Assessment of IgM enzyme immunoassay and IgG avidity assay for distinguishing between primary and secondary immune response to rubella vaccine

Reduction in Rubella Virus Active Cases among Children and Adolescents after Rubella Vaccine Implementation in Tanzania: A Call for Sustained High Vaccination Coverage

Rubella virus (RV) infection in susceptible women during the first trimester of pregnancy is associated with congenital Rubella syndrome (CRS). In countries where a vaccination program is implemented, active case surveillance is emphasized. This report documents the magnitude of active cases before and after vaccine implementation in Tanzania. A total of 8750 children and adolescents with signs and symptoms of RV infection were tested for Rubella IgM antibodies between 2013 and 2019 using enzyme immunoassay followed by descriptive analysis. The median age of participants was 3.8 (IQR: 2−6.4) years. About half (4867; 55.6%) of the participants were aged 1−5 years. The prevalence of RV active cases was 534 (32.6%, 95% CI: 30.2−34.9) and 219 (3.2%, 95% CI: 2.7−3.6) before and after vaccine implementation, respectively. Before vaccination, the highest prevalence was recorded in Pemba (78.6%) and the lowest was reported in Geita (15.6%), whereas, after vaccination, the prevalence ranged between 0.5% in Iringa and 6.5% in Pemba. Overall, >50% of the regions had a >90% reduction in active cases. The significant reduction in active cases after vaccine implementation in Tanzania underscores the need to sustain high vaccination coverage to prevent active infections and eventually eliminate CRS, which is the main goal of Rubella vaccine implementation.

Modified ELISA for antibody avidity evaluation: The need for standardization

Antibody avidity is an important parameter to evaluate immune response, being useful to evaluate vaccine responses and helping to distinguish acute and latent infection. The antibody avidity can be measured by different methods, yet the most common is a modified ELISA. The utilization of commercial kits or in-house methods to evaluate antibody avidity have been adopted more and more, although the lack of standardization between different assays may generate a lot of variation in the process, making it hard to compare the results generated.

Challenges of measles and rubella laboratory diagnostic in the era of elimination

The Member States of the WHO European Region adopted the goal of measles and rubella elimination more than 10 years ago, but so far only 21 of 53 countries have reached this target. Laboratory investigation of suspected cases is essential to support disease elimination efforts. Therefore, WHO maintains a network of accredited laboratories providing high-quality testing. Laboratory investigation heavily relies on specific IgM serology and increasingly on virus detection by reverse transcription (RT)-PCR, but other methods such as IgG avidity testing and genetic characterization of virus strains have gained in importance. In elimination settings, often few samples from suspected cases are available for testing, but testing proficiency must be maintained. The predictive value of an IgM-positive result decreases and other rash-fever disease aetiologies become more important. In addition, cases with a rash after measles/rubella vaccination or with mild disease after waning of vaccine-induced antibodies are seen more often. Thus, it is necessary to perform comprehensive and potentially time-consuming and costly investigations of every suspected case using quality-controlled laboratory methods. At the same time rapid feedback to public health officers is required for timely interventions. The introduction of new laboratory methods for comprehensive case investigations requires training of staff under the supervision of WHO-accredited reference laboratories and the definition of appropriate test algorithms. Clinical, laboratory, and epidemiological data are essential for final case classification and investigation of chains of transmission in the endgame of measles and rubella elimination.

Acute Rubella Virus Infection among Women with Spontaneous Abortion in Mwanza City, Tanzania

INTRODUCTION

Acute rubella virus infection in early pregnancy has been associated with poor pregnancy outcome ranging from spontaneous abortion, stillbirth and multiple birth defects known as Congenital Rubella Syndrome (CRS). Despite its importance the prevalence of acute rubella virus infections is not known among women with spontaneous abortion in most centres in developing countries.

AIM

The present study was aimed to determine the seroprevalence of acute rubella infection among women with spontaneous abortion in Mwanza city.

MATERIALS AND METHODS

A total of 268 women with spontaneous abortion were enrolled from four different hospitals in Mwanza city between November 2015 and April 2016. Blood samples were collected; sera were extracted and stored at -80°C until processing. Acute rubella virus infection was diagnosed by the detection of rubella specific IgM antibodies using indirect Enzyme Linked Immunosorbent Assay (ELISA) as per manufacturer's instructions. Data were analysed by using STATA version 11.

RESULTS

The mean age of enrolled women was 26.3±5.6 years. The prevalence of acute rubella virus infection was found to be 9/268 (3.7%, 95% CI: 1-5). Only women residing in urban areas (AOR: 5.65, 95% CI: 1.15-27.77, p=0.035) were found to predict acute rubella virus infection among cases with spontaneous abortion in Mwanza city.

CONCLUSION

About four out of hundred women residing in urban areas with spontaneous abortion in Mwanza are acutely infected with rubella virus highlighting the potential of this virus in contributing to poor pregnancy outcome in this setting.

Serological evidence of acute rubella infection among under-fives in Mwanza: a threat to increasing rates of congenital rubella syndrome in Tanzania

Background

Control of rubella infection is essential for preventing congenital rubella syndrome (CRS) and one of the important steps is to define a target population for vaccination. Therefore this study was done to determine serological evidence of acute rubella infection among under-fives in order to anticipate the magnitude of rubella virus transmission in Tanzania.

Methods

A cross-sectional study involving children aged between 1 and 59 months was conducted between September and October 2014 before national rubella vaccination campaigns commenced. Rubella IgM antibodies were detected using commercial indirect enzyme-linked immunosorbent assay (ELISA). Data were analyzed using STATA version 11.

Results

A total of230 under-fives were enrolled, their median age was 14 (Interquartile range (IQR) 7–26) months. The overall seroprevalence of rubella IgM antibodies was 10.9 % (25/230) with two confirmed cases of CRS. Two-sample Wilcoxon rank-sum test showed that the median age of rubella IgM seropositive children was significantly higher than that of IgM seronegative children (39 IQR: 18-51months vs. 14 IQR: 7–24 months, P < 0.001). On multivariate logistic regression analysis increase in age (OR: 1.07, 95 % CI; 1.03–1.1, P < 0.001) and residing in rural areas (OR: 8.07, 95 % CI; 1.43–45.6, P = 0.018) were independently found to predict acute rubella infection among under-fives.

Conclusion

Our findings indicate that rubella virus is prevalent in our setting posing a risk of transmitting to childbearing aged women hence increasing the risk of CRS. Increasing prevalence of acute infection with age in under-fives indicates the protective role of maternal antibodies among infants. The sustained vaccination programme of under-fives as effective measure to control CRS should be emphasized in developing countries.

Serological makers of rubella infection in Africa in the pre vaccination era: a systematic review

BACKGROUND

Rubella infections in susceptible women during early pregnancy often results in congenital rubella syndrome (CRS). World Health Organisation (WHO) recommends that countries without vaccination programmes to assess the burden of rubella infection and CRS. However; in many African countries there is limited data on epidemiology of rubella infection and CRS. This review was undertaken to assess the serological markers and genotypes of rubella virus on the African continent in order to ascertain the gap for future research.

FINDINGS

A systematic search of original literatures from different electronic databases using search terms such as 'rubella' plus individual African countries such as 'Tanzania', 'Kenya', 'Nigeria' etc. and different populations such as 'children', 'pregnant women' etc. in different combinations was performed. Articles from countries with rubella vaccination programmes, outbreak data and case reports were excluded. Data were entered in a Microsoft Excel sheet and analyzed. A total of 44 articles from 17 African countries published between 2002 and 2014 were retrieved; of which 36 were eligible and included in this review. Of all population tested, the natural immunity of rubella was found to range from 52.9 to 97.9 %. In these countries, the prevalence of susceptible pregnant women ranged from 2.1 to 47.1 %. Rubella natural immunity was significantly higher among pregnant women than in general population (P < 0.001). Acute rubella infection was observed to be as low as 0.3 % among pregnant women to 45.1 % among children. All studies did not ascertain the age-specific prevalence, thus it was difficult to calculate the rate of infection with increase in age. Only two articles were found to report on rubella genotypes. Of 15 strains genotyped; three rubella virus genotypes were found to circulate in four African countries.

CONCLUSION

Despite variations in serological assays, the seroprevalence of IgG rubella antibodies in Africa is high with a substantial number of women of childbearing age being susceptible to rubella infection. Standardized sero-epidemiological data in various age groups as well as CRS data are important to implement cost-effective vaccination campaigns and control strategies.

Screening cytomegalovirus, rubella and toxoplasma infections in pregnant women with unknown pre-pregnancy serological status

PURPOSE

To determine the prevalence of acute cytomegalovirus (CMV), rubella and T. gondii infections among pregnant women who had no serological status tested for these microorganisms prior to pregnancy in a metropolitan area.

METHODS

A cross-sectional study was undertaken between January 2009 and January 2013 in 1,258 women presenting for their first antenatal visit (between 6 and 11 weeks of gestation). All women were tested for IgG and IgM antibodies. Subsequently, avidity test was utilized for inconclusive results. They were followed until delivery and all newborns were examined by a pediatrician.

RESULTS

Presence of IgM antibody positivity alone was not detected in any women. Avidity test excluded primary infection in 15 out of 16 (93.7 %) women who were positive for both IgG and IgM antibodies. Amniocentesis was performed in one case with borderline IgG avidity for T. gondii. No primary infections were detected in any newborn for the infections screened. The prevalences of IgG antibodies were 95 % for rubella, 84.1 % for CMV and 23.1 % for T. gondii.

CONCLUSIONS

Assessment of IgG and IgM antibodies followed by IgG avidity testing for inconclusive results may be an acceptable approach in pregnant women with unknown serological status prior to pregnancy. Utilization of IgG avidity as a supplemental test prevented unnecessary intervention in IgG and IgM antibodies positive patients. No primary infection was detected for CMV, rubella and T. gondii infections in the urban population screened.

[Long effect of a booster on rubella antibodies from each original HI titer following vaccination]

This study was performed to clarify which titers of a pre-existing antibody could be efficiently boosted by vaccination and to assess the persistence of the antibodies. Two hundred healthy volunteer students with HI antibody titers of < or = 1:32 were enrolled. There were 6-16% of subjects with the negative HI antibody who had B-cell memory against rubella, because the EIA-IgM antibody remained negative and/or the avidity of the EIA-IgG antibody was high after vaccination. Furthermore most of them had already been vaccinated just once before. The ratio of those in whom the antibody levels increased significantly at one month after vaccination were 98%, 87%, 67% and 32% in subjects with an HI antibody titer of <1:8, < or =1: 8, < or =1:16 and < or =1:32 at pre-vaccination, respectively. The titers decreased significantly at two years after vaccination, however the ratio of decrease under each original level being 4%, 21.9%, 42.6% and 73.5% in each group of <1:8, < or =1: 8, < or =1:16 and < or = 1: 32, respectively. In comparison with the numbers of the subjects with <1: 8, the ones with < or = 1: 8, < or = 1:16 and < or = 1:32 increased 1.5-, 2.5- and 4.7-fold, respectively. Therefore, the recommendation of an HI antibody titer < or = 1:16 for vaccination in Japan is thought to be loose, although this is to decrease the risk of congenital rubella syndrome. We think that a new assay for cellular immunity for rubella should be developed in the future in order to ascertain whether congenital rubella syndrome will be prevented or not.

Unusual patterns of IgG avidity in some young children following two doses of the adjuvanted pandemic H1N1 (2009) influenza virus vaccine

During the 2009-2010 H1N1 influenza pandemic, an adjuvanted monovalent vaccine containing ∼25% of the normal antigen dose and AS03 adjuvant was widely used in Canada. This vaccine was found to be well-tolerated and immunogenic in young children (D. W. Scheifele et al., Pediatr. Infect. Dis. J. 30:402-407, 2011). We report here additional analyses to further characterize the humoral response to this vaccine. We measured standard hemagglutination inhibition (HAI) and microneutralization (MN) titers, as well as influenza virus-specific IgG avidity and subclass distribution by enzyme-linked immunosorbent assay in 73 subjects. Sera were collected before (day 0) and 3 weeks after each dose of vaccine (days 21 and 42). Most children (55/73) had undetectable HAI and MN titers at day 0 (presumed to be antigen naive) and mounted good responses at days 21 and 42. The majority of these children (43/55) had the expected pattern of an increasing IgG avidity index (AI) after each dose of vaccine (not detected [ND], 0.30, and 2.97 at days 0, 21, and 42, respectively). The avidity responses in the remaining children (12/55) were quite different, with AIs increasing abruptly after the first dose and then declining after the second dose of vaccine (ND, 8.83, and 7.15, respectively). These children also had higher concentrations of influenza virus-specific IgG1 and IgG3 antibodies at day 21. Although the antibody titers were similar, some antigen-naive children demonstrated an unusual pattern of avidity maturation after two immunizations with AS03-adjuvanted, low-dose influenza virus vaccine. These data suggest the presence of subtle differences in the quality of the antibodies produced by some subjects in response to this vaccine.

Performance characteristics of current-generation Immulite 2000 TORCH Assays

The performances of seven Immulite 2000 (Siemens Healthcare Diagnostics) TORCH (Toxoplasma gondii, other microorganisms, rubella virus, cytomegalovirus, and herpes simplex virus) assays were evaluated in comparison with the performances of the ETI-MAX 3000 (DiaSorin) TORCH assays. The two systems demonstrated good agreement, and given their sensitivity, specificity, and positive predictive value, they can be used with confidence for TORCH prenatal screening.

Incorporation of antigens into viral capsids augments immunogenicity of adeno-associated virus vector-based vaccines

Genetic modification of adeno-associated virus (AAV) capsids has previously been exploited to redirect viral tropism. Here we demonstrate that engineering of AAV capsids as scaffolds for antigen display augments antigen-specific immunogenicity. Combining antigen display with vector-mediated overexpression resulted in a single-shot prime-boost vaccine. This new class of vaccines induced immune responses significantly faster and an IgG antibody pool of higher avidity than conventional vectors, highlighting the potency of capsid modification in vaccine development.

The enigmatic autoimmune response in endemic pemphigus foliaceus

Endemic pemphigus foliaceus, known as Fogo Selvagem (FS) in Brazil, is a disease characterized by subcorneal blisters and IgG4 anti-dermoglein 1 (Dsg1) autoantibodies. Epidemiological studies of FS strongly an environmental etiology. A 15-year surveillance of the Limao Verde Amerindian reservation in Brazil has uncovered information on the transition of the autoimmune response from the pre-clinical stage to disease state. This incubation time may evolve over several years. The serological markers of the pre-clinical state of FS are IgM anti-Dsg1, IgE and non-IgG4 autoantibodies against Dsg1. The disease stage of FS is characterized by the rise of pathogenic IgG4 anti-Dsg1 autoantibodies. In this review, the authors reviewed the literature on the relevance of the humoral autoimmune response of FS as well as the possible environmental triggers of anti-Dsg1 autoantibody formation. Based on epidemiological observations, the authors hypothesize that the pathogenic IgG4 response in FS may be triggered by hematophagous insect bites.

Advances in pemphigus and its endemic pemphigus foliaceus (Fogo Selvagem) phenotype: a paradigm of human autoimmunity

Pemphigus encompasses a group of organ specific, antibody mediated autoimmune diseases of the skin characterized by keratinocyte detachment that leads to the development of blisters and erosions, which can become life-threatening. The pathogenic autoantibodies recognize desmogleins, which are members of the desmosomal cadherin family of cell adhesion molecules. Desmoglein 3 is targeted in pemphigus vulgaris while desmoglein 1 is targeted in pemphigus foliaceus and its endemic form, Fogo Selvagem. This review will briefly define the salient features of pemphigus and the proposed steps in pathogenesis. We will then summarize the most recent advances in three important areas of investigation: (i) epidemiologic, genetic, and immunologic features of Fogo Selvagem, (ii) molecular mechanisms of injury to the epidermis, and (iii) novel therapeutic strategies targeting specific steps in disease pathogenesis. The advances in each of these three seemingly separate areas contribute to the overall understanding of the pemphigus disease model. These recent advancements also underscore the dynamic interplay between the treatment of patients in a clinical setting and basic science research and have led to an integrative understanding of disease pathogenesis and treatment, allowing pemphigus to serve as a paradigm of human autoimmunity.

The IgM anti-desmoglein 1 response distinguishes Brazilian pemphigus foliaceus (fogo selvagem) from other forms of pemphigus

Fogo selvagem (FS) and pemphigus foliaceus (PF) possess pathogenic IgG anti-desmoglein 1-(Dsg1) autoantibodies. Although PF occurs sporadically, FS is endemic in Limao Verde (LV), Brazil (3.4% prevalence). IgM anti-Dsg1 were detected in 58% FS LV patients (n=31), 19% of FS patients from Hospital-Campo Grande (n=57), 19% from Hospital-Goiania (n=42), 12% from Hospital-Sao Paulo (n=56), 10% of PF patients from United States (n=20), and 0% of PF patients from Japan (n=20). Pemphigus vulgaris (n=40, USA and Japan), bullous pemphigoid (n=40, USA), and healthy donors (n=55, USA) showed negligible percentages of positive sera. High percentages of positive IgM anti-Dsg1 were found in healthy donors from four rural Amerindian populations (42% of 243) as compared with urban donors (14% of 81; P<0.001). More than 50% of healthy donors from LV (n=99, age 5-20 years) possess IgM anti-Dsg1 across ages, whereas IgG-anti-Dsg1 was detected in 2.9% (age 5-10 years), 7.3% (age 11-15 years), and 29% of donors above age 16. IgM anti-Dsg1 epitopes are Ca2+ and carbohydrate-independent. We propose that IgM anti-Dsg1 are common in FS patients in their native environment and uncommon in other pemphigus phenotypes and in FS patients who migrate to urban hospitals. Recurrent environmental antigenic exposure may lead to IgM and IgG responses that trigger FS. JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article please go to http://network.nature.com/group/jidclub.

Evaluation of the new ARCHITECT Rubella IgM assay

BACKGROUND

Rubella infections are usually characterized by mild self-limiting courses in immunocompetent individuals. However, infections in pregnant women during the first trimester of pregnancy pose a high risk of congenital rubella syndrome possibly resulting in severe defects in the unborn child. Rubella serology of a primary rubella infection is mainly determined by diagnostic confirmation of levels of specific IgM.

STUDY DESIGN

Here, we report on the performance of the Rubella IgM assay in development on the ARCHITECT instrument, a fully automated high throughput chemiluminescent microparticle immunoassay platform. Sensitivity was examined using commercially available seroconversion panels from vaccinated individuals; specificity was addressed by testing populations of pregnant women, blood donors and hospitalized patients. In addition, the potential for assay interference was evaluated by testing samples of several disease states. As methods of comparison AxSYM, BioMérieux VIDAS and Behring Rubella IgM assays were used.

RESULTS

The study demonstrates that the ARCHITECT Rubella IgM assay shows improved specificity compared to AxSYM and Behring. Seroconversion sensitivity is equivalent on all assays evaluated.

CONCLUSION

Together with high throughput, optimized specificity and suppression of rheumatoid factor (RF) interference the ARCHITECT assay provides a useful improvement for the diagnosis of rubella serology.

Evaluation of commercial rubella immunoglobulin G avidity assays

We compared the performances of five commercial rubella virus immunoglobulin G (IgG) avidity assays. The Adaltis (kappa = 0.28) and Diesse (kappa = 0.33) assays showed poor correlation, the Behring assay (kappa = 0.68) showed good correlation, and the Euroimmun (kappa = 0.95) and Radim (kappa = 0.94) assays showed excellent correlation with a well-established in-house rubella virus IgG avidity assay. The Euroimmun and Radim assays were statistically significantly better than the other commercial assays (P < 0.01).

Evaluation of immunity against rubella in Iranian after mass campaign for measles-rubella vaccination on December 2003

BACKGROUND

Prevention of congenital rubella syndrome (CRS) is the main goal of rubella immunization. The World Health Organization (WHO) recommends that countries undertaking measles elimination should take the opportunity to eliminate rubella as well through use of measles-rubella (MR) or measles-mumps-rubella (MMR) vaccine in their childhood immunization programs and campaigns. On December 2003, during a mass campaign for measles-rubella vaccination in Iran, more than 33 million doses of vaccine were administered to 5- to 25-year-old males and females.

METHODS

In this study, immunoglobulin (Ig)G avidity assay was used to evaluate the rubella vaccine produced immunity among susceptible populations.

RESULTS

Findings indicated that 61.9% of vaccinees (1202 out of 1940) were immune against rubella before vaccination, and 38.1% (738 out of 1940) were susceptible to rubella before vaccination. Our results also showed that 98% of the susceptible group (723 out of 738) acquired immunity against rubella after vaccination, and 2% of them (15 out of 738) did not acquire vaccine-induced immunity to rubella.

CONCLUSION

Findings revealed that mass vaccination in December 2003 provided appropriate immune coverage among vaccinees. Also, rubella vaccine induced favorable immunity in a part of the childbearing age female (15-25 years) population, which could prevent congenital rubella syndrome among those females.