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Ocular distribution, spectrum of activity, and in vivo viral neutralization of a fully humanized anti-herpes simplex virus IgG Fab fragment following topical application.

ABSTRACT: Herpes simplex ocular infection is a major cause of corneal blindness. Local antiviral treatments exist but are associated with corneal toxicity, and resistance has become an issue. We evaluated the biodistribution and efficacy of a humanized anti-herpes simplex virus (anti-HSV) IgG FAb fragment (AC-8; 53 kDa) following repeated topical administration. AC-8 was found in the corneal epithelium, anterior stroma, subepithelial stromal cells, and retinal glial cells, with preferential entry through the ocular limbus. AC-8 was active against 13 different strains of HSV-1, with 50% and 90% mean effective concentrations (MEC(50) and MEC(90), respectively) ranging from 0.03 to 0.13 μg/ml, indicating broad-spectrum activity. The in vivo efficacy of AC-8 was evaluated in a mouse model of herpes-induced ocular disease. Treatment with low-dose AC-8 (1 mg/ml) slightly reduced the ocular disease scores. A greater reduction of the disease scores was observed in the 10-mg/ml AC-8-treated group, but not as much as with trifluridine (TFT). AC-8 treatment reduced viral titers but less than trifluridine. AC-8 did not display any toxicity to the cornea or other structures in the eye. In summary, topical instillation of an anti-HSV FAb can be used on both intact and ulcerated corneas. It is well tolerated and does not alter reepithelialization. Further studies to improve the antiviral effect are needed for AC-8 to be considered for therapeutic use.

SUBMITTER: Berdugo M

PROVIDER: S-EPMC3294958 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Ocular distribution, spectrum of activity, and in vivo viral neutralization of a fully humanized anti-herpes simplex virus IgG Fab fragment following topical application.

Berdugo Marianne M Larsen Inna V IV Abadie Claire C Deloche Catherine C Kowalczuk Laura L Touchard Elodie E Dubielzig Richard R Brandt Curtis R CR Behar-Cohen Francine F Combette Jean-Marc JM

Antimicrobial agents and chemotherapy 20111227 3

Herpes simplex ocular infection is a major cause of corneal blindness. Local antiviral treatments exist but are associated with corneal toxicity, and resistance has become an issue. We evaluated the biodistribution and efficacy of a humanized anti-herpes simplex virus (anti-HSV) IgG FAb fragment (AC-8; 53 kDa) following repeated topical administration. AC-8 was found in the corneal epithelium, anterior stroma, subepithelial stromal cells, and retinal glial cells, with preferential entry through ...[more]

PMID: 22203590

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Project description:Study questionHow does the placenta protect the fetus from immune rejection by the mother?Summary answerThe placenta can produce IgG that is glycosylated at one of its Fab arms (asymmetric IgG; aIgG) which can interact with other antibodies and certain leukocytes to affect local immune reactions at the junction between the two genetically distinct entities.What is known alreadyThe placenta can protect the semi-allogenic fetus from immune rejection by the immune potent mother. aIgG in serum is increased during pregnancy and returns to the normal range after giving birth. aIgG can react to antigens to form immune complexes which do not cause a subsequent immune effector reaction, including fixing complements, inducing cytotoxicity and phagocytosis, and therefore has been called 'blocking antibody'.Study design, size, durationEighty-eight human placentas, four trophoblast cell lines (TEV-1, JAR, JEG and BeWo), primary culture of human placental trophoblasts and a gene knock-out mouse model were investigated in this study.Participants/materials, setting, methodsThe general approach included the techniques of cell culture, immunohistochemistry, in situ hybridization, immuno-electron microscopy, western blot, quantitative PCR, protein isolation, glycosylation analysis, enzyme digestion, gene sequencing, mass spectrophotometry, laser-guided microdissection, enzyme-linked immunosorbent assay, pulse chase assay, double and multiple staining to analyze protein and DNA and RNA analysis at the cellular and molecular levels.Main results and the role of chanceThree major discoveries were made: (i) placental trophoblasts and endothelial cells are capable of producing IgG, a significant portion of which is aberrantly glycosylated at one of its Fab arms to form aIgG; (ii) the asymmetrically glycosylated IgG produced by trophoblasts and endothelial cells can react to immunoglobulin molecules of human, rat, mouse, goat and rabbit at the Fc portion; (iii) asymmetrically glycosylated IgG can react to certain leukocytes in the membrane and cytoplasm, while symmetric IgG from the placenta does not have this property.Limitations, reasons for cautionMost of the experiments were performed in vitro. The proposed mechanism calls for verification in normal and abnormal pregnancy.Wider implications of the findingsThis study identified a number of new phenomena suggesting that aIgG produced by the placenta would be able to react to detrimental antibodies and leukocytes and interfere with their immune reactions against the placenta and the fetus. This opens a new dimension for further studies on pregnancy physiology and immunology. Should the mechanism proposed here be confirmed, it will have a direct impact on our understanding of the physiology and pathology of human reproduction and offer new possibilities for the treatment of many diseases including spontaneous abortion, infertility and pre-eclampsia. It also sheds light on the mechanism of immune evasion in general including that of cancer.

Project description:The neutralizing antibody (nAb) response against the influenza virus hemagglutinin (HA) fusion glycoprotein is important for preventing viral infection, but we lack a comprehensive understanding of the mechanisms by which these antibodies act. Here we investigated the effect of nAb binding and the role of IgG bivalency in the inhibition of HA function for nAbs targeting distinct HA epitopes. HC19 targets the receptor binding pocket at the distal end of HA, while FI6v3 binds primarily to the HA2 fusion subunit toward the base of the stalk. Surprisingly, HC19 inhibited the ability of HA to induce lipid mixing by preventing the structural rearrangement of HA under fusion-activating conditions. These results suggest that nAbs such as HC19 not only act by blocking receptor binding but also inhibit key late-stage HA conformational changes required for fusion. Intact HC19 IgG was also shown to cross-link separate virus particles, burying large proportions of HA within aggregates where they are blocked from interacting with target membranes; Fabs yielded no such aggregation and displayed weaker neutralization than IgG, emphasizing the impact of bivalency on the ability to neutralize virus. In contrast, the stem-targeting nAb FI6v3 did not aggregate particles. The Fab fragment was significantly less effective than IgG in preventing both membrane disruption and fusion. We infer that interspike cross-linking within a given particle by FI6v3 IgG may be critical to its potent neutralization, as no significant neutralization occurred with Fabs. These results demonstrate that IgG bivalency enhances HA inhibition through functionally important modes not evident in pared-down Fab-soluble HA structures.IMPORTANCE The influenza virus hemagglutinin (HA) fusion glycoprotein mediates entry into target cells and is the primary antigenic target of neutralizing antibodies (nAbs). Our current structural understanding of mechanisms of antibody (Ab)-mediated neutralization largely relies on the high-resolution characterization of antigen binding (Fab) fragments in complex with soluble, isolated antigen constructs by cryo-electron microscopy (EM) single-particle reconstruction or X-ray crystallography. Interactions between full-length IgG and whole virions have not been well characterized, and a gap remains in our understanding of how intact Abs neutralize virus and prevent infection. Using structural and biophysical approaches, we observed that Ab-mediated inhibition of HA function and neutralization of virus infectivity occur by multiple coexisting mechanisms, are largely dependent on the specific epitope that is targeted, and are highly dependent on the bivalent nature of IgG molecules.

Dataset Information

Ocular distribution, spectrum of activity, and in vivo viral neutralization of a fully humanized anti-herpes simplex virus IgG Fab fragment following topical application.

Publications

Ocular distribution, spectrum of activity, and in vivo viral neutralization of a fully humanized anti-herpes simplex virus IgG Fab fragment following topical application.

Similar Datasets

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