Impact of HLA Polymorphism on the Immune Response to Bacillus Anthracis Protective Antigen in Vaccination versus Natural Infection.

The causative agent of anthrax, Bacillus anthracis, evades the host immune response and establishes infection through the production of binary exotoxins composed of Protective Antigen (PA) and one of two subunits, lethal factor (LF) or edema factor (EF). The majority of vaccination strategies have focused upon the antibody response to the PA subunit. We have used a panel of humanised HLA class II transgenic mouse strains to define HLA-DR-restricted and HLA-DQ-restricted CD4+ T cell responses to the immunodominant epitopes of PA. This was correlated with the binding affinities of epitopes to HLA class II molecules, as well as the responses of two human cohorts: individuals vaccinated with the Anthrax Vaccine Precipitated (AVP) vaccine (which contains PA and trace amounts of LF), and patients recovering from cutaneous anthrax infections. The infected and vaccinated cohorts expressing different HLA types were found to make CD4+ T cell responses to multiple and diverse epitopes of PA. The effects of HLA polymorphism were explored using transgenic mouse lines, which demonstrated differential susceptibility, indicating that HLA-DR1 and HLA-DQ8 alleles conferred protective immunity relative to HLA-DR15, HLA-DR4 and HLA-DQ6. The HLA transgenics enabled a reductionist approach, allowing us to better define CD4+ T cell epitopes. Appreciating the effects of HLA polymorphism on the variability of responses to natural infection and vaccination is vital in planning protective strategies against anthrax.

A Probody T Cell-Engaging Bispecific Antibody Targeting EGFR and CD3 Inhibits Colon Cancer Growth with Limited Toxicity.

T cell-engaging bispecific antibodies (TCB) are highly potent therapeutics that can recruit and activate cytotoxic T cells to stimulate an antitumor immune response. However, the development of TCBs against solid tumors has been limited by significant on-target toxicity to normal tissues. Probody therapeutics have been developed as a novel class of recombinant, protease-activated antibody prodrugs that are "masked" to reduce antigen binding in healthy tissues but can become conditionally unmasked by proteases that are preferentially active in the tumor microenvironment (TME). Here, we describe the preclinical efficacy and safety of CI107, a Probody TCB targeting EGFR and CD3. In vitro, the protease-activated, unmasked CI107 effectively bound EGFR and CD3 expressed on the surface of cells and induced T-cell activation, cytokine release, and cytotoxicity toward tumor cells. In contrast, dually masked CI107 displayed a >500-fold reduction in antigen binding and >15,000-fold reduction in cytotoxic activity. In vivo, CI107 potently induced dose-dependent tumor regression of established colon cancer xenografts in mice engrafted with human peripheral blood mononuclear cells. Furthermore, the MTD of CI107 in cynomolgus monkeys was more than 60-fold higher than that of the unmasked TCB, and much lower levels of toxicity were observed in animals receiving CI107. Therefore, by localizing activity to the TME and thus limiting toxicity to normal tissues, this Probody TCB demonstrates the potential to expand clinical opportunities for TCBs as effective anticancer therapies for solid tumor indications. SIGNIFICANCE: A conditionally active EGFR-CD3 T cell-engaging Probody therapeutic expands the safety window of bispecific antibodies while maintaining efficacy in preclinical solid tumor settings.

Nonclinical Efficacy and Safety of CX-2029, an Anti-CD71 Probody-Drug Conjugate.

Probody therapeutics (Pb-Txs) are conditionally activated antibody-drug conjugates (ADCs) designed to remain inactive until proteolytically activated in the tumor microenvironment, enabling safer targeting of antigens expressed in both tumor and normal tissue. Previous attempts to target CD71, a highly expressed tumor antigen, have failed to establish an acceptable therapeutic window due to widespread normal tissue expression. This study evaluated whether a probody-drug conjugate targeting CD71 can demonstrate a favorable efficacy and tolerability profile in preclinical studies for the treatment of cancer. CX-2029, a Pb-Tx conjugated to maleimido-caproyl-valine-citrulline-p-aminobenzyloxycarbonyl-monomethyl auristatin E, was developed as a novel cancer therapeutic targeting CD71. Preclinical studies were performed to evaluate the efficacy and safety of this anti-CD71 PDC in patient-derived xenograft (PDX) mouse models and cynomolgus monkeys, respectively. CD71 expression was detected at high levels by IHC across a broad range of tumor and normal tissues. In vitro, the masked Pb-Tx form of the anti-CD71 PDC displayed a >50-fold reduced affinity for binding to CD71 on cells compared with protease-activated, unmasked anti-CD71 PDC. Potent in vivo tumor growth inhibition (stasis or regression) was observed in >80% of PDX models (28/34) at 3 or 6 mg/kg. Anti-CD71 PDC remained mostly masked (>80%) in circulation throughout dosing in cynomolgus monkeys at 2, 6, and 12 mg/kg and displayed a 10-fold improvement in tolerability compared with an anti-CD71 ADC, which was lethal. Preclinically, anti-CD71 PDC exhibits a highly efficacious and acceptable safety profile that demonstrates the utility of the Pb-Tx platform to target CD71, an otherwise undruggable target. These data support further clinical development of the anti-CD71 PDC CX-2029 as a novel cancer therapeutic.

Fluorinated synthetic anion carriers: experimental and computational insights into transmembrane chloride transport.

A series of fluorinated tripodal tris-thioureas function as highly active anion transporters across lipid bilayers and cell membranes. Here, we investigate their mechanism of action using anion transport assays in cells and synthetic vesicles and molecular modelling of transporter-lipid interactions. When compared with non-fluorinated analogues, fluorinated compounds demonstrate a different mechanism of membrane transport because the free transporter cannot effectively diffuse through the membrane. As a result, in H+/Cl- cotransport assays, fluorinated transporters require the presence of oleic acid to form anionic oleate complexes for recycling of the transporter, whereas non-fluorinated analogues readily diffuse through the membrane as free transporters and show synergistic transport with the proton transporter gramicidin. Molecular dynamics simulations revealed markedly stronger transporter-lipid interactions for fluorinated compounds compared with non-fluorinated analogues and hence, higher energy barriers for fluorinated compounds to cross the membrane as free transporters. With use of appropriate proton transporters to ensure measurement of the correct rate-limiting steps, the transport rates determined in synthetic vesicle assays show excellent agreement with the anion transport rates determined in cell-based assays. We conclude that integration of computational and experimental methods provides a strategy to optimise transmembrane anion transporter design for biomedical applications.

The multifaceted roles of tumor-associated proteases and harnessing their activity for prodrug activation.

The role of proteases in cancer was originally thought to be limited to the breakdown of basement membranes and extracellular matrix (ECM), thereby promoting cancer cell invasion into surrounding normal tissues. It is now well understood that proteases play a much more complicated role in all stages of cancer progression and that not only tumor cells, but also stromal cells are an important source of proteases in the tumor microenvironment. Among all the proteolytic enzymes potentially associated with cancer, some proteases have taken on heightened importance due to their significant up-regulation and ability to participate at multiple stages of cancer progression and metastasis. In this review, we discuss some of the advances in understanding of the roles of several key proteases from different classes in the development and progression of cancer and the potential to leverage their upregulated activity for the development of novel targeted treatment strategies.

CD4+ T Cells Targeting Dominant and Cryptic Epitopes from Bacillus anthracis Lethal Factor.

Anthrax is an endemic infection in many countries, particularly in the developing world. The causative agent, Bacillus anthracis, mediates disease through the secretion of binary exotoxins. Until recently, research into adaptive immunity targeting this bacterial pathogen has largely focused on the humoral response to these toxins. There is, however, growing recognition that cellular immune responses involving IFNγ producing CD4+ T cells also contribute significantly to a protective memory response. An established concept in adaptive immunity to infection is that during infection of host cells, new microbial epitopes may be revealed, leading to immune recognition of so called 'cryptic' or 'subdominant' epitopes. We analyzed the response to both cryptic and immunodominant T cell epitopes derived from the toxin component lethal factor and presented by a range of HLA-DR alleles. Using IFNγ-ELISpot assays we characterized epitopes that elicited a response following immunization with synthetic peptide and the whole protein and tested their capacities to bind purified HLA-DR molecules in vitro. We found that DR1 transgenics demonstrated T cell responses to a greater number of domain III cryptic epitopes than other HLA-DR transgenics, and that this pattern was repeated with the immunodominant epitopes, as a greater proportion of these epitopes induced a T cell response when presented within the context of the whole protein. Immunodominant epitopes LF457-476 and LF467-487 were found to induce a T cell response to the peptide, as well as to the whole native LF protein in DR1 and DR15, but not in DR4 transgenics. The analysis of Domain I revealed the presence of several unique cryptic epitopes all of which showed a strong to moderate relative binding affinity to HLA-DR4 molecules. However, none of the cryptic epitopes from either domain III or I displayed notably high binding affinities across all HLA-DR alleles assayed. These responses were influenced by the specific HLA alleles presenting the peptide, and imply that construction of future epitope string vaccines which are immunogenic across a wide range of HLA alleles could benefit from a combination of both cryptic and immunodominant anthrax epitopes.

Highly effective yet simple transmembrane anion transporters based upon ortho-phenylenediamine bis-ureas.

Simple, highly fluorinated receptors are shown to function as highly effective transmembrane anion antiporters with the most active transporters rivalling the transport efficacy of natural anion transporter prodigiosin for bicarbonate.

Anthrax lethal factor as an immune target in humans and transgenic mice and the impact of HLA polymorphism on CD4+ T cell immunity.

Bacillus anthracis produces a binary toxin composed of protective antigen (PA) and one of two subunits, lethal factor (LF) or edema factor (EF). Most studies have concentrated on induction of toxin-specific antibodies as the correlate of protective immunity, in contrast to which understanding of cellular immunity to these toxins and its impact on infection is limited. We characterized CD4+ T cell immunity to LF in a panel of humanized HLA-DR and DQ transgenic mice and in naturally exposed patients. As the variation in antigen presentation governed by HLA polymorphism has a major impact on protective immunity to specific epitopes, we examined relative binding affinities of LF peptides to purified HLA class II molecules, identifying those regions likely to be of broad applicability to human immune studies through their ability to bind multiple alleles. Transgenics differing only in their expression of human HLA class II alleles showed a marked hierarchy of immunity to LF. Immunogenicity in HLA transgenics was primarily restricted to epitopes from domains II and IV of LF and promiscuous, dominant epitopes, common to all HLA types, were identified in domain II. The relevance of this model was further demonstrated by the fact that a number of the immunodominant epitopes identified in mice were recognized by T cells from humans previously infected with cutaneous anthrax and from vaccinated individuals. The ability of the identified epitopes to confer protective immunity was demonstrated by lethal anthrax challenge of HLA transgenic mice immunized with a peptide subunit vaccine comprising the immunodominant epitopes that we identified.

Tumor-specific activation of an EGFR-targeting probody enhances therapeutic index.

Target-mediated toxicity constitutes a major limitation for the development of therapeutic antibodies. To redirect the activity of antibodies recognizing widely distributed targets to the site of disease, we have applied a prodrug strategy to create an epidermal growth factor receptor (EGFR)-directed Probody therapeutic-an antibody that remains masked against antigen binding until activated locally by proteases commonly active in the tumor microenvironment. In vitro, the masked Probody showed diminished antigen binding and cell-based activities, but when activated by appropriate proteases, it regained full activity compared to the parental anti-EGFR antibody cetuximab. In vivo, the Probody was largely inert in the systemic circulation of mice, but was activated within tumor tissue and showed antitumor efficacy that was similar to that of cetuximab. The Probody demonstrated markedly improved safety and increased half-life in nonhuman primates, enabling it to be dosed safely at much higher levels than cetuximab. In addition, we found that both Probody-responsive xenograft tumors and primary tumor samples from patients were capable of activating the Probody ex vivo. Probodies may therefore improve the safety profile of therapeutic antibodies without compromising efficacy of the parental antibody and may enable the wider use of empowered antibody formats such as antibody-drug conjugates and bispecifics.

Aggregating sustainability indicators: beyond the weighted sum.

Sustainability analysts and environmental decision makers often overcome the difficulty of interpreting comprehensive environmental profiles by aggregating the results using multi-criteria decision analysis (MCDA) methods. However, the wide variety of methodological approaches to weighting and aggregation introduces subjectivity and often uncertainty. It is important to select an approach that is consistent with the decision maker's information needs, but scant practical guidance is available to environmental managers on how to do this. In this paper, we aim to clarify the theoretical implications of an analyst's choice of MCDA method. By systematically examining the methodological decisions that must be made by the analyst at each stage of the assessment process, we aim to improve analysts' understanding of the relationship between MCDA theory and practice, and enable them to apply methods that are consistent with a decision maker's needs in any given problem context.

Screening of peptide libraries against protective antigen of Bacillus anthracis in a disposable microfluidic cartridge.

Bacterial surface peptide display has gained popularity as a method of affinity reagent generation for a wide variety of applications ranging from drug discovery to pathogen detection. In order to isolate the bacterial clones that express peptides with high affinities to the target molecule, multiple rounds of manual magnetic activated cell sorting (MACS) followed by multiple rounds of fluorescence activated cell sorting (FACS) are conventionally used. Although such manual methods are effective, alternative means of library screening which improve the reproducibility, reduce the cost, reduce cross contamination, and minimize exposure to hazardous target materials are highly desired for practical application. Toward this end, we report the first semi-automated system demonstrating the potential for screening bacterially displayed peptides using disposable microfluidic cartridges. The Micro-Magnetic Separation platform (MMS) is capable of screening a bacterial library containing 3 × 10¹° members in 15 minutes and requires minimal operator training. Using this system, we report the isolation of twenty-four distinct peptide ligands that bind to the protective antigen (PA) of Bacilus anthracis in three rounds of selection. A consensus motif WXCFTC was found using the MMS and was also found in one of the PA binders isolated by the conventional MACS/FACS approach. We compared MMS and MACS rare cell recovery over cell populations ranging from 0.1% to 0.0000001% and found that both magnetic sorting methods could recover cells down to 0.0000001% initial cell population, with the MMS having overall lower standard deviation of cell recovery. We believe the MMS system offers a compelling approach towards highly efficient, semi-automated screening of molecular libraries that is at least equal to manual magnetic sorting methods and produced, for the first time, 15-mer peptide binders to PA protein that exhibit better affinity and specificity than peptides isolated using conventional MACS/FACS.

A synergistic approach to anion antiport.

A synergistic approach to Cl(-)/HCO(3)(-) antiport has been demonstrated in POPC lipid bilayers using an ion selective electrode assay showing that, when using combinations of carriers each optimised for a particular component of the transport process, enhanced rates of transport are observed.

A dual host approach to transmembrane transport of salts.

A dual host approach for M(+)/Cl(-) co-transport has been shown to be effective in lipid bilayers consisting of POPC using fluorescence-based transport assays.

Tripodal transmembrane transporters for bicarbonate.

Easy-to-make tripodal tris-thiourea receptors based upon tris(2-aminoethyl)amine are capable of chloride/bicarbonate transport and as such represent a new class of bicarbonate transport agent.

Anion-anion proton transfer in hydrogen bonded complexes.

Complexation of dihydrogen phosphate by an anion receptor containing six hydrogen bond donor groups has been shown to reduce the pK(a) of the bound anionic species to such an extent that addition of further aliquots of dihydrogen phosphate result in deprotonation of the bound species with the resultant formation of a monohydrogen phosphate receptor complex. X-ray crystallographic studies confirm monohydrogen phosphate complex formation in the solid state. In this way, this study explains the formation of complexes with unusual stoichiometries when investigating the binding of dihydrogenphosphate anion to hydrogen-bonding receptors.

Seroprevalence and epidemiological characteristics of Mycobacterium avium subsp. paratuberculosis on 114 cattle farms in south west England.

Between December 2002 and April 2006, 114 cattle farms in the south west of England were visited at least once, with 100 farms visited three times. A total of 29,782 serum samples were collected from 15,736 individually identified cattle. The sera were tested for the presence of antibodies against Mycobacterium avium subsp. paratuberculosis (MAP) using an indirect enzyme-linked immunosorbent assay (ELISA). The mean seroprevalence in herds sampled three times was 7.1%; 10.1% of cattle had at least one positive result. There were 78%, 75% and 75% dairy herds with at least one positive bovine at the first, second and third routine visits, respectively. In comparison, 44%, 42% and 46% suckler herds had at least one positive bovine for the first, second and third routine visits, respectively. In most herds (>90%), within herd seroprevalence of MAP remained stable over time. Markov chain Monte Carlo (MCMC) simulation methods were used to re-estimate the test sensitivity and specificity. The sensitivity results were 33.3% (95% CI, 28.8-37.8%), 34.5% (95% CI, 30.3-38.8%) and 34.8% (95% CI, 30.8-38.9%) for the first, second and third routine visits and the specificity results were 99.7% (95% CI, 99.3-99.9%), 99.8% (95% CI, 99.4-99.9%) and 99.7% (95% CI, 99.3-99.9%) for the first, second and third routine visits, respectively. The expected true prevalence was also estimated, 11 (21.1%) suckler herds and 1 (2.1%) dairy herd were predicted to be truly free from infection during the study period. The seroprevalence of antibodies against MAP increased with cattle age. There was a significantly higher seroprevalence of MAP in dairy breeds of cattle compared with suckler breeds of cattle. This was more pronounced in Channel Island breeds. Smaller dairy herds (<100 cattle) had a relatively lower seroprevalence of MAP than dairy herds with >/=100 cattle. In 8 (42%) of the 19 herds with > or =100 cattle born into the same herd, seropositive cattle were clustered by birth month whilst in the remaining herds clustering was not apparent. Daughters were significantly more likely to be MAP seropositive when born to a seropositive dam.

A four year longitudinal sero-epidemiological study of bovine herpesvirus type-1 (BHV-1) in adult cattle in 107 unvaccinated herds in south west England.

BACKGROUND: Bovine herpesvirus type-1 (BHV-1) is an important pathogen of cattle that presents with a variety of clinical signs, including the upper respiratory tract infection infectious bovine rhinotracheitis (IBR). A seroepidemiological study of BHV-1 antibodies was conducted in England from 2002 - 2004: 29,782 blood samples were taken from 15,736 cattle from 114 herds which were visited on up to three occasions. Antibody concentration was measured using a commercial ELISA. Farm management information was collected using an interview questionnaire, and herd size and cattle movements were obtained from the cattle tuberculosis testing database and the British Cattle Movement Service. Hierarchical statistical models were used to investigate associations between cattle and herd variables and the continuous outcome percentage positive (PP) values from the ELISA test in unvaccinated herds. RESULTS: There were 7 vaccinated herds, all with at least one seropositive bovine. In unvaccinated herds 83.2% had at least one BHV-1 seropositive bovine, and the mean cattle and herd BHV-1 seroprevalence were 42.5% and 43.1% respectively. There were positive associations between PP value, age, herd size, presence of dairy cattle. Adult cattle in herds with grower cattle had lower PP values than those in herds without grower cattle. Purchased cattle had significantly lower PP values than homebred cattle, whereas cattle in herds that were totally restocked after the foot-and-mouth epidemic in 2001 had significantly higher PP values than those in continuously stocked herds. Samples taken in spring and summer had significantly lower PP values than those taken in winter, whereas those taken in autumn had significantly higher PP values than those taken in winter. The risks estimated from a logistic regression model with a binary outcome (seropositive yes/no) were similar. CONCLUSION: The prevalence of BHV-1 seropositivity in cattle and herds has increased since the 1970s. Although the study population prevalence of BHV-1 was temporally stable during study period, the associations between serological status and cattle age, herd size, herd type, presence of young stock and restocked versus continuously stocked herds indicate that there is heterogeneity between herds and so potential for further spread of BHV-1 within and between herds.

A four year longitudinal sero-epidemiology study of Neospora caninum in adult cattle from 114 cattle herds in south west England: associations with age, herd and dam-offspring pairs.

BACKGROUND: Neosporosis caused by the protozoan parasite Neospora caninum, is an economically important cause of abortion, stillbirth, low milk yield, reduced weight gain and premature culling in cattle. Consequently, a seroepidemiological study of N. caninum antibodies was conducted in England with 29,782 samples of blood taken from 15,736 cattle from 114 herds visited on three occasions at yearly intervals. Herds were categorised into lower (< 10%) and higher (> or = 10%) median herd seroprevalence. Hierarchical models were run to investigate associations between the sample to positive (S/P) ratio and herd and cattle factors. RESULTS: Ninety-four percent of herds had at least one seropositive cow; 12.9% of adult cattle had at least one seropositive test. Approximately 90% of herds were seropositive at all visits; 9 herds (8%) changed serological status between visits. The median N. caninum seroprevalence in positive herds was 10% (range 0.4% to 58.8%). There was a positive association between the serostatus of offspring and dams that were ever seropositive. In the hierarchical model of low seroprevalence herds there was no significant association between S/P ratio and cattle age. There was a significantly lower S/P ratio in cattle in herds that were totally restocked after the foot-and-mouth epidemic of 2001 compared with those from continuously stocked herds and cattle purchased into these herds had a higher S/P ratio than homebred cattle. In the model of high seroprevalence herds the S/P ratio increased with cattle age, but was not associated with restocking or cattle origin. CONCLUSION: There were no strong temporal changes in herd seroprevalence of N. caninum but 90% of herds had some seropositive cattle over this time period. Vertical transmission from seropositive dams appeared to occur in all herds. In herds with a high seroprevalence the increasing S/P ratio in 2-4 year old cattle is suggestive of exposure to N. caninum: horizontal transmission between adult cattle, infection from a local source or recrudescence and abortions. Between-herd movements of infected cattle enhance the spread of N. caninum, particularly into low seroprevalence herds. Some restocked herds had little exposure to N. caninum, while in others infection had spread in the time since restocking.