eCD4-Ig promotes ADCC activity of sera from HIV-1-infected patients.

Antibody-dependent cell-mediated cytotoxity (ADCC) can eliminate HIV-1 infected cells, and may help reduce the reservoir of latent virus in infected patients. Sera of HIV-1 positive individuals include a number of antibodies that recognize epitopes usually occluded on HIV-1 envelope glycoprotein (Env) trimers. We have recently described eCD4-Ig, a potent and exceptionally broad inhibitor of HIV-1 entry that can be used to protect rhesus macaques from multiple high-dose challenges with simian-human immunodeficiency virus AD8 (SHIV-AD8). Here we show that eCD4-Ig bearing an IgG1 Fc domain (eCD4-IgG1) can mediate efficient ADCC activity against HIV-1 isolates with differing tropisms, and that it does so at least 10-fold more efficiently than CD4-Ig, even when more CD4-Ig molecules bound cell surface-expressed Env. An ADCC-inactive IgG2 form of eCD4-Ig (eCD4-IgG2) exposes V3-loop and CD4-induced epitopes on cell-expressed trimers, and renders HIV-1-infected cells susceptible to ADCC mediated by antibodies of these classes. Moreover, eCD4-IgG2, but not IgG2 forms of the broadly neutralizing antibodies VRC01 and 10-1074, enhances the ADCC activities of serum antibodies from patients by 100-fold, and significantly enhanced killing of two latently infected T-cell lines reactivated by vorinostat or TNFα. Thus eCD4-Ig is qualitatively different from CD4-Ig or neutralizing antibodies in its ability to mediate ADCC, and it may be uniquely useful in treating HIV-1 infection or reducing the reservoir of latently infected cells.

Dose-response curve slope helps predict therapeutic potency and breadth of HIV broadly neutralizing antibodies.

A new generation of HIV broadly neutralizing antibodies (bnAbs) with remarkable potency, breadth and epitope diversity has rejuvenated interest in immunotherapeutic strategies. Potencies defined by in vitro IC50 and IC80 values (50 and 80% inhibitory concentrations) figure prominently into the selection of clinical candidates; however, much higher therapeutic levels will be required to reduce multiple logs of virus and impede escape. Here we predict bnAb potency at therapeutic levels by analysing dose-response curve slopes, and show that slope is independent of IC50/IC80 and specifically relates to bnAb epitope class. With few exceptions, CD4-binding site and V3-glycan bnAbs exhibit slopes >1, indicative of higher expected therapeutic effectiveness, whereas V2-glycan, gp41 membrane-proximal external region (MPER) and gp120-gp41 bnAbs exhibit less favourable slopes <1. Our results indicate that slope is one major predictor of both potency and breadth for bnAbs at clinically relevant concentrations, and may better coordinate the relationship between bnAb epitope structure and therapeutic expectations.

Treatment of advanced human immunodeficiency virus type 1 disease with the viral entry inhibitor PRO 542.

Viral entry inhibitors represent an emerging mode of therapy for human immunodeficiency virus type 1 (HIV-1) infection. PRO 542 (CD4-immunoglobulin G2) is a tetravalent CD4-immunoglobulin fusion protein that broadly neutralizes primary HIV-1 isolates. PRO 542 binds to the viral surface glycoprotein gp120 and blocks attachment and entry of virus into CD4(+) cells. Previously, PRO 542 demonstrated antiviral activity without significant toxicity when tested at single doses ranging to 10 mg/kg. In this study, 12 HIV-infected individuals were treated with 25-mg/kg single-dose PRO 542 and then monitored for safety, antiviral effects, and PRO 542 pharmacokinetics for 6 weeks. The study examined two treatment cohorts that differed in the extent of HIV-1 disease progression. PRO 542 at 25 mg/kg was well tolerated and demonstrated a serum half-life of 3 days. Statistically significant acute reductions in HIV-1 RNA levels were observed across all study patients, and greater antiviral effects were observed in the cohort of patients with more advanced HIV-1 disease. In advanced disease (HIV-1 RNA > 100,000 copies/ml; CD4 lymphocytes < 200 cells/mm(3)), PRO 542 mediated an 80% response rate and statistically significant approximately 0.5 log(10) mean reductions in viral load for 4 to 6 weeks posttreatment. Similar findings were obtained in an analysis of all (n = 11) advanced disease patients treated to date with single doses of PRO 542 ranging from 1 to 25 mg/kg. In addition, a significant correlation was observed between antiviral effects observed in vivo and viral susceptibility to PRO 542 in vitro. The findings support continued development of PRO 542 for salvage therapy of advanced HIV-1 disease.

Gene therapy for human immunodeficiency virus infection in the humanized SCID mouse model.

BACKGROUND: The humanized SCID mouse model is an attractive tool for testing gene therapy to combat human immunodeficiency virus infection in vivo. OBJECTIVES: To devise a more specific gene therapy directed against HIV, replacing the formerly used interferon with either soluble CD4 molecule immunoadhesin (sCD4-IgG) and/or anti-gp41 monoclonal antibody (2F5), or HIV-negative transdominants genes (Tat, Rev). METHODS: Human monocytoid cell line (U937) was transfected with IFN alpha, beta or gamma genes. 3T3 murine fibroblastic cell line was transfected with sCD4-IgG or 2F5, or both genes, and a human T4 cell line (CEM) was grafted to SCID mice. Negative transdominant genes (Tat, Rev or both) were also transduced in CEM T cell line. Animals were then challenged with HIV-1, Viral load was followed. RESULTS: IFN alpha or beta were potent anti-HIV, reducing viral load in vivo and inhibiting reverse transcriptase activity in human-removed cells from animals. sCD4-IgG immunoadhesin and gp41 monoclonal antibody resulted in a dramatic reduction of HIV-1 cellular and plasmatic viral load in humanized SCID mice. The simultaneous introduction of negative Tat and Rev genes resulted in a synergistic inhibition of HIV-1 replication in vivo. CONCLUSIONS: Despite the marked reduction of HIV-1 propagation by IFN genes or by negative Tat and Rev transdominants, the gene therapy using soluble CD4 immunoadhesin or anti-gp41 was a more efficient preventive treatment against HIV infection.

A modified SCID mouse model of HIV infection with utility for testing anti-HIV therapies.

Using human tumor cells we have developed a mouse model of active HIV infection that may be used for testing antiviral agents, although it does not reflect the pathogenesis of human infection. Irradiated SCID/NOD mice are injected with a tumor of human CD4+ lymphoma cells susceptible to infection and at a separate site, tumor cells persistently infected with either primary or T cell line-adapted strains of HIV. The spread of infection from the infected to the susceptible tumor is monitored as plasma p24 and the presence of HIV-infected cells in the spleen. We have used this model to examine the relative efficacy of neutralizing anti-HIV antibodies to halt the spread of infection. We have found that the tetrameric CD4-antibody fusion protein, CD4-IgG2, is highly effective compared to an anti-V3 loop antibody. This animal model, while not replicating the human disease, allows for the simultaneous testing of efficacy, toxicity, and pharmacokinetics of potential new antiviral therapies. The model can easily be powered to enable comparisons between different therapeutic agents and dosing regimens.

In vivo efficacy of anti-glycoprotein 41, but not anti-glycoprotein 120, immunotoxins in a mouse model of HIV infection.

Immunotoxins (ITs) targeting the HIV envelope protein are among the most efficacious antiviral therapies when tested in vitro. Yet a first-generation IT targeted to gp120, CD4-PE40 (chimeric immunotoxin using CD4 and the translocation and enzymatic domains of Pseudomonas exotoxin A), showed limited promise in initial clinical testing, highlighting the need for improved ITs. We have used a new mouse model of HIV infection to test the comparative efficacy of anti-HIV ITs targeted to gp120 or to gp41. Irradiated SCID/nonobese diabetic mice are injected with a tumor of human CD4(+) cells susceptible to infection and at a separate site persistently HIV-infected cells. The spread of infection from infected to susceptible tumor is monitored by plasma p24 and the presence of HIV-infected cells in the spleen. Anti-gp41 ITs in combination with tetrameric CD4-human Ig fusion protein have pronounced anti-HIV effects. Little if any anti-HIV efficacy was found with either CD4-PE40 or an Ab-targeted anti-gp120 IT. These data support continued exploration of the utility of ITs for HIV infection, particularly the use of anti-gp41 ITs in combination with soluble CD4 derivatives.

Recombinant CD4-IgG2 in human immunodeficiency virus type 1-infected children: phase 1/2 study. The Pediatric AIDS Clinical Trials Group Protocol 351 Study Team.

The use of recombinant CD4-IgG2 in pediatric human immunodeficiency virus type 1 (HIV-1) infection was evaluated by single and multidose intravenous infusions in 18 children in a phase 1/2 study. The study drug was well tolerated, and dose proportionality was observed in terms of area under time-concentration curve and peak serum concentration. Acute decreases of >0.7 log(10) copies/mL in serum HIV-1 RNA concentration were seen in 4 of the 6 children treated with 4 weekly 10 mg/kg doses. At 14 days after treatment, 3 children had sustained reductions in serum HIV-1 RNA; the other children had rebounded to baseline levels or above. By 28 days after therapy, the peak HIV-1 cellular infectious units was reduced in all 6 children, including the 2 who had experienced an earlier transient increase in values. Thus, recombinant CD4-IgG2 treatment of HIV-1-infected children appears to be well tolerated and capable of reducing HIV-1 burden.

Single-dose safety, pharmacology, and antiviral activity of the human immunodeficiency virus (HIV) type 1 entry inhibitor PRO 542 in HIV-infected adults.

PRO 542 (CD4-IgG2) is a recombinant antibody-like fusion protein wherein the Fv portions of both the heavy and light chains of human IgG2 have been replaced with the D1D2 domains of human CD4. Unlike monovalent and divalent CD4-based proteins, tetravalent PRO 542 potently neutralizes diverse primary human immunodeficiency virus (HIV) type 1 isolates. In this phase 1 study, the first evaluation of this compound in humans, HIV-infected adults were treated with a single intravenous infusion of PRO 542 at doses of 0.2-10 mg/kg. PRO 542 was well tolerated, and no dose-limiting toxicities were identified. Area under the concentration-time curve, and peak serum concentrations increased linearly with dose, and a terminal serum half-life of 3-4 days was observed. No patient developed antibodies to PRO 542. Preliminary evidence of antiviral activity was observed as reductions in both plasma HIV RNA and plasma viremia. Sustained antiviral effects may be achieved with repeat dosing with PRO 542.

Nutrición y SIDA / Nutrition and AIDS

La infección por el VIH en la infancia es un importante problema sanitario. Se calcula que cada año nacen 400-600 hijos de madres seropositivas.El diagnóstico precoz de la infección por el VIH en el niño, es de gran importancia para instaurar lo antes posible tratamiento antirretroviral, profilaxis de infecciones oportunistas, inmunización activa y pasiva, así como un soporte psicosocial y nutricional adecuado.Estos niños presentan una disregulación en el metabolismo de las citocinas que parecen jugar un importante papel en la malnutrición, la cual es de etiología multifactorial y puede presentarse en cualquier momento evolutivo de la enfermedad.Sería importante determinar los índices nutricionales con mayor poder discriminativo para valorar la malnutrición; pues se ha encontrado una correlación entre el deterioro de la situación clínica, inmunológica y nutricional.Las nuevas estrategias terapéuticas de la desnutrición en niños con infección por VIH, se basan en la administración de acetato de megestrol y hormona de crecimiento cuyo efecto parece ser beneficioso (AU)

Gene transfer of anti-gp41 antibody and CD4 immunoadhesin strongly reduces the HIV-1 load in humanized severe combined immunodeficient mice.

OBJECTIVE: To study the anti-HIV-1 effects of the delivery of anti-gp41 monoclonal antibody (mAb) and soluble CD4 (sCD4) immunoadhesin by genetically modified cells in HIV-1-infected, humanized severe combined immunodeficient (SCID) mice. DESIGN: The complementary DNA of mAb 2F5, an anti-HIV-1 gp41 antibody, and of sCD4-IgG chimeric immunoadhesin were transferred into 3T3 cells using Moloney murine leukaemia virus vectors. The cells were then incorporated into a collagen structure called the neo-organ, which allowed the continuous production of the therapeutic molecules. METHODS: The antiviral effects in vivo of 2F5 or sCD4-IgG or both compounds were evaluated in neo-organ-implanted SCID mice that were grafted with human CD4 CEM T cells and challenged with HIV-1 Lai or MN. RESULTS: In SCID mice implanted with 2F5 neo-organs, antibody plasma levels reached 500-2000 ng/ml. Viral loads after HIV-1 challenge were significantly reduced in neo-organ-implanted HIV-infected mice. Although 29 x 10(7) and 13 x 10(8) HIV-1-RNA copies/ml were detected at 12 days in the controls (mice injected with Lai and MN, respectively) less than 16.5 x 10(3) HIV-1-RNA copies/ml were observed in all implanted mice injected with either Lai or MN. The intracellular viral load was also reduced in CD4 cells recovered from the implanted mice. Comparable antiviral effects were obtained with CD4-IgG neo-organs. CONCLUSION: Our results confirm the anti-HIV properties of 2F5 and sCD4-IgG continuously produced in vivo after ex-vivo gene therapy in SCID mice.

Technology evaluation: PRO-542, Progenics Pharmaceuticals inc.

Progenics's rCD4-IgG2 (PRO-542) is a recombinant fusion protein, which has been developed using the company's Universal Antiviral Binding (UnAB) technology, and is in phase I/II clinical trials for the treatment of human immunodeficiency virus type I (HIV-1) infection [273391]. At the beginning of 1997, Progenics received a Phase II Small Business Innovation Research Program (SBIR) grant from the National Institute of Allergy and Infectious diseases (NIAID) to fund the development of PRO-542 [236048]. A further grant of $2.7 million was awarded in August 1998 for the clinical evaluation of PRO-542 and other anti-HIV therapies [294200]. Progenics is collaborating with the Aaron Diamond AIDS Research Center (ADARC) in New York and the Center for Disease Control and Prevention in Atlanta [178410]. In February 2000, Progenics and Genzyme Transgenics Corp signed an agreement to continue the development of a transgenic source of PRO-542. Genzyme will develop transgenic goats that produce PRO-542 in their milk in exchange for undisclosed fees and milestone payments. Genzyme will supply PRO-542 to Progenics for clinical trials with a possibility for eventual commercial supply [357291]. Following on from this, in October 2000, Progenics received an SBIR grant to fund a two-year project with Genzyme Transgenics into the development of cost-effective methods for the manufacture of PRO-542, by optimization of the production of the drug in the milk of transgenic dairy animals [385982]. In August 2000, Punk, Ziegel & Company predicted that Progenics Pharmaceuticals will become sustainably profitable in 2003 following the launch of PRO-542 and GMK (Progenics Pharmaceuticals) in 2002 [390063].

The relationship between pityriasis rubra pilaris and inflammatory arthritis: case report and response of the arthritis to anti-tumor necrosis factor immunotherapy.

Pityriasis rubra pilaris (PRP) refers to a group of erythematous, scaling dermatologic conditions that have been associated with seronegative arthritis. We report a case of polyarthritis in a young man with PRP in which magnetic resonance imaging suggested an entheseal-based pathology for the joint disease. The arthritis, but not the skin condition, demonstrated dramatic response to anti-tumor necrosis factor immunotherapy.

Immunoadhesins as research tools and therapeutic agents.

An immunoadhesin is a fusion protein that combines the target-binding region of a receptor, an adhesion molecule, a ligand, or an enzyme, with the Fc region of an Ig. Immunoadhesins provide a unique tool for identifying unknown binding targets and for elucidating molecular interactions that control biological function. Recent studies suggest that immunoadhesins also may be useful therapeutically, as inhibitors of autoimmune and inflammatory diseases.

Influence of endosome-destabilizing peptides on efficacy of anti-HIV immunotoxins.

The effects on immunotoxin efficacy of fusogenic peptides derived from influenza virus hemagglutinin have been studied. These peptides have an amphipathic nature and change conformation from random at pH 7 to helical at pH 5. Fusogenic peptides are reported to destabilize endosomal membranes, resulting in the release of contents into the cytoplasm. The use of two related fusogenic peptides to enhance the efficacy of anti-HIV immunotoxins is described. The direct toxicity of the peptides was tested on HIV-infected H9/NL4-3 cells. Peptide HA24 was considerably more toxic than HA23. The peptides were mixed with two different immunotoxins. Immunotoxin action was enhanced by both peptides, with HA24 providing greater enhancement than HA23. Immunotoxins were then constructed by coupling HA23 or HA24 to the targeting antibody with disulfide-containing linkers. Peptide HA23 enhanced the activity of the immunotoxin 4-5-fold. Surprisingly, HA24 significantly inhibited immunotoxin activity. Coupling the peptides to the immunotoxin had no effect on antigen binding characteristics or the activity of the toxic moiety. Bafilomycin A1, an agent that inhibits vacuolar acidification, markedly potentiated the effects of all immunotoxins. These results demonstrate that amphipathic peptides can influence the efficacy of immunotoxins, but in sometimes unpredictable ways.

Treatment of severe cutaneous lupus erythematosus with a chimeric CD4 monoclonal antibody, cM-T412.

BACKGROUND: Monoclonal CD4 antibodies are among the most potent immunomodulatory agents in various experimental models of autoimmune disease, including murine lupus erythematosus. OBJECTIVE: The aim of this study was to evaluate the toxicity and therapeutic efficacy of a chimeric monoclonal CD4 antibody, cM-T412, in patients with cutaneous lupus erythematosus (LE). METHODS: Five patients with severe cutaneous LE lesions received intravenously a total of 275, 400, or 475 mg of cM-T412 in single doses of 20 to 50 mg during a period of 5 to 8 weeks. RESULTS: CD4 antibody treatment induced a long-lasting decrease in disease activity. It resulted in healing of LE skin lesions, a reconstituted responsiveness to conventional treatment, or both. Despite a substantial depletion of circulating CD4+ T lymphocytes, no clinical signs of immunosuppression were noted. CONCLUSION: Monoclonal CD4 antibodies should be considered as a novel treatment for the management of severe cutaneous LE.