Structure-Guided Approach for the Development of MUC1-Glycopeptide-Based Cancer Vaccines with Predictable Responses

Mucin-1 (MUC1) glycopeptides are exceptional candidates for potential cancer vaccines. However, their autoantigenic nature often results in a weak immune response. To overcome this drawback, we carefully engineered synthetic antigens with precise chemical modifications. To be effective and stimulate an anti-MUC1 response, artificial antigens must mimic the conformational dynamics of natural antigens in solution and have an equivalent or higher binding affinity to anti-MUC1 antibodies than their natural counterparts. As a proof of concept, we have developed a glycopeptide that contains noncanonical amino acid (2S,3R)-3-hydroxynorvaline. The unnatural antigen fulfills these two properties and effectively mimics the threonine-derived antigen. On the one hand, conformational analysis in water shows that this surrogate explores a landscape similar to that of the natural variant. On the other hand, the presence of an additional methylene group in the side chain of this analog compared to the threonine residue enhances a CH/π interaction in the antigen/antibody complex. Despite an enthalpy-entropy balance, this synthetic glycopeptide has a binding affinity slightly higher than that of its natural counterpart. When conjugated with gold nanoparticles, the vaccine candidate stimulates the formation of specific anti-MUC1 IgG antibodies in mice and shows efficacy comparable to that of the natural derivative. The antibodies also exhibit cross-reactivity to selectively target, for example, human breast cancer cells. This investigation relied on numerous analytical (e.g., NMR spectroscopy and X-ray crystallography) and biophysical techniques and molecular dynamics simulations to characterize the antigen-antibody interactions. This workflow streamlines the synthetic process, saves time, and reduces the need for extensive, animal-intensive immunization procedures. These advances underscore the promise of structure-based rational design in the advance of cancer vaccine development.

Structure-based Design of Anti-cancer Vaccines: The Significance of Antigen Presentation to Boost the Immune Response

Immunotherapy, alone or in combination with other therapies, is widely used against cancer. Glycoprotein Mucin 1 (MUC1), which is overexpressed and aberrantly glycosylated in tumor cells, is one of the most promising candidates to engineer new cancer vaccines. In this context, the development of stable antigens that can elicit a robust immune response is mandatory. Here, we describe the design and in vivo biological evaluation of three vaccine candidates based on MUC1 glycopeptides that comprise unnatural elements in their structure. By placing the Tn antigen (GalNAcα-O-Ser/Thr) at the center of the design, the chemical modifications include changes to the peptide backbone, glycosidic linkage, and at the carbohydrate level. Significantly, the three vaccines elicit robust immune responses in mice and produce antibodies that can be recognized by several human cancer cells. In all cases, a link was stablished between the conformational changes induced by the new elements in the antigen presentation and the immune response induced in mice. According to our data, the development of effective MUC1-based vaccines should use surrogates that mimic the conformational space of aberrantly glycosylated MUC1 glycopeptides found in tumors.

Synthesis, conformational analysis and in vivo assays of an anti-cancer vaccine that features an unnatural antigen based on an sp2-iminosugar fragment

The Tn antigen (GalNAc-α-1-O-Thr/Ser) is a well-known tumor-associated carbohydrate determinant. The use of glycopeptides that incorporate this structure has become a significant and promising niche of research owing to their potential use as anticancer vaccines. Herein, the conformational preferences of a glycopeptide with an unnatural Tn antigen, characterized by a threonine decorated with an sp²-iminosugar-type α-GalNAc mimic, have been studied both in solution, by combining NMR spectroscopy and molecular dynamics simulations, and in the solid state bound to an anti-mucin-1 (MUC1) antibody, by X-ray crystallography. The Tn surrogate can mimic the main conformer sampled by the natural antigen in solution and exhibits high affinity towards anti-MUC1 antibodies. Encouraged by these data, a cancer vaccine candidate based on this unnatural glycopeptide and conjugated to the carrier protein Keyhole Limpet Hemocyanin (KLH) has been prepared and tested in mice. Significantly, the experiments in vivo have proved that this vaccine elicits higher levels of specific anti-MUC1 IgG antibodies than the analog that bears the natural Tn antigen and that the elicited antibodies recognize human breast cancer cells with high selectivity. Altogether, we compile evidence to confirm that the presentation of the antigen, both in solution and in the bound state, plays a critical role in the efficacy of the designed cancer vaccines. Moreover, the outcomes derived from this vaccine prove that there is room for exploring further adjustments at the carbohydrate level that could contribute to designing more efficient cancer vaccines.

An anti-cancer vaccine based on an unnatural antigen with an sp²-iminosugar fragment.

The Use of Fluoroproline in MUC1 Antigen Enables Efficient Detection of Antibodies in Patients with Prostate Cancer

A structure-based design of a new generation of tumor-associated glycopeptides with improved affinity against two anti-MUC1 antibodies is described. These unique antigens feature a fluorinated proline residue, such as a (4S)-4-fluoro-l-proline or 4,4-difluoro-l-proline, at the most immunogenic domain. Binding assays using biolayer interferometry reveal 3-fold to 10-fold affinity improvement with respect to the natural (glyco)peptides. According to X-ray crystallography and MD simulations, the fluorinated residues stabilize the antigen-antibody complex by enhancing key CH/π interactions. Interestingly, a notable improvement in detection of cancer-associated anti-MUC1 antibodies from serum of patients with prostate cancer is achieved with the non-natural antigens, which proves that these derivatives can be considered better diagnostic tools than the natural antigen for prostate cancer.

The synergy of ChemMatrix resin and pseudoproline building blocks renders RANTES, a complex aggregated chemokine

Traditionally, solid-phase synthesis has relied on polystyrene-based resins for the synthesis of all kinds of peptides. However, due to their high hydrophobicity, these resins have certain limitations, particularly in the synthesis of complex peptides, and in such cases, poly(ethylene glycol) (PEG)-based resins are often found to give superior results. Another powerful strategy for expediting the assembly of complex peptides is to employ pseudoproline dipeptides. These derivatives disrupt the interactions among chains that are usually the cause of poor coupling yields in aggregated sequences. Here we report on an efficient stepwise solid-phase synthesis of RANTES (1-68) by combining the advantages of the totally PEG-based ChemMatrix resin and pseudoproline dipeptides.

ChemMatrix, a poly(ethylene glycol)-based support for the solid-phase synthesis of complex peptides

CM (ChemMatrix) resin is a new, totally poly(ethylene glycol) (PEG)-based resin, made exclusively from primary ether bonds and, therefore, highly chemically stable. It exhibits good loading and is user-friendly because of its free-flowing form upon drying. It performs excellently for the preparation of hydrophobic, highly structured, and poly-Arg peptides, as compared to polystyrene (PS) resins. In the most striking example, stepwise solid-phase assembly of the highly complex beta-amyloid (1-42) peptide resulted in a crude material of 91% purity. In contrast, literature procedures using PS or PEG-PS-based resins for this peptide required convergent approaches, additional time-consuming steps, or both. In addition to the difficulties of its synthesis, characterization of the beta-amyloid (1-42) peptide as a monomer is also a challenge, and methods for characterization by HPLC and MALDI-TOF have also been developed.

[Minimal changes nephrotic syndrome associated to penicillamine treatment]

We describe three patients with minimal change nephrotic syndrome associated with penicillamine treatment. Two patients had systemic sclerosis and one had rheumatoid arthritis. Cumulative dose of D-penicillamine was similar in all cases, and nephrotic syndrome appeared after 15-33 months of treatment. The drug was stopped and nephrotic syndrome disappeared in 2-4 months, suggesting a possible causal relationship between penicillamine and minimal change disease.

A novel CD18 genomic deletion in a patient with severe leucocyte adhesion deficiency: a possible CD2/lymphocyte function-associated antigen-1 functional association in humans

Leucocyte adhesion deficiency (LAD) is an autosomal-recessive genetic disease that is characterized clinically by severe bacterial infections and caused by mutations in the CD18 gene that codes for the beta2 integrin subunit. A patient with a severe LAD phenotype was studied and the molecular basis of the disease was identified as a single homozygous defect in a Herpes virus saimiri (HVS)-transformed T-cell line. The defect identified involves a deletion of 171 bp in the cDNA that encodes part of the proteic extracellular domain. This genetic abnormality was further studied at the genomic DNA level and found to consist of a deletion of 169 bp (from -37 of intron 4 to +132 of exon 5), which abolishes the normal splicing and results in the total skipping of exon 5. The 171-bp shortened 'in-frame' mRNA not only resulted in the absence of CD18 expression on the cell surface but also in its absence in the cytoplasm of HVS T-cell lines. Functionally, the LAD-derived HVS T-cell lines showed a severe, selective T-cell activation impairment in the CD2 (but not in the CD3) pathway. This defect was not reversible when exogenous interleukin-2 (IL-2) was added, suggesting that there is also a functional interaction of the lymphocyte function-associated antigen-1 (LFA-1) protein in the CD2 signal transduction pathway in human T cells, as has been previously reported in mice and in the human Papillon-Lefèvre syndrome. Thus, HVS transformation is not only a suitable model for T-cell immunodeficiency studies and characterization, but is also a good system for investigating the immune system in pathological conditions. It may also be used in the future in cellular models for in vitro gene-therapy trials.

Prognosis of acute tubular necrosis: an extended prospectively contrasted study

The ability to predict the outcome in acute tubular necrosis (ATN) remains elusive despite considerable efforts. Accurate prediction is a crucial priority and has large economical and ethical implications, mainly to judge when treatment is futile and further efforts only prolong miserable agony. To analyze the influence of risk factors in the prognosis of ATN, we applied, in an initial phase, a prospective protocol of demographic data, cause of renal failure, diuresis, need of dialysis and clinical conditions in 228 patients using multiple linear and logistic regression models. In a control phase with 100 consecutive patients, we checked the accuracy of the results previously obtained, evaluating further the overall population of 328 patients in a synthetic phase. Finally, the validation of the equations obtained was verified in 25 patients from another hospital. As a complement of this 4-phase study, detailed statistical comparisons between both linear and logistic multiple regression models were undertaken. Correlation between probability of death obtained with equations from the initial phase applied to control patients and real evolution of these patients, survival or death, was excellent. The study of the synthetic phase revealed coma, assisted respiration, hypotension, oliguria and jaundice as having an independent positive influence on mortality and nephrotoxic etiology and normal consciousness on good prognosis. For the linear model, the same cut-off point of discriminant score (0.9) above which there were no chances for survival could be established in the 4 phases. With the logistic model, it only was found at later phases. The multiple linear was better than the logistic regression model in terms of better correlation with real mortality, better sensitivity and specificity intervals, easier use of discriminant cut-off point and better adjustment of distribution of standardized residuals to expected normal function. Early prognosis of ATN is possible and can be given using simple clinical features. A discriminant score allows to distinguish patients without chances for survival. The multiple linear is better than the logistic regression model in the prediction of the outcome in ATN.

Growth hormone response to acute growth hormone releasing hormone administration in uraemic patients on haemodialysis

To examine the response of growth hormone (GH) to growth hormone releasing factor (GHRF) in patients on haemodialysis, we performed the acute GHRF test (50 micrograms administered intravenously as a bolus) in 10 uraemic male patients on haemodialysis and eight normal controls. Each patient was tested before and after a haemodialysis session (at 08.30 and 12.30). Controls were tested on the same time schedule. At 08.30, patients had significantly greater basal and peak GH values (2.5 +/- 0.6 and 27.8 +/- 5.5 micrograms/l) than controls (0.68 +/- and 11.5 +/- 4 micrograms/l). After the haemodialysis session, basal and peak values declined significantly (P less than 0.01) in the uraemic group (0.5 +/- 0.03 and 3.1 +/- 1.1 micrograms/l), whereas the controls did not show such a change in the 12.30 test. Basal and intratest glycaemic values were comparable both before and after haemodialysis. After dialysis test results did not change either with the use of glucose-free dialysate or with bicarbonate buffer. Uraemic patients display a greater GH response to GHRF injection than normal subjects, and this response decreases after haemodialysis. The degree of reduction has no relationship with either glycaemia or the dialysate buffer. We suggest that other GH secretion regulating factors are altered by the haemodialysis procedure.

Anticardiolipin antibodies and lupus anticoagulant in end-stage renal disease

Anticardiolipin antibodies are autoantibodies clinically associated with hypercoagulability. Systemic thrombosis and thrombosis of the vascular access for haemodialysis coexist with immunoregulation abnormalities in end-stage renal disease (ESRD). The aim of the present study was to analyse the incidence of thrombotic episodes and the presence of anticardiolipin antibodies and lupus anticoagulant in 73 patients with ESRD--51 on haemodialysis and 22 on conservative treatment. Four (18%) patients on conservative treatment had IgG-anticardiolipin, three of them also having lupus anticoagulant. Sixteen (31%) patients on haemodialysis showed IgG-anticardiolipin and 11 (22%) lupus anticoagulant; overall, 19 (37%) patients on haemodialysis had IgG-anticardiolipin and/or lupus anticoagulant. This greater incidence in haemodialysis was associated with a more frequent use of cuprophane membranes (68% versus 34%, P less than 0.05). Six patients with ESRD--one on conservative treatment--met criteria for the diagnosis of primary antiphospholipid syndrome, clinically characterised by thrombosis of the vascular access. IgG-anticardiolipin and/or lupus anticoagulant are frequently found in ESRD and their incidence increases with haemodialysis, probably due to some kind of membrane bioincompatibility. IgG-anticardiolipin and lupus anticoagulant can be associated with thrombotic episodes, being constituents of an ESRD-related antiphospholipid syndrome.

Easy and early prognosis in acute tubular necrosis: a forward analysis of 228 cases

Multiple factors still influence the high rate of mortality in acute tubular necrosis. Trying to analyze the influence of each risk factor present in an individual patient and the possible interdependence between these factors, as well as to obtain an early prognosis, we have applied a forward analysis to demographic data, acute renal failure origin, need of dialysis, diuresis and clinical conditions in 228 patients, using a multiple linear regression model contained in a computer package. Based on this approach we have found that three variables: deep neurological coma, persistent blood hypotension and assisted respiration have significant influence on mortality. Also, a regression equation was obtained which could be applied as a discriminant score to patient prognosis. This score, calculated with the three aforementioned variables and oliguria when the nephrologist sees the patient for the first time, allows an easy and early prognosis in each patient with acute tubular necrosis.

Veno-occlusive hepatic disease of the liver in renal transplantation: is azathioprine the cause?

Five male patients with veno-occlusive disease of the liver (VOD) were observed in 200 consecutive renal transplants (RT) treated with azathioprine and prednisone. Mild liver enzymatic increases not justified by other reasons were detected between 2 and 9 months after RT. All 5 patients developed portal hypertension and died between 18 and 79 months following RT. Diagnosis of VOD was histological; in 3 cases diagnosis was made while the patients were still alive. In our patients, 9 previous viral hepatotropic infections (5 during hemodialysis and 4 after TR) were demonstrated. Due to the reported low incidence of VOD in RT patients, when many of them have been treated with azathioprine, the etiological role of this drug must be questioned. However, the possible association of a previous hepatotropic viral infection and the use of an immunosuppressive agent should be considered as a probable cause of VOD in kidney grafts.