Rafael Delgado

C-Type Lectins DC-SIGN and L-SIGN Mediate Cellular Entry by Ebola Virus in cis and in trans

ABSTRACT Ebola virus is a highly lethal pathogen responsible for several outbreaks of hemorrhagic fever. Here we show that the primate lentiviral binding C-type lectins DC-SIGN and L-SIGN act as cofactors for cellular entry by Ebola virus. Furthermore, DC-SIGN on the surface of dendritic cells is able to function as a trans receptor, binding Ebola virus-pseudotyped lentiviral particles and transmitting infection to susceptible cells. Our data underscore a role for DC-SIGN and L-SIGN in the infective process and pathogenicity of Ebola virus infection.

Membrane raft microdomains mediate lateral assemblies required for HIV-1 infection

HIV‐1 infection triggers lateral membrane diffusion following interaction of the viral envelope with cell surface receptors. We show that these membrane changes are necessary for infection, as initial gp120–CD4 engagement leads to redistribution and clustering of membrane microdomains, enabling subsequent interaction of this complex with HIV‐1 co‐receptors. Disruption of cell membrane rafts by cholesterol depletion before viral exposure inhibits entry by both X4 and R5 strains of HIV‐1, although viral replication in infected cells is unaffected by this treatment. This inhibitory effect is fully reversed by cholesterol replenishment of the cell membrane. These results indicate a general mechanism for HIV‐1 envelope glycoprotein‐mediated fusion by reorganization of membrane microdomains in the target cell, and offer new strategies for preventing HIV‐1 infection.

Filamin-A regulates actin-dependent clustering of HIV receptors

Human immunodeficiency virus (HIV)-1 infection requires envelope (Env) glycoprotein gp120-induced clustering of CD4 and coreceptors (CCR5 or CXCR4) on the cell surface; this enables Env gp41 activation and formation of a complex that mediates fusion between Env-containing and target-cell membranes. Kinetic studies show that viral receptors are actively transported to the Env-receptor interface in a process that depends on plasma membrane composition and the actin cytoskeleton. The mechanisms by which HIV-1 induces F-actin rearrangement in the target cell remain largely unknown. Here, we show that CD4 and the coreceptors interact with the actin-binding protein filamin-A, whose binding to HIV-1 receptors regulates their clustering on the cell surface. We found that gp120 binding to cell receptors induces transient cofilin-phosphorylation inactivation through a RhoA–ROCK-dependent mechanism. Blockade of filamin-A interaction with CD4 and/or coreceptors inhibits gp120-induced RhoA activation and cofilin inactivation. Our results thus identify filamin-A as an adaptor protein that links HIV-1 receptors to the actin cytoskeleton remodelling machinery, which may facilitate virus infection.

Lopinavir-ritonavir monotherapy versus lopinavir-ritonavir and two nucleosides for maintenance therapy of HIV.

Background:Prior attempts to reduce the number of drugs needed to maintain viral suppression in patients with suppressed HIV replication while receiving three antiretroviral drugs have been unsuccessful. Methods:In 205 patients with suppressed HIV replication on lopinavir-ritonavir and two nucleosides, this randomized, open-label, non-inferiority clinical trial compared the strategies of continuation of triple therapy versus lopinavir-ritonavir monotherapy followed by reinduction with two nucleosides if virological rebound occurred without genotypic resistance to lopinavir-ritonavir. The primary endpoint was proportion of patients without therapeutic failure, defined as confirmed HIV RNA higher than 500 copies/mL (with exclusion of patients receiving monotherapy who resuppressed to < 50 copies/mL after resuming baseline nucleosides), or loss to follow-up, or change of randomized therapy other than reinduction. Results:At week 48, the percentage of patients without therapeutic failure was 94% in the monotherapy group versus 90% in the triple therapy group (difference,-4%; upper limit of 95% confidence interval for difference, 3.4%). The percentage of patients with HIV RNA 50 copies/mL at 48 weeks by intention-to-treat, missing data or reinductions considered as failures, were 85% in the monotherapy group versus 90% in the triple therapy group (P = 0.31; 95% upper limit of 95% confidence interval for difference, 14%). Conclusion:In this trial, 48 weeks of lopinavir-ritonavir monotherapy with reintroduction of nucleosides as needed was non-inferior to continuation of two nucleosides and lopinavir-ritonavir in patients with prior stable suppression. However, episodes of low level viremia were more common in patients receiving monotherapy. (ClinicalTrials. gov number, NCT00114933).

GENERATION OF RETROVIRAL VECTOR FOR CLINICAL STUDIES USING TRANSIENT TRANSFECTION

Transient transfection of 293T cells was utilized to produce high-titer murine recombinant retroviral vectors for clinical studies. This system was initially optimized by gene transfer using different retroviral envelope proteins into activated human CD4+ T lymphocytes in vitro. Higher titer and infectivity were obtained than with stable murine producer lines; titers of 0.3-1 x 10(7) infectious units per milliliter for vectors encoding the green fluorescent protein (GFP) were achieved. Virions pseudotyped with envelope proteins from gibbon ape leukemia virus or amphotropic murine leukemia virus resulted in gene transfer of > or = 50% in CD4+ human T lymphocytes with this marker. Gene transfer of Rev M10 with this vector conferred resistance to HIV infection compared with negative controls in the absence of drug selection. Thus, the efficiency of transduction achieved under these conditions obviated the need to include selection to detect biologic effects in T cells. Finally, a protocol for the production of large-scale supernatants using transient transfection was optimized up to titers of 1.9 x 10(7) IU/ml. These packaging cells can be used to generate high-titer virus in sufficient quantities for clinical studies and will facilitate the rapid, cost-effective generation of improved retroviral, lentiviral, or other viral vectors for human gene therapy.

Lopinavir-ritonavir monotherapy versus lopinavir-ritonavir and 2 nucleosides for maintenance therapy of HIV: 96-week analysis.

Background:The OK04 trial has shown that 48 weeks of lopinavir-ritonavir monotherapy with reintroduction of nucleosides as needed was noninferior to continuation of triple therapy with 2 nucleosides and lopinavir-ritonavir in patients with prior stable suppression. However, it is still uncertain if this experimental strategy can maintain suppression in the long term. Methods:Patients entered this noninferiority trial (upper limit 95% confidence interval: +12%) with no history of virological failure while receiving a protease inhibitor and receiving 2 nucleosides plus lopinavir/ritonavir, with HIV RNA <50 copies per milliliter for more than 6 months. Primary end point was percent of patients without therapeutic failure, defined as confirmed HIV RNA >500 copies per milliliter with exclusion of monotherapy patients who resuppressed to <50 copies per milliliter after resuming baseline nucleosides, or loss to follow-up, or change of randomized therapy other than reinduction. Results:Through 96 weeks, percentage of patient without therapeutic failure was 87% (monotherapy, n = 100) vs. 78% (triple therapy, n = 98; 95% confidence interval: −20% to +1.2%). Percentage with HIV RNA <50 copies per milliliter (intention to treat, missing = failure, reinduction = failure): 77% (monotherapy) vs. 78% (triple therapy). Low-level viral rebound was more frequent in the monotherapy group. Twelve patients in the monotherapy group (12%) needed reinduction with nucleosides. Discontinuations due to adverse events were significantly more frequent in the triple therapy group (8%) than in the monotherapy group (0%); P = 0.003. Conclusions:At 96-week lopinavir/ritonavir monotherapy with reintroduction of nucleosides as needed was noninferior to continuation of triple therapy. Incidence of adverse events leading to treatment discontinuation was significantly lower with monotherapy. (ClinicalTrials.gov number, NCT00114933).

Mannosyl glycodendritic structure inhibits DC-SIGN-mediated Ebola virus infection in cis and in trans.

ABSTRACT We have designed a glycodendritic structure, BH30sucMan, that blocks the interaction between dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) and Ebola virus (EBOV) envelope. BH30sucMan inhibits DC-SIGN-mediated EBOV infection at nanomolar concentrations. BH30sucMan may counteract important steps of the infective process of EBOV and, potentially, of microorganisms shown to exploit DC-SIGN for cell entry and infection.

Glycofullerenes inhibit viral infection.

Water-soluble glycofullerenes based on a hexakis-adduct of [60]fullerene with an octahedral addition pattern are very attractive compounds providing a spherical presentation of carbohydrates. These tools have been recently described and they have been used to interact with lectins in a multivalent manner. Here, we present the use of these glycofullerenes, including new members with 36 mannoses, as compounds able to inhibit a DC-SIGN-dependent cell infection by pseudotyped viral particles. The results obtained in these experiments demonstrate for the first time that these glycoconjugates are adequate to inhibit efficiently an infection process, and therefore, they can be considered as very promising and interesting tools to interfere in biological events where lectins such as DC-SIGN are involved.

Rapid Detection of Herpes Simplex Virus DNA in Genital Ulcers by Real-Time PCR Using SYBR Green I Dye as the Detection Signal

ABSTRACT We have evaluated a real-time PCR procedure based on the LightCycler technology for rapid detection of herpes simplex virus (HSV) in genital lesions. Two sets of primers, corresponding to the thymidine kinase and DNA polymerase regions, were used for the amplification reactions in separate capillaries containing the SYBR Green I dye as detection signal. In 28 of 118 samples (24%), HSV was isolated by conventional cell culture. All cell culture-positive samples were also positive by real-time PCR. Six additional cell culture-negative samples were positive by PCR with both sets of primers. Total processing time was less than 3 h. Real-time PCR using SYBR Green I as detection signal is a sensitive procedure for the rapid diagnosis of HSV in genital lesions.

Pseudosaccharide Functionalized Dendrimers as Potent Inhibitors of DC-SIGN Dependent Ebola Pseudotyped Viral Infection

The development of compounds with strong affinity for the receptor DC-SIGN is a topic of remarkable interest due to the role that this lectin plays in several pathogen infection processes and in the modulation of the immune response. DC-SIGN recognizes mannosylated and fucosylated oligosaccharides in a multivalent manner. Therefore, multivalent carbohydrate systems are required to interact in an efficient manner with this receptor and compete with the natural ligands. We have previously demonstrated that linear pseudodi- and pseudotrisaccharides are adequate ligands for DC-SIGN. In this work, we show that multivalent presentations of these glycomimetics based on polyester dendrons and dendrimers lead to very potent inhibitors (in the nanomolar range) of cell infection by Ebola pseudotyped viral particles by blocking DC-SIGN receptor. Furthermore, SPR model experiments confirm that the described multivalent glycomimetic compounds compete in a very efficient manner with polymannosylated ligands for binding to DC-SIGN.