Peptide and peptide mimetic inhibitors of antigen presentation by HLA-DR class II MHC molecules. Design, structure-activity relationships, and X-ray crystal structures

Molecular features of ligand binding to MHC class II HLA-DR molecules have been elucidated through a combination of peptide structure-activity studies and structure-based drug design, resulting in analogues with nanomolar affinity in binding assays. Stabilization of lead compounds against cathepsin B cleavage by N-methylation of noncritical backbone NH groups or by dipeptide mimetic substitutions has generated analogues that compete effectively against protein antigens in cellular assays, resulting in inhibition of T-cell proliferation. Crystal structures of four ternary complexes of different peptide mimetics with the rheumatoid arthritis-linked MHC DRB10401 and the bacterial superantigen SEB have been obtained. Peptide-sugar hybrids have also been identified using a structure-based design approach in which the sugar residue replaces a dipeptide. These studies illustrate the complementary roles played by phage display library methods, peptide analogue SAR, peptide mimetics substitutions, and structure-based drug design in the discovery of inhibitors of antigen presentation by MHC class II HLA-DR molecules.

Prevalence of autoantibodies to ribosomal P proteins in juvenile-onset systemic lupus erythematosus compared with the adult disease

OBJECTIVE

To determine the prevalence of anti-ribosomal P (anti-P) proteins in several groups of patients with juvenile-onset systemic lupus erythematosus (SLE) in comparison with the prevalence in adult SLE.

METHODS

Serum samples were pooled together from 3 cohorts of patients with juvenile-onset SLE in 3 different medical centers and from a miscellaneous group of juvenile-onset SLE patients whose samples were sent by regional physicians. Sera were studied for the presence of anti-P using 2 assays: Western blot with ribosomes as antigen, and an enzyme-linked immunosorbent assay with the COOH-terminal 22 amino acids of the ribosomal P protein in a multiantigenic peptide format as antigen. Sera found positive by both tests were considered positive for anti-P antibodies. Findings from similar studies involving a large cohort of patients with adult-onset SLE from Oklahoma City were used for comparison.

RESULTS

The prevalence of anti-P antibodies in the pooled sample of juvenile-onset SLE sera was 45 of 108, or 42%, while in the adult cohort from Oklahoma City, 20 of 260, or 7.7%, were positive for anti-P (odds ratio [OR] 9.6, P < 10(-8) by Fisher's exact test). In addition, it was shown that 12 of 13 patients with both anti-P and anti-double-stranded DNA (anti-dsDNA) in the juvenile SLE cohort had nephritis, while only 8 of 22 patients without both antibodies were nephritic (OR 21.0, P < 10(-8)). It was also shown that in 9 illustrative cases, the levels of anti-P and anti-dsDNA antibodies usually varied together and in concordance with the clinical activity as measured by the SLE Disease Activity Index (SLEDAI). Finally, anti-P-positive and anti-P-negative patients had a similar prevalence of anti-dsDNA, anti-Ro/SSA, and anti-La/SSB antibodies, but patients with anti-P had a higher prevalence of anti-U1 RNP and anti-Sm (P = 0.041 and P = 0.0385, respectively, by Fisher's exact test).

CONCLUSION

Antibodies to ribosomal P protein are more prevalent in juvenile-onset SLE than in adult-onset SLE. Levels of antibodies to ribosomal P protein vary with the clinical disease activity as measured by the SLEDAI, often in concordance with the levels of anti-dsDNA. The presence of both anti-P and anti-dsDNA antibodies was powerfully associated with nephritis in the cohort of patients for whom comprehensive clinical and serologic data were available.

Cross-cultural adaptation and validation of an Argentine Spanish Version of the Stanford Childhood Health Assessment Questionnaire

OBJECTIVES

To translate into Argentine Spanish and cross-culturally adapt the Childhood Health Assessment Questionnaire (CHAQ) and validate the adapted instrument in Argentine patients with juvenile rheumatoid arthritis (JRA).

METHODS

Five bilingual Argentine pediatric rheumatologists translated into Argentine Spanish and cross-culturally adapted the United States English CHAQ. Pretesting was done in a sample of 23 parents using a probe question technique. Parents of 70 patients with JRA and 21 healthy children (controls) participated in the validation phase. All were from Argentina.

RESULTS

The mean disability index (DI) scores for patients with systemic, polyarticular, or pauciarticular onset JRA were 0.64, 0.32, and 0.1, respectively. Healthy controls averaged 0.2. Intercomponent correlations were between 0.4 and 0.9, suggesting internal consistency, but also some redundancy. Test-retest reliability, studied at a 1-week interval, was moderate (mean DI 0.44 [in clinic] and 0.29 [one week later], Pearson's correlation = 0.82). We compared CHAQ scores from 15 parents with those of their children > 10 years of age. Significantly higher DI scores were given by patients than their respective parents (P > 0.019), but the pairwise scores (parent-patient) were highly correlated (r = 0.986).

CONCLUSIONS

Cross-cultural adaptation of the US CHAQ to Argentina required few changes. Although DI scores for all patient subgroups were higher than for controls subjects, the scores were low, particularly for those with pauciarticular disease. Prospective studies designed to examine the sensitivity to change and predictive validity will help to assess further the usefulness of the adapted CHAQ in the Argentine population.

Protein farnesyltransferase: structure and implications for substrate binding

The rat protein farnesyltransferase crystal structure has been solved by multiple isomorphous replacement methods at a resolution of 2.75 A. The three-dimensional structure, together with recent data on the effects of several mutations, led us to propose a model for substrate binding which differs from the model presented by Park et al. based on their independent structure determination [Park, H. -W., Boduluri, S. R., Moomaw, J. F., Casey, P. J., and Beese, L. S. (1997) Science 275, 1800-1804]. Both farnesyl diphosphate and peptide substrates can be accommodated in the hydrophobic active-site barrel, with the sole charged residue inside the barrel, Arg202 of the beta-subunit, forming a salt bridge with the negatively charged carboxy terminus of peptide substrates. Our proposals are based in part on the observation of electron density in the active site which can be modeled as bound farnesyl diphosphate carried through the enzyme purification. In addition, our model explains in structural terms the results of mutational studies which have identified several residues critical for substrate specificity and catalysis.

Regression of calcinosis during diltiazem treatment in juvenile dermatomyositis

An 8-year-old girl with juvenile dermatomyositis (DM) developed dystrophic calcifications 26 months after diagnosis. She also had severe steroid induced bone loss (osteoporosis). The calcifications turned into generalized heterotopic calcinosis with an exoskeleton-like pattern, despite successful treatment of her myopathy with methylprednisolone and immunosuppressive drugs. She was subsequently treated with oral diltiazem (5 mg/kg/day) to control calcinosis and oral pamidronate (4 mg/kg/day) in addition to calcium and vitamin D supplementation, which she had been taking for 3 years. After 21 months of treatment, clinical and radiological examination revealed dramatic regression of the calcinosis. Bone mass reached normal levels, as determined by bone absorptiometry. Diltiazem alone or in combination with other drugs could be a useful therapy in patients with juvenile DM and pronounced calcifications.

Assisted fertilization with epididymal spermatozoa

In vitro fertilization is used for several years as a technique for resolving infertility problems due to moderate or severe oligospermia. More recently, techniques of micro-insemination of oocytes have also become available for cases of extremely severe oligospermia which cannot be resolved by classical I.V.F. Nevertheless, although these particular techniques have already led to results which have gone far beyond initial hopes, they are not able to resolve all cases of male sterility. There are indeed many situations of excretory azoospermia associated with normal spermatogenesis; the spermatozoa remain trapped in a more or less extensive part of the epididymis because its passage is blocked, either because of post-infectious sclerosis, or of agenesis of a variably extensive area of the Wolffian duct. Post-inflammatory occlusions can be treated by micro-surgery, whereas in cases of agenesis, attempts to collect spermatozoa by means of an artificial spermatocele have led to far too many failures, and this technique has now been abandoned, in spite of some successful pregnancies. The extraordinary development of in vitro fertilization techniques has led to the logical idea that it might be possible to collect epididymal spermatozoa for oocyte fertilization.

Assisted reproductive technologies in severe male infertility

The increasing incidence of male subfertility as an indication for ART is first discussed. The tendency to use assisted reproduction techniques in such cases is attributed to the disappointing results of classical treatments. The Authors deal with two problems: the choice of the best treatment methods of the sperm and the choice of the best technique of ART for treating male infertility. The analysis of 138 couples treated for male subfertility showed that the centrifugation on discontinuous Percoll gradients (CDPG) and especially on the mini-Percoll (mini CDPG) offers the best results if compared with pellet swim up and other techniques. With reference to the technique of choice, an accurate analysis of tubal (TET and ZIFT) and uterine (IVF/ET) transfers shows that no advantage seems to be obtained with the more sophisticated and exacting tubal transfer. This final conclusion is presently evaluated on the basis of a retrospective study.

High levels of plasma atrial natriuretic factor and impaired left ventricular diastolic function in hypertensives without left ventricular hypertrophy

OBJECTIVE

To seek possible correlations between plasma atrial natriuretic factor (ANF) and left ventricular diastolic function (LVDF) in hypertensive patients.

DESIGN

Since LVDF abnormalities can be detected in patients with normal left ventricular mass, we studied a group of hypertensive patients without left ventricular hypertrophy.

METHODS

Untreated hypertensive patients (n = 23) and normotensive control subjects (n = 19) were studied. LVDF indices were obtained by M-mode and pulsed Doppler echocardiography. Blood samples for plasma ANF were taken in the recumbent position from subjects on normal-sodium intake.

RESULTS

Plasma ANF levels were significantly higher in hypertensive patients than in normotensive subjects. All indices for systolic function were normal in both normotensive subjects and hypertensive patients. Left atrial diameter was significantly higher for hypertensive patients than for normotensive subjects. Considering LVDF, all indices for ventricular filling were found to be altered, on average, in hypertensive patients, the only exception being peak early velocity. In addition, significant correlations were found between plasma ANF and the pulsed Doppler parameters of left ventricular filling, peak atrial velocity and the peak early:peak atrial velocity ratio. Overall correlations between plasma ANF and left atrial diameter, and between left atrial diameter and left ventricular mass index were also observed.

CONCLUSIONS

The high levels of plasma ANF observed in our hypertensive patients and their correlation with the LVDF indices (which mainly reflect the atrial contribution to ventricular filling) could be the result of an increased atrial stretch due to diastolic ventricular dysfunction. This may exist in hypertensive patients before the development of ventricular hypertrophy.

Relationship between plasma atrial natriuretic factor and urinary kallikrein excretion in essential hypertensives

In order to seek possible relationships between renal kallikrein and atrial natriuretic factor (ANF), we measured urinary kallikrein (UK) and ANF in 84 normal subjects (NS) and in 104 uncomplicated essential hypertensives (HP). Atrial natriuretic factor was significantly higher in HP than in NS (38.5 +/- 1.3 vs 29.0 +/- 1.3 pg/mL, P less than .01), whereas UK was significantly lower in HP than in NS (11.1 +/- 0.9 v 15.3 +/- 0.6 nkatal/24 h, P less than .01). Calculating the 95% of the percentile distribution of the single values of UK in the group of NS we were able to show that 24 out of 104 HP had a UK which fell below the lowest limit (4.5 nkat/24 h) of the normal range. We therefore divided our HP into two subgroups: patients with normal kallikrein excretion (NK) (n = 80; mean UK 13.8 +/- 0.8 nkat/24 h) and patients with low kallikrein excretion (LK) (n = 24; mean UK 2.3 +/- 0.3 nkat/24 h). Normal kallikrein patients had a mean plasma ANF value of 31.9 +/- 1.2 pg/mL which was almost superimposable to that found in NS; on the contrary, the mean plasma level of ANF in LK patients (50.7 +/- 2.2 pg/mL) was significantly higher than that measured in NK patients and in NS (P less than .01 v NK patients and NS, respectively). Since a low urinary kallikrein excretion may represent a marker of an impaired production of renal kallikrein, the high levels of ANF found in the LK subgroup could be the result of a compensatory response of the atrium attempting to maintain sodium and volume homeostasis.

High expression of ras p21 correlates with increased rate of abnormal mitosis in NIH3T3 cells

The modulation of responsive genes by hormonal stimulation is an attractive in vitro model system for the study of a wide variety of biological processes. Using this methodology we have investigated the effect of the human oncogene protein p21ras on mitosis using mouse mammary tumor virus long terminal repeat (MMTV-LTR)-directed gene expression. Following the induction of p21 protein, abnormal mitotic figures were scored in metaphase and anaphase. Elevated expression of p21 was associated with marked increase in the proportion of abnormal mitoses most significantly during the metaphase. Concomitant with a three fold increase in p21 levels, abnormal mitosis rose from 14.0% to 27.25%. The increase in abnormal mitosis corresponded to a 225% increase in abnormal metaphase. The p21-induced mitotic abnormalities were exhibited as lagging chromosomes in prometaphase, 3 group metaphase and C-metaphase. In addition, high expression of p21 was accompanied by significant changes in the cell morphology and fine ultrastructure, e.g. disorganization of actin, the extensive formation of microvilli on the plasma membrane and marked dilatation of the rough endoplasmic reticulum. The mitotic and structural changes were reversible upon removal of dexamethasone and decline of p21 production to its basal levels. Our results identify an important biological effect of ras p21 during mitosis and the early stages of neoplastic transformation.

[Cardiovascular involvement and relative risk factors in systemic sclerosis. Personal contribution]

In systemic sclerosis (SS), cardiovascular commitment was recorded in an autopsy series, in widely different percentages, from 12 to 81%. On the other hand, clinical diagnosis of cardiopathy is made in far fewer cases. In addition, the coexistence of renal and/or pulmonary commitment makes difficult separation between primary and secondary heart damage. In 22 patients (2 m, 20 f) aged between 34 and 75 (average 55 +/- 11) with SS, a study has been made of the a) prevalence of cardiovascular commitment; b) the significance of the classic risk factors; c) the erythrocyte filtration time or TF (index of microangiopathic damage). Metabolic stability, fibrinogen, haematocrit and TF (Reid et al. method) were assessed in each patient. Nine patients (40.9%) presented ischaemic cardiopathy (myocardial infarction in three and effort angina in six), one (4.5%) presented hypertensive cardiopathy. Conduction disturbances were observed in five patients (22.7%). Whereas a statistically significant increase in TF was observed in cardiopaths, no differences in plasma levels of glucose, cholesterol or fibrinogen were observed. The incidence of smoking and the familial factor were also insignificant.

[The use of dynamic electrocardiographic monitoring in scleroderma patients]

A comparative analysis of arrhythmias by "basal" electrocardiogram (ECG) and by continuous 24-hour Holter electrocardiogram monitoring was performed in 17 patients with systemic sclerosis (16 women and one man). Our study confirms that rhythm disturbances are better detectable using Holter monitoring. In fact, no patients had ventricular arrhythmias detected by ECG; on the contrary, Holter monitoring revealed ventricular arrhythmias in nine patients (53.3%). This method also revealed a ventricular tachycardia, not detected by ECG. In two patients ventricular repolarisation abnormalities without symptoms was revealed.