The CXCL12/CXCR4 Signaling Pathway: A New Susceptibility Factor in Human Papillomavirus Pathogenesis.

The productive human papillomavirus (HPV) life cycle is tightly linked to the differentiation and cycling of keratinocytes. Deregulation of these processes and stimulation of cell proliferation by the action of viral oncoproteins and host cell factors underlies HPV-mediated carcinogenesis. Severe HPV infections characterize the wart, hypogammaglobulinemia, infection, and myelokathexis (WHIM) immunodeficiency syndrome, which is caused by gain-of-function mutations in the CXCR4 receptor for the CXCL12 chemokine, one of which is CXCR41013. We investigated whether CXCR41013 interferes in the HPV18 life cycle in epithelial organotypic cultures. Expression of CXCR41013 promoted stabilization of HPV oncoproteins, thus disturbing cell cycle progression and proliferation at the expense of the ordered expression of the viral genes required for virus production. Conversely, blocking CXCR41013 function restored virus production and limited HPV-induced carcinogenesis. Thus, CXCR4 and its potential activation by genetic alterations in the course of the carcinogenic process can be considered as an important host factor for HPV carcinogenesis.

HPV-18 E2

The Human Papillomavirus (HPV) E4 is known to be synthesized as an E1^E4 fusion resulting from splice donor and acceptor sites conserved across HPV types. Here we demonstrate the existence of 2 HPV-18 E2^E4 transcripts resulting from 2 splice donor sites in the 5' part of E2, while the splice acceptor site is the one used for E1^E4. Both E2^E4 transcripts are up-regulated by keratinocyte differentiation in vitro and can be detected in clinical samples containing low-grade HPV-18-positive cells from Pap smears. They give rise to two fusion proteins in vitro, E2^E4-S and E2^E4-L. Whereas we could not differentiate E2^E4-S from E1^E4 in vivo, E2^E4-L could be formally identified as a 23 kDa protein in raft cultures in which the corresponding transcript was also found, and in a biopsy from a patient with cervical intraepithelial neoplasia stage I-II (CINI-II) associated with HPV-18, demonstrating the physiological relevance of E2^E4 products.

Modulation of HIV Binding to Epithelial Cells and HIV Transfer from Immature Dendritic Cells to CD4 T Lymphocytes by Human Lactoferrin and its Major Exposed LF-33 Peptide.

Lactoferrin (LF), a multifunctional molecule present in human secretions, has potent inhibitory activities against human immunodeficiency virus (HIV). The aim of the study was to evaluate whether human LF (hLF) and its exposed domain LF-33 represented by the peptide (LF-33-GRRRRSVQWCAVSQPEATKCFQWQRNMRKVRGP) involved in LF-HIV gag binding and endotoxines neutralization, may inhibit early steps of HIV mucosal transmission. Human LF and the peptide LF-33 inhibited the attachment of primary X4-tropic HIV-1(NDK) and R5-tropic HIV-1(JR-CSF) strains to human endometrial (HEC-1) and colorectal (HT-29) CD4-negative epithelial cells, the purified hLF being more potent (up to 80%) than the LF-33 peptide. In addition, the hLF, but not the LF-33 peptide, inhibited up to 40% the transfer in trans of HIV-1(JR-CSF) and HIV-1(NDK,) from immature dendritic cells to CD4 T lymphocytes, likely in a DC-SIGN-dependent manner. Altogether, these findings demonstrate that hLF can interfere with HIV-1 mucosal transmission by blocking virus attachment to epithelial cells and by inhibiting virus transfer from dendritic cells to CD4 T cells, two crucial steps of HIV dissemination from mucosae to lymphoid tissue.

A pivotal role for CXCL12 signaling in HPV-mediated transformation of keratinocytes: clues to understanding HPV-pathogenesis in WHIM syndrome.

The WHIM syndrome, which features high susceptibility to human papillomavirus (HPV) infection, is a rare immunodeficiency associated with autosomal dominant heterozygous mutations of the CXCR4 chemokine receptor. CXCL12 and its receptors, CXCR4 and CXCR7, are linked to tumorigenesis, and we reported that abnormal expression of CXCL12 in epidermal keratinocytes correlates with HPV infection. However, the HPV-related pathologies observed in WHIM patients remain mechanistically unexplained. We show that keratinocytes immortalized by oncogenic HPV16 or HPV18 upregulate CXCL12 and its receptors in a manner dependent upon expression of the viral proteins E6 and E7. Autocrine signaling activated by CXCL12-engagement of its receptors controls motility and survival of the infected cells. Strikingly, expression of a WHIM syndrome-related gain-of-function CXCR4 mutant confers transforming capacity to HPV18-immortalized keratinocytes. These results establish a pivotal role for CXCL12 signaling in HPV-mediated transformation and provide a mechanistic basis for understanding HPV pathogenesis in WHIM syndrome.

Human TRIM gene expression in response to interferons.

BACKGROUND: Tripartite motif (TRIM) proteins constitute a family of proteins that share a conserved tripartite architecture. The recent discovery of the anti-HIV activity of TRIM5alpha in primate cells has stimulated much interest in the potential role of TRIM proteins in antiviral activities and innate immunity. PRINCIPAL FINDINGS: To test if TRIM genes are up-regulated during antiviral immune responses, we performed a systematic analysis of TRIM gene expression in human primary lymphocytes and monocyte-derived macrophages in response to interferons (IFNs, type I and II) or following FcgammaR-mediated activation of macrophages. We found that 27 of the 72 human TRIM genes are sensitive to IFN. Our analysis identifies 9 additional TRIM genes that are up-regulated by IFNs, among which only 3 have previously been found to display an antiviral activity. Also, we found 2 TRIM proteins, TRIM9 and 54, to be specifically up-regulated in FcgammaR-activated macrophages. CONCLUSIONS: Our results present the first comprehensive TRIM gene expression analysis in primary human immune cells, and suggest the involvement of additional TRIM proteins in regulating host antiviral activities.

Lack of endogenous TRIM5alpha-mediated restriction in rhesus macaque dendritic cells.

Rhesus macaques are resistant to infection by HIV-1 as a result of an innate cellular restriction mechanism attributable to the expression of rhTRIM5alpha, a member of the large tripartite motif (TRIM) protein family. TRIM5alpha-mediated restriction, which occurs before reverse transcription through targeting of the HIV-1 capsid, has been identified in a number of macaque primary cells and cell lines and is thought to occur in all macaque cell types. We report, however, that rhesus macaque dendritic cells (DCs) lack TRIM5alpha-mediated restriction and are equally permissive to HIV-1 infection as human DCs. Evidence suggests that, although TRIM5alpha RNA levels are normal in these cells, the protein may be dysfunctional. We propose that abrogation of TRIM5alpha-mediated restriction in DCs, although still operative in cells that replicate HIV-1 (macrophages, T lymphocytes), illustrates the need for innate mechanisms to not inhibit adaptive immune responses to ensure an optimal fight against pathogens.

Implication of TRIM alpha and TRIMCyp in interferon-induced anti-retroviral restriction activities.

BACKGROUND: TRIM5 alpha is a restriction factor that interferes with retroviral infections in a species-specific manner in primate cells. Although TRIM5 alpha is constitutively expressed, its expression has been shown to be up-regulated by type I interferon (IFN). Among primates, a particular case exists in owl monkey cells, which express a fusion protein between TRIM5 and cyclophilin A, TRIMCyp, specifically interfering with HIV-1 infection. No studies have been conducted so far concerning the possible induction of TRIMCyp by IFN. We investigated the consequences of IFN treatment on retroviral restriction in diverse primate cells and evaluated the implication of TRIM5 alpha or TRIMCyp in IFN-induced anti-retroviral activities. RESULTS: First, we show that human type I IFN can enhance TRIM5 alpha expression in human, African green monkey and macaque cells, as well as TRIMCyp expression in owl monkey cells. In TRIM5 alpha-expressing primate cell lines, type I IFN has little or no effect on HIV-1 infection, whereas it potentiates restriction activity against N-MLV in human and African green monkey cells. In contrast, type I IFN treatment of owl monkey cells induces a great enhancement of HIV-1 restriction, as well as a strain-tropism independent restriction of MLV. We were able to demonstrate that TRIM5 alpha is the main mediator of the IFN-induced activity against N-MLV in human and African green monkey cells, whereas TRIMCyp mediates the IFN-induced HIV-1 restriction enhancement in owl monkey cells. In contrast, the type I IFN-induced anti-MLV restriction in owl monkey cells is independent of TRIMCyp expression. CONCLUSION: Together, our observations indicate that both TRIM5 alpha and TRIMCyp are implicated in IFN-induced anti-retroviral response in primate cells. Furthermore, we found that type I IFN also induces a TRIMCyp-independent restriction activity specific to MLV in owl monkey cells.

Differential modulation of human lactoferrin activity against both R5 and X4-HIV-1 adsorption on epithelial cells and dendritic cells by natural antibodies.

Human lactoferrin (Lf) is an iron binding glycoprotein that is present in several mucosal secretions. Many biological functions have been ascribed to Lf. In the present study, we showed that Lf limited specifically adsorption of R5- and X4-HIV-1-free particles on endometrial epithelial HEC-1A cells, by inhibiting virus adsorption on heparan-sulfated proteoglycans. But, Lf did not interfere with both R5 and X4-HIV transcytosis. We showed also the efficacy of Lf in preventing R5 and X4-HIV capture by dendritic cells. Conversely, we demonstrated that Lf-reacting natural Abs (NAbs) present within i.v. Ig-enhanced HIV attachment on dendritic cells by forming HIV-Lf-NAbs. HIV particles were able to directly interact with Lf following its interaction with NAbs. We also found Lf-reacting natural Abs within cervicovaginal secretions, suggesting the existence of Lf-NAbs complexes in women genital tract in vivo. In conclusion, this study highlights Lf as a potent microbicides and reports new function for NAbs within the genital compartment that may compartment that may abolish the inhibitory activity of microbicide compounds. Thus, we proposed a model in which Lf would appear as a double-edged sword that could have beneficial or detrimental effects depending on both cellular and molecular environments. This study highlights the use of Lf derivates as microbicide candidates to limit such interferences.

Dihydropteroate synthase mutations in the folP1 gene predict dapsone resistance in relapsed cases of leprosy.

Molecular detection was compared with the mouse footpad inoculation test for detection of dapsone resistance in 38 strains of Mycobacterium leprae. Mutations of the folP1 gene (at codons 53 or 55) were found in 6 of 6 strains with high-level resistance, in 3 of 4 strains with intermediate-level resistance, and in 1 of 6 strains with low-level resistance, but not in 22 dapsone-susceptible strains. In cases of infection with strains of M. leprae carrying the folP1 mutation, therapy with dapsone may be replaced by therapy with a fluoroquinolone.

Characterization of two candidate genes, NCoA3 and IRF8, potentially involved in the control of HIV-1 latency.

BACKGROUND: The persistence of latent HIV-1 reservoirs is the principal barrier preventing the eradication of HIV-1 infection in patients by current antiretroviral therapy. It is thus crucial to understand the molecular mechanisms involved in the establishment, maintenance and reactivation of HIV-1 latency. Since chromatin remodeling has been implicated in the transcriptional reactivation of the HIV-1 promoter, we assessed the role of the histone deacetylase inhibitor sodium butyrate (NaB) on two HIV-1 latently infected cell lines (U1 and ACH-2) gene expression. RESULTS: Analysis of microarrays data led us to select two candidate genes: NCoA3 (Nuclear Receptor Coactivator 3), a nuclear receptor coactivator and IRF8 (Interferon Regulatory Factor 8), an interferon regulatory factor. NCoA3 gene expression is upregulated following NaB treatment of latently infected cells whereas IRF8 gene expression is strongly downregulated in the promonocytic cell line following NaB treatment. Their differential expressions were confirmed at the transcriptional and translational levels. Moreover, NCoA3 gene expression was also upregulated after treatment of U1 and ACH-2 cells with phorbol myristyl acetate (PMA) but not trichostatin A (TSA) and after treatment with NaB of two others HIV-1 latently infected cell lines (OM10.1 and J1.1). IRF8 gene is only expressed in U1 cells and was also downregulated after treatment with PMA or TSA. Functional analyses confirmed that NCoA3 synergizes with Tat to enhance HIV-1 promoter transcription and that IRF8 represses the IRF1-mediated activation through the HIV-1 promoter Interferon-stimulated response element (ISRE). CONCLUSION: These results led us to postulate that NCoA3 could be involved in the transcriptional reactivation of the HIV-1 promoter from latency and that IRF8 may contribute to the maintenance of the latent state in the promonocytic cell line. Implication of these factors in the maintenance or reactivation of the viral latency may provide potential new targets to control HIV-1 replication in latent viral reservoirs.