Efficacy and safety of tildrakizumab for plaque psoriasis with continuous dosing, treatment interruption, dose adjustments and switching from etanercept: results from phase III studies

Background

Chronic psoriasis may require medication adjustments over time.

Objectives

To evaluate the efficacy/safety of tildrakizumab in subgroups from the reSURFACE studies (N = 1862) that received continuous dosing, higher/lower dosing, treatment interruption/reinitiation and initiation.

Methods

Responders [Psoriasis Area and Severity Index (PASI) ≥ 75%] and partial responders (PASI ≥ 50% to < 75%) in Part 3 of the reSURFACE studies (weeks 28–52 or week 64) who received tildrakizumab 200 mg or 100 mg were rerandomized to the same dosage (T100/T100 or T200/T200), a higher/lower dosage (T100/T200 or T200/T100) or placebo (PBO) (T100/PBO or T200/PBO). Patients receiving PBO who relapsed were reinitiated to tildrakizumab. Etanercept (ETN) week‐28 partial responders and nonresponders (PASI < 50%) received tildrakizumab 200 mg (ETN/T200).

Results

Among T100/T100 and T200/T200 week‐28 partial responders, the proportion of patients who achieved as‐observed PASI 75 responses increased over time. Among T100/T200 week‐28 partial responders, PASI 75 responses increased from week 32 (38·5%) to week 52 (63·2%) and remained consistent in T200/T100 week‐28 responders. Among patients who relapsed in the T100/PBO and T200/PBO groups, 86% and 83% of those who reinitiated tildrakizumab achieved PASI 75 by week 64, respectively. Among ETN/T200 week‐28 partial responders, PASI 75 responses (nonresponder imputation) increased from week 32 (24·1%) to week 52 (74·7%). PASI 90, PASI 100 and Physician's Global Assessment responses were consistent with PASI 75 results. Treatment was well tolerated.

Conclusions

Patients generally fared well with tildrakizumab maintenance, reinitiation, dose adjustment or initiation.

What's already known about this topic?

Tildrakizumab demonstrated significant efficacy vs. placebo with a positive safety profile during the first 28 weeks of treatment in two randomized double‐blind trials.

What does this study add?

Treatment scenarios with tildrakizumab, such as long‐term continuous dosing (up to 64 weeks), treatment interruption/reinitiation and switching from another biologic, can be part of the management of plaque psoriasis with a reasonable expectation of efficacy and tolerability.

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Efficacy of tildrakizumab for moderate-to-severe plaque psoriasis: pooled analysis of three randomized controlled trials at weeks 12 and 28

BACKGROUND

Efficacy of tildrakizumab for plaque psoriasis was demonstrated in randomized, placebo-controlled trials.

OBJECTIVE

To consolidate tildrakizumab efficacy results by pooling data.

METHODS

Data (N = 2081) from tildrakizumab 100 mg, tildrakizumab 200 mg and placebo groups in three trials were pooled.

RESULTS

Proportions of Psoriasis Area and Severity Index (PASI) 75 responders at week 12 were better with tildrakizumab 100 mg (62.3%) and tildrakizumab 200 mg (64.8%) vs. placebo (5.6%; P < 0.0001) and for PASI 90, PASI 100 and Physician's Global Assessment (PGA) 'clear' or 'minimal' vs. placebo (P < 0.0001). Responses increased from weeks 12 to 28. Week 12 PASI and PGA responses to tildrakizumab vs. placebo were numerically greater in patients with lower vs. higher bodyweight and were better with tildrakizumab 200 mg than tildrakizumab 100 mg for patients with higher bodyweight. Week 12 PASI 75 responses vs. placebo with tildrakizumab 100 mg were similar between patients with (55.0%) or without (56.7%) prior biologics. PASI 90, PASI 100 and PGA responses were generally higher in patients without prior biologics. Week 8 PASI 50 response predicted PASI 90 response.

CONCLUSION

Pooled data confirmed the efficacy of tildrakizumab for moderate-to-severe plaque psoriasis.

Characterization of Spin on Glass Using Thermo Analytical Techniques and Ftir Spectroscopy

The curing of a commercial ethoxymethyl-phosphosiloxane at different temperatures and under various gas ambients was characterised using NMR, thermoanalytical techniques, and FTIR spectroscopy. DSC (Differential Scanning Calorimetry) and DTG (Differential Thermo Gravimetry) were employed to characterize the reactions that occur during thermal treatments in O2 or N2 atmospheres. FTIR spectroscopy and CP (Cross Polarization) 133C - NMR were used to detect the presence of the hydroxyl and organic groups in the cured samples. The experimental results identified three different temperatures (400,580,700°C) that define important stages of the curing reaction. In particular, for annealing at temperatuires up to 580°C in 02, DSC, DTG and FTIR spectra showed the elimination of the organic groups. However, when the annealing was carried out in N2 up to 700°C, these groups are retained.

Programmed death-1 receptor and interleukin-10 in liver transplant recipients at high risk for late cytomegalovirus disease

Despite significant advances in antiviral treatment, solid organ transplant (SOT) recipients remain at heightened risk for developing late cytomegalovirus (CMV) disease. Elevated inhibitory immune signaling suggests a state of immune impairment in SOT recipients, who do not control CMV infection and develop severe clinical symptoms after discontinuation of antiviral prophylaxis. We longitudinally monitored the negative immune modulator programmed death (PD)-1 receptor on both CD4 and CD8 T cells, co-expressing the CD137 surface marker of recent activation, in a liver transplant cohort. Liver recipients who progressed to CMV disease expressed elevated levels of PD-1 on CD137(+) CD4 and CD8 T cells, following stimulation with either full-length peptide libraries or CMV lysate. This novel approach, applicable to a multitude of human leukocyte antigen types, enhances the usefulness of the PD-1 measurements as a clinical strategy to predict late CMV disease. In parallel, we detected an increased level of the immunosuppressive cytokine interleukin (IL)-10, in plasma of liver recipients diagnosed with CMV disease. CMV-specific T cells were still functional when both PD-1 and IL-10 were upregulated; however they showed a marked proliferation deficit, which may limit their ability to contain viremia and lead to CMV disease. Our preliminary observations support further investigation of dual monitoring of PD-1 and IL-10, as potential immune markers of CMV disease.

A fusion protein of HCMV IE1 exon4 and IE2 exon5 stimulates potent cellular immunity in an MVA vaccine vector

A therapeutic CMV vaccine incorporating an antigenic repertoire capable of eliciting a cellular immune response has yet to be successfully implemented for patients who already have acquired an infection. To address this problem, we have developed a vaccine candidate derived from modified vaccinia Ankara (MVA) that expresses three immunodominant antigens (pp65, IE1, IE2) from CMV. The novelty of this vaccine is the fusion of two adjacent exons from the immediate-early region of CMV, their successful expression in MVA, and robust immunogenicity in both primary and memory response models. Evaluation of the immunogenicity of the viral vaccine in mouse models shows that it can stimulate primary immunity against all three antigens in both the CD4(+) and CD8(+) T cell subsets. Evaluation of human PBMC from healthy CMV-positive donors or patients within 6 months of receiving hematopoietic cell transplant shows robust stimulation of existing CMV-specific CD4(+) and CD8(+) T cell subsets.

Extended theoretical analysis of irreversible protein thermal unfolding

The theoretical analysis of the protein denaturation model which includes an irreversible, exothermic and rate-limited step has been improved and applied to the DSC profile of Azurin. The two-step nature of the irreversible denaturation of globular proteins is usually depicted in the following simplified scheme: N <--> U <--> F, which is known as the Lumry and Eyring model. In most of the works concerning the thermal unfolding of proteins, it is usually assumed that the irreversible step of the process does not take place significantly during the short time the protein spends in the temperature range of the DSC transition, or if this is not the case, that this irreversible step occurs with a negligible thermal effect. As we will show, this last assumption cannot be accepted acritically; in fact we have found that in the case of Azurin an evident exothermic effect occurs at the end of the transition. In order to fit the experimental Cp(exc) profile of Azurin, we have analyzed a model in which the exothermic effects of the irreversible step and the variations of DeltaH with temperature are taken into account. Our model was first tested simulating a series of profiles and considering the effects of the variation of the parameters on the shape of the curves, and successfully used to fit the experimental calorimetric profile of Azurin.

Theoretical basis for differential scanning calorimetric analysis of multimeric proteins

A new general equation simulating irreversible DSC transitions of multimeric proteins was developed. The equation put forward here is the result of an improved mathematical re-elaboration of the classical Lumry-Eyring models, where no restrictive a priori assumptions are made on the kinetic constraints of the denaturation process, or on the enthalpy of the final denatured state. In order to test the wide applicability of this new effective theoretical tool, a series of DSC transitions were simulated with the aim of determining the effects of all relevant thermodynamic, kinetic or experimental parameters on the shape of DSC profiles. Moreover, the classical equations used widely in DSC investigations for the calculus in both kinetic parameters and changes of molecularity, were studied in the light of the model developed here, highlighting, in each case, their rather limited applicability. The new approach proposed in this article was applied to study the thermal denaturation of an hexameric protein (Glucosamine-6-phosphate deaminase), putting in evidence the practical applicability of the theoretical equations developed.

The effect of copper/zinc replacement on the folding free energy of wild type and Cys3Ala/Cys26Ala azurin

The effect of copper/zinc metal ion replacement on the folding free energy of wild type (w.t.) and disulfide bridge depleted (C3A/C26A) azurin has been investigated by differential scanning calorimetry (DSC) and fluorescence techniques. The denaturation experiments have shown that, in both cases, the thermal transitions of the zinc derivative of azurins can be depicted in terms of the classical Lumry-Eyring model, N if U-->F, thus resembling the unfolding path of the two copper proteins. The thermally induced transition of Zn azurin, monitored by fluorescence occurs at lower temperature than the DSC scans indicating that a local conformational rearrangement of the Trp microenvironment, takes place before protein denaturation. For Zn C3A/C26A azurin, the two techniques reveal the same transition temperature. Comparison of the thermodynamic data shows that the presence of Zn in the active site stabilises the three-dimensional structure of azurin only when the disulfide bridge is present. Compared to the copper form of the protein, the unfolding temperature of Zn azurin has increased by 4 degrees C, while the unfolding free energy, deltaG, is 31 kJ/mol higher. Both enthalpic and entropic factors contribute to the observed DeltaG increase. However, the copper/zinc replacement has no effect on the unfolding free energy of C3A/C26A azurin. Taking Cu azurin w.t. as the reference state, for both Cu and Zn C3A/C26A azurin the unfolding free energy is decreased by about 28 kJ/mol, indicating that metal substitution is not able to compensate the destabilising effect induced by the disulfide bridge depletion. It is noteworthy that the thermal denaturation of the Zn derivative, which thermodynamically is the most stable form of azurin, is also characterized by the highest value of the activation energy, E(a), as derived from the kinetic stability analysis.

New microencapsulated sunscreens: technology and comparative evaluation

The aim of this work is to obtain new technologically improved microencapsulated sunscreens characterised by UV-radiation stability, good substantivity, low toxicity, a better tolerability and easiness to formulation. For this purpose we prepared two different systems using semisynthetic Hyaluronic Acid (HA) benzyl ester and a synthetic polymer (patent pending). We obtained these systems using two different methodologies: emulsification/solvent evaporation and emulsification/solvent extraction. The comparison between the two formulated systems was carried out in terms of their chemical-physical and biological properties.

Kinase-deficient CMVpp65 triggers a CMVpp65 specific T-cell immune response in HLA-A*0201.Kb transgenic mice after DNA immunization

CMVpp65, a candidate component of human cytomegalovirus (CMV) vaccines, has phosphokinase (PK) activity that could affect vaccine safety. A mutated form of CMVpp65 substituting asparagine for lysine at the adenosine triphosphate (ATP)-binding site (CMVpp65mII) is kinase-deficient. Using DNA immunizations in a transgenic human leucocyte antigen (HLA)A*0201.Kb mouse model, the mutated CMVpp65 induced cytotoxic T lymphocytes (CTL) immunity similarly to native CMVpp65. Murine CTL lines generated from these immunizations killed human cells either after sensitization with CMVpp65-specific peptides or after infection with either CMV-Towne strain or rvac-pp65. It is proposed that CMVpp65mII be evaluated in candidate vaccines for CMV.

Determination of levamisole in animal tissues using liquid chromatography with ultraviolet detection

An efficient and sensitive liquid chromatographic method is described for the determination of the anthelminthic drug levamisole, in muscle, liver, kidney and fat of sheep, pigs and poultry, using thiabendazole as internal standard. Samples were extracted by homogenizing with chloroform, and were applied to Supelco Si solid-phase extraction columns and eluted with methanol. Chromatographic analysis was performed on a LiChrospher 60 RP-Select B column using methanol/ammonium acetate buffer 0.05 M (55/65, v/v) as mobile phase and reading at 220 nm. The quantification limit for the assay was 4 ng/g. Mean recoveries were about 84% for liver, 85% for kidney, 89% for muscle and 84% for fat. The assay has been used for statutory testing purposes.

Status of Cytomegalovirus Prevention and Treatment in 2000

Cytomegalovirus (CMV) infection continues to be a problem in selected populations following hematopoietic stem cell transplantation (SCT). Although there have been no new antiviral agents for management of this infection in recent years, the methods for using the existing agents have improved with newer assays for detection of virus. In addition, our understanding of immunity to CMV has undergone considerable expansion. This paper will address these new aspects relating to CMV infection in the setting of SCT. In Section I Dr. Zaia reviews the pathogenesis of CMV and the current epidemiology of CMV disease following marrow or blood allo-SCT with emphasis on late-onset disease. The current lab tests available for preemptive management are summarized including the role for conventional shell vial cultures, and a comparison of the CMV antigenemia assay with the new nucleic acid-based assays, including the hybrid capture assay, the NASBA assay, and "real-time" PCR assays. Use of antiviral agents with these tests in the preemptive management of CMV infection is discussed. Ultimately, what is necessary is restoration of adequate CMV immunity, and that requires understanding the basics of the CMV-specific immune response. In Section II, Dr. Sissons traces the evolution of the CTL response from primary infection into memory and reviews recent advances in the understanding of cytotoxic T cell based immunity to CMV, based on the use of T cell clonotypic analysis and markers of T cell memory and activation, with conventional CTL functional assays. In Section III Dr. Riddell presents approaches to correction of the problem of CMV pathogenesis, namely direct restoration of the CMV-specific cellular immune deficiency. Attempts at passive therapies will be reviewed with the focus on current problems and approaches to these problems. In Section IV, Dr. Diamond presents work on the identification of multiple HLA-allele specific cytotoxic T cell epitopes specific for CMV-pp65 and - pp150. Specific epitopes are recognized by CMV-seropositive individuals including healthy donors, SCT recipients, and AIDS patients, indicating their potential usefulness as vaccines. One of these epitopes is recognized by most individuals who express the HLA A(*)0201 Class I allele. Pre-clinical evaluation in HLA2.1 transgenic mice of vaccine structures utilizing this epitope, and alternative delivery systems are described. Possible methods for vaccination of donor and/or recipient of a SCT as well as their limitations, utilizing synthetic or viral vaccines, are discusseed.

Human immunodeficiency virus-infected patients receiving highly active antiretroviral therapy maintain activated CD8+ T cell subsets as a strong adaptive immune response to cytomegalovirus

CD8(+) T lymphocyte function specific for human cytomegalovirus (CMV) was evaluated in 14 patients infected with human immunodeficiency virus (HIV) receiving highly active antiretroviral therapy (HAART) and 26 CMV-seropositive donors without HIV infection. Fifty-seven percent of the HIV-infected group had CMV-specific cytolytic activity in freshly isolated peripheral blood mononuclear cells (PBMC) against targets expressing CMV pp65. Both interferon (IFN)-gamma secretion by CD8(+) T cells and the frequency of human leukocyte antigen (HLA)-tetramer-positive T cells in HLA-A*0201-positive HIV-infected subjects correlated with CMV-specific cytolysis. In contrast, PBMC from healthy CMV-seropositive donors did not have either measurable CMV-specific cytolysis or secretion of IFN-gamma without in vitro stimulation. The T helper response to CMV antigens was vigorous in healthy CMV-seropositive donors but low in the cohort of HIV-infected patients. Potent CD8(+) cytotoxic T lymphocyte responses to CMV in HIV-infected patients receiving HAART is the converse of what is found in healthy CMV-seropositive subjects and may be the predominant adaptive immune response against CMV in HIV-infected patients.

Enhanced immune activity of cytotoxic T-lymphocyte epitope analogs derived from positional scanning synthetic combinatorial libraries

The pp65(495-503) cytotoxic T-lymphocyte (CTL) epitope from cytomegalovirus (CMV) is universally recognized among CMV+ individuals who express an allele of the human leukocyte antigen A (HLA-A*0201). The relative binding affinity of the epitope to HLA-A*0201 is moderate, and its increased activity might prove beneficial in its use as a CTL epitope vaccine. A new approach to enhance the activity of T-cell epitopes is the use of positional scanning synthetic combinatorial libraries (PS-SCLs). Using a nonamer PS-SCL, the pp65(495-503) epitope was modified after screening a CMV-specific T-cell clone (TCC) (3-3F4) from which the native peptide sequence was derived. Two peptides with amino acid substitutions at P1, P3, P7, and P8 are between 10(3) and 10(4) more active than the native epitope. Although the native CTL epitope terminates as a free acid, both tetrasubstituted peptides only function as CTL epitopes when the carboxyl terminus is amidated. Selective substitution of the native sequence based on PS-SCL screening results identified 3 amidated monosubstituted and disubstituted peptides that are better recognized than the native epitope by TCCs from a cohort expressing HLA-A*0201. In vitro stimulation of peripheral blood mononuclear cells with each of the peptide epitope analogs stimulated memory CTLs, which recognized CMV-infected targets among a high percentage of CMV+ individuals. Binding studies of peptide analogs with HLA-Ig (immunoglobulin) dimers and 2 different TCCs correlated with in vitro lysis results. These data suggest that increasing the activity of CTL epitopes while maintaining broad recognition is possible, which holds promise for vaccine development in infectious disease and cancer.

Population coverage by HLA class-I restricted cytotoxic T-lymphocyte epitopes

Vaccination using cytotoxic T-lymphocyte (CTL) epitopes has become a widely used immunization strategy, especially because their structure makes them an attractive alternative to the delivery of whole proteins as immunogens. Nonetheless, their use is limited, in particular because of their specificity, being recognized only by cognate HLA alleles. The potential for immunizing a substantial portion of an ethnically diverse population using a modest number of peptides has been aided by the identification of HLA supertypes. However, the derivation of epitopes is often guided by methods that do not guarantee cross-reactivity, so we consider the feasibility of providing vaccine coverage to a multi-ethnic population under different assumptions. In particular, two large datasets are used to estimate the number of peptides needed to provide > or =90% group-specific coverage of a multiethnic population, when specificity is assumed to be either to a single serologic or molecular type. These assumptions are evaluated utilizing a clinically important epitope repertoire derived from two human cytomegalovirus proteins, and data on the in vitro memory response elicited by these peptides is presented. In summary, our combined theoretical and empiric studies suggest that 90% coverage of some ethnic groups is attainable with 11 uniquely defined HLA-restricted CTL epitopes. The derivation of four or more additional CTL epitopes is needed to attain 90% coverage of Blacks or Asians, the minimally covered groups. Ninety percent coverage of all major ethnic groups in a multi-ethnic population appears feasible without relying on cross-reactivity, but may require two to three times more CTL epitopes than estimated for serologic data, homogenous populations, or HLA alleles grouped as supertypes.

Infrequent occurrence of natural mutations in the pp65(495-503) epitope sequence presented by the HLA A*0201 allele among human cytomegalovirus isolates

To determine if mutations of an immunodominant HLA-restricted cytomegalovirus (CMV) peptide sequence occur in nature, the sequence corresponding to the HLA A*0201-specific peptide CMVpp65(495-503) was determined in 50 human CMV isolates. Rare mutations were detected; 6 of 50 were silent mutations at the amino terminus of the peptide, while 3 of 50 were mutations of the native methionine residue to isoleucine (M499I). The observed M499I mutation in three isolates decreased cytolytic targeting.

Free energy for blue copper protein unfolding determined by electrospray ionisation mass spectrometry

An electrospray ionisation (ESI) mass spectrometric method for the determination of the free energy (DeltaG) of unfolding of proteins is described. The method was tested using three blue copper proteins: wild type azurin, Cys-3Ala/Cys-26Ala (C3A/C26A) azurin mutant and wild-type amicyanin. The time course of the denaturation process of the proteins dissolved in methanol/water (50:50, v/v, pH 3.5) was followed by recording ESI mass spectra at time intervals. The spectra showed two series of peaks, corresponding to the native holo-protein and the unfolded apo-protein. From the intensity ratio of these two series of peaks at increasing time and at equilibrium, the free energy for the unfolding process for the three proteins could be determined. To evaluate the reliability of the thermodynamic data obtained by the ESI mass spectrometric approach, the denaturation process was followed by UV-VIS spectroscopy. The two sets of data obtained by these independent methods were in good agreement indicating that the ESI-MS approach can be used to obtain reliable quantitative information about the protein unfolding process. In principle, this approach can be applied to other proteins and requires very low amounts of sample, due to the intrinsic sensitivity of mass spectrometry. This may prove particularly useful when the amount of sample available prevents the use of current methods.

Access to pyrrolo- and pyrido[1,2-a]indole derivatives by intramolecular nitrone cycloadditions. Effect of steric factors on the regioselective product formation

On starting from N-allyl-substituted 2-indolecarbaldehydes and exploiting the intramolecular nitrone cycloaddition methodology, we synthesized a number of the title fused-ring indole derivatives in racemic as well as enantiopure form.

A spectroscopic and calorimetric investigation on the thermal stability of the Cys3Ala/Cys26Ala azurin mutant

The disulfide bond connecting Cys-3 and Cys-26 in wild type azurin has been removed to study the contribution of the -SS- bond to the high thermal resistance previously registered for this protein (. J. Phys. Chem. 99:14864-14870). Site-directed mutagenesis was used to replace both cysteines for alanines. The characterization of the Cys-3Ala/Cys-26Ala azurin mutant has been carried out by means of electron paramagnetic resonance spectroscopy at 77 K, UV-VIS optical absorption, fluorescence emission and circular dichroism at room temperature. The results show that the spectral features of the Cys-3Ala/Cys-26Ala azurin resemble those of the wild type azurin, indicating that the double mutation does not affect either the formation of the protein's overall structure or the assembly of the metal-binding site. The thermal unfolding of the Cys-3Ala/Cys-26Ala azurin has been followed by differential scanning calorimetry, optical absorption variation at lambda(max) = 625 nm, and fluorescence emission using 295 nm as excitation wavelength. The analysis of the data shows that the thermal transition from the native to the denaturated state of the modified azurin follows the same multistep unfolding pathway as observed in wild type azurin. However, the removal of the disulfide bridge results in a dramatic reduction of the thermodynamic stability of the protein. In fact, the transition temperatures registered by the different techniques are down-shifted by about 20 degrees C with respect to wild type azurin. Moreover, the Gibbs free energy value is about half of that found for the native azurin. These results suggest that the disulfide bridge is a structural element that significantly contributes to the high stability of wild type azurin.

The antiviral activity of a synthetic peptide derived from the envelope SU glycoprotein of feline immunodeficiency virus maps in correspondence of an amphipathic helical segment

In a previous paper (Lombardi et al., Virology 220, 274-284, 1996), we-reported that a 20-amino acid synthetic peptide derived from a conserved region of the SU glycoprotein of feline immunodeficiency virus (FIV), i.e., 225EGPTLGNWAREIWATLFKKA244, bound the surface of FIV-permissive cells and inhibited FIV infection of CrFK and lymphoid cells. In this paper, we report, by the use of N- and C-terminus deleted synthetic analogs and by glycine scanning experiments that the minimal sequence needed for the full antiviral activity of the peptide maps in correspondence of amino acids 229LGNWAREIWATL240 and that either tryptophans residues at sequence position 232 or 237 are essential for such activity. Circular dichroism (CD) studies indicate that in the presence of a hydrophobic environment the 225E-A244 peptide adopts a structure containing an amphipathic alpha-helical segment of approximately 7 residues, corresponding to 2 helical turns, likely in correspondence of the sequence 231(N)WAREIW(A)238. Such a helical segment of FIV SU glycoprotein may play a role in viral envelope fusion role with the host cell membrane, thus proving critical for cell infection.

Anomalous phase transition in dipalmitoylphosphatidylethanolamine/palmitoylphosphatidylcho line/water system

An anomalous phase transition with a marked rise in specific heat, the isobaric thermal expansion coefficient, and the compressibility coefficient at 62.5 degrees C for an equimolar mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and 1-palmitoyl-sn-glycero-3-phosphocholine (PLPC), in water (34 wt.%) has been shown by differential scanning calorimetry, scanning dilatometry and isothermal compressibility measurements. This transition occurs 15 degrees C above a first-order transition observed in the same system. (31)P and (2)H nuclear magnetic resonance results are consistent with the occurrence of 'defects' in the bilayer in the temperature range between the first and the anomalous phase transitions. It is proposed that conically, PLPC molecules prefer regions with high curvature in the defective bilayer, while DPPE molecules are mostly confined to the flat regions of the bilayers.

Most potential linear B cell epitopes of Env glycoproteins of feline immunodeficiency virus are immunogenically silent in infected cats

A battery of sixty-six 20- to 23-amino acid synthetic peptides, partially overlapping by 10-12 amino acids, spanning the entire sequence of the envelope (Env) glycoproteins of the Petaluma isolate of feline immunodeficiency virus (FIV-Pet), has been used to map Env linear B cell epitopes. By screening FIV-infected cat sera for anti-peptide reactivity, the existence of two immunodominat domains, namely the V3 region of the surface (SU) glycoprotein and the domain including the highly conserved sequence QNQFF of the transmembrane (TM) glycoprotein, was detected; antibody-binding sites were also mapped in the domain overlapping the cleavage site between SU and TM encompassing the V6 variable region. Moreover, at least two novel linear B epitopes, the former spanning residues 427M-H446 and the latter spanning residues 737N-N756 and likely representing a "type-specific" determinant, have been revealed. The battery of synthetic peptides was then used to immunize outbred Swiss mice in the attempt to reveal other potential sites of immunogenicity of the Env glycoproteins. Analysis of peptide-immunized mouse sera for anti-peptide reactivity revealed more numerous B cell epitopes, generally mapping in different peptides, as compared with those defined in the feline system. None of the mouse anti-peptide sera, however, proved neutralizing for FIV-Pet.

Inhibition of feline immunodeficiency virus infection in vitro by envelope glycoprotein synthetic peptides

Sixty-six 20- to 23-amino-acid synthetic peptides, partially overlapping by 10-12 amino acids, spanning the entire sequence of the envelope SU and TM glycoproteins of the Petaluma isolate of FIV, have been used to investigate the Env domains involved in viral infection. Peptides 5 to 7, spanning amino acids 225E-P264 located in a conserved region of the SU protein, and peptides 58 to 61, spanning amino acids 767N-P806 and encompassing hypervariable region 8 of TM protein, exhibited a remarkable and specific antiviral effect against the homologous and one heterologous isolate, as judged by inhibition of FIV-induced syncytium formation and p25 production in CrFK cells. Peptides 5 and 7, but not peptides 58 and 59, also inhibited viral replication of a fresh FIV isolate on nontransformed lymphoid cells. By flow cytometry, peptides 5, 7, 58, and 59 were shown to bind the surface of FIV permissive cells. The antiviral activity of peptides 5 and 7, however, was time-dependent, as inhibition of FIV replication was seen when the peptides were administered before or within 3 hr after virus inoculation; in contrast, TM peptides 58 and 59 exerted a potent inhibitory effect when added up to 24 hr after virus inoculation. Circular dychroism analysis showed that peptide 5 folds to a helical conformation in the presence of a hydrophobic environment. Although the basis for the antiviral action of the peptides is not understood, our data suggest that the inhibitory peptides may act by interacting with cell-surface molecules involved in viral infection.

Enzyme support systems for biosensor applications based on gold-coated nylon meshes

A novel experimental protocol for enzyme immobilization based on the use of a very permeable support is described and applied to the development of an acetylcholinesterase (AChE) based biosensor. In this system, the enzyme was immobilized onto a gold-coated nylon mesh via a self-assembled monolayer of a bifunctional reagent, cystamine, preadsorbed onto the gold surface. This support has been characterized by optical microscopy and electrochemical measurements of permeability. In the assembled biosensor, the AChE modified mesh was placed over a glassy carbon electrode and the response to 4-aminophenylacetate, used as substrate, was monitored via the enzymatic reaction product, 4-aminophenol, by oxidation at +0.25 V vs. SSCE. This approach to biosensor design has been extended to the determination of organophosphorus and carbamate pesticides by their inhibition of AChE enzymatic activity.

Epitope mapping of the V3 domain of feline immunodeficiency virus envelope glycoprotein by monoclonal antibodies

A panel of six IgG monoclonal antibodies (MAbs) was produced by immunizing mice with a 22 amino acid synthetic peptide, designated V3.3, of the third variable region of feline immunodeficiency virus (FIV) envelope glycoprotein. This peptide is known to induce neutralizing antibodies in cats. In ELISA all MAbs reacted with purified SDS-disrupted FIV and in flow cytometry all MAbs stained permeated, persistently infected FL4 cells but not unfixed FL4 cells; this indicated that the MAbs recognize essentially cryptic epitopes of the gp100 V3 loop. By direct ELISA using partially overlapping synthetic peptides and by competition binding studies, the anti-V3.3 MAbs were shown to detect at least four distinct epitopes, two located in the amino-terminal half and two in the carboxy-terminal half of the sequence. When tested for neutralizing activity by the syncytium inhibition assay in Crandell feline kidney cells, all anti-V3.3 MAbs neutralized FIV at high dilution. However, at low dilution two MAbs exhibited much less neutralizing activity. These results indicate that the V3 region of FIV contains multiple epitopes involved in neutralization.

Identification of a linear neutralization site within the third variable region of the feline immunodeficiency virus envelope

Synthetic peptides have been used to map linear B-cell epitopes of the third variable (V3) region of the feline immunodeficiency virus (FIV) external membrane glycoprotein gp120. The analysis of sera from naturally and experimentally FIV-infected cats by Pepscan and enzyme immunoassay with four partially overlapping peptides evidenced three antibody-binding domains, two of which mapped in the carboxyl-terminal half of V3. In particular, the V3.3 sequence (Gly-392-Phe-413) turned out to be important for in vitro neutralization of the virus in that the peptide inhibited the FIV-neutralizing activity of pooled immune cat sera, and on the other hand, cat sera raised against this peptide effectively neutralized FIV infectivity for Crandell feline kidney cells.

Inhibition of serine proteinases belonging to the chymotrypsin superfamily by the cyclic thiolic compound YS3025: a comparative crystallographic study

The synthetic cyclic thiolic compound 3-[2-(2-thiophencarboxythio)]-propanoyl-4-thiazolidin carboxylic acid (YS3025) acts as an effective inhibitor of bovine alpha-chymotrypsin. In the present communication YS3025 binding studies are extended to bovine beta-trypsin and porcine pancreatic elastase, by means of crystallographic difference Fourier techniques. For all the enzymes considered, the thiopencarbonyl moiety of YS3025 is located at the entrance of the inhibited proteinase primary specificity pocket (S1), covalently linked to the catalytic Ser195 OG atom, and forming an acyl-enzyme complex. These observations allow to select between alternative binding (and inhibition) mechanisms for YS3025 and related molecules to serine proteinases belonging to the chymotrypsin superfamily.

Serine proteinase inhibition by the cyclic thiolic compound YS3025: a crystallographic study

In order to unravel the serine proteinase inhibition mechanism by cyclic thiolic compounds, the X-ray crystal structure of bovine alpha-chymotrypsin inhibited by 3-[2-(2-thiophencarboxythio)]-propanoyl-4-thioazolidin carboxylic acid (YS3025) has been studied by means of difference Fourier techniques and refined at 2.8 A resolution (R-factor = 0.174). The thiophencarbonyl moiety of YS3025 is covalently linked, in the acyl-enzyme complex, to Ser195 OG atom of bovine alpha-chymotrypsin, and located at the entrance of the proteinase primary specificity subsite (S1). The present data confirm previous hypotheses raised on the inhibition mechanism of serine proteinases, based on solution studies of human leukocyte elastase in the presence of the YS3025 parent compound 2-[3-thiophencarboxythio]-N-[dihydro-2(3H)- thiophenone-3-il]-propionamide (MR889).

Liposomes as a potential drug carrier for citicoline (CDP-choline) and the effect of formulation conditions on encapsulation efficiency

In this paper we report the investigation of the potential of liposomes as drug carrier for citicoline (1; CDP-choline). The aim of our work is to improve the pharmacokinetic and pharmacodynamic parameters of the drug to facilitate the overcoming of the blood-brain barrier. The thermotropic behaviour of hydrated dispersions of various phospholipids and their mixtures containing 1 have been investigated by differential scanning calorimetry (DSC) to have a clear view of the interaction between the drug and the liposome phospholipids. By the values of transition peak temperature (Tm) and transition enthalpy (delta H) we note a strong interaction between 1 and the polar heads of L-alpha-dipalmitoylphosphatidic acid (DPPA) and L-alpha-dipalmitoylphosphatidylserine (DPPS), whereas there is not any considerable interaction between the drug and L-alpha-dipalmitoylphosphatidylcholine (DPPC) or L-alpha-dimyristoylphosphatidylcholine (DMPC); in any case no interaction occurs between 1 and the hydrophobic part of the phospholipid. So we conclude that all the drug is fitted into the aqueous spaces. The results of the encapsulation efficiency experiments demonstrate how the encapsulation capacity increase with using charged phospholipids, reaching the top with DPPA. Moreover, it was noted that the presence of Cholesterol (Chol) enhances the encapsulation capacity (EC) and drug content (DC) values of DPPC, a neutral phospholipid. The size of the liposomes was determined by light scattering (LS).

Evaluation of 2-(2-thiophenecarboxy)benzoic acid and related active metabolites in biological samples

This paper describes a quantitative assay of 2-(2-thiophenecarboxy)benzoic acid and its systemic metabolites, namely salicylic acid and thiophenecarboxylic acid, by high-performance liquid chromatography with ultraviolet detection at 254 nm. Analytes were extracted from acidified samples with tert.-butylmethyl ether and separated with an RP-18 column (150 mm x 3 mm I.D., 5 microns particle size) with a mixture of 0.01 M potassium phosphate and methanol (70:30, v/v) at pH 3.1. The method proved to have the validation required for pharmacokinetic investigations in animals and humans.