Serum Concentrations of IgG4 in the Spanish Adult Population: Relationship with Age, Gender, and Atopy

Intact natalizumab pharmacokinetics is impacted by endogenous IgG4 concentration

BACKGROUND

Natalizumab (NAT) pharmacokinetics and pharmacodynamics are complicated by arm exchange with endogenous IgG4, resulting in a mixture of a more potent intact, bivalent form and a less potent, functionally monovalent form. Total NAT and endogenous IgG4 concentrations vary considerably across patients. This study assessed the concentration of intact NAT, and how it relates to total NAT and endogenous IgG4 levels in blood and saliva.

METHODS

Paired serum and saliva samples from a small cohort of relapsing-remitting multiple sclerosis patients were measured for levels of intact NAT, total NAT, IgG and IgG4.

RESULTS

Intact NAT concentration was dependent on both total NAT and endogenous IgG4 levels. Low endogenous IgG4 led to a higher ratio of intact NAT to total NAT, while the opposite was observed in subjects with high endogenous IgG4. Serum and saliva measurements show good concordance.

CONCLUSIONS

Intact NAT concentration is influenced by both NAT pharmacokinetics and endogenous IgG4 levels. Patients with low IgG4 levels can have high concentrations of intact NAT even with lower levels of total NAT, which may explain cases of NAT-associated progressive multifocal leukoencephalopathy (PML) in such patients. Monitoring both forms of NAT could better guide dosing, maximizing drug efficacy and safety.

Implication of allergy and atopy in IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a chronic multi-organic immune fibrosing disease. It affects preferentially men around middle age and almost any organs can be involved; however, lymph nodes, submandibular and lacrimal glands, pancreas, and retroperitoneum are the most affected. The mainstay treatment is corticosteroids, sometimes adjuncts with DMARDs or rituximab as steroid sparing agents. Th2 inflammation is implicated in the pathophysiology of the disease. Several reports indicate that allergy and/or atopy often affect patients with IgG4-RD. The frequency varies greatly between studies with allergies/allergic diseases reported in 18-76% while atopy is reported in 14-46%. In studies including both, they affect 42 and 62% of patients. Rhinitis and asthma are the most frequent allergic diseases. IgE and blood eosinophiles are often elevated and few studies report that basophils and mast cells could participate in the disease pathogenesis; however, the implication of allergy and atopy remain unclear. No common allergen has been identified and IgG4 production seems to be polyclonal. Although a direct causal effect is unlikely, they could potentially shape the clinical phenotype. Allergies/allergic diseases and/or atopy are reported to be more frequent in IgG4-RD patients presenting head, neck, and thoracic involvement, with higher IgE and eosinophils and less frequent in retroperitoneal fibrosis; however, studies regarding allergy and atopy in IgG4-RD are highly heterogenous. The aim of this article is to review what is currently known about the allergy and atopy in the context of Ig4-RD.

Changes in risk factors for food sensitization in early life: Analysis over a period of 10 years

Background

Although epidemiological trends of childhood food sensitization (FS) in IgE-mediated food allergy were reported in China, few studies have examined at changes in its risk factors.

Objective

To investigate the change in early-life risk factors associated with childhood food sensitization during 2009–2019 in China.

Methods

Data from two cross-sectional surveys conducted in 2009 and 2019 (401 and 513 children, respectively) were analyzed. The results of skin prick tests and information on food sensitization-related risk factors in children were summarized, including family history of atopic disease (FHA), demographic characteristics, method of delivery, feeding patterns, sibship size, pet ownership, and vitamin D supplementation. Binary logistic regression was used to calculate the odds ratio and the regression coefficient β-value of risk factors in the 2009 and 2019 surveys separately. Then, coefficient β-value differences between the two surveys were analyzed by the bdiff command in STATA to describe the change in risk factors over 10 years.

Results

The 2009 survey revealed that FHA, age, only child, and feeding patterns were associated with food sensitization. The 2019 survey showed that food sensitization was affected by age, sex, and feeding patterns. However, from 2009 to 2019, the probability of food sensitization in the only-child group significantly increased by 226.0% (β-value difference = 0.81, P = 0.024) and decreased by 65.0% in female children (β-value difference = −1.06, P = 0.008). The effect of age on food sensitization decreased by 50.0% (β-value difference = −0.69, P < 0.001) over 10 years.

Conclusion

The effect of FHA and common lifestyle factors on food sensitization did not significantly change during 2009−2019. However, the influence of demographic characteristics on food sensitization has changed since 2009; that is, older age, male gender, and only child are more likely to develop food sensitization, which needs to be considered in future epidemiological surveys.

Clinical Trial Registration

http://www.chictr.org.cn/, identifier ChiCTR1900024338.

Peptide Mimotope-Enabled Quantification of Natalizumab Arm Exchange During Multiple Sclerosis Treatment

BACKGROUND

Natalizumab, a therapeutic antibody used to treat multiple sclerosis, undergoes in vivo Fab arm exchange to form a monovalent bispecific antibody. Although highly efficacious, the immunosuppressive activity of natalizumab has been associated with JC polyomavirus-driven progressive multifocal leukoencephalopathy (PML). Development of assays that can distinguish between and quantify bivalent (unexchanged) and monovalent (exchanged) forms of natalizumab in clinical samples may be useful for optimizing extended interval dosing and reducing the risk of PML.

METHODS

In vitro natalizumab arm exchange was conducted, along with peptide mimotope and anti-idiotype surface capture chemistry, to enable the development of enzyme-linked immunosorbent assays.

RESULTS

An assay using a unique peptide Veritope TM was developed, which can exclusively bind to bivalent natalizumab. In combination with enzyme-linked immunosorbent assays that quantifies total natalizumab, the assay system allows quantification of both natalizumab forms.

CONCLUSIONS

In this article, a novel assay for the quantification of unexchanged and exchanged natalizumab variants in clinical samples was developed. This assay will enable investigations into the clinical significance of the relationship of PK/PD with the monovalent-to-bivalent ratio, as it relates to the efficacy of the drug and risk of PML.

Identification of risk factors for elevated serum IgG4 levels in subjects in a large-scale health checkup cohort study

Introduction

To allow the identification of IgG4-related disease (IgG4-RD) from a subclinical phase as it is important to understand the risk of elevated serum IgG4 levels. We planned to evaluate serum IgG4 levels in the participants of the Nagasaki Islands Study (NaIS), a large-scale health checkup cohort study.

Methods

This study included 3,240 individuals who participated in the NaIS between 2016 and 2018 and consented to participate in the study. Serum IgG4, IgG, and IgE levels and human leukocyte antigen (HLA) genotyping results of the NaIS subjects as well as lifestyle habits and peripheral blood test results were analyzed. The magnetic bead panel assay (MBA) and the standard nephelometry immunoassay (NIA) were used to measure serum IgG4 levels. The data were evaluated using multivariate analysis to identify lifestyle and genetic factors associated with elevated serum IgG4 levels.

Results

Serum IgG4 levels measured with the NIA and MBA showed a tight positive correlation between the two groups (correlation coefficient 0.942). The median age of the participants in the NaIS was 69 years [63-77]. The median serum IgG4 level was 30.2 mg/dL [IQR 12.5-59.8]. Overall, 1019 (32.1%) patients had a history of smoking. When the subjects were stratified into three groups based on the smoking intensity (pack-year), the serum IgG4 level was significantly higher among those with a higher smoking intensity. Accordingly, the multivariate analysis identified a significant relationship between smoking status and serum IgG4 elevation.

Conclusion

In this study, smoking was identified as a lifestyle factor correlating positively with elevated serum IgG4 levels.

Time-related variation in IgG subclass concentrations in a group of healthy Danish adults

Introduction

Immunoglobulin G subclass measurements are important for the diagnostic work‐up of immunodeficiencies and immunoglobulin G4 (IgG4) related diseases. It is currently unknown whether a single sampling is truly representative for an individual's IgG subclass concentrations. This study aimed to investigate whether IgG and IgG subclass concentrations in healthy individuals are stable over time.

Method

With a span of median 42 weeks, four samples from each of 54 (34M, 20F) healthy adult volunteers (24–66 years) were analyzed for IgG and IgG1–4 using turbidimetry. Concentrations were compared within and between individuals.

Results

IgG and IgG subclass concentrations followed either a normal (IgG, IgG1, and IgG3) or log normal (IgG2 and IgG4) distribution. Immunoglobulin 4 demonstrated by far the widest range of concentrations between individuals (670‐fold: 0.004–2.68 g/L). Immunoglobulin G subclass variations within individuals were expressed as pooled standard deviations (PSD). These ranged from 0.056 (IgG4) to 0.955 g/L (IgG) and correlated with mean concentration of IgG or the particular IgG subclass. As a consequence, the relative PSDs (i.e., PSD divided by mean IgG or IgG subclass concentration) fell within a narrow range: 5.82%–10.1%. Based on these numbers, the 95%‐upper one‐sided confidence limits for intraindividual IgG and IgG subclass variation was calculated to range from 9.82% (IgG2) to 16.9% (IgG4).

Conclusion

The study documents that IgG or IgG subclass concentrations within healthy individuals are very stable over at least 42 weeks. The expected variation for IgG4 concentrations at a 95% confidence level does not exceed ±16.9%.

Likely questionnaire-diagnosed food allergy in 78, 890 adults from the northern Netherlands

BACKGROUND

It is challenging to define likely food allergy (FA) in large populations which limited the number of large studies regarding risk factors for FA.

OBJECTIVE

We studied the prevalence and characteristics of self-reported FA (s-rFA) in the large, population-based Dutch Lifelines cohort and identified associated risk factors.

METHODS

Likely food allergic cases (LikelyFA) were classified based on questionnaire reported characteristics consistent with FA. Subjects with atypical characteristics were classified as Indeterminate. We investigated 13 potential risk factors for LikelyFA such as birth mode and living on a farm and addressed health-related quality of life (H-RQOL).

RESULTS

Of the 78, 890 subjects, 12.1% had s-rFA of which 4.0% and 8.1% were classified as LikelyFA and Indeterminate, respectively. Younger age, female sex, asthma, eczema and nasal allergy increased the risk of LikelyFA (p-value range <1.00*10-250-1.29*10-7). Living in a small city/large village or suburb during childhood was associated with a higher risk of LikelyFA than living on a farm (p-value = 7.81*10-4 and p = 4.84*10-4, respectively). Subjects classified as Indeterminate more often reported depression and burn-out compared to those without FA (p-value = 1.46*10-4 and p = 8.39*10-13, respectively). No association was found with ethnicity, (duration of) breastfeeding, birth mode and reported eating disorder. Mental and physical component scores measuring H-RQOL were lower in both those classified as LikelyFA and Indeterminate compared to those without FA.

CONCLUSION

The prevalence of s-rFA among adults is considerable and one-third reports characteristics consistent with LikelyFA. Living on a farm decreased the risk of LikelyFA. The association of poorer H-RQOL as well as depression and burn-out with questionable self-perceived FA is striking and a priority for future study.

IgG1 and IgG4 antibodies against Aedes aegypti salivary proteins and risk for dengue infections

Dengue virus (DENV) is an arbovirus responsible for a significant number of deaths in Latin America. This virus is transmitted through the bite of Aedes aegypti, the main mosquito vector, and Ae. albopictus. During blood uptake, the mosquito injects its saliva into the host to facilitate the feeding process. Mosquito saliva contains potent immunogens capable of inducing antibody production directly related to mosquito bite exposure intensity and disease risk. In this study, we first determined the DENV infection status by two different DENV non-structural protein 1 (NS1) based rapid tests and qRT-PCR, then measured the levels of IgG1 and IgG4 antibodies against salivary proteins of Ae. aegypti female mosquitoes in volunteers living in a dengue endemic area. Our results show that people with a positive DENV diagnosis present higher levels of IgG4 antibodies than people with a negative diagnostic test, and that these antibody levels were higher in people with secondary DENV infections. With this study, we show that detection of IgG4 antibodies against mosquito saliva may be a reliable method to evaluate the risk of dengue infection.

Adverse reactions to food: the female dominance - A secondary publication and update

Gender-specific differences are evident in food intolerance and allergy. In this review, we will highlight and summarize the dissimilarities in prevalence of adverse food reactions, focusing on IgE-mediated food allergies and intolerances regarding frequency of symptoms and predisposing factors. After puberty, females suffer more frequently from food-related symptoms than males. Several factors may be responsible for this observation, for example hormonal effects, gender-specific behavior, perception of risk, or intake of medications. In this context, concrete studies related to adverse food reactions are still lacking.