HIV-1 pseudotype virus containing a Cocal virus genome and an HIV envelope: construction, assay and use

The role of myeloid receptors on murine plasmacytoid dendritic cells in induction of type I interferon

This study tested the hypothesis that a set of predominantly myeloid restricted receptors (F4/80, CD36, Dectin-1, CD200 receptor and mannan binding lectins) and the broadly expressed CD200 played a role in a key function of plasmacytoid DC (pDC), virally induced type I interferon (IFN) production. The Dectin-1 ligands zymosan, glucan phosphate and the anti-Dectin-1 monoclonal antibody (mAb) 2A11 had no effect on influenza virus induced IFNα/β production by murine splenic pDC. However, mannan, a broad blocking reagent against mannose specific receptors, inhibited IFNα/β production by pDC in response to inactivated influenza virus. Moreover, viral glycoproteins (influenza virus haemagglutinin and HIV-1 gp120) stimulated IFNα/β production by splenocytes in a mannan-inhibitable manner, implicating the function of a lectin in glycoprotein induced IFN production. Lastly, the effect of CD200 on IFN induction was investigated. CD200 knock-out macrophages produced more IFNα than wild-type macrophages in response to polyI:C, a MyD88-independent stimulus, consistent with CD200's known inhibitory effect on myeloid cells. In contrast, blocking CD200 with an anti-CD200 mAb resulted in reduced IFNα production by pDC-containing splenocytes in response to CpG and influenza virus (MyD88-dependent stimuli). This suggests there could be a differential effect of CD200 on MyD88 dependent and independent IFN induction pathways in pDC and macrophages. This study supports the hypothesis that a mannan-inhibitable lectin and CD200 are involved in virally induced type I IFN induction.

Adaptation of chimeric retroviruses in vitro and in vivo: isolation of avian retroviral vectors with extended host range

We have designed and characterized two new replication-competent avian sarcoma/leukosis virus-based retroviral vectors with amphotropic and ecotropic host ranges. The amphotropic vector RCASBP-M2C(797-8), was obtained by passaging the chimeric retroviral vector RCASBP-M2C(4070A) (6) in chicken embryos. The ecotropic vector, RCASBP(Eco), was created by replacing the env-coding region in the retroviral vector RCASBP(A) with the env region from an ecotropic murine leukemia virus. It replicates efficiently in avian DFJ8 cells that express murine ecotropic receptor. For both vectors, permanent cell lines that produce viral stocks with titers of about 5 x 10(6) CFU/ml on mammalian cells can be easily established by passaging transfected avian cells. Some chimeric viruses, for example, RCASBP(Eco), replicate efficiently without modifications. For those chimeric viruses that do require modification, adaptation by passage in vitro or in vivo is a general strategy. This strategy has been used to prepare vectors with altered host range and could potentially be used to develop vectors that would be useful for targeted gene delivery.

Coreceptor requirements of primary HIV type 1 group O isolates from Cameroon

HIV-1 group O has its epicenter in Cameroon and neighboring countries and is responsible for 3 to 5% of all HIV infections in this region. It is believed that HIV-1 group O was introduced into the human population by a separate cross-species transmission, occurring independently of the HIV-1 (group M and group N) and HIV-2 transmissions. We have studied the coreceptor requirements of 12 primary HIV-1 O-type isolates from individuals with different clinical symptoms. Only 2 of these 12 viruses showed a syncytium-inducing phenotype after infection of primary peripheral blood mononuclear cells (PBMCs) and were infectious for the T cell line C8166. These isolates used CXCR4 as a coreceptor for entry, whereas the remaining isolates used only CCR5 efficiently. One isolate was able to use BOB and CCR8 as coreceptors in addition to CXCR4. All group O isolates tested were efficiently inhibited by SDF-1 or RANTES, the natural ligands of CXCR4 and CCR5, respectively. These results indicate that CXCR4 and CCR5 are the principal coreceptors for HIV-1 O-type viruses. Most of the HIV-1 group O isolates studied were derived from patients at later stages of the disease. Although HIV-1 group O and group M infections do not differ in their pathogenesis, the studied isolates did not evolve to use a broad range of coreceptors as described for HIV-1 group M and HIV-2.

Cell-surface heparan sulfate facilitates human immunodeficiency virus Type 1 entry into some cell lines but not primary lymphocytes

Many viruses have evolved to exploit cell-surface glycosaminoglycans (GAG), particularly heparan sulfate, to facilitate their attachment and infection of host cells. Here, the case for the involvement of heparan sulfate GAG in cellular infection by human immunodeficiency virus Type 1 (HIV-1) compared with herpes simplex virus Type 1 (HSV-1) is re-examined. It is shown that HIV-1 infection is facilitated by heparan sulfate GAG in only one of three highly permissive cell lines tested, whereas HSV-1 infection is facilitated to varying extents in all three. To evaluate the physiological relevance of these findings, primary peripheral blood lymphocytes (PBL), the physiological host for HIV-1, were examined. It was found that treatment of PBL with heparitinase, to remove any traces of heparan sulfate GAG, did not alter their sensitivity to infection by either lymphocyte-tropic, X4-type strain HIV-1IIIB, nor the monocyte-tropic, R5-type strain, HIV-1Ba-L. It is concluded that heparan sulfate GAG has little physiological role in the infection of lymphocytes by HIV-1 and that evidence derived from studies on immortalized cell lines suggesting a significant role must be interpreted with caution.

Biological characterization of human immunodeficiency virus type 1 clones derived from different organs of an AIDS patient by long-range PCR

In order to characterize the biological properties of human immunodeficiency virus type 1 (HIV-1) variants from different tissues (peripheral blood mononuclear cells [PBMC], lymph node, spleen, brain, and lung) of one patient, we have chosen long-range PCR to amplify virtually full-length HIV proviruses and to construct replication-competent viruses by adding a patient-specific 5' long terminal repeat. To avoid selection during propagation in CD4+ target cells, we transfected 293 cells and used the supernatants from these cells as challenge viruses for tropism studies after titration on human PBMC. Despite differences in the V3 loop of the major variants found in brain and lung compared to lymphoid tissues all recombinant HIV clones obtained showed identical cell tropism and replicative kinetics. After infection of human PBMC these viruses replicated with similar kinetics, with a slow/low-titer, non-syncytium-inducing phenotype. In contrast to the prediction of macrophage tropism, drawn from the V3 loop sequence, none of these viruses infected monocyte-derived macrophages. The challenge of blood dendritic cells by these recombinant viruses in the presence of tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor, and interleukin-4 resulted in a productive infection only after adding stimulated CD4+ T lymphocytes. Therefore, the biological properties of the HIV-1 variants derived from nonlymphoid tissue of this patient did not differ from those of HIV-1 variants from lymphoid tissue with respect to tropism for primary cells such as PBMC, macrophages, and blood dendritic cells.

Gene therapy for ovarian cancer: development of novel treatment strategies

In the last decade, advances in molecular biology have lead to the development of techniques that permit the manipulation of mammalian cell DNA for diagnostic and therapeutic purposes. Gene therapy has subsequently evolved as a treatment option in patients with malignancies. In this article, we have summarized current strategies in gene therapy for ovarian cancer.

The bicyclams, a new class of potent human immunodeficiency virus inhibitors, block viral entry after binding

The bicyclams represent a new class of highly potent and selective HIV inhibitors. Time-of-addition experiments have previously shown that these compounds interfere with an early event in the viral replicative cycle. Additional experiments have now been carried out in order to investigate in more detail the mechanism of action of these promising compounds. As described in this paper, PCR experiments revealed that no viral DNA was formed following viral infection, thus confining the target(s) of action of the bicyclams to an early stage of HIV infection. An assay, using pseudotype virions containing the envelope of HIV-1 and the genome of a plaque-forming virus (Cocal Virus), pointed to viral entry as the main target of the bicyclams. HIV-1 strains resistant to two prototype bicyclams, JM2763 and SID791 (JM3100), were raised. Results obtained with SID791 with respect to syncytium formation induced by SID791-sensitive and -resistant HIV-1 strains and the cross-resistance observed for dextran sulfate, suggest inhibition of binding and/or fusion as a plausible target of SID791. Additional experiments enabled us to exclude SID791 and JM2763 as binding inhibitors and to conclude that bicyclams block the entry of cell-bound virus. Furthermore, a monoclonal antibody recognising the V3 loop of wild-type gp120 did not bind to this region in the two bicyclam-resistant strains. Our results point to gp120 as a possible target for the HIV-inhibitory effects of the bicyclams.

The alpha-glucosidase inhibitor N-butyldeoxynojirimycin inhibits human immunodeficiency virus entry at the level of post-CD4 binding

The alpha-glucosidase inhibitor N-butyldeoxynojirimycin (NB-DNJ) is a potent inhibitor of human immunodeficiency virus (HIV) replication and syncytium formation in vitro. However, the exact mechanism of action of NB-DNJ remains to be determined. In this study we have examined the impairment of HIV infectivity mediated by NB-DNJ. By two independent HIV entry assays [PCR-based HIV entry assay and entry of Cocal(HIV) pseudotypes], the reduction in infectivity was found to be due to an impairment of viral entry. No effect of NB-DNJ treatment was seen on the kinetics of the interaction between gp120 and CD4 (surface plasmon resonance; BIAcore) or on the binding of virus particles to H9 cells (using radiolabeled virions). We therefore conclude that a major mechanism of action of NB-DNJ as an inhibitor of HIV replication is the impairment of viral entry at the level of post-CD4 binding, due to an effect on viral envelope components.