Alterations in the innate and adaptive immune system in a real-world cohort of multiple sclerosis patients treated with ocrelizumab

B cell depletion by the anti-CD20 antibody ocrelizumab is effective in relapsing-remitting (RR) and primary progressive (PP) multiple sclerosis (MS). We investigated immunological changes in peripheral blood of a real-world MS cohort after 6 and 12 months of ocrelizumab. All RRMS and most PPMS patients (15/20) showed treatment response. Ocrelizumab not only reduced CD20+ B cells, but also numbers of CD20+ T cells. Absolute numbers of monocytes, dendritic cells and CD8+ T cells were increased, while CD56hi natural killer cells were reduced after ocrelizumab. The residual B cell population shifted towards transitional and activated, IgA+ switched memory B cells, double negative B cells, and antibody-secreting cells. Delaying the treatment interval by 2-3 months increased mean B cell frequencies and enhanced naive B cell repopulation. Ocrelizumab reduced plasma levels of interleukin(IL)-12p70 and interferon(IFN)-α2. These findings will contribute to understanding ineffective treatment responses, dealing with life-threatening infections and further unravelling MS pathogenesis.

Cohort profile: the ESC EURObservational Research Programme Non-ST-segment elevation myocardial infraction (NSTEMI) Registry

AIMS

The European Society of Cardiology (ESC) EURObservational Research Programme (EORP) Non-ST-segment elevation myocardial infarction (NSTEMI) Registry aims to identify international patterns in NSTEMI management in clinical practice and outcomes against the 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without ST-segment-elevation.

METHODS AND RESULTS

Consecutively hospitalised adult NSTEMI patients (n = 3620) were enrolled between 11 March 2019 and 6 March 2021, and individual patient data prospectively collected at 287 centres in 59 participating countries during a two-week enrolment period per centre. The registry collected data relating to baseline characteristics, major outcomes (in-hospital death, acute heart failure, cardiogenic shock, bleeding, stroke/transient ischaemic attack, and 30-day mortality) and guideline-recommended NSTEMI care interventions: electrocardiogram pre- or in-hospital, pre-hospitalization receipt of aspirin, echocardiography, coronary angiography, referral to cardiac rehabilitation, smoking cessation advice, dietary advice, and prescription on discharge of aspirin, P2Y12 inhibition, angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB), beta-blocker, and statin.

CONCLUSION

The EORP NSTEMI Registry is an international, prospective registry of care and outcomes of patients treated for NSTEMI, which will provide unique insights into the contemporary management of hospitalised NSTEMI patients, compliance with ESC 2015 NSTEMI Guidelines, and identify potential barriers to optimal management of this common clinical presentation associated with significant morbidity and mortality.

POS0982 ANTIBODIES TO TWO NOVEL PEPTIDES IN NEW ONSET AXIAL SPONDYLOARTHRITIS

Background

Diagnosis of axial spondyloarthritis (axSpA) is challenging since clinical manifestations often overlap with other disorders and a specific laboratory test for diagnosis is lacking. Previously, we identified antibodies to 3 Hasselt University (UH)-axSpA peptides which could provide a novel tool for diagnosis of a subset of axSpA patients. Validation of antibody reactivity in plasma samples of early axSpA patients (disease duration < 5 years) from the UH and the Leuven Spondyloarthritis (Biologics) Cohort ((Bio)SPAR) cohorts revealed antibody reactivity against at least one of these 3 peptide targets in 14.2% of early axSpA patients (22/155)1.

Objectives

We aim to validate the diagnostic potential of the antibodies to these 3 peptides in a third independent cohort of new onset axSpA patients and controls.

Methods

Using enzyme-linked immunosorbent assays (ELISA), presence of antibodies to the 3 peptides was determined in 188 serum samples of the Belgian Inflammatory Arthritis and Spondylitis (Be-Giant) cohort, 74 controls with nonspecific chronic low back pain (CLBP) and 112 age and gender-matched healthy controls from the UH cohort. Patients were classified as having axSpA according to the ASAS classification criteria and had a mean age of 32.7 years. We further investigated whether clinical and disease characteristics were correlated with antibody reactivity.

Results

The presence of antibodies against 2 of the 3 UH-axSpA peptides was confirmed in the Be-Giant cohort. Antibody reactivity against 1 of the 2 UH-axSpA peptides was found in 11.2 % of newly diagnosed axSpA patients (21/188) compared to 3.6% (4/112, p=0.0290) in HC and 6.8% (5/74, p=0.3619) in CLBP. We did not detect a significant difference in age, sex, HLA–B27 status, enthesitis, symptom duration, treatment, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), BathAnkylosing Spondylitis Functional Index (BASFI), erythrocyte sedimentation rate (ESR), or C-reactive protein (CRP) levels between axSpA patients with and those without antibody reactivity against these 2 UH-axSpA peptides.

Conclusion

The presence of antibodies to 2 UH-axSpA peptides was confirmed in an independent cohort of newly diagnosed axSpA patients and could be of added value for discriminating axSpA patients from HC in the Be-Giant cohort.

References

[1]Quaden D, Vandormael P, Ruytinx P, Geusens P, Corten K, Vanhoof J, et al. Antibodies against three novel peptides in early axial spondyloarthritis patients from two independent cohorts. Arthritis & rheumatology (Hoboken, NJ). 2020.

Disclosure of Interests

None declared

POS0144 NOVEL ANTIBODY BIOMARKERS THAT PREDICT FAILURE TO ACHIEVE EARLY AND SUSTAINED DISEASE REMISSION OR LOW DISEASE ACTIVITY AFTER INTENSIVE FIRST-LINE THERAPY IN RHEUMATOID ARTHRITIS

Background

Current EULAR guidelines for the management of rheumatoid arthritis (RA) recommend the use of classical synthetic disease-modifying anti-rheumatic drugs (csDMARDs), combined with short-term use of glucocorticoids (GC) as first-line therapy. Still, finding out which patients will show a poor response to such intensive first-line therapy is currently based on trial and error. Therefore, we recently performed a screening for novel antibody biomarkers that could predict the lack of response to csDMARD/GC combination therapy, resulting in identification of antibodies to 6 novel University Hasselt (UH)-RA antigens.

Objectives

The aim of this study was to validate these novel antibody biomarkers for their potential to identify at baseline, which RA patients fail to reach remission (rem-), or low disease activity (LDA), after intensive csDMARD therapy.

Methods

Presence of antibodies to the identified UH-RA antigens was measured using ELISA in 179 baseline samples from participants of the CareRA trial, which evaluated the efficacy of different first-line combination therapies1. Baseline antibody reactivity was correlated with remission or LDA, over a two-year follow-up period, according to the Disease Activity Score based on 28 joints with C-reactive protein (DAS28CRP), the DAS28 with erythrocyte sedimentation rate (DAS28ESR), and the clinical/simplified disease activity index (CDAI/SDAI).

Results

Baseline antibody reactivity against a panel of 3 antigens was higher in patients failing to reach DAS28CRP (31 vs 15%, p=0.007) or DAS28ESR (30 vs 14%, p=0.007) remission at week 8, or those failing to reach SDAI (36 vs 17%, p=0.018) or CDAI (37 vs 17%, p= 0.01) LDA at week 8, compared to RA patients that did reach these respective disease states. Baseline antibody reactivity correlated with lack of DAS28CRP remission after 8, 16, 40 and 52 weeks of first-line therapy, and was present in one in three DAS28CRP rem- patients, and in one in two DAS28CRP rem- patients that were seronegative for RF and ACPA. For each of the remission criteria studied (DAS28CRP, DAS28ESR, SDAI and CDAI), baseline antibody reactivity against these antigens was significantly higher in RA patients that did not maintain sustained remission (resp. 25 vs 12%, p=0.029; 24 vs 11%, p=0.041; 24 vs 4%, p=0.009; 24 vs 4%, 0.011), or sustained LDA (resp. 29 vs 13%, p=0.007; 27 vs 11%, p=0.008; 29 vs 14%, p=0.018; 29 vs 14%, p=0.013) between week 8 and week 52, compared to patients that did reach these respective disease states.

Conclusion

We have identified a set of 3 antibody biomarkers that predict the failure to achieve early and sustained remission and LDA in response to intensive first-line RA therapy. Therefore, the presence of these antibodies might indicate the need for another first-line treatment option in a personalized medicine approach.

References

[1]Stouten V, Westhovens R, Pazmino S, De Cock D, Van der Elst K, Joly J, Verschueren P; CareRA study group. (2019) Effectiveness of different combinations of DMARDs and glucocorticoid bridging in early rheumatoid arthritis: two-year results of CareRA. Rheumatology (Oxford). 58(12):2284-2294.

Disclosure of Interests

Patrick Vandormael: None declared, Astrid Pues: None declared, Ellen Sleurs: None declared, Jori Liesenborgs: None declared, Patrick Verschueren Speakers bureau: Eli Lilly, MSD, Galapagos, Roularta, Consultant of: Galapagos, Gilead, Pfizer, Sidekick Health, Eli Lilly, Nordic Pharma, ABBVIE, Celltrion, BMS, UCB, Grant/research support from: Holder of the Pfizer Chair Management of Early Rheumatoid Arthritis at KU Leuven, Veerle Somers Grant/research support from: research grant from Pfizer.

FRI0596 NOVEL AUTOANTIBODY BIOMARKERS FOR THE PREDICTION OF THERAPY RESPONSE IN RHEUMATOID ARTHRITIS

Background:

Rheumatoid arthritis (RA) is an autoimmune disorder that is characterized by chronic inflammation of the joint synovium and presence of autoantibodies in most patients. For RA, many treatments are currently available but each treatment will only induce disease remission in a subset of patients. Moreover, finding out which patients respond well to first-line therapy with classical synthetic disease modifying anti-rheumatic drugs (csDMARDs), still largely depends on trial and error.

Objectives:

In this study, we aim to find novel RA autoantibody biomarkers that predict therapy response to csDMARDs before the initiation of treatment.

Methods:

In the CareRA trial, a Flemish multicenter study of different treatment regimes, serum samples were collected from RA patients that did or did not show disease remission (DAS28(CRP)<2.6) in response to csDMARDs, combined with a step down glucocorticoid treatment. In our study, baseline samples, collected before the start of treatment, were used to determine predictive antibody reactivity. A cDNA phage display library, representing the antigens from RA synovial tissue, was constructed and screened for antibody reactivity in baseline serum samples of RA patients that failed to reach remission at week 16. Using enzyme-linked immunosorbent assays (ELISA), antibody reactivity against the identified antigens was initially determined in pooled baseline serum samples of RA patients that did (n=50) or did not (n=40) reach disease remission at week 16. Antigenic targets that showed increased antibody reactivity in pools from patients that did not reach disease remission, were further validated in individual serum samples of 69 RA patients that did not reach DAS28(CRP) remission at week 16, and 122 RA patients that did.

Results:

Screening and validation of antibody reactivity resulted in 41 novel antigens. The retrieved antigenic sequences correspond to (parts of) known proteins and to randomly formed peptides. A panel of 3 of these peptide antigens could be composed, whose baseline antibody reactivity correlated with lack of therapy response at week 16. Presence of antibodies against at least one of these 3 antigens was significantly higher in individual samples of RA patients that did not reach DAS28(CRP) remission (43 vs. 29%, p=0.041), or that failed to reach ACR 70 (42 vs. 26%, p=0.029) response criteria at week 16, compared to RA patients that did reach these respective criteria. In addition, RA patients which were positive for this antibody panel at baseline, also showed less DAS(CRP) remission at week 4 and week 8.

Conclusion:

We have identified a set of 3 antibody biomarkers that can predict failure of early disease remission after first-line RA therapy, which might contribute to personalized medicine decisions.

Disclosure of Interests:

Patrick Vandormael: None declared, Astrid Pues: None declared, Ellen Sleurs: None declared, Patrick Verschueren Grant/research support from: Pfizer unrestricted chair of early RA research, Speakers bureau: various companies, Veerle Somers Grant/research support from: Research grant from Pfizer and BMS

AB1257 SCREENING FOR IMMUNOGLOBULIN A ANTIBODY REACTIVITY IN EARLY AXIAL SPONDYLOARTHRITIS IDENTIFIES NOVEL ANTIGENIC TARGETS

Background:

Although autoantibodies are not generally considered to be a hallmark of axial spondyloarthritis (axSpA), increasing evidence suggests the presence of autoantibodies in a subset of axSpA patients. Most of these described antibodies are of the immunoglobulin G (IgG) isotype while other antibody isotypes are less well studied. Antibodies of the IgA isotype can be of interest due to the strong link between gut inflammation and spondyloarthropathies.

Objectives:

The aim of this study was to identify and characterize novel IgA isotype (auto)antibodies specific for early axSpA patients.

Methods:

An axSpA cDNA phage display library, representing the antigenic repertoire from axSpA hip synovium, was constructed and screened for reactivity with IgA antibodies in plasma of early axSpA patients (n=10). Using enzyme-linked immunosorbent assays (ELISA), antibody reactivity against 173 identified targets was initially determined in pooled plasma of early axSpA patients (n=60) and healthy controls (HC,n=30), collected at Hasselt University. Antigenic targets that showed increased IgA reactivity in axSpA plasma pools were further validated in individual plasma samples of early axSpA patients (n=79) and HC (n=101).

Results:

We identified 10 novel Hasselt University (UH) axSpA peptide targets with increased IgA antibody reactivity in pooled axSpA plasma. At present, validation of 8 UH-axSpA-IgA peptide targets in individual plasma samples revealed antibody reactivity against at least one of these targets in 32% of early axSpA patients (25/79) compared to 26% in HC (31/101,p=0.4082). By combining the 3 UH-axSpA-IgA peptides with the highest positive likelihood ratio (LR+) into a panel, an increased overall specificity of 90% (10/101) could be achieved, with an associated sensitivity of 24% (19/79,p=0.0138) resulting in a LR+ of 2.4. Antibody reactivity testing of the remaining 2 UH-axSpA-IgA peptide targets is currently ongoing.

Conclusion:

The increased reactivity of IgA (auto)antibodies against several novel antigenic peptide targets underscores the role of the humoral immune response in axSpA, and might indicate a potential link with mucosal inflammation. IgA antibody reactivity against these novel peptide targets will be further validated in independent cohorts of early axSpA patients as well as in patients with chronic low back pain.

Disclosure of Interests:

Patrick Vandormael: None declared, Dana Quaden: None declared, Pieter Ruytinx: None declared, Joyce Janssens: None declared, Johan Vanhoof: None declared, Piet Geusens Grant/research support from: Pfizer, Abbott/Abbvie, Janssen, Celgene, Lilly, Amgen, MSD, UCB, Will, Roche, BMS, Novartis, Sanofi, Consultant of: Pfizer, Abbott/Abbvie, Janssen, Celgene, Lilly, Amgen, MSD, UCB, Will, Roche, BMS, Novartis, Sanofi, Veerle Somers Grant/research support from: Research grant from Pfizer and BMS

P4415Long obstructive sleep apneas as a biomarker of atrial fibrillation

Background

Even though obstructive sleep apnea (OSA) is strongly associated with atrial fibrillation (AF), the use of traditional OSA scoring by apnea hypopnea index (AHI) did not result in improved arrhythmia outcomes in recent randomized trials. Longer OSA episodes lead to stronger pro-arrhythmic changes, and whether very long OSA episodes are more prevalent in AF patients remains unknown.

Purpose

We hypothesized that AF patients with mild-moderate OSA manifest greater percentage of long (>20s), very long (>30s), and extremely long (>40s) OSA episodes, compared to control OSA patients matched to AHI, age and sex.

Methods

From patients studied with diagnostic polysomnography in our laboratory between 2016 and 2018, we selected 22 patients with mild-moderate untreated OSA of which 11 patients had history of paroxysmal AF and 11 patients did not have any cardiac history. The length, oxygen desaturation, and relationship to neighboring events was manually re-measured in all recorded apnea and hypopnea events.

Results

In the 22 included patients (age 62.5±9.1 years, AHI 12.8±6.1, 40% female) we recorded 1021 apneas: 508 in the AF group and 513 in the control group. AF patients had longer apneas compared to the patients without AF history (mean length 28.7±11.7s vs. 23.3±9.9s; p<0.0001). The proportion of apneas that were long (>20s), very long (>30s), and extremely long (>40s) was greater in the AF group as compared to the control (p=0.0039, p=0.0215, p=0.0104, respectively; see figure). The acute oxygen saturation drops (>2%) during apneas were comparable between the AF group and control groups (p=0.13), but the long (>20s) apneas were prone to greater oxygen desaturations.

Length of Apneas

Conclusions

While traditional scoring of OSA focuses on episodes lasting >10s, our data newly show that longer durations of OSA events are particularly prevalent in AF patients. These results, combined with recent mechanistic studies showing that longer apneas exert greater pro-arrhythmic effect on atrial conduction, suggest that novel scoring of OSA placing more weight on longer apneas should be explored, especially when screening and titrating OSA therapy in patients at risk of AF.

Anti-SPAG16 antibodies in primary progressive multiple sclerosis are associated with an elevated progression index

BACKGROUND AND PURPOSE

Sperm-associated antigen 16 (SPAG16), a sperm protein which is upregulated in reactive astrocytes in multiple sclerosis (MS) lesions, has recently been identified as a novel autoantibody target in MS. The aim of this study was to investigate whether anti-SPAG16 antibody levels differ between MS subtypes (relapsing-remitting, RR; primary or secondary progressive, PP, SP) and whether antibody positivity is associated with clinical characteristics.

METHODS

Plasma anti-SPAG16 antibody levels were determined by recombinant protein enzyme-linked immunosorbent assay (ELISA) in 374 MS patients (274 RRMS, 39 SPMS and 61 PPMS) and 106 healthy controls.

RESULTS

Significantly elevated anti-SPAG16 antibodies were found in 22% of MS patients with 93% specificity. Anti-SPAG16 seropositivity was associated with an increased Expanded Disability Status Scale (EDSS) in overall MS. A higher proportion of PPMS patients showed anti-SPAG16 antibody reactivity (34%) compared to RRMS (19%) and SPMS (26%), and presented with higher anti-SPAG16 antibody levels. Seropositive PPMS patients had a significantly increased progression index compared to seronegative patients.

CONCLUSIONS

Anti-SPAG16 antibodies are associated with an increased EDSS in overall MS, indicating that they are linked to a worse MS disease outcome. Moreover, the presence of anti-SPAG16 antibodies may be a biomarker for a more severe disease in PPMS patients, as indicated by an increased progression index.

A novel method for making human monoclonal antibodies

We have developed a B cell immortalization method for low B cell numbers per well using simultaneous B cell stimulation by CpG2006 and B cell infection by Epstein-Barr virus (EBV), followed by an additional CpG2006 and interleukin-2 (IL-2) stimulus. Using this method, immunoglobulin G (IgG)-producing immortalized B cell lines were generated from peripheral blood IgG⁺CD22⁺ B cells with an efficiency of up to 83%. Antibody can already be obtained from the culture supernatant after 3–4 weeks. Moreover, clonality analysis demonstrated monoclonality in 87% of the resulting immortalized B cell lines. Given the high immortalization efficiency and monoclonality rate, evidence is provided that no further subcloning is necessary. An important application of this B cell immortalization method is the characterization of (autoreactive) antibodies from patients with autoimmune disease. This could eventually lead to the identification of new autoantigens, disease markers or targets for therapy.

Analysis of antibody reactivity in paired cerebrospinal fluid and serum of a relapsing remitting multiple sclerosis patient

Increasing evidence indicates an involvement of B cells in multiple sclerosis (MS). However, little is known about antigenic targets recognized by antibodies present in blood and cerebrospinal fluid (CSF) of MS patients. This study was therefore aimed at identifying the antigen reactivity of antibodies present in CSF and compares the identified antibody profile with that of the serum of the same patient using cDNA phage display. Selection rounds on paired CSF and serum of this patient identified 13 antigenic targets of which 5 were enriched by serum antibodies and 2 were identified by CSF antibodies. Interestingly, the six remaining antigenic targets were shown to be recognized by both CSF and serum antibodies. These findings point towards both common as well as distinct antibody profiles in CSF and serum of MS patients.

B cell characterization and reactivity analysis in multiple sclerosis

B cells are one of the key players in the pathogenesis of multiple sclerosis (MS). The peripheral B cell distributions are similar in healthy persons and MS patients. In healthy controls, B cells are rarely present in the cerebrospinal fluid (CSF) while in MS patients, a clonally expanded B cell population is detected. This consists of memory B cells, centroblasts and antibody-secreting plasma blasts and plasma cells that are responsible for intrathecal immunoglobulin G production and oligoclonal band formation in more than 90% of MS patients. Unfortunately, the targets of the autoreactive B cells and antibodies remain largely unknown. Various candidate antigens have been identified but often their involvement in the disease process is still unclear. Most studies characterizing these target antigens examined autoantibodies by analyzing sera or CSF of MS patients. An alternative approach is focusing on the clonally expanded B cells. In this way B cells directed against myelin, astroglia and axons have been denoted in MS patients. B cell immortalization, that is based on the antibody-producing potential of Epstein–Barr virus (EBV) transformed B cells, can be used to expand B cells from MS patients for the production of antibodies, that ultimately can be analysed for target identification.

Exploring cDNA Phage Display for Autoantibody Profiling in the Serum of Multiple Sclerosis Patients: Optimization of the Selection Procedure

We applied a cDNA phage display method called serological antigen selection (SAS) to identify immunogenic targets that evoke an autoantibody response in the serum of multiple sclerosis (MS) patients. This method involves the display of a cDNA expression library, in this study a MS brain library, on filamentous phage and subsequent selection using patient immunoglobulin G (IgG). To apply the SAS technology for autoantibodies in the serum of MS patients, an optimization was necessary to deplete cDNA products that encode IgG fragments derived from B cells present in the MS brain plaques. We describe a differential screening procedure in which positive selection rounds on MS serum and negative selection rounds on healthy control serum were alternated to optimize the selection procedure. As a result, a substantial decrease of IgG-displaying phage clones was observed after each negative selection round, thereby preventing an overgrowth of IgG-displaying phage clones. Our depletion strategy was therefore successful in preventing the enrichment of IgG-displaying phage clones. This approach will facilitate the identification of possible MS-related antigens.

Profiling the autoantibody repertoire by serological antigen selection

The identification of disease related autoantigens targeted by pathogenic T- and B-cell responses is crucial for the development of improved therapies for autoimmune diseases. To identify immunogenic targets recognized by the humoral immune response, we have recently applied a novel and powerful molecular approach, named 'serological antigen selection' (SAS). This method involves the display of a cDNA expression library on filamentous phage and subsequent selection on patient immunoglobulin G (IgG). In the present study, we have cloned a cDNA repertoire from a multiple sclerosis (MS) patient in pVI phage display vectors and performed selections on pooled MS cerebrospinal fluid (CSF) samples immobilized with anti-human IgG. To further streamline this procedure, we report an optimized SAS procedure in which we have successfully established methods for enrichment of MS-specific candidate antigens. In conclusion, the broad applicability of the SAS method makes it a highly promising method for investigating the autoimmune repertoire.

Information domain analysis of cardiovascular variability signals: evaluation of regularity, synchronisation and co-ordination

A unifying general approach to measure regularity, synchronisation and co-ordination is proposed. This approach is based on conditional entropy and is specifically designed to deal with a small amount of data (a few hundred samples). Quantitative and reliable indexes of regularity, synchronisation and co-ordination (ranging from 0 to 1) are derived in a domain (i.e. the information domain) different from time and frequency domains. The method is applied to evaluate regularity, synchronisation and co-ordination among cardiovascular beat-to-beat variability signals during sympathetic activation induced by head-up tilt (T), during the perturbing action produced by controlled respiration at 10, 15 and 20 breaths/min (CR10, CR15 and CR20), and after peripheral muscarinic blockade provoked by the administration of low and high doses of atropine (LD and HD). It is found that: (1) regularity of the RR interval series is around 0.209; (2) this increases during T, CR10 and HD; (3) the systolic arterial pressure (SAP) series is more regular (0.406) and its regularity is not affected by the specified experimental conditions; (4) the muscle sympathetic (MS) series is a complex signal (0.093) and its regularity is not influenced by HD and LD; (5) the RR interval and SAP series are significantly, though weakly, synchronised (0.093) and their coupling increases during T, CR10 and CR15; (6) the RR interval and respiration are coupled (0.152) and their coupling increases during CR10; (7) SAP and respiration are significantly synchronised (0.108) and synchronisation increases during CR10; (8) MS and respiration are uncoupled and become coupled (0.119) after HD; (9) the RR interval, SAP and respiration are significantly co-ordinated (0.118) and co-ordination increases during CR10 and CR15; (10) during HD the co-ordination among SAP, MS and the respiratory signal is larger than that among the RR interval, SAP, MS and the respiratory signal, thus indicating that the RR interval contributes towards reducing co-ordination.

Correlation of blood pressure in normotensive and hypertensive individuals with platelet but not lymphocyte intracellular free calcium concentrations

1. Fifty-two normotensive and essential hypertensive subjects were studied. Intracellular free calcium concentration [( Ca2+]i) was measured in lymphocytes (37 subjects) and platelets (18 subjects) by means of the fluorescent indicators, quin 2 and fura-2. In 31 subjects, plasma ionized calcium concentration was also measured. 2. There was a positive correlation between platelet [Ca2+]i and systolic blood pressure (r = 0.485, P less than 0.05), diastolic blood pressure (r = 0.542, P less than 0.02) and mean blood pressure (r = 0.534, P less than 0.02). 3. No statistically significant relationship was observed between plasma ionized calcium and blood pressure. 4. No relationship was found between lymphocyte [Ca2+]i and blood pressure, or between lymphocyte [Ca2+]i and plasma ionized calcium. 5. There was no relationship between [Ca2+]i of lymphocytes and platelets measured simultaneously from the same subject. 6. These findings reconcile previous conflicting reports and show a relationship between platelet but not lymphocyte [Ca2+]i and blood pressure in man.

Changes in autonomic regulation induced by physical training in mild hypertension

The adaptive effects of physical training on cardiovascular control mechanisms were studied in 11 subjects with mild hypertension. In these subjects we assessed the gain of the heart period-systolic arterial pressure relationship in the unfit and the fit state by using 1) an open loop approach, whereby the gain is expressed by the slope of the regression of heart period as a function of systolic arterial pressure, during a phenylephrine-induced pressure rise and 2) a closed loop approach with proper simplification, whereby the gain is expressed by the index alpha, obtained through simultaneous spectral analysis of the spontaneous variabilities of heart period and systolic arterial pressure. Both methods indicated that training significantly increased the gain of the relationship between heart period and systolic arterial pressure at rest and reduced arterial pressure and increased heart period significantly. This gain was drastically reduced during bicycle exercise both in the unfit and fit state. In a second group of normotensive (n = 7; systolic pressure, 133 +/- 3 mm Hg) and hypertensive (n = 7; systolic pressure, 180 +/- 10 mm Hg) subjects undergoing 24-hour diagnostic continuous electrocardiographic and high fidelity arterial pressure monitoring, the index alpha was significantly reduced in the hypertensive group at rest. Furthermore, when analyzed continuously over the entire 24-hour period, this index underwent minute-to-minute changes with lower values during the day and higher values during the night. We propose the index alpha as a quantitative indicator of the changes in the gain of baroreceptor mechanisms occurring with physical training in mild hypertension and during a 24-hour period in ambulatory subjects.

Is the antihypertensive effect of captopril influenced by the dosage frequency? A study with ambulatory monitoring

When captopril was first introduced for the management of hypertension, its short plasma half-life led to its use as a thrice daily regimen. However, further experience suggests that the biological action is more prolonged than the plasma half-life might suggest. This study examined the effect of varying the frequency of administration (once, twice and three times daily) of a fixed daily dosage of 75 mg captopril on ambulatory BP in a double-blind cross-over study in 15 patients with mild to moderate hypertension. Each patient had six ambulatory BP recordings with placebo alternating with active phase. The three regimens (75 mg daily, 37.5 mg twice daily and 25 mg three times daily) reduced the daily mean BP equally and significantly compared with placebo. Three patients with very high pretreatment plasma renin values showed some loss of BP control immediately prior to the first dose in the morning in the 75 mg single dose phase (i.e. 24 hours post dose); but group analysis showed no difference in mean BP at this time point with the three treatment regimens. We conclude that in spite of its short plasma half-life, captopril can effectively control BP over the whole day with a once daily regimen.

The use of ambulatory blood pressure monitoring to improve the accuracy and reduce the numbers of subjects in clinical trials of antihypertensive agents

A low-cost ambulatory blood pressure measuring device has been developed from a commercially available stationary apparatus. The device, which has been compared for accuracy with a mercury manometer, has functioned satisfactorily as an ambulatory monitor for 4 years. To minimize errors, blood pressure readings were made in the sitting position at half-hourly intervals over the waking day. The utility of the device in clinical trials has been investigated. On repeated readings no placebo effect on blood pressure was detectable and the mean difference between two readings in 42 subjects was 1.9/-0.33 mmHg. The standard deviation of the difference were 8.1/5.6 mmHg. This should make it possible to detect differences of 8/5 mmHg between two treatments in about 16 subjects. There was no detectable tendency for blood pressure to change during the day but the variability between readings was substantially increased if the observation periods were reduced to 4 h.