Comparative Risk of Angioedema With Sacubitril-Valsartan vs Renin-Angiotensin-Aldosterone Inhibitors

BACKGROUND

Data on angioedema risk among sacubitril-valsartan (SV) users in real-world settings are limited.

OBJECTIVES

We sought to evaluate the risk of angioedema among SV new users compared with angiotensin-converting enzyme (ACE) inhibitor and angiotensin-receptor-blocker (ARB) new users separately.

METHODS

We conducted a propensity score-matched cohort study, comparing SV new users (no use of SV, ACE inhibitor, ARB 6 months before) and SV new users with prior use (within 183 or 14 days) of ACE inhibitor or ARB (ACE inhibitor-SV and ARB-SV users; recent ACE inhibitor-SV and recent ARB-SV users, respectively) vs ACE inhibitor and ARB new users separately.

RESULTS

Compared with ACE inhibitor, SV new (HR: 0.18; 95% CI: 0.11-0.29) and ACE inhibitor-SV users (HR: 0.31; 95% CI: 0.23-0.43) showed lower risk of angioedema. On the other hand, there was no difference in angioedema risk when SV new users (HR: 0.59; 95% CI: 0.35-1.01) or ARB-SV users (HR: 0.85; 95% CI: 0.58-1.26) were compared with ARB new users. Compared with SV new users, ACE inhibitor-SV users (HR: 1.62; 95% CI: 0.91-2.89) trended toward higher angioedema risk, which intensified when the ACE inhibitor to SV switch occurred within 14 days (recent ACE inhibitor-SV) (HR: 1.98; 95% CI: 1.11-3.53). Similarly, ARB-SV users (HR: 2.03; 95% CI: 1.16-3.54) experienced an increased risk compared with SV new users, which intensified for the more recent switchers (recent ARB-SV) (HR: 2.45; 95% CI: 1.36-4.43).

CONCLUSIONS

We did not observe an increased risk of angioedema among SV new users compared with ACE inhibitor or ARB users. However, there was an increased risk of angioedema among SV users who recently switched from ACE inhibitor or ARB compared with SV new users.

Use of Intrauterine Devices and Risk of Human Immunodeficiency Virus Acquisition Among Insured Women in the United States

Concerns have been raised about progestin-containing contraceptives and the risk of human immunodeficiency virus (HIV) acquisition. Based on health insurance data from women in the United States with intrauterine device (IUD) insertions during 2011-2018, there was no increased risk of incident HIV diagnosis for levonorgestrel-releasing IUDs versus copper IUDs.

Interventions and Operations 5 Years After Bariatric Surgery in a Cohort From the US National Patient-Centered Clinical Research Network Bariatric Study

Importance

Additional data comparing longer-term problems associated with various bariatric surgical procedures are needed for shared decision-making.

Objective

To compare the risks of intervention, operation, endoscopy, hospitalization, and mortality up to 5 years after 2 bariatric surgical procedures.

Design, Setting, and Participants

Adults who underwent Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) between January 1, 2005, and September 30, 2015, within the National Patient-Centered Clinical Research Network. Data from 33 560 adults at 10 centers within 4 clinical data research networks were included in this cohort study. Information was extracted from electronic health records using a common data model and linked to insurance claims and mortality indices. Analyses were conducted from January 2018 through October 2019.

Exposures

Bariatric surgical procedures.

Main Outcomes and Measures

The primary outcome was time until operation or intervention. Secondary outcomes included endoscopy, hospitalization, and mortality rates.

Results

Of 33 560 adults, 18 056 (54%) underwent RYGB, and 15 504 (46%) underwent SG. The median (interquartile range) follow-up for operation or intervention was 3.4 (1.6-5.0) years for RYGB and 2.2 (0.9-3.6) years for SG. The overall mean (SD) patient age was 45.0 (11.5) years, and the overall mean (SD) patient body mass index was 49.1 (7.9). The cohort was composed predominantly of women (80%) and white individuals (66%), with 26% of Hispanic ethnicity. Operation or intervention was less likely for SG than for RYGB (hazard ratio, 0.72; 95% CI, 0.65-0.79; P < .001). The estimated, adjusted cumulative incidence rates of operation or intervention at 5 years were 8.94% (95% CI, 8.23%-9.65%) for SG and 12.27% (95% CI, 11.49%-13.05%) for RYGB. Hospitalization was less likely for SG than for RYGB (hazard ratio, 0.82; 95% CI, 0.78-0.87; P < .001), and the 5-year adjusted cumulative incidence rates were 32.79% (95% CI, 31.62%-33.94%) for SG and 38.33% (95% CI, 37.17%-39.46%) for RYGB. Endoscopy was less likely for SG than for RYGB (hazard ratio, 0.47; 95% CI, 0.43-0.52; P < .001), and the adjusted cumulative incidence rates at 5 years were 7.80% (95% CI, 7.15%-8.43%) for SG and 15.83% (95% CI, 14.94%-16.71%) for RYGB. There were no differences in all-cause mortality between SG and RYGB.

Conclusions and Relevance

Interventions, operations, and hospitalizations were relatively common after bariatric surgical procedures and were more often associated with RYGB than SG.

Trial Registration

ClinicalTrials.gov identifier: NCT02741674.

Complementary Use of U.S. FDA's Adverse Event Reporting System and Sentinel System to Characterize Direct Oral Anticoagulants-Associated Cutaneous Small Vessel Vasculitis

BACKGROUND

Cutaneous small vessel vasculitis (CSVV) has been reported after exposure to direct oral anticoagulants (DOACs), such as dabigatran, rivaroxaban, apixaban, and edoxaban.

OBJECTIVE

We used the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) to describe clinical characteristics associated with CSVV among DOAC-exposed patients. Furthermore, we characterized this signal in the Sentinel System to relate the clinical data from the individual FAERS cases to population-based electronic healthcare data.

METHODS

We queried FAERS for all cases of CSVV associated with DOACs from U.S. approval date of each DOAC through March 16, 2018. Within the Sentinel System, we identified incident CSVV cases using ICD-9 and ICD-10 diagnosis codes among adults aged ≥ 30 years who received a DOAC in the prior 90 days between January 1, 2010, and June 30, 2018. We excluded patients with evidence of select autoimmune diagnoses in the 183 days prior to their CSVV diagnoses and reported patient characteristics in the 183-day period prior to CSVV diagnoses.

RESULTS

In FAERS, we identified 50 cases of CSVV reported with rivaroxaban (n=26), apixaban (n=14), dabigatran (n=9), and edoxaban (n=1). Approximately 50% of the cases reported time to onset within 10 days after DOAC exposure. When specified, the predominant type of CSVV reported was leukocytoclastic vasculitis (n=31), followed by Henoch-Schonlein purpura (n=4). Hospitalization occurred in most of the cases (n=37). Switching of the offending agent after the development of CSVV was reported (n=26). Three rivaroxaban (n=3) cases and one dabigatran case (n=1) reported positive rechallenge. In the Sentinel system, we identified 3659 CSVV cases with prior DOAC exposure, with 85% of events occurring within 10 days.

CONCLUSIONS

The assessment of FAERS cases, combined with the temporal clustering of the Sentinel System cases suggest a possible causal relationship of DOACs and CSVV. Future efforts should characterize the risk of CSVV among the various DOAC users.

Comparing the 5-Year Diabetes Outcomes of Sleeve Gastrectomy and Gastric Bypass: The National Patient-Centered Clinical Research Network (PCORNet) Bariatric Study

Question

How do type 2 diabetes (T2DM) outcomes compare across the 2 most common bariatric procedures?

Findings

In this cohort study of 9710 adults with T2DM who underwent bariatric surgery, most patients who had Roux-en-Y gastric bypass or sleeve gastrectomy experienced T2DM remission at some point over 5 years of follow-up. Patients who had Roux-en-Y gastric bypass showed slightly higher T2DM remission rates, better glycemic control, and fewer T2DM relapse events than patients who had sleeve gastrectomy.

Meaning

Understanding diabetes outcomes of different bariatric procedures will help surgeons and patients with diabetes make informed health care choices.

Importance

Bariatric surgery can lead to substantial improvements in type 2 diabetes (T2DM), but outcomes vary across procedures and populations. It is unclear which bariatric procedure has the most benefits for patients with T2DM.

Objective

To evaluate associations of bariatric surgery with T2DM outcomes.

Design, Setting, and Participants

This cohort study was conducted in 34 US health system sites in the National Patient-Centered Clinical Research Network Bariatric Study. Adult patients with T2DM who had bariatric surgery between January 1, 2005, and September 30, 2015, were included. Data analysis was conducted from April 2017 to August 2019.

Interventions

Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG).

Main Outcome and Measures

Type 2 diabetes remission, T2DM relapse, percentage of total weight lost, and change in glycosylated hemoglobin (hemoglobin A_1c).

Results

A total of 9710 patients were included (median [interquartile range] follow-up time, 2.7 [2.9] years; 7051 female patients [72.6%]; mean [SD] age, 49.8 [10.5] years; mean [SD] BMI, 49.0 [8.4]; 6040 white patients [72.2%]). Weight loss was significantly greater with RYGB than SG at 1 year (mean difference, 6.3 [95% CI, 5.8-6.7] percentage points) and 5 years (mean difference, 8.1 [95% CI, 6.6-9.6] percentage points). The T2DM remission rate was approximately 10% higher in patients who had RYGB (hazard ratio, 1.10 [95% CI, 1.04-1.16]) than those who had SG. Estimated adjusted cumulative T2DM remission rates for patients who had RYGB and SG were 59.2% (95% CI, 57.7%-60.7%) and 55.9% (95% CI, 53.9%-57.9%), respectively, at 1 year and 86.1% (95% CI, 84.7%-87.3%) and 83.5% (95% CI, 81.6%-85.1%) at 5 years postsurgery. Among 6141 patients who experienced T2DM remission, the subsequent T2DM relapse rate was lower for those who had RYGB than those who had SG (hazard ratio, 0.75 [95% CI, 0.67-0.84]). Estimated relapse rates for those who had RYGB and SG were 8.4% (95% CI, 7.4%-9.3%) and 11.0% (95% CI, 9.6%-12.4%) at 1 year and 33.1% (95% CI, 29.6%-36.5%) and 41.6% (95% CI, 36.8%-46.1%) at 5 years after surgery. At 5 years, compared with baseline, hemoglobin A_1c was reduced 0.45 (95% CI, 0.27-0.63) percentage points more for patients who had RYGB vs patients who had SG.

Conclusions and Relevance

In this large multicenter study, patients who had RYGB had greater weight loss, a slightly higher T2DM remission rate, less T2DM relapse, and better long-term glycemic control compared with those who had SG. These findings can help inform patient-centered surgical decision-making.

Use of Sodium-Glucose Cotransporter 2 Inhibitors in Patients With Type 1 Diabetes and Rates of Diabetic Ketoacidosis

OBJECTIVE

To estimate real-world off-label use of sodium-glucose cotransporter 2 (SGLT2) inhibitors in patients with type 1 diabetes, estimate rates of diabetic ketoacidosis (DKA), and compare them with DKA rates observed in sotagliflozin clinical trials.

RESEARCH DESIGN AND METHODS

We identified initiators of SGLT2 inhibitors in the Sentinel System from March 2013 to June 2018, determined the prevalence of type 1 diabetes using a narrow and a broad definition, and measured rates of DKA using administrative claims data. Standardized incidence ratios (SIRs) were calculated using age- and sex-specific follow-up time in Sentinel and age- and sex-specific DKA rates from sotagliflozin trials 309, 310, and 312.

RESULTS

Among 475,527 initiators of SGLT2 inhibitors, 0.50% and 0.92% met narrow and broad criteria for type 1 diabetes, respectively. Rates of DKA in the narrow and broad groups were 7.3/100 person-years and 4.5/100 person-years, respectively. Among patients who met narrow criteria for type 1 diabetes, rates of DKA were highest for patients aged 25-44 years, especially females aged 25-44 years (19.7/100 person-years). More DKA events were observed during off-label use of SGLT2 inhibitors in Sentinel than would be expected based on sotagliflozin clinical trials (SIR = 1.83; 95% CI 1.45-2.28).

CONCLUSIONS

Real-world off-label use of SGLT2 inhibitors among patients with type 1 diabetes accounted for a small proportion of overall SGLT2 inhibitor use. However, the risk for DKA during off-label use was notable, especially among young, female patients. Although real-word rates of DKA exceeded the expectation based on clinical trials, results should be interpreted with caution due to differences in study methods, patient samples, and study drugs.

Comparative Effectiveness and Safety of Bariatric Procedures for Weight Loss: A PCORnet Cohort Study

BACKGROUND

There has been a dramatic shift in use of bariatric procedures, but little is known about their long-term comparative effectiveness.

OBJECTIVE

To compare weight loss and safety among bariatric procedures.

DESIGN

Retrospective observational cohort study, January 2005 to September 2015. (ClinicalTrials.gov: NCT02741674).

SETTING

41 health systems in the National Patient-Centered Clinical Research Network.

PARTICIPANTS

65 093 patients aged 20 to 79 years with body mass index (BMI) of 35 kg/m2 or greater who had bariatric procedures.

INTERVENTION

32 208 Roux-en-Y gastric bypass (RYGB), 29 693 sleeve gastrectomy (SG), and 3192 adjustable gastric banding (AGB) procedures.

MEASUREMENTS

Estimated percent total weight loss (TWL) at 1, 3, and 5 years; 30-day rates of major adverse events.

RESULTS

Total numbers of eligible patients with weight measures at 1, 3, and 5 years were 44 978 (84%), 20 783 (68%), and 7159 (69%), respectively. Thirty-day rates of major adverse events were 5.0% for RYGB, 2.6% for SG, and 2.9% for AGB. One-year mean TWLs were 31.2% (95% CI, 31.1% to 31.3%) for RYGB, 25.2% (CI, 25.1% to 25.4%) for SG, and 13.7% (CI, 13.3% to 14.0%) for AGB. At 1 year, RYGB patients lost 5.9 (CI, 5.8 to 6.1) percentage points more weight than SG patients and 17.7 (CI, 17.3 to 18.1) percentage points more than AGB patients, and SG patients lost 12.0 (CI, 11.6 to 12.5) percentage points more than AGB patients. Five-year mean TWLs were 25.5% (CI, 25.1% to 25.9%) for RYGB, 18.8% (CI, 18.0% to 19.6%) for SG, and 11.7% (CI, 10.2% to 13.1%) for AGB. Patients with diabetes, those with BMI less than 50 kg/m2, those aged 65 years or older, African American patients, and Hispanic patients lost less weight than patients without those characteristics.

LIMITATION

Potential unobserved confounding due to nonrandomized design; electronic health record databases had missing outcome data.

CONCLUSION

Adults lost more weight with RYGB than with SG or AGB at 1, 3, and 5 years; however, RYGB had the highest 30-day rate of major adverse events. Small subgroup differences in weight loss outcomes were observed.

PRIMARY FUNDING SOURCE

Patient-Centered Outcomes Research Institute.

Combining distributed regression and propensity scores: a doubly privacy-protecting analytic method for multicenter research

Purpose

Sharing of detailed individual-level data continues to pose challenges in multi-center studies. This issue can be addressed in part by using analytic methods that require only summary-level information to perform the desired multivariable-adjusted analysis. We examined the feasibility and empirical validity of 1) conducting multivariable-adjusted distributed linear regression and 2) combining distributed linear regression with propensity scores, in a large distributed data network.

Patients and methods

We compared percent total weight loss 1-year postsurgery between Roux-en-Y gastric bypass and sleeve gastrectomy procedure among 43,110 patients from 36 health systems in the National Patient-Centered Clinical Research Network. We adjusted for baseline demographic and clinical variables as individual covariates, deciles of propensity scores, or both, in three separate outcome regression models. We used distributed linear regression, a method that requires only summary-level information (specifically, sums of squares and cross products matrix) from sites, to fit the three ordinary least squares linear regression models. A comparison set of analyses that used pooled deidentified individual-level data from sites served as the reference.

Results

Distributed linear regression produced results identical to those from the corresponding pooled individual-level data analysis for all variables in all three models. The maximum numerical difference in the parameter estimate or standard error for all the variables was 3×10^-11 across three models.

Conclusion

Distributed linear regression analysis is a feasible and valid analytic method in multicenter studies for one-time continuous outcomes. Combining distributed regression with propensity scores via modeling offers more privacy protection and analytic flexibility.

Comparative effectiveness of bariatric procedures among adolescents: the PCORnet bariatric study

Background

Bariatric surgery has been used for treatment of severe obesity in adolescents but most studies have been small and limited in follow-up.

Objectives

We hypothesized that electronic health record data could be used to compare effectiveness of bariatric procedures in adolescents.

Setting

Data were obtained from clinical research networks using a common data model to extract data from each site.

Methods

Adolescents who underwent a primary bariatric procedure from 2005 through 2015 were identified. The percent change in body mass index (BMI) at 1, 3, and 5 years was estimated using random effects linear regression for patients undergoing all operations. Propensity score adjusted estimates and 95% confidence intervals were estimated for procedures with >25 patients at each time period.

Results

This cohort of 544 adolescents was predominantly female (79%) and White (66%), with mean (±standard deviation) age of 17.3 (±1.6) years and mean BMI of 49.8 (± 7.8) kg/m². Procedures included Roux-en-Y gastric bypass (RYGB; n = 177), sleeve gastrectomy (SG; n = 306), and laparoscopic adjustable gastric banding (n = 61). For those undergoing RYGB, SG, and laparoscopic adjustable gastric banding, mean (95% confidence interval) BMI changes of −31% (−30% to −33%), −28% (−27% to −29%), and −10% (−8% to −12%), were estimated at 1 year. For RYGB and SG, BMI changes of −29% (−26% to −33%) and −25% (−22% to −28%) were estimated at 3 years.

Conclusions

Adolescents undergoing SG and RYGB experienced greater declines in BMI at 1- and 3-year follow-up time points, while laparoscopic adjustable gastric banding was significantly less effective for BMI reduction. (Surg Obes Relat Dis 2018;000:1–13.)

Advances in the synthesis of acyclic peroxides

This review summarises the many developments in the synthesis of acyclic peroxides, with a particular focus on the past 20 years, and seeks to update organic chemists about these new approaches.

Three MYB transcription factors control pollen tube differentiation required for sperm release

In flowering plants, immotile sperm cells develop within the pollen grain and are delivered to female gametes by a pollen tube. Upon arrival at the female gametophyte, the pollen tube stops growing and releases sperm cells for successful fertilization. Several female signaling components essential for pollen tube reception have been identified; however, male components remain unknown. We show that the expression of three closely related MYB transcription factors is induced in pollen tubes by growth in the pistil. Pollen tubes lacking these three transcriptional regulators fail to stop growing in synergids, specialized cells flanking the egg cell that attract pollen tubes and degenerate upon pollen tube arrival. myb triple-mutant pollen tubes also fail to release their sperm cargo. We define a suite of pollen tube-expressed genes regulated by these critical MYBs and identify transporters, carbohydrate-active enzymes, and small peptides as candidate molecular mediators of pollen tube-female interactions necessary for flowering plant reproduction. Our data indicate that de novo transcription in the pollen tube nucleus during growth in the pistil leads to pollen tube differentiation required for release of sperm cells.

Do individuals with substance abuse diagnoses incur higher charges than individuals with other chronic conditions?

Concerns about high costs have led to limits on the services covered by most insurance plans for substance abuse treatment. But, the commonly used comparison group for cost analyses, all enrollees in a health-care plan, may not be appropriate because addiction is a chronic condition. Therefore, to determine whether substance abusers incur higher charges than patients with other serious chronic conditions, we used health insurance information for employees and dependents over 3 years (1989 to 1991) for two firms with a total of almost 40,000 employees to do alternate comparisons. We compared average annual charges for patients with the following diagnoses: substance abuse, substance abuse with mental illness, arthritis, asthma, and diabetes. Patients who undergo treatment for abusing alcohol, drugs, or both often (but not always) incur higher charges than people with other chronic conditions. Clear differences in average charges emerge between patients with and without mental health claims.

Characteristics of private-sector managed care for mental health and substance abuse treatment

OBJECTIVE

This study examined diversity during the late 1980s in managed care programs for mental health, alcohol abuse, and drug abuse to identify ways in which research can generate more meaningful data on the effectiveness of utilization review programs.

METHODS

Telephone interviews were conducted with representatives of utilization review programs for employee health insurance plans in 31 firms that employed 2.1 million people in 1990. Questions addressed qualifications of personnel, clinical criteria to authorize care, integration with employee assistance plans, penalties for not complying with utilization review procedures, outpatient review, and carve out of mental health and substance abuse review.

RESULTS

Large variations in utilization review programs were found. Programs employed a range of review personnel and used a variety of clinical criteria to authorize care. More than two-thirds did not carve out mental health and substance abuse review from medical-surgical review. Some firms' employee assistance plans were integrated with utilization review programs, while others remained unintegrated. Penalties for not following program procedures varied widely, as did review of outpatient services.

CONCLUSIONS

Because of trends toward even more diversity in utilization review programs in the 1990s, research that identifies the specific features of managed care programs that hold most promise for controlling costs while maintaining quality of care will increasingly be needed.

Studies on antigen binding by intact and hinge-deleted chimeric antibodies

A matched set of chimeric IgG1 and IgG4 antibodies were used to investigate the role of the IgG hinge in binding to Ag with differing space between the epitopes. Antibodies bearing identical V regions and either IgG1 or IgG4 C regions were engineered with and without hinges. We measured the binding of these antibodies to the peptide CYYYEEEEY and to CYYYEEEEY-BSA conjugates with decreasing numbers of peptides per BSA molecule. We earlier showed that V region differences in antibodies could affect Ag binding patterns in solid-phase but not solution-phase assays; however, both types of assay yielded similar results for the hinge-deleted antibodies. Binding of CYYYEEEEY-BSA by hinge-deleted and intact IgG1 was similar, but intact IgG1 bound free peptide better than did hinge-deleted IgG1. Intact IgG4 antibody bound less well to CYYYEEEEY and CYYYEEEEY-BSA than did IgG1 but, surprisingly, hinge-deleted IgG4 showed better binding than did intact IgG4 and was more like the IgG1 antibodies in binding affinity. Thus, the IgG4 hinge may impart a structural constraint that prevents high affinity binding to Ag. The hinge-deleted IgG4 antibody did not activate C, although it bound Ag similarly to IgG1. This study is the first to address the effect of the IgG hinge on Ag binding by using well defined Ag with different epitope densities. Our results may provide an explanation for the apparent low affinity of IgG4 antibodies.

Studies on antigen binding by intact and hinge-deleted chimeric antibodies

A matched set of chimeric IgG1 and IgG4 antibodies were used to investigate the role of the IgG hinge in binding to Ag with differing space between the epitopes. Antibodies bearing identical V regions and either IgG1 or IgG4 C regions were engineered with and without hinges. We measured the binding of these antibodies to the peptide CYYYEEEEY and to CYYYEEEEY-BSA conjugates with decreasing numbers of peptides per BSA molecule. We earlier showed that V region differences in antibodies could affect Ag binding patterns in solid-phase but not solution-phase assays; however, both types of assay yielded similar results for the hinge-deleted antibodies. Binding of CYYYEEEEY-BSA by hinge-deleted and intact IgG1 was similar, but intact IgG1 bound free peptide better than did hinge-deleted IgG1. Intact IgG4 antibody bound less well to CYYYEEEEY and CYYYEEEEY-BSA than did IgG1 but, surprisingly, hinge-deleted IgG4 showed better binding than did intact IgG4 and was more like the IgG1 antibodies in binding affinity. Thus, the IgG4 hinge may impart a structural constraint that prevents high affinity binding to Ag. The hinge-deleted IgG4 antibody did not activate C, although it bound Ag similarly to IgG1. This study is the first to address the effect of the IgG hinge on Ag binding by using well defined Ag with different epitope densities. Our results may provide an explanation for the apparent low affinity of IgG4 antibodies.

Variable region differences affect antibody binding to immobilized but not soluble antigen

We have examined the antigen binding characteristics of two chimeric IgG1 antibodies that differ only in the heavy chain variable region. Antibodies 10B and B11 were expressed from two different anti-(Tyr,Glu)-Ala-Lys murine VH genes joined to human IgG1 constant region genes in a murine anti-(Tyr,Glu)-Ala-Lys heavy chain loss variant hybridoma. The binding characteristics of the antibodies to (Tyr,Glu)-Ala-Lys and to a peptide conjugate, CYYYEEEEY:BSA, were measured in solution and solid phase assays. The antibodies exhibited similar affinities and binding characteristics when assayed in solution assays. However, when we measured binding of antibodies to immobilized antigens, we found that antibody affinity depended on the epitope density in the immobilized immune complexes. The binding of antibody 10B and of B11 to immobilized (Tyr,Glu)-Ala-Lys and to CYYYEEEEY:BSA were similar at high antigen density, but antibody B11 bound less well at lower antigen density. Fab fragments of 10B bound to immobilized (Tyr,Glu)-Ala-Lys and CYYYEEEEY:BSA, but Fab fragments of B11 did not bind to (Tyr,Glu)-Ala-Lys and bound less well to CYYYEEEEY:BSA than 10B Fabs.

Effect of H chain V region on complement activation by immobilized immune complexes

Activation of C by immune complexes (IC) in tissues and the inflammatory consequences are major determinants in the pathogenesis of many autoimmune disorders. To assess the factors involved in C activation by such IC, we examined the binding of C components by chimeric IgG1 antibodies bound to immobilized Ag. We previously reported that alterations in the H chain V regions can affect the binding of first component of C (C1q) and a major breakdown product of the third C component (C3b) when otherwise identical antibodies were bound to immobilized (Tyr, Glu)-Ala-Lys. To evaluate C activation of these antibodies in well defined IC, we utilized a 9-amino acid peptide conjugated to BSA as Ag. The peptide:BSA conjugate was bound similarly by the two IgG1 antibodies which differed mainly in the CDR3 regions, but also in 9 other amino acids in the H chain V region. When soluble IC were prepared with the two antibodies, they activated C similarly. However, C activation by solid phase Ag:antibody complexes differed; we found that antibody 10B bound more C1q and C3b than antibody B11 did, unless the Ag was present at high density on the plates. These data suggest that the variable region differences affect C activation by these antibody when they are bound to immobilized Ag. Furthermore, these results underscore the differences in C activation by the same antibody depending upon whether the IC are free in solution or immobilized.

Effect of H chain V region on complement activation by immobilized immune complexes

Activation of C by immune complexes (IC) in tissues and the inflammatory consequences are major determinants in the pathogenesis of many autoimmune disorders. To assess the factors involved in C activation by such IC, we examined the binding of C components by chimeric IgG1 antibodies bound to immobilized Ag. We previously reported that alterations in the H chain V regions can affect the binding of first component of C (C1q) and a major breakdown product of the third C component (C3b) when otherwise identical antibodies were bound to immobilized (Tyr, Glu)-Ala-Lys. To evaluate C activation of these antibodies in well defined IC, we utilized a 9-amino acid peptide conjugated to BSA as Ag. The peptide:BSA conjugate was bound similarly by the two IgG1 antibodies which differed mainly in the CDR3 regions, but also in 9 other amino acids in the H chain V region. When soluble IC were prepared with the two antibodies, they activated C similarly. However, C activation by solid phase Ag:antibody complexes differed; we found that antibody 10B bound more C1q and C3b than antibody B11 did, unless the Ag was present at high density on the plates. These data suggest that the variable region differences affect C activation by these antibody when they are bound to immobilized Ag. Furthermore, these results underscore the differences in C activation by the same antibody depending upon whether the IC are free in solution or immobilized.

Alteration in H chain V region affects complement activation by chimeric antibodies

Chimeric antibodies to the synthetic polypeptide (Tyr, Glu)-Ala-Lys ((T,G)-A-L) were used to examine C activation by human IgG1. Two IgG1 antibodies, which contained mouse L chains and H chains with mouse V domains and human C domains, differed only in their VH domain. Ag binding and C activation by these antibodies were analyzed by ELISA. When limiting amounts of Ag were used in the assays, the antibodies required different quantities of Ag for optimal binding, suggesting that the antibodies bind to different epitopes on the (T,G)-A-L molecule. However, when competitive inhibition assays were performed with an optimal concentration of Ag, there were no differences in relative binding affinities for (T,G)-A-L or dissociation characteristics of the antibodies. C activation was examined at optimal Ag concentration to ensure equivalent binding of two IgG1 antibodies to Ag. After combination with immobilized Ag, these two antibodies bearing different V regions exhibited marked differences in the binding of C components C1q and C3d. When present in equal amounts in the assay, antibody 10B activated C and bound more C1q and C3d than antibody B11. These results indicate that V region differences can affect C activation by IgG.

Alteration in H chain V region affects complement activation by chimeric antibodies

Chimeric antibodies to the synthetic polypeptide (Tyr, Glu)-Ala-Lys ((T,G)-A-L) were used to examine C activation by human IgG1. Two IgG1 antibodies, which contained mouse L chains and H chains with mouse V domains and human C domains, differed only in their VH domain. Ag binding and C activation by these antibodies were analyzed by ELISA. When limiting amounts of Ag were used in the assays, the antibodies required different quantities of Ag for optimal binding, suggesting that the antibodies bind to different epitopes on the (T,G)-A-L molecule. However, when competitive inhibition assays were performed with an optimal concentration of Ag, there were no differences in relative binding affinities for (T,G)-A-L or dissociation characteristics of the antibodies. C activation was examined at optimal Ag concentration to ensure equivalent binding of two IgG1 antibodies to Ag. After combination with immobilized Ag, these two antibodies bearing different V regions exhibited marked differences in the binding of C components C1q and C3d. When present in equal amounts in the assay, antibody 10B activated C and bound more C1q and C3d than antibody B11. These results indicate that V region differences can affect C activation by IgG.

Binding of double-stranded DNA to glomeruli of rats in vivo

In vivo binding of double-stranded DNA (dsDNA) to renal glomeruli of rats was examined. 125I-dsDNA (600 basepairs) was perfused with 131I-IgG as a blood marker into the right renal artery of normal rats, and blood flow was restored. After 10 minutes, isolated glomeruli showed a specific uptake of DNA, which increased in a saturable fashion with increasing doses of administered DNA. To exclude the possibility that 125I in the glomeruli represented only DNA breakdown products, we extracted the DNA from the glomeruli for analysis by polyacrylamide gel electrophoresis. The extracted DNA was 120-200 bp in size, which is large enough to bind antibodies to DNA. In contrast, the radioactivity of DNA taken up by the liver or renal tissues other than glomeruli was predominantly trichloroacetic acid soluble, i.e., less than 15 bp. Immunofluorescence studies showed that antibodies to DNA, administered after DNA, were present in glomeruli. Our data indicate that dsDNA binds to glomeruli in vivo in a saturable manner, and remains large enough to be antigenic. Therefore, the binding of DNA to glomeruli, followed by interaction with antibodies to dsDNA may be a mechanism for DNA-anti-DNA complex formation in glomeruli in patients with systemic lupus erythematosus.

Complement fixation by small, DNase-resistant DNA-anti-DNA immune complexes

125I-ds DNA-anti-DNA immune complexes (IC) formed at antibody excess and containing DNA of 300-350 base pairs (bp) fixed complement, incorporated C3b and bound to the C3b receptors (CR1) on human red blood cells (RBC). When the IC were treated with DNase to generate small, DNase-resistant IC, some of the IC incorporated C3b, but did not bind to RBC. In order to examine C3b incorporation and RBC binding by IC of specific sizes, the DNase treated IC were fractionated by sucrose density gradient (SDG) ultracentrifugation. Small IC containing one, two, three or four IgG molecules per fragment of 125I-ds DNA were identified by autoradiography after electrophoresis of the SDG fractions on 3-12% linear polyacrylamide gradient gels. The SDG fractions were tested for C3b incorporation and RBC binding ability. There was neither C3b incorporation nor RBC binding activity in fractions which corresponded to 9-11S (containing IC with one IgG/DNA). Fractions which corresponded to 12-22S (containing IC with up to four IgG/DNA fragment) demonstrated increased C3b incorporation with increased size, but did not show significant RBC binding activity. Fractions with IC containing four or more IgGs (22-24S) incorporated C3b and bound to RBC at approximately the same level. It is concluded that DNase digested IC which contain three-four IgG/DNA fragment are large enough to activate complement and incorporate C3b, but are too small to bind to RBC CR1. These IC could therefore escape rapid clearance from the circulation via the erythrocyte CR1 clearance mechanism. Such IC could persist in the circulation and potentially elicit pathogenic effects in patients with systemic lupus erythematosus.

In vivo studies with the novel anticancer agent mitozolomide (NSC 353451) on Lewis lung carcinoma

Mitozolomide is one of the most effective drugs against Lewis lung carcinoma in the mouse. Two IP doses of 40 mg/kg (days 6 and 15 after IM transplantation of 3LL) or four doses of 20 mg/kg given at various intervals (starting from day 6) increased survival time by 100%. A single IP dose of 80 mg/kg was toxic, and 10 mg/kg was ineffective even when this dose was given on eight occasions. The pharmacokinetics of mitozolomide was investigated in 3LL-bearing mice by HPLC assay. Peak drug levels were achieved in tumor 15 min after IP treatment, after which they declined according to first-order kinetics, with a half-life of 80-100 min (the same as in plasma). No dose-dependent kinetics was observed. Flow cytometry studies showed an accumulation of 3LL cells in G2M 24 h after drug treatment. This cell cycle perturbation was reversed 96 h after the inactive dose of 10 mg/kg, but not after the effective dose of 40 mg/kg.

Dynamics of interaction between complement-fixing antibody/dsDNA immune complexes and erythrocytes. In vitro studies and potential general applications to clinical immune complex testing

Soluble antibody/3H-double-stranded PM2 DNA (dsDNA) immune complexes were briefly opsonized with complement and then allowed to bind to human erythrocytes (via complement receptors). The cells were washed and subsequently a volume of autologous blood in a variety of media was added, and the release of the bound immune complexes from the erythrocytes was studied as a function of temperature and time. After 1-2 h, the majority of the bound immune complexes were not released into the serum during blood clotting at either 37 degrees C or room temperature, but there was a considerably greater release of the immune complexes into the plasma of blood that was anticoagulated with EDTA. Similar results were obtained using various conditions of opsonization and also using complexes that contained lower molecular weight dsDNA. Thus, the kinetics of release of these antibody/dsDNA immune complexes differed substantially from the kinetics of release of antibody/bovine serum albumin complexes that was reported by others. Studies using the solution phase C1q immune complex binding assay confirmed that in approximately half of the SLE samples that were positive for immune complexes, there was a significantly higher level of detectable immune complexes in plasma vs. serum. Freshly drawn erythrocytes from some SLE patients exhibiting this plasma/serum discrepancy had IgG antigen on their surface that was released by incubation in EDTA plasma. Thus, the higher levels of immune complexes observed in EDTA plasma vs. serum using the C1q assay may often reflect the existence of immune complexes circulating in vivo bound to erythrocytes.

Complement-component-C3-opsonized immunoglobulin G anti-DNA antibodies do not bind effectively to red blood cells unless aggregated on a high-Mr DNA matrix

Large, soluble ds (double-stranded) DNA-IgG (immunoglobulin G) anti-dsDNA immune complexes (greater than or equal to 200 S) that were previously opsonized with complement were digested with DNAase. The small complement-component-C3-fragment-labelled IgG (11-14 S) that was then isolated did not bind effectively to complement receptor type 1 on human red blood cells. However, when this IgG was immune-complexed with 3H-labelled PM2 (bacteriophage directed against a marine Pseudomonas) dsDNA (Mr approximately 6 X 10(6), substantial binding of both the DNA antigen and IgG to the erythrocytes was demonstrable.

Suramin inhibits the binding of complement-fixing antibody/double-stranded DNA immune complexes to CR1

The effects of varying concentrations of heparin and suramin on the complement-mediated binding of antibody/double-stranded DNA immune complexes to red blood cells (RBCs) and Raji cells have been investigated. If the immune complexes are briefly opsonized with complement, suramin can block binding to both cell types, and heparin can block binding to RBCs. In addition, if these complexes are first allowed to bind to RBCs or Raji cells, relatively brief incubations in suramin are sufficient to cause release of the complexes from the cells' C3b receptors. The potential clinical and diagnostic implications of these findings are discussed.

The kinetics of [3H]-dsDNA/anti-DNA immune complex formation, binding by red blood cells, and release into serum: effect of DNA molecular weight and conditions of antibody excess

[3H]dsDNA/anti-DNA immune complexes (IC) formed, fixed complement, and bound rapidly to red blood cells (RBC) in whole blood (less than 5 min), but were released from the cells more slowly. The rate of release was dependent on both the antibody:DNA ratio and the m.w. of the DNA in the complex. For example, complexes formed with high m.w. DNA (6 X 10(6) daltons) were released more slowly (t1/2 = 60 min) than complexes formed with lower m.w. DNA (2 to 6 X 10(5) daltons, t1/2 = 15 to 20 min). The [3H]dsDNA/anti-DNA complexes, which were released from the cells as intact antigen/antibody/complement complexes, did not rebind to RBC, but did bind to Raji cells and could be precipitated by monoclonal antibody to C3d. When these released IC (RIC) containing high m.w. DNA were incubated with additional anti-DNA antibody and fresh complement, they rebound to RBC. However, RIC containing lower m.w. DNA (5 X 10(5) daltons) did not rebind to RBC under the same conditions. These data suggest that IC containing high m.w. DNA bind to and remain bound to RBC more effectively than IC containing lower m.w. DNA, and thus may be more easily cleared from the circulation by the RBC IC clearance mechanism. Thus, the size of the DNA in the IC may be a significant factor in the pathogenicity of DNA/anti-DNA complexes in SLE.

The kinetics of [3H]-dsDNA/anti-DNA immune complex formation, binding by red blood cells, and release into serum: effect of DNA molecular weight and conditions of antibody excess

[3H]dsDNA/anti-DNA immune complexes (IC) formed, fixed complement, and bound rapidly to red blood cells (RBC) in whole blood (less than 5 min), but were released from the cells more slowly. The rate of release was dependent on both the antibody:DNA ratio and the m.w. of the DNA in the complex. For example, complexes formed with high m.w. DNA (6 X 10(6) daltons) were released more slowly (t1/2 = 60 min) than complexes formed with lower m.w. DNA (2 to 6 X 10(5) daltons, t1/2 = 15 to 20 min). The [3H]dsDNA/anti-DNA complexes, which were released from the cells as intact antigen/antibody/complement complexes, did not rebind to RBC, but did bind to Raji cells and could be precipitated by monoclonal antibody to C3d. When these released IC (RIC) containing high m.w. DNA were incubated with additional anti-DNA antibody and fresh complement, they rebound to RBC. However, RIC containing lower m.w. DNA (5 X 10(5) daltons) did not rebind to RBC under the same conditions. These data suggest that IC containing high m.w. DNA bind to and remain bound to RBC more effectively than IC containing lower m.w. DNA, and thus may be more easily cleared from the circulation by the RBC IC clearance mechanism. Thus, the size of the DNA in the IC may be a significant factor in the pathogenicity of DNA/anti-DNA complexes in SLE.

Quantitative determination of anti-dsDNA antibodies and antibody/dsDNA stoichiometries in prepared, soluble complement-fixing antibody/dsDNA immune complexes

We have investigated quantitatively the complement-mediated binding of prepared, soluble 125I-7S IgG antibody/3H-dsDNA immune complexes to human red blood cells (RBCs). We have performed these studies by using a detailed modification of the RBC-CF assay [Pedersen et al., J. Immun. Meth. 38, 269-280 (1980)] which now allows for the simultaneous measurement of both 3H-DNA and 125I-binding to the cells. Our results indicate that, in the case of three SLE patients, their anti-dsDNA antibody titers are sufficiently high that a small fraction of their 125I-7S IgG antibodies (ca 0.1-0.2%) can be identified as specifically anti-dsDNA. We have also used an indirect method (with 125I-labelled rabbit anti-human IgG) for the determination of IgG anti-dsDNA antibodies in complement-fixing antibody/dsDNA immune complexes that bind to RBCs, and the results of these measurements are in reasonable agreement with the direct binding experiments. These studies have also allowed us to estimate the antibody/DNA stoichiometries in complement-fixing immune complexes. The results of these experiments may provide a useful standard for the analysis of monoclonal anti-dsDNA antibodies.

Quantitative analyses of complement fixation in three immune complex systems

The quantitative interaction of three different immune complex systems with complement has been investigated. dsDNA/anti-DNA, heat-aggregated IgG subfractions, and human IgG/rabbit anti-human IgG complexes were tested for their ability to consume complement (immune haemolysis assay) and to bind to red blood cells in a complement-mediated reaction (the RBC-CF assay). Our results indicate that some physical and immunological properties of the dsDNA/anti-DNA immune complex systems are significantly different from those of immune complexes that involve more common globular protein antigens. This difference in properties may help explain the role of dsDNA/anti-DNA immune complexes in systemic lupus erythematosus pathogenesis.

Studies on the kinetics of binding of complement-fixing dsdna/anti-dsdna immune complexes to the red blood cells of normal individuals and patients with systemic lupus erythematosus

The kinetics of binding of prepared complement opsonized 3H-dsDNA/anti-DNA immune complexes to normal red blood cells (RBCs) and to RBCs with lowered immune complex binding capacity from certain patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis was examined. Normal RBCs bound the immune complexes rapidly and reached equilibrium in about 4 minutes at 37 degrees C, while the SLE RBCs not only bound less immune complex but required up to 30 minutes to reach equilibrium. Chemical modification of normal RBCs with moderate amounts of dithiothreitol, an agent that destroys the binding activity of the C3b receptor (CR1), produced RBCs that mimicked the equilibrium and kinetic binding properties of the SLE RBCs. These observations, taken in conjunction with a detailed examination of the temperature dependence of the binding kinetics, suggest that CR1 reorganization on the RBC surface to form binding clusters may be an essential step in the complement mediated binding of immune complexes to RBCs. The implications of these findings with respect to the clearance of immune complexes from the circulation of patients with autoimmune diseases are discussed.

Growth and reproduction of two species of Akodon and their hybrids

Growth and reproduction of Akodon molinae (A.m.), A. dolores (A.d.) (Rodentia: Cricetidae), and their hybrids are described. A.d. showed less fertility under animal room conditions, fewer "successful" matings, similar litter sizes, and an altered sex proportion as compared to A.m.; A.d. ovulatory index is supposed to be higher than mean litter size. X-linked lethal gene(s) and chromosome polymorphisms are possible causes of these variations. Interspecific crosses showed a marked seasonal (summer) tendency in parturitions. Intraspecific matings also produced young during winter. F1 hybrids showed a reversed tendency, while F2 matings returned to the parental pattern. A.d. male X A.m. female and F1 crosses presented larger litter sizes than the other pairings. A.m. exhibited sexual differences in weight after 60 days of age. A.d. and F1 hybrids did not show significant differences in weight of both sexes at any age. A.m. males and females were heavier than A.d. individuals except 12 months after birth. F1 hybrids born to A.m. male were heavier at birth than the A.d. female s interspecific offspring, and may be interpreted as a maternal influence of the A.m. females. Hybrids were heavier than their parents at birth and some of them were also heavier at 21 days, and probably is due to pseudoheterosis. The comparison of body measurements between sexes of both species did not give conclusive results. A.m. females were larger than females of A.d. Males of both species showed similar total lengths; A.m. males had larger body lengths and shorter tails. Body measurements were not related to weight variations. However, differences in weight and measurements between sexes appeared simultaneously at 2-6 months. This probably reflected the attainment of maturity.

The complement-mediated binding of soluble antibody/dsDNA immune complexes to human neutrophils

The complement-mediated binding of soluble antibody/3H-dsDNA immune complexes (prepared in vitro) to human polymorphonuclear leukocytes (PMN) has been investigated quantitatively. Studies with isolated complement components in conjunction with experiments on the binding of these complexes to human red blood cells suggest that the binding to both cell types is mediated predominantly by CR1 (C4b-C3b) receptors but that CR3 (iC3b or C3d-g) receptors may play a role in binding to PMN but probably not to RBC. Our results also indicate that under the standard conditions of these assays (37 degrees C, 20 to 40 min incubations) there is no significant internalization of the soluble antibody/dsDNA immune complexes after they are bound by the PMN.

Decreased complement mediated binding of antibody/3H-dsDNA immune complexes to the red blood cells of patients with systemic lupus erythematosus, rheumatoid arthritis, and hematologic malignancies

The complement mediated binding of prepared antibody/3H-dsDNA immune complexes to the red blood cells obtained from a number of patient populations has been investigated. Patients with solid tumors have binding activity similar to that seen in a normal group of individuals. However, a significant fraction of patients with systemic lupus erythematosus, rheumatoid arthritis, and hematologic malignancies have lowered binding activity compared with normal subjects. Quantitative studies indicate the lowered activity probably arises due to a decrease in complement receptors on the respective red blood cells. The potential importance and implications of these findings are briefly discussed.

The complement-mediated binding of soluble antibody/dsDNA immune complexes to human neutrophils

The complement-mediated binding of soluble antibody/3H-dsDNA immune complexes (prepared in vitro) to human polymorphonuclear leukocytes (PMN) has been investigated quantitatively. Studies with isolated complement components in conjunction with experiments on the binding of these complexes to human red blood cells suggest that the binding to both cell types is mediated predominantly by CR1 (C4b-C3b) receptors but that CR3 (iC3b or C3d-g) receptors may play a role in binding to PMN but probably not to RBC. Our results also indicate that under the standard conditions of these assays (37 degrees C, 20 to 40 min incubations) there is no significant internalization of the soluble antibody/dsDNA immune complexes after they are bound by the PMN.