Monoclonal antibodies to meningococcal factor H binding protein with overlapping epitopes and discordant functional activity

Background

Meningococcal factor H binding protein (fHbp) is a promising vaccine candidate. Anti-fHbp antibodies can bind to meningococci and elicit complement-mediated bactericidal activity directly. The antibodies also can block binding of the human complement down-regulator, factor H (fH). Without bound fH, the organism would be expected to have increased susceptibility to bacteriolysis. Here we describe bactericidal activity of two anti-fHbp mAbs with overlapping epitopes in relation to their different effects on fH binding and bactericidal activity.

Methods and Principal Findings

Both mAbs recognized prevalent fHbp sequence variants in variant group 1. Using yeast display and site-specific mutagenesis, binding of one of the mAbs (JAR 1, IgG3) to fHbp was eliminated by a single amino acid substitution, R204A, and was decreased by K143A but not by R204H or D142A. The JAR 1 epitope overlapped that of previously described mAb (mAb502, IgG2a) whose binding to fHbp was eliminated by R204A or R204H substitutions, and was decreased by D142A but not by K143A. Although JAR 1 and mAb502 appeared to have overlapping epitopes, only JAR 1 inhibited binding of fH to fHbp and had human complement-mediated bactericidal activity. mAb502 enhanced fH binding and lacked human complement-mediated bactericidal activity. To control for confounding effects of different mouse IgG subclasses on complement activation, we created chimeric mAbs in which the mouse mAb502 or JAR 1 paratopes were paired with human IgG1 constant regions. While both chimeric mAbs showed similar binding to fHbp, only JAR 1, which inhibited fH binding, had human complement-mediated bactericidal activity.

Conclusions

The lack of human complement-mediated bactericidal activity by anti-fHbp mAb502 appeared to result from an inability to inhibit binding of fH. These results underscore the importance of inhibition of fH binding for anti-fHbp mAb bactericidal activity.     

Diphenylcyclohexylamine derivatives as new potent multidrug resistance (MDR) modulators

A series of compounds with a diphenylmethyl cyclohexyl skeleton, loosely related to verapamil, has been synthesized and tested as MDR modulators on anthracycline-resistant erythroleukemia K 562 cells. Their residual cardiovascular action (negative inotropic and chronotropic activity as well as vasorelaxant activity) was evaluated on guinea-pig isolated atria preparations and on guinea-pig aortic strip preparations. Most compounds of the series possess a good MDR-reverting activity together with a low cardiovascular action. Among them, compounds 3a1, 7a, and 8a are more potent than verapamil as MDR reverters and lack any cardiovascular action; they can represent useful leads for the development of new safe MDR reversing drugs.     

Deregulation of transition metals homeostasis is a key feature of cadmium toxicity in Salmonella

Cadmium is a highly toxic metal whose presence in the environment represents a challenge for all forms of life. To improve our knowledge on cadmium toxicity, we have explored Salmonella Typhimurium responses to this metal. We have found that cadmium induces the concomitant expression of the cation efflux pump ZntA and of the high affinity zinc import system ZnuABC. This observation suggests that cadmium accumulation within the cell induces a condition of apparent zinc starvation, possibly due to the ability of this metal to compete with zinc for the metal binding site of proteins. This hypothesis is supported by the finding that strains lacking ZntA or ZnuABC are hyper-susceptible to cadmium and that the cadmium-induced growth defect of a znuABC mutant strain is largely relieved by zinc supplementation. A similar growth defect was observed for a mutant with impaired ability to acquire iron, whereas cadmium does not affect growth of a strain defective in manganese import. Cadmium also influences the expression and activity of the two cytoplasmic superoxide dismutases FeSOD and MnSOD, which are required to control cadmium-mediate oxidative stress. Exposure to cadmium causes a reduction of FeSOD activity in Salmonella wild type and the complete abrogation of its expression in the strain defective in iron import. In contrast, although MnSOD intracellular levels increase in response to cadmium, we observed discrepancies between protein levels and enzymatic activity which are suggestive of incorporation of non-catalytic metals in the active site or to cadmium-mediated inhibition of manganese import. Our results indicate that cadmium interferes with the ability of cells to manage transition metals and highlight the close interconnections between the homeostatic mechanisms regulating the intracellular levels of different metals.     

Characterization of Human γδ T Lymphocytes Infiltrating Primary Malignant Melanomas

T lymphocytes are often induced naturally in melanoma patients and infiltrate tumors. Given that γδ T cells mediate antigen-specific killing of tumor cells, we studied the representation and the in vitro cytokine production and cytotoxic activity of tumor infiltrating γδ T cells from 74 patients with primary melanoma. We found that γδ T cells represent the major lymphocyte population infiltrating melanoma, and both Vδ1⁺ and Vδ2⁺ cells are involved. The majority of melanoma-infiltrating γδ cells showed effector memory and terminally-differentiated phenotypes and, accordingly, polyclonal γδ T cell lines obtained from tumor-infiltrating immune cells produced IFN-γ and TNF-α and were capable of killing melanoma cell lines in vitro. The cytotoxic capability of Vδ2 cell lines was further improved by pre-treatment of tumor target cells with zoledronate. Moreover, higher rate of γδ T cells isolation and percentages of Vδ2 cells correlate with early stage of development of melanoma and absence of metastasis. Altogether, our results suggest that a natural immune response mediated by γδ T lymphocytes may contribute to the immunosurveillance of melanoma.     

Effect of peginterferon beta-1a on MRI measures and achieving no evidence of disease activity: results from a randomized controlled trial in relapsing-remitting multiple sclerosis

Background

Subcutaneous peginterferon beta-1a provided clinical benefits at Year 1 (placebo-controlled period) of the 2-Year Phase 3 ADVANCE study in relapsing-remitting multiple sclerosis (RRMS). Here we report the effect of peginterferon beta-1a on brain magnetic resonance imaging (MRI) lesions, and no evidence of disease activity (NEDA; absence of clinical [relapses and 12-week confirmed disability progression] and MRI [gadolinium-enhancing, and new or newly-enlarging T2 hyperintense lesions] disease activity) during Year 1.

Methods

RRMS patients (18–65 years; Expanded Disability Status Scale score ≤5) were randomized to double-blind placebo or peginterferon beta-1a 125 μg every 2 or 4 weeks. Sensitivity analyses of last observation carried forward and composite disease activity (using minimal MRI allowance definitions) were conducted.

Results

1512 patients were randomized and dosed (placebo n?=?500; peginterferon beta-1a every 2 [n?=?512] or 4 [n?=?500] weeks). Every 2 week dosing significantly reduced, versus placebo and every 4 week dosing, the number of new or newly-enlarging T2 hyperintense lesions at Weeks 24 (by 61% and 51%, respectively) and 48 (secondary endpoint; by 67% and 54%, respectively); all p?<?0.0001. Every 2 week dosing also provided significant reductions versus placebo and every 4 week dosing in the number of new T1 hypointense, gadolinium-enhancing, and new active (gadolinium-enhancing plus non-enhancing new T2) lesions (all p?<?0.0001), as well as the volume of T2 and T1 lesions (p?<?0.05) at Weeks 24 and 48. Significantly more patients dosed every 2 weeks had NEDA versus placebo and every 4 weeks (all p?<?0.01) from baseline to Week 48 (33.9% versus 15.1% and 21.5%, respectively [odds ratios, ORs: 2.89 and 1.87]), from baseline to Week 24 (41.0% versus 21.9% and 30.7%, [ORs: 2.47 and 1.57]) and from Week 24 to Week 48 (60.2% versus 28.9% and 36.6%, [ORs: 3.71 and 2.62]). Consistent results were seen when allowing for minimal MRI activity.

Conclusion

During Year 1 of ADVANCE, significantly more RRMS patients receiving peginterferon beta-1a every 2 weeks had NEDA, and early and sustained improvements in all MRI endpoints, versus placebo and every 4 week dosing. NEDA sensitivity analyses align with switch strategies in clinical practice settings and provide insight into future responders/non-responders.

Trial registration

ClinicalTrials.gov: https://clinicaltrials.gov/ct2/show/NCT00906399

     

The abundance of urban endotoxins as measured with an impinger-based sampling strategy

Endotoxins are components of Gram-negative bacteria with inherently high pro-inflammatory potential. In an urban environment, airborne endotoxins may associate with pollutants such as particulate matter, increasing the severity of the immune response by acting as a natural adjuvant to augment inflammatory respiratory disease development. Here, we present a closer look at outdoor urban endotoxins by applying a microbial-targeted collection strategy. Results from 87 samples distributed throughout the city of Antwerp ranged from 0.45 to 93.71 EU/m³, with a geometric mean of 4.49 EU/m³ and 95% confidence interval of 3.53–5.71 EU/m³. Sample collection was also coupled with the use of a Coulter counter, for which the particle count (2.5–10 μm/m³) showed a significant correlation with endotoxin concentration (R²?=?0.24; p?<?0.0001; n?=?64). In addition, the analysis of the cultivable bacterial colony-forming units on Reasoner’s 2A agar (expressed CFU/m³) showed to be a good indicator for airborne endotoxins (R²?=?0.57; p?<?0.0001; n?=?58). Moreover, identification of dominant bacterial colonies on these culture plates gave some indications on potential sources of these urban outdoor bacteria and endotoxins.