Structural basis of polyethylene glycol recognition by antibody.

BACKGROUND: Polyethylene glycol (PEG) is widely used in industry and medicine. Anti-PEG antibodies have been developed for characterizing PEGylated drugs and other applications. However, the underlying mechanism for specific PEG binding has not been elucidated. METHODS: The Fab of two cognate anti-PEG antibodies 3.3 and 2B5 were each crystallized in complex with PEG, and their structures were determined by X-ray diffraction. The PEG-Fab interactions in these two crystals were analyzed and compared with those in a PEG-containing crystal of an unrelated anti-hemagglutinin 32D6-Fab. The PEG-binding stoichiometry was examined by using analytical ultracentrifuge (AUC). RESULTS: A common PEG-binding mode to 3.3 and 2B5 is seen with an S-shaped core PEG fragment bound to two dyad-related Fab molecules. A nearby satellite binding site may accommodate parts of a longer PEG molecule. The core PEG fragment mainly interacts with the heavy-chain residues D31, W33, L102, Y103 and Y104, making extensive contacts with the aromatic side chains. At the center of each half-circle of the S-shaped PEG, a water molecule makes alternating hydrogen bonds to the ether oxygen atoms, in a similar configuration to that of a crown ether-bound lysine. Each satellite fragment is clamped between two arginine residues, R52 from the heavy chain and R29 from the light chain, and also interacts with several aromatic side chains. In contrast, the non-specifically bound PEG fragments in the 32D6-Fab crystal are located in the elbow region or at lattice contacts. The AUC data suggest that 3.3-Fab exists as a monomer in PEG-free solution but forms a dimer in the presence of PEG-550-MME, which is about the size of the S-shaped core PEG fragment. CONCLUSIONS: The differing amino acids in 3.3 and 2B5 are not involved in PEG binding but engaged in dimer formation. In particular, the light-chain residue K53 of 2B5-Fab makes significant contacts with the other Fab in a dimer, whereas the corresponding N53 of 3.3-Fab does not. This difference in the protein-protein interaction between two Fab molecules in a dimer may explain the temperature dependence of 2B5 in PEG binding, as well as its inhibition by crown ether.

An Effective Neutralizing Antibody Against Influenza Virus H1N1 from Human B Cells.

Influenza is a contagious acute respiratory disease caused by the influenza virus infection. Hemagglutinin (HA) is an important target in the therapeutic treatment and diagnostic detection of the influenza virus. Influenza A virus encompasses several different HA subtypes with different strains, which are constantly changing. In this study, we identified a fully human H1N1 neutralizing antibody (32D6) via an Epstein-Barr virus-immortalized B cell-based technology. 32D6 specifically neutralizes the clinically isolated H1N1 strains after the 2009 pandemic but not the earlier strains. The epitope was identified through X-ray crystallographic analysis of the 32D6-Fab/HA1 complex structure, which revealed a unique loop conformation located on the top surface of HA. The major region is composed of two peptide segments (residues 172-177 and 206-213), which form an abreast loop conformation. The residue T262 between the two loops forms a conformational epitope for recognition by 32D6. Three water molecules were observed at the interface of HA and the heavy chain, and they may constitute a stabilizing element for the 32D6-HA association. In addition, each 32D6-Fab is likely capable of blocking one HA trimer. This study provides important information on the strain specificity of 32D6 for the therapeutic treatment and detection of viral infection.

Adjuvant heparanase inhibitor PI-88 therapy for hepatocellular carcinoma recurrence.

AIM: To demonstrate that administering heparanase inhibitor PI-88 at 160 mg/d is safe and promising in reducing hepatocellular carcinoma (HCC) recurrence for up to 3 year following curative resection. METHODS: A total of 143 patients (83.1% of the 172 participants in the phase II study) participated in the follow-up study. Of these patients, 50 had received no treatment, 48 had received 160 mg/d PI-88, and 45 had received 250 mg/d PI-88 during the phase II trial. Safety parameters and the following efficacy endpoints were investigated: (1) time to recurrence; (2) disease-free survival; and (3) overall survival. RESULTS: PI-88 at 160 mg/d delayed the onset and frequency of HCC recurrence, and provided a clinically significant survival advantage for up to 3 years after treatment compared with those of the control group: (1) the recurrence-free rate increased from 50% to 63%, and (2) time to recurrence at the 36th percentile was postponed by 78%. The efficacy of administering PI-88 at 250 mg/d was confounded by a high dropout rate (11 out of 54 patients). Additionally, subgroup analyses of patients with (1) multiple tumors or a single tumor ≥ 2 cm; and (2) hepatitis B or C revealed that administering PI-88 at 160 mg/d conferred the most significant survival advantage (56.8% improvement in disease-free survival, P = 0.045) for patients with both risk factors for recurrence. CONCLUSION: Administering PI-88 at 160 mg/d is a safe and well-tolerated dosage that may confer significant clinical benefits for patients with HCC.

Telomerase-specific oncolytic adenoviral therapy for orthotopic hepatocellular carcinoma in HBx transgenic mice.

The telomerase-specific replication-competent oncolytic adenovirus, Telomelysin, was developed for virus-mediated preferential lysis of tumor cells. Its selectivity is derived from a human telomerase reverse transcriptase (hTERT) promoter-driven active viral replication, which occurs in cancer cells with high telomerase activity but not in normal cells lacking such activity. Because the TERT activity is elevated in most cases of hepatocellular carcinoma (HCC), the current study aims to investigate whether Telomelysin can be used for treatment of HCC. The oncolytic effect of Telomelysin has been investigated both in vitro using cell culture and in vivo using an immunocompetent in situ orthotopic HCC model. In this model, HCC developed spontaneously in the liver of HBx transgenic mice, which is pathologically and genetically similar to human HCC. In cell culture assay, Telomelysin lyses HCC cell lines at a low multiplicity of infection (MOI), ranging 0.77-6.35 (MOI [PFU/cell]). In the orthotopic HCC model, Telomelysin showed a potent oncolytic effect on HCC but spared normal liver tissue. Dose escalation analysis identified a safety dose of 1.25 × 10(8) PFU for this model. The effect of multiple injections of Telomelysin was also evaluated in this immunocompetent HCC model. We found that the virus replicates in HCC after a second intratumoral injection despite an immune response induced by the previous injection. This preclinical study shows that Telomelysin can be used for treatment of human HCC at an appropriate dosage and that its tumor-killing activity persists after multiple injections.

Heparanase inhibitor PI-88 as adjuvant therapy for hepatocellular carcinoma after curative resection: a randomized phase II trial for safety and optimal dosage.

BACKGROUND/AIMS: Hepatocellular carcinoma recurrence after curative treatment adversely influences clinical outcome. It is important to explore adjuvant therapies. This phase II/stage 1 multi-center, randomized trial investigated the safety, optimal dosage and preliminary efficacy of PI-88, a novel heparanase inhibitor, in the setting of post-operative recurrence of HCC according to a Simon's 2-stage design. METHODS: Three groups were included: one untreated arm (Group A) and two PI-88 arms (Group B: 160 mg/day; Group C: 250 mg/day). Treatment groups received PI-88 over nine 4-week treatment cycles, followed by a 12-week treatment-free period. Safety and optimal dosage were assessed. RESULTS: Overall, 172 patients were randomized and 168 were included in the intention-to-treat (ITT) population. Treatment-related adverse effects included cytopenia, injection site hemorrhage, PT prolongation, etc. Four serious adverse events were possibly related to PI-88 treatment. One (1.8%) group B patients and six (10.5%) group C had hepatotoxicity-related withdrawals. Among the ITT population, 29 patients (50%) in Group A, 35 (63%) in Group B, and 22 (41%) in Group C remained recurrence-free at completion. Calculated T(1) value suggested 160 mg/day treatment satisfied the criteria for the next stage of the trial. CONCLUSIONS: PI-88 at 160 mg/day is optimal and safe, and shows preliminary efficacy as an adjunct therapy for post-operative HCC.

Interstitial laser photocoagulation for treatment of benign prostatic hypertrophy: outcomes and cost effectiveness.

BACKGROUND: We examined the efficiency and cost effectiveness of a temperature feedback diode-laser system in the treatment of benign prostatic hypertrophy (BPH). METHODS: One hundred twenty patients with symptomatic BPH were included in this study between October 1997 and January 1998. Sixty of them were treated by transurethral resection of the prostate (TUR-P), and 60 patients were treated by temperature feedback interstitial laser coagulation (ILC). Direct and indirect cost parameters, such as operative time, operation-related consumables, duration of hospitalization, and amount of medication used were compared between the 2 groups. RESULTS: All subjective and objective urinary parameters exhibited significant improvement 12 months after ILC. A reduction of 26.8% (46.6 to 34.1 ml) of the pretreatment prostate volume was observed at 12 months following ILC. The duration of hospital stay, operative time, and postoperative medications were significantly lower for those receiving ILC (5.9 to 2.5 days, p < 0.001) than for those who underwent TUR-P. The variety of laboratory tests needed for preoperative evaluation was no less when ILC was chosen for treating BPH (p = 0.849). Indirect costs, such as investment in laser equipment and laser accessories were higher in the ILC group (p < 0.001). CONCLUSION: The low morbidity profile, particularly the absence of retrograde ejaculation, makes ILC a valuable and attractive option for treatment of BPH patients who wish to retain their ejaculation ability, who have serious underlying diseases, or who have surgical risks for TUR-P or other invasive modalities.