Using hiPSC-CMs to Examine Mechanisms of Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal inherited cardiac arrhythmia condition, triggered by physical or acute emotional stress, that predominantly expresses early in life. Gain-of-function mutations in the cardiac ryanodine receptor gene (RYR2) account for the majority of CPVT cases, causing substantial disruption of intracellular calcium (Ca²⁺ ) homeostasis particularly during the periods of β-adrenergic receptor stimulation. However, the highly variable penetrance, patient outcomes, and drug responses observed in clinical practice remain unexplained, even for patients with well-established founder RyR2 mutations. Therefore, investigation of the electrophysiological consequences of CPVT-causing RyR2 mutations is crucial to better understand the pathophysiology of the disease. The development of strategies for reprogramming human somatic cells to human induced pluripotent stem cells (hiPSCs) has provided a unique opportunity to study inherited arrhythmias, due to the ability of hiPSCs to differentiate down a cardiac lineage. Employment of genome editing enables generation of disease-specific cell lines from healthy and diseased patient-derived hiPSCs, which subsequently can be differentiated into cardiomyocytes. This paper describes the means for establishing an hiPSC-based model of CPVT in order to recapitulate the disease phenotype in vitro and investigate underlying pathophysiological mechanisms. The framework of this approach has the potential to contribute to disease modeling and personalized medicine using hiPSC-derived cardiomyocytes. © 2021 Wiley Periodicals LLC.

Efficacy and long-term outcomes of palivizumab prophylaxis to prevent respiratory syncytial virus infection in infants with cystic fibrosis in Northern Ireland

BACKGROUND

RSV causes considerable morbidity and mortality in children. In cystic fibrosis (CF) viral infections are associated with worsening respiratory symptoms and bacterial colonization. Palivizumab is effective in reducing RSV hospitalization in high risk patient groups. Evidence regarding its effectiveness and safety in CF is inconclusive. CF screening in N. Ireland enabled timely palivizumab prophylaxis, becoming routine in 2002.

OBJECTIVES

To determine the effect of palivizumab on RSV-related hospitalization and compare lung function and bacterial colonization at age 6 years for those born pre- and post-introduction of palivizumab prophylaxis.

METHODS

A retrospective audit was conducted for all patients diagnosed with CF during the period from 1997 to 2007 inclusive. RSV-related hospitalization, time to Pseudomonas aeruginosa (PA) 1st isolate, lung function and growth parameters were recorded. Comparisons were made for outcomes pre- and post-introduction of routine palivizumab administration in 2002. A cost evaluation was also performed.

RESULTS

Ninety-two children were included; 47 pre- and 45 post-palivizumab introduction. The overall RSV-positive hospitalization rate was 13%. The relative risk of RSV infection in palivizumab non-recipients versus recipients was 4.78 (95%CI: 1.1-20.7), P = 0.027. Notably, PA 1st isolate was significantly earlier in the palivizumab recipient cohort versus non-recipient cohort (median 57 vs. 96 months, P < 0.025) with a relative risk of 2.5. Chronic PA infection at 6 years remained low in both groups, with similar lung function and growth parameters. Total costs were calculated at £96,127 ($151,880) for the non-recipient cohort versus £137,954 ($217,967) for the recipient cohort.

CONCLUSION

Palivizumab was effective in reducing RSV-related hospitalization infection in CF patients. Surprisingly, we found a significantly earlier time to 1st isolate of PA in palivizumab recipients which we could not explain by altered or improved diagnostic tests.

Current trends in Antenatal Screening Services: Results from a regional survey

OBJECTIVE

To identify variations in current antenatal screening programmes across one region and compare results with a previous survey.

DESIGN

A cross section descriptive survey.

SETTING

All maternity units within the region of Northern Ireland.

SAMPLE

Eleven maternity units were invited and ten agreed to participate.

MAIN OUTCOME MEASURES

The number of written policies for individual screening tests; the range of screening tests offered; the frequency of training opportunities for health professionals; and the information systems in place to record data.

RESULTS

There is variation in service provision across maternity units and, in particular, inconsistency in the offer of serum screening tests for Down syndrome. A lack of training opportunities for health professionals involved in offering screening was highlighted, and no common information system employed.

CONCLUSION

While improvements have been made since 2002, variations persist. This is leading to inequalities in the provision of antenatal screening services across Northern Ireland.

Assessing disability progression with the Multiple Sclerosis Functional Composite

BACKGROUND

The initial Multiple Sclerosis Functional Composite (MSFC) proposal was a three-part composite of quantitative measures of ambulation, upper extremity function, and cognitive function expressed as a single composite Z-score. However, the clinical meaning of an MSFC Z-score change is not obvious. This study instead used MSFC component data to define a patient-specific disease progression event.

OBJECTIVE

Evaluate a new method for analyzing disability progression using the MSFC.

METHODS

MSFC progression was defined as worsening from baseline on scores of at least one MSFC component by 20% (MSFC Progression-20) or 15% (MSFC Progression-15), sustained for >or=3 months. Progression rates were determined using data from natalizumab clinical studies (Natalizumab Safety and Efficacy in Relapsing Remitting Multiple Sclerosis [AFFIRM] and Safety and Efficacy of Natalizumab in Combination With Interferon Beta-1a in Patients With Relapsing Remitting Multiple Sclerosis [SENTINEL]). Correlations between MSFC progression and other clinical measures were determined, as was sensitivity to treatment effects.

RESULTS

Substantial numbers of patients met MSFC progression criteria, with MSFC Progression-15 being more sensitive than MSFC Progression-20, at both 1 and 2 years. MSFC Progression-20 and MSFC Progression-15 were related significantly to Expanded Disability Status Scale (EDSS) score change, relapse rate, and the SF-36 Physical Component Summary (PCS) score change. MSFC Progression-20 and MSFC Progression-15 at 1 year were predictive of EDSS progression at 2 years. Both MSFC progression end points demonstrated treatment effects in AFFIRM, and results were replicated in SENTINEL.

CONCLUSION

MSFC Progression-20 and MSFC Progression-15 are sensitive measures of disability progression; correlate with EDSS, relapse rates, and SF-36 PCS; and are capable of demonstrating therapeutic effects in randomized, controlled clinical studies.

Effect of plasma exchange in accelerating natalizumab clearance and restoring leukocyte function

BACKGROUND

Accelerating the clearance of therapeutic monoclonal antibodies (mAbs) from the body may be useful to address uncommon but serious complications from treatment, such as progressive multifocal leukoencephalopathy (PML). Treatment of PML requires immune reconstitution. Plasma exchange (PLEX) may accelerate mAb clearance, restoring the function of inhibited proteins and increasing the number or function of leukocytes entering the CNS. We evaluated the efficacy of PLEX in accelerating natalizumab (a therapy for multiple sclerosis [MS] and Crohn disease) clearance and alpha4-integrin desaturation. Restoration of leukocyte transmigratory capacity was evaluated using an in vitro blood-brain barrier (ivBBB).

METHODS

Twelve patients with MS receiving natalizumab underwent three 1.5-volume PLEX sessions over 5 or 8 days. Natalizumab concentrations and alpha4-integrin saturation were assessed daily throughout PLEX and three times over the subsequent 2 weeks, comparing results with the same patients the previous month. Peripheral blood mononuclear cell (PBMC) migration (induced by the chemokine CCL2) across an ivBBB was assessed in a subset of six patients with and without PLEX.

RESULTS

Serum natalizumab concentrations were reduced by a mean of 92% from baseline to 1 week after three PLEX sessions (p < 0.001). Although average alpha4-integrin saturation was not reduced after PLEX, it was reduced to less than 50% when natalizumab concentrations were below 1 mug/mL. PBMC transmigratory capacity increased 2.2-fold after PLEX (p < 0.006).

CONCLUSIONS

Plasma exchange (PLEX) accelerated clearance of natalizumab, and at natalizumab concentrations below 1 mug/mL, desaturation of alpha4-integrin was observed. Also, CCL2-induced leukocyte transmigration across an in vitro blood-brain barrier was increased after PLEX. Therefore, PLEX may be effective in restoring immune effector function in natalizumab-treated patients.

International Bordetella pertussis assay standardization and harmonization meeting report. Centers for Disease Control and Prevention, Atlanta, Georgia, United States, 19-20 July 2007

An international meeting on Bordetella pertussis assay standardization and harmonization was held at the Centers for Disease Control and Prevention (CDC), Atlanta, GA, 19–20 July 2007. The goal of the meeting was to harmonize the immunoassays used for pertussis diagnostics and vaccine evaluation, as agreed upon by academic and government researchers, regulatory authorities, vaccine manufacturers, and the World Health Organization (WHO).

The primary objectives were (1) to provide epidemiologic, laboratory, and statistical background for support of global harmonization; (2) to overview the current status of global epidemiology, pathogenesis and immunology of pertussis; (3) to develop a consensus opinion on existing gaps in understanding standardization of pertussis assays used for serodiagnosis and vaccine evaluation; and (4) to search for a multicenter process for addressing these priority gaps. Presentations and discussions by content experts addressed these objectives. A prioritized list of action items to improve standardization and harmonization of pertussis assays was identified during a group discussion at the end of the meeting. The major items included: (1) to identify a group that will organize, prepare, maintain, and distribute proficiency panels and key reagents such as reference and control sera; (2) to encourage the development and identification of one or more reference laboratories that can serve as an anchor and resource for other laboratories; (3) to define a performance-based assay method that can serve as a reference point for evaluating laboratory differences; (4) to develop guidance on quality of other reagents, e.g., pertussis toxin and other antigens, and methods to demonstrate their suitability; (5) to establish an international working group to harmonize the criteria to evaluate the results obtained on reference and proficiency panel sera; (6) to create an inventory to determine the amount of appropriate and well-characterized sera that are available globally to be used as bridging reagents for vaccine licensure; and (7) to seek specific guidance from regulatory authorities regarding the expectations and requirements for the licensure of new multicomponent pertussis vaccines.

Reversal of islet GIP receptor down-regulation and resistance to GIP by reducing hyperglycemia in the Zucker rat

In type 2 diabetes (T2DM) beta-cell responsiveness to glucose-dependent insulinotropic polypeptide (GIP) is reduced. In a model of T2DM, the VDF Zucker rat, GIP receptor mRNA and protein levels were shown to be down-regulated. Possible restoration of responsiveness to GIP in Zucker rats by reducing hyperglycemia has been examined. ZDF rats with extreme hyperglycemia demonstrated greater islet GIP receptor mRNA down-regulation (94.3+/-3.8%) than ZF rats (48.8+/-22.8%). GIP receptor mRNA levels in ZDF rats returned to 83.0+/-17.9% of lean following normalization of hyperglycemia by phlorizin treatment and pancreas perfusions demonstrated markedly improved GIP responsiveness. Treatment of VDF rats with a DP IV inhibitor (P32/98) resulted in improved glucose tolerance and restored sensitivity to GIP in isolated pancreata. These findings support the proposal that GIP receptor down-regulation in rodent T2DM is secondary to chronic hyperglycemia and that normalization of glycemia can restore GIP sensitivity.

Evaluation of PorB variable region typing of Neisseria gonorrhoeae using PCR-ELISA in samples collected from men who have sex with men

A polymerase chain reaction (PCR)-based enzyme-linked immunosorbent assay (ELISA) methodology was developed to characterize Neisseria gonorrhoeae porB gene variable regions (VR); the methodology was evaluated in comparison to porB VR typing by checkerboard hybridization. Clinical noncultured samples from 35 men who have sex with men (MSM), positive by nucleic amplification assays for N. gonorrhoeae, were typed using a panel of 40 oligonucleotide probes to porB VRs and compared to checkerboard hybridization. Complete concordance was observed between the two methods at PIB VRs 1, 3, and 7. At the more degenerate VRs 5 and 6, PCR ELISA resulted in obtaining more typeable VRs than checkerboard hybridization due to single nucleotide mismatches. By PCR ELISA, two predominant PIB porB types were identified in 58% of the samples and the remaining 16 samples had one of six other porB types. Both PCR ELISA and checkerboard hybridization methods of porB VR typing allowed characterization of N. gonorrhoeae from noncultured clinical samples including throat and rectal swabs and discriminated N. gonorrhoeae from N. meningitidis present in some of the samples. PCR ELISA is a rapid, relatively inexpensive and alternative molecular typing method for N. gonorrhoeae, suitable for use in conjunction with molecular diagnostic tests.

The incidence and significance of anti-natalizumab antibodies: Results from AFFIRM and SENTINEL

OBJECTIVE

To determine the incidence and clinical effects of antibodies that develop during treatment with natalizumab.

METHODS

In two randomized, double-blind, placebo-controlled studies (natalizumab safety and efficacy in relapsing remitting multiple sclerosis [MS, AFFIRM] and safety and efficacy of natalizumab in combination with interferon beta-1a [INF beta]1a] in patients with relapsing remitting MS [SENTINEL]) of patients with relapsing multiple sclerosis, blood samples were obtained at baseline and every 12 weeks to determine the presence of antibodies against natalizumab. Antibodies to natalizumab were measured using an ELISA. Patients were categorized as "transiently positive" if they had detectable antibodies (>or=0.5 microg/mL) at a single time point or "persistently positive" if they had antibodies at two or more time points >or=6 weeks apart.

RESULTS

In the AFFIRM study, antibodies were detected in 57 of 625 (9%) of natalizumab-treated patients: Twenty (3%) were transiently positive and 37 (6%) were persistently positive. Persistently positive patients showed a loss of clinical efficacy as measured by disability progression (p <or= 0.05), relapse rate (p = 0.009), and MRI (p <or= 0.05) compared with antibody-negative patients. In transiently positive patients, full efficacy was achieved after approximately 6 months of treatment, the time when patients were becoming antibody negative. The incidence of infusion-related adverse events was significantly higher in persistently positive patients. Results of SENTINEL were similar to AFFIRM, except with regard to sustained disability progression; differences between persistently positive and antibody-negative patients were not statistically significant.

CONCLUSIONS

The incidence of persistent antibody positivity associated with natalizumab is 6%. Reduced clinical efficacy is apparent in persistently positive patients. Patients with a suboptimal clinical response or persistent infusion-related adverse events should be considered for antibody testing.

Natalizumab reduces visual loss in patients with relapsing multiple sclerosis

OBJECTIVE

To examine the effects of natalizumab on low-contrast letter acuity as a prespecified tertiary endpoint in two randomized clinical trials and to evaluate the usefulness of low-contrast letter acuity testing as a candidate test of visual function in multiple sclerosis (MS).

METHODS

AFFIRM and SENTINEL were randomized, double-blind, placebo-controlled, multicenter, phase 3 clinical trials of natalizumab in relapsing MS. Natalizumab was evaluated as monotherapy in AFFIRM and as add-on to interferon beta-1a in SENTINEL. Vision testing was performed at 100% contrast (visual acuity) and low-contrast (2.5% and 1.25%).

RESULTS

The risk of clinically significant visual loss (predefined as a two-line worsening of acuity sustained over 12 weeks) at the lowest contrast level (1.25%) was reduced in the natalizumab treatment arms by 35% in AFFIRM (hazard ratio = 0.65; 95% CI: 0.47 to 0.90; p = 0.008) and by 28% in SENTINEL (hazard ratio = 0.72; 95% CI: 0.54 to 0.98; p = 0.038, Cox proportional hazards models). Mean changes in vision scores from baseline were also significantly different, reflecting worsening in non-natalizumab groups.

CONCLUSIONS

Natalizumab reduces visual loss in patients with relapsing multiple sclerosis. Low-contrast acuity testing has the capacity to demonstrate treatment effects and is a strong candidate for assessment of visual outcomes in future multiple sclerosis trials.

MRI outcomes in a placebo-controlled trial of natalizumab in relapsing MS

BACKGROUND

In a 2-year, placebo-controlled trial (the Natalizumab Safety and Efficacy in Relapsing Remitting Multiple Sclerosis [AFFIRM] study), involving 942 patients with relapsing multiple sclerosis (MS), natalizumab significantly reduced the relapse rate by 68% and progression of sustained disability by 42% vs placebo. We report the effect of natalizumab on MRI measures from the AFFIRM study.

METHODS

The number and volume of gadolinium (Gd)-enhancing, new or enlarging T2-hyperintense, and new T1-hypointense lesions and brain parenchymal fraction were measured from annual scans obtained at baseline, 1 year, and 2 years.

RESULTS

Compared with placebo, natalizumab produced a 92% decrease in Gd-enhancing lesions (means 2.4 vs 0.2; p < 0.001), an 83% decrease in new or enlarging T2-hyperintense lesions (means 11.0 vs 1.9; p < 0.001), and a 76% decrease in new T1-hypointense lesions (means 4.6 vs 1.1; p < 0.001) over 2 years. Median T2-hyperintense lesion volume increased by 8.8% in the placebo group and decreased by 9.4% in the natalizumab group (p < 0.001); median T1-hypointense lesion volume decreased by 1.5% in the placebo group and decreased by 23.5% in the natalizumab group (p < 0.001). Brain atrophy was greater in year 1 and less in year 2 in natalizumab-treated patients.

CONCLUSION

Natalizumab has a sustained effect in preventing the formation of new lesions in patients with relapsing multiple sclerosis.

Structure-activity relationships of glucose-dependent insulinotropic polypeptide (GIP)

Six GIP(1-NH2) analogs were synthesized with modifications (de-protonation, N-methylation, reversed chirality, and substitution) at positions 1, 3, and 4 of the N-terminus, and additionally, a cyclized GIP derivative was synthesized. The relationship between altered structure to biological activity was assessed by measuring receptor binding affinity and ability to stimulate adenylyl cyclase in CHO-K1 cells transfected with the wild-type GIP receptor (wtGIPR). These structure-activity relationship studies demonstrate the importance of the GIP N-terminus and highlight structural constraints that can be introduced in GIP analogs. These analogs may be useful starting points for design of peptides with enhanced in vivo bioactivity.

Genetic and immunologic characterization of a novel serotype 4, 15 strain of Neisseria meningitidis

The porin proteins of Neisseria meningitidis are important components of outer membrane protein (OMP) vaccines. The class 3 porin gene, porB, of a novel serogroup B, serotype 4, 15 isolate from Chile (Ch501) was found to be VR1-4, VR2-15, VR3-15 and VR4-15 by porB variable region (VR) typing. Rabbit immunization studies using outer membrane vesicles revealed immunodominance of individual PorB (class 3) VR epitopes. The predominant anti-Ch501 PorB response was directed to the VR1 epitope. Anti-PorB VR1 mediated killing was suggested by the bactericidal activity of Ch501 anti-sera against a type 4 strain not expressing PorA or class 5 OMPs. Studies that examine the molecular epidemiology of individual porB VRs, and the immune responses to PorB epitopes, may contribute to the development of broadly protective group B meningococcal vaccines.

Characterization of the carboxyl-terminal domain of the rat glucose-dependent insulinotropic polypeptide (GIP) receptor. A role for serines 426 and 427 in regulating the rate of internalization

Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal hormone involved in the regulation of insulin secretion. In non-insulin-dependent diabetes mellitus insulin responses to GIP are blunted, possibly due to altered signal transduction or reduced receptor number. Site-directed mutagenesis was used to construct truncated GIP receptors to study the importance of the carboxyl-terminal tail (CT) in binding, signaling, and receptor internalization. Receptors truncated at amino acids 425, 418, and 405, expressed in COS-7 or CHO-K1 cells, exhibited similar binding to wild type receptors. GIP-dependent cAMP production with the 405 mutant was decreased in COS-7 cells. Maximal cAMP production in CHO-K1 cells was reduced with all truncated forms. Binding was undetectable with a receptor truncated at amino acid 400; increasing tail length by adding 5 alanines restored binding and signaling. Mutants produced by alanine scanning of residues 394-401, adjacent to transmembrane domain 7, were all functional. CT truncation by 30 or more amino acids, mutation of serines 426/427, singly or combined, or complete CT serine knockout all reduced receptor internalization rate. The majority of the GIP receptor CT is therefore not required for signaling, a minimum chain length of approximately 405 amino acids is needed for receptor expression, and serines 426 and 427 are important for regulating rate of receptor internalization.

Improved glucose tolerance in rats treated with the dipeptidyl peptidase IV (CD26) inhibitor Ile-thiazolidide

The incretins glucose-dependent insulinotropic polypeptide (GIP1-42) and truncated forms of glucagon-like peptide-1 (GLP-1) are hormones released from the gut in response to ingested nutrients, which act on the pancreas to potentiate glucose-induced insulin secretion. These hormones are rapidly inactivated by the circulating enzyme dipeptidyl peptidase IV ([DPIV] CD26). This study describes the effect on glucose tolerance and insulin secretion of inhibiting endogenous DPIV in the rat using Ile-thiazolidide, a specific DPIV inhibitor. High-performance liquid chromatography (HPLC) analysis of plasma following in vivo administration of 125I-labeled peptides showed that inhibition of DPIV by about 70% prevented the degradation of 90.0% of injected 125I-GLP-17-36 after 5 minutes, while only 13.4% remained unhydrolyzed in rats not treated with the DPIV-inhibiting agent after only 2 minutes. Ile-thiazolidide treatment also increased the circulating half-life of intact GLP-17-36 released in response to intraduodenal (ID) glucose (as measured by N-terminal specific radioimmunoassay [RIA]). In addition, inhibition of DPIV in vivo resulted in an earlier increase and peak of plasma insulin and a more rapid clearance of blood glucose in response to ID glucose challenge. When considered with the HPLC data, these results suggest that the altered insulin profile is an incretin-mediated response. DPIV inhibition resulting in improved glucose tolerance may have therapeutic potential for the management of type 2 diabetes mellitus.

Evaluation of pertussis in U.S. Marine Corps trainees

One hundred twenty male U.S. Marine Corps trainees with histories of at least 7 days of cough underwent evaluation for Bordetella pertussis infection by culture, B. pertussis-specific polymerase chain reaction (PCR) analysis, and serology. Antibody levels in preexposure, acute-phase, and convalescent-phase serum samples were measured in a microagglutination assay and in enzyme linked immunosorbent assays (ELISAs) for IgG and IgA antibodies to pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae types 2 and 3. Culture and PCR analysis revealed that none of the patients were positive for B. pertussis; however, 20 of 120 trainees had serological evidence of B. pertussis infection. Of these cases, one was confirmed by a rise in the level of antibody to pertussis toxin, and six were classified as probable by increases in levels of antibodies measured by two or more assays. Of the 20 individuals with serological evidence of infection, 16 had rises in levels of antibodies to fimbriae or agglutinating antibodies. The utility of ELISA for detecting antibodies to fimbriae and the microagglutination assay for diagnosing pertussis in adults should be evaluated by application to larger and more diverse study populations. These results indicate that pertussis should be considered in the diagnosis of coughing illness in military populations.

A comparison of enzyme immunoassays used to measure serum antibodies to components of Bordetella pertussis

To evaluate the comparability of immunoassays, the Center for Biologics Evaluation and Research organized an international collaborative study in which 33 laboratories participated. For a coded panel of 21 samples, each laboratory measured IgG antibodies to specific proteins of Bordetella pertussis using assay systems currently in place. Analyses were performed to evaluate the assay precision and the quantitative agreement among laboratories. Data from a subset of 12 laboratories are used to illustrate points relevant to the use of immunoassays in seven vaccine efficacy studies. Differences among the laboratories in assay precision for samples with known two-fold differences indicate that serological case definitions must take into consideration the characteristics of the assays and the concentration of antibody in the samples. Assays performed in different laboratories to assess vaccine immunogenicity may generate similar results but critical comparisons will probably require samples to be tested in the same laboratory at the same time.

Collaborative study for the evaluation of enzyme-linked immunosorbent assays used to measure human antibodies to Bordetella pertussis antigens

Acellular pertussis vaccines are being evaluated in multiple clinical studies, and human immunogenicity data will likely be pivotal in the appraisal of vaccine responses between populations and the responses to different vaccine combinations. Antibody response to pertussis antigens is also used in the diagnosis of pertussis. An international study was designed to assess the comparability of data generated in different laboratories by enzyme-linked immunosorbent assays (ELISAs). Thirty-three participating laboratories were asked to quantitate specific antibody to pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), or fimbrial proteins (FIM) in 21 samples. Samples were to be assayed in triplicate in five independent assays by each ELISA routinely performed in the laboratory to assess intra-assay, interassay, and population variability. The mean sample values were used to compare quantitative results among the laboratories. Thirteen of the 32 laboratories which submitted evaluable data for an assay to measure antibodies to PT, 12 of 30 laboratories with assays for FHA, 10 of 17 laboratories with assays for PRN, and 6 of 13 laboratories with assays for FIM maintained a coefficient of variation below 20% for 75% of the samples tested. Assays that measure antibodies to FIM appear to be less precise than the other assays. Precision varied among laboratories that used similar methods. The relative values of intra- and interassay variabilities were not consistent for a given assay within a laboratory, indicating that the sources of these variability components may be unrelated. Precision and agreement appeared less reliable for samples with low antibody levels. Ranking and regression analyses suggest that some laboratories generated comparable quantitative results, although direct comparison or combination of results from different laboratories remains difficult to support. Calibration to the U.S. Reference Pertussis Antisera appears to have been successful at standardizing the results in some laboratories. Statistical analyses are affected by assay precision and are not necessarily reliable sole predictors of biologically relevant differences in quantitative results. If results from different laboratories must be compared, appropriate studies of precision and quantitative agreement should be conducted to support the specific comparisons.

The effect of HN-65021 on responses to angiotensin II in human forearm vasculature

We studied the effect of (2-butyl-4-chloro-1[[2'-(1H-tetrazol-5-yl) [1,1'-biphenyl]methyl]-1H-imadazole-5-carboxylic acid,-1-(ethoxycarbonyloxy) ethyl-ester (HN-65021), on angiotensin II induced vasoconstriction in forearm vasculature of eight healthy men. Placebo and HN-65021 (5, 10 and 100 mg) were administered orally. Forearm blood flow was measured by venous occlusion plethysmography during rising dose brachial artery infusions of angiotensin II (0.3-1000 pmol min-1) 2 h after dosing. HN-65021 inhibited angiotensin II, causing a shift to the right of the dose-response curve. Angiotensin II (100 pmol min-1) decreased mean blood flow in the infused arm by 63.1 +/- 3.2% when infused following placebo and by 49.9 +/- 4.3%, 50.7 +/- 3.5% and 36.4 +/- 2.8% following HN-65021 doses of 5.10 and 100 mg respectively. These results demonstrate that HN-65021 antagonises angiotensin II receptor mediated vasoconstriction in human forearm resistance vessels.

Description and evaluation of serologic assays used in a multicenter trial of acellular pertussis vaccines

OBJECTIVE

To describe and evaluate the assays used to measure the antibody responses in infants to 13 experimental acellular pertussis vaccines and 2 licensed whole-cell pertussis vaccines.

METHODS

During a 53-week period, preimmunization and postimmunization sera were assayed for immunoglobulin G antibodies to pertussis toxin, filamentous hemagglutinin, pertactin, and a mixture of type 2 and type 3 fimbriae by enzyme-linked immunosorbent assay (ELISA), for whole-cell agglutinins (AGG), and for pertussis toxin-neutralizing antibodies by the Chinese hamster ovary cell assay. All ELISA reagents were characterized to assure antigen and isotype specificity of the assays. Intralaboratory reproducibility and temporal stability were evaluated by analysis of results of control sera and by assessment of the response to the control whole-cell vaccine. Interlaboratory reproducibility was assessed by repeating the assays on preimmunization and postimmunization sera for 10% of the infants in a second laboratory.

RESULTS

For control sera having antibody concentrations at least four times the minimum level of detection, the coefficients of variation within and between the ELISAs consistently were less than 20%. Trend analysis indicated that none of the assays drifted by more than 20% during the study period, and no significant drift was seen in the response to the control whole-cell vaccine. Results from the two laboratories correlated well; correlation coefficients were .93 or greater for the four ELISAs, .79 for the Chinese hamster ovary cell assay, and .82 for the AGG assay. For four of the six assays, there was either no difference or a modest (< 15%) difference in the geometric mean values for sera tested in both laboratories. Larger quantitative differences were observed for the AGG (45% difference) and pertactin (61% difference) assays.

CONCLUSION

Assay reproducibility and stability indicate that the standardized methods can be transferred between laboratories, and that the results accrued during a 1-year period for the 15 vaccines can be compared.

Relationships between functional assays and enzyme immunoassays as measurements of responses to acellular and whole-cell pertussis vaccines

OBJECTIVE

To examine the relationships between functional assays and antigen-specific enzyme immunoassays in sera from a multicenter trial of 13 different experimental acellular pertussis vaccines and 2 licensed whole-cell vaccines, and to determine whether correlations previously observed among assays of specimens from pertussis patients and whole-cell vaccinees would apply to specimens from infants immunized with purified components in acellular vaccines.

METHODS

Postimmunization sera were assayed for immunoglobulin G antibodies to pertussis toxin (PT), filamentous hemagglutinin, pertactin (PRN), and a mixture of types 2 and 3 fimbriae (FIM) by enzyme-linked immunosorbent assay, for whole-cell agglutinins (AGGs) and for PT-neutralizing antibodies by the Chinese hamster ovary (CHO) cell assay. Assay results were compared for individual sera, as well as for geometric mean antibody concentrations or titers (GMTs) calculated by vaccine or overall.

RESULTS

For the 15 vaccines, the PT GMTs were highly correlated with the CHO assay GMTs (r = .92), and the FIM GMTs were highly correlated with the AGG GMTs (r = .96). For individual postvaccination sera, there was a significant correlation between the CHO titers and levels of antibody to PT whether the 15 vaccines were considered separately (.59 < or = r < or = .85) or combined (r = .81). For individual sera from infants immunized with the two whole-cell vaccines or any of the four acellular vaccines containing FIM, a strong correlation between AGG titer and FIM antibody was observed whether the vaccines were considered separately (.83 < or = r < or = .91) or together (r = .86). One vaccine without detectable FIM produced a measurable AGG response; for this vaccine, a moderate but significant correlation (R = .58) between PRN antibody and AGG titer was observed.

CONCLUSION

These data indicate that appropriate antigen-specific enzyme-linked immunosorbent assays will furnish results similar to those provided by the CHO and AGG assays in the evaluation of the immunogenicity of component vaccines. Antibodies to FIM seem to include the most important AGGs; however, there is evidence that agglutination by PRN antibody may be detected in the absence of antibody to FIM.

Human antibody response to the B oligomer of pertussis toxin

To determine whether antibodies to the B oligomer of pertussis toxin (PT) were present in patients diagnosed with pertussis or vaccinees who had received diphtheria-tetanus-whole-cell pertussis vaccine, we analyzed serum samples from 5 patients and 10 vaccinees by both enzyme-linked immunosorbent assay (ELISA) and Western immunoblotting techniques. Antibodies to the B oligomer were detected by ELISA in all samples containing antibodies to holotoxin. Western immunoblotting procedures were less efficient than ELISA techniques for detecting antibodies to the B oligomer. Antibodies which inhibit the ability of the B oligomer to agglutinate erythrocytes were detected in purified human immunoglobulin preparations. In addition, serum samples containing antibodies to PT inhibited the binding of purified B oligomer and holotoxin to a 165-kDa glycoprotein which has been considered a potential PT receptor in Chinese hamster ovary (CHO) cells. These results suggest that antibodies to the B oligomer contribute to the human serologic response to PT, but their detection and characterization require appropriate methods.