retained their antiviral activities in the presence of cervical secretions and over a broad pH range. There was little reduction in cell viability following repeated exposure of human endocervical cells to these compounds, although a reduction in secretory leukocyte protease inhibitor levels was observed. These studies support further development and rigorous evaluation of these candidate microbicides.

Defensins: natural anti-HIV peptides

Mammalian defensins are small cationic antimicrobial peptides predominantly found in leukocytes and epithelial cells engaged in host defense. These peptides act as effector molecules in innate immunity as well as regulators in adaptive immunity. Increasing evidence indicates that defensins are effective inhibitors of HIV-1. While the level of defensins in HIV-1 infected individuals has not been determined, neutropenia and neutrophil dysfunction associated with HIV disease progression may result in altered alpha-defensin production. This review provides an overview of the structure and function of defensins, and focuses on the anti-HIV-1 activity of defensins and the mechanism of this activity. Although many questions remain, studying the complex function of defensins in innate immunity against HIV has implications for our further understanding of disease progression and for the development of novel approaches to prevention and therapy.

Podocan, a novel small leucine-rich repeat protein expressed in the sclerotic glomerular lesion of experimental HIV-associated nephropathy

Growing evidence suggests that human immunodeficiency virus (HIV)-1 infection of podocytes plays a central role in the glomerular disease of HIV-associated nephropathy (HIVAN). As an approach to identify host genes involved in the pathogenesis of the sclerotic glomerular lesion in HIVAN, representational difference analysis of cDNA was used to identify differentially expressed genes in HIV-1 transgenic and nontransgenic podocytes. We isolated a novel member of the small leucine-rich repeat (SLR) protein family, podocan, that is expressed at high levels in the HIV-1 transgenic podocytes. In normal embryonic kidney, a 3.2-kb podocan transcript was detected at low levels, and expression increased dramatically within 24 h following birth. Expression of a 2.3-kb transcript became evident after birth and gradually increased to 50% of the total podocan RNA in the mature kidney. Phylogenetically, podocan represents a new class in the SLR protein gene family, an expanding protein family sharing homology with the small leucine-rich repeat proteoglycans. The 3.2-kb transcript encodes a predicted 611-amino acid secretory protein with 20 leucine-rich repeats, a unique N-terminal cysteine-rich cluster pattern and a highly acidic C-terminal domain. In situ hybridization of normal kidney revealed podocan mRNA expression in podocytes and likely vascular endothelial cells within the glomerulus. The immunohistochemical staining pattern of podocan protein in normal kidney glomeruli was consistent with that of the glomerular basement membrane, and staining was markedly increased in sclerotic glomerular lesions in the transgenic HIVAN model. Thus, podocan defines a new class within the SLR protein family and is a previously unrecognized component of the sclerotic glomerular lesion that develops in the course of experimental HIVAN.

CAF-mediated human immunodeficiency virus (HIV) type 1 transcriptional inhibition is distinct from alpha-defensin-1 HIV inhibition

CD8(+) T lymphocytes can inhibit human immunodeficiency virus type 1 (HIV-1) replication by secreting a soluble factor(s) known as CD8(+) T-lymphocyte antiviral factor (CAF). One site of CAF action is inhibition of HIV-1 RNA transcription, particularly at the step of long terminal repeat (LTR)-driven gene expression. The inhibitory effect of CAF on HIV-1 LTR activation is mediated through STAT1 activation. A recent study reports that alpha-defensins 1 to 3 account for CAF activity against HIV-1. Here, we address whether alpha-defensins, particularly alpha-defensin-1, contribute to CAF-mediated inhibition of HIV-1 transcription. Both recombinant alpha-defensin-1 and CAF derived from herpesvirus saimiri (HVS)-transformed CD8(+) cells inhibited HIV-1 infection and gene expression. For both factors, the inhibition of HIV-1 infection did not occur at the level of viral entry. Pretreatment of cells with alpha-defensin-1 followed by a washing out prior to infection blocked infection by HIV-1, indicating that direct inactivation of virions was not required for its inhibitory effect. In contrast to CAF, alpha-defensin-1 did not inhibit phorbol myristate acetate- or Tat-mediated HIV-1 LTR activation in a transient transfection system, nor did it activate STAT1 tyrosine phosphorylation. Furthermore, alpha-defensins 1 to 3 were below the level of detection in a panel of HVS-transformed CD8(+) cells with potent HIV-1 inhibitory activity and a neutralizing antibody against alpha-defensins 1 to 3 did not reverse the inhibitory effect of CAF on HIV-1 gene expression in infected cells and on HIV-1 LTR activation in transfected cells. Taken together, our results suggest that alpha-defensin-1 inhibits HIV-1 infection following viral entry but that alpha-defensins 1 to 3 are not responsible for the HIV-1 transcriptional inhibition by CAF.

Development of topical microbicides for prevention of human immunodeficiency virus and herpes simplex virus

Topical microbicides, designed for vaginal or rectal administration, are needed to prevent human immunodeficiency virus (HIV) and other sexually transmitted infections (STI). Presently marketed topical microbicides are cytotoxic and damage the vaginal epithelium with frequent use. Rational development of new candidate compounds should build on knowledge of the pathways of microbial invasion. The establishment of assays and models that predict efficacy and safety is critical. Comprehensive pre-clinical evaluation of promising microbicides should include rigorous assessment of the effects of repeated application of topical agents on mucosal inflammatory cells, cytokines, and the genital tract virus population. These studies will lay the groundwork for future clinical trials.

Mutations in the chemokine receptor gene CXCR4 are associated with WHIM syndrome, a combined immunodeficiency disease

WHIM syndrome is an immunodeficiency disease characterized by neutropenia, hypogammaglobulinemia and extensive human papillomavirus (HPV) infection. Despite the peripheral neutropenia, bone marrow aspirates from affected individuals contain abundant mature myeloid cells, a condition termed myelokathexis. The susceptibility to HPV is disproportionate compared with other immunodeficiency conditions, suggesting that the product of the affected gene may be important in the natural control of this infection. We describe here the localization of the gene associated with WHIM syndrome to a region of roughly 12 cM on chromosome 2q21 and the identification of truncating mutations in the cytoplasmic tail domain of the gene encoding chemokine receptor 4 (CXCR4). Haplotype and mutation analyses in a pedigree transmitting myelokathexis as an apparently autosomal recessive trait support genetic heterogeneity for this aspect of the WHIM syndrome phenotype. Lymphoblastoid cell lines carrying a 19-residue truncation mutation show significantly greater calcium flux relative to control cell lines in response to the CXCR4 ligand, SDF-1, consistent with dysregulated signaling by the mutant receptor. The identification of mutations in CXCR4 in individuals with WHIM syndrome represents the first example of aberrant chemokine receptor function causing human disease and suggests that the receptor may be important in cell-mediated immunity to HPV infection.

Phosphatidylinositol 3-kinase regulates human immunodeficiency virus type 1 replication following viral entry in primary CD4+ T lymphocytes and macrophages

Human immunodeficiency virus (HIV) gp120 induces multiple cellular signaling pathways, including the phosphatidylinositol 3-kinase (PI3-kinase) pathway. The role of the PI3-kinase pathway in HIV-1 replication is not understood. Here we examined whether HIV-1 gp120 upregulates the PI3-kinase pathway and whether PI3-kinase activity plays a role in virus replication in primary human CD4(+) T cells and macrophages. Soluble and virion-associated HIV-1 gp120 induced calcium mobilization and phosphorylation of the PI3-kinase downstream effectors PKB/Akt and p70 S6 kinase. gp120-induced PI3-kinase activity and calcium mobilization were inhibited by pertussis toxin and blocking antibodies directed against CCR5 and CXCR4, suggesting that the signaling is mediated through the chemokine receptor. The PI3-kinase inhibitor LY294002 inhibited infection of CD4(+) T cells and macrophages with X4 and R5 HIV-1-pseudotyped viruses at concentrations that did not induce cell toxicity or downregulate HIV-1 coreceptor expression. When gp120-induced signaling was bypassed with the vesicular stomatitis virus G envelope protein, infection was still sensitive to PI3-kinase inhibition, suggesting that basal PI3-kinase activity is required for infection. LY294002 inhibited HIV-1 infection when added after viral entry and did not affect formation of the HIV-1 reverse transcriptase products R/U5 and long terminal repeat/Gag in the presence of the inhibitor. However, when the inhibitor was added after viral integration had occurred, no inhibition of HIV infection was observed. Our studies show that inhibition of the PI3-kinase signaling pathway suppresses virus infection post-viral entry and post-reverse transcription but prior to HIV gene expression. This type of host-virus interaction has implications for anti-HIV therapeutics that target cellular signaling machinery.

Mandelic acid condensation polymer: novel candidate microbicide for prevention of human immunodeficiency virus and herpes simplex virus entry

Presently marketed vaginal barrier methods are cytotoxic and damaging to the vaginal epithelium and natural vaginal flora when used frequently. Novel noncytotoxic agents are needed to protect men and women from sexually transmitted diseases. One novel candidate is a mandelic acid condensation polymer, designated SAMMA. The spectrum and mechanism of antiviral activity were explored using clinical isolates and laboratory-adapted strains of human immunodeficiency virus (HIV) and herpes simplex virus (HSV). SAMMA is highly effective against all CCR5 and CXCR4 isolates of HIV in primary human macrophages and peripheral blood mononuclear cells. SAMMA also inhibits infection of cervical epithelial cells by HSV. Moreover, it exhibits little or no cytotoxicity and has an excellent selectivity index. SAMMA, although not a sulfonated or sulfated polymer, blocks the binding of HIV and HSV to cells by targeting the envelope glycoproteins gp120 and gB-2, respectively, and also inhibits HSV entry postattachment. SAMMA is an excellent, structurally novel candidate microbicide that warrants further preclinical evaluation.

HIV-1 Nef induces proliferation and anchorage-independent growth in podocytes

HIV-associated nephropathy (HIVAN) is now the third leading cause of end-stage renal disease in the African American population. HIV-1 infects renal tubular and glomerular epithelial cells or podocytes, cells that are a critical part of the filtration barrier. HIV-1 infection induces the loss of podocyte differentiation markers and increases podocyte proliferation. It has been previously shown that HIV-infection induces loss of contact inhibition. Here, the HIV-1 gene responsible for proliferative changes is identified by using cultured podocytes in vitro. The HIV-1 proviral construct, pNL4-3 was rendered noninfectious by replacing the HIV-1 gag/pol sequences with an EGFP reporter gene (pNL4-3: DeltaG/P-EGFP). This construct was then pseudotyped with VSV.G envelope to infect podocytes that were conditionally immortalized with SV-40 T antigen. In addition, mutated constructs were engineered with premature stop codons in the HIV-1 env, vif, vpr, vpu, nef, or rev genes. The parental construct and all the other mutated constructs, with the exception of nef, induced proliferation under nonpermissive conditions and anchorage-independent growth (colony formation in soft agar) under permissive conditions. In contrast, deletion of nef markedly reduced proliferation and colony formation. Although tat alone, or tat plus rev induced marginal levels of anchorage-independent growth, coexpression with nef significantly increased colony formation. Finally, stable expression of Nef in a retroviral vector, pBabe-puro, was sufficient to induce increased proliferation and colony formation. Moreover, nef induced saturation density and loss of contact inhibition. These data indicate that Nef induces multiple proliferative effects in podocytes in culture and that nef may therefore be an important gene in the pathogenesis of HIVAN in vivo.

Replication and compartmentalization of HIV-1 in kidney epithelium of patients with HIV-associated nephropathy

HIV-associated nephropathy is a clinicopathologic entity that includes proteinuria, focal segmental glomerulosclerosis often of the collapsing variant, and microcystic tubulointerstitial disease. Increasing evidence supports a role for HIV-1 infection of renal epithelium in the pathogenesis of HIV-associated nephropathy. Using in situ hybridization, we previously demonstrated HIV-1 gag and nef mRNA in renal epithelial cells of patients with HIV-associated nephropathy. Here, to investigate whether renal epithelial cells were productively infected by HIV-1, we examined renal tissue for the presence of HIV-1 DNA and mRNA by in situ hybridization and PCR, and we molecularly characterized the HIV-1 quasispecies in the renal compartment. Infected renal epithelial cells were removed by laser-capture microdissection from biopsies of two patients, DNA was extracted, and HIV-1 V3-loop or gp120-envelope sequences were amplified from individually dissected cells by nested PCR. Phylogenetic analysis of kidney-derived sequences as well as corresponding sequences from peripheral blood mononuclear cells of the same patients revealed evidence of tissue-specific viral evolution. In phylogenetic trees constructed from V3 and gp120 sequences, kidney-derived sequences formed tissue-specific subclusters within the radiation of blood mononuclear cell-derived viral sequences from both patients. These data, along with the detection of HIV-1-specific proviral DNA and mRNA in tubular epithelium cells, argue strongly for localized replication of HIV-1 in the kidney and the existence of a renal viral reservoir.

Lentiviral gene transduction of kidney

Gene transfer into kidney holds great potential as a novel therapeutic approach. We have studied the transduction of kidney in vivo after delivery of lentiviral vectors by various routes of administration. A lentiviral vector expressing the bacterial lacZ gene from the cytomegalovirus early promoter was used. The lentiviral vector was delivered into the kidneys of BALB/c mice by retrograde infusion into the ureter, by injection into the renal vein or artery, or by direct injection into the renal parenchyma. Expression of the reporter gene was achieved independently of the route of administration, although it appeared more efficient after parenchymal or ureteral administration. After parenchymal or ureteral infusion, expression of the transgene was localized to the outer medulla and corticomedullary junction. In the case of parenchymal injection, expression of the reporter gene extended to the cortex. Detection of the transgene in the renal proximal tubules was confirmed by in situ polymerase chain reaction after parenchymal or ureteral infusion. On delivery of the lentiviral vector through the renal artery or vein, expression of the reporter gene was markedly lower than was observed with parenchymal or ureteral infusion and was limited to the inner medullary collecting ducts. No apparent histological abnormality was observed after virus administration and transgene expression was stable for at least 3 months. These results provide the first evidence that lentiviral vectors can stably transduce renal cells in vivo and may be effective vehicles for gene delivery to the kidney.