Analysis of mumps vaccine failure by means of avidity testing for mumps virus-specific immunoglobulin G

Antibody Avidity Maturation Following Booster Vaccination with an Intranasal Adenovirus Salnavac Vaccine

BACKGROUND

The COVID-19 pandemic has led to the rapid development of new vaccines and methods of testing vaccine-induced immunity. Despite the extensive research that has been conducted on the level of specific antibodies, less attention has been paid to studying the avidity of these antibodies. The avidity of serum antibodies is associated with a vaccine showing high effectiveness and reflects the process of affinity maturation. In the context of vaccines against SARS-CoV-2, only a limited number of studies have investigated the avidity of antibodies, often solely focusing on the wild-type virus following vaccination. This study provides new insights into the avidity of serum antibodies following adenovirus-based boosters. We focused on the effects of an intranasal Salnavac booster, which is compared, using a single analytical platform, to an intramuscular Sputnik V.

METHODS

The avidity of RBD-specific IgGs and IgAs was investigated through ELISA using urea and biolayer interferometry.

RESULTS

The results demonstrated the similar avidities of serum antibodies, which were induced by both vaccines for six months post-booster. However, an increase in antibody avidity was observed for the wild-type and Delta variants, but not for the BA.4/5 variant.

CONCLUSIONS

Collectively, our data provide the insights into antibody avidity maturation after the adenovirus-based vaccines against SARS-CoV-2.

Identifying a Level of Neutralizing Antibody That Correlates With Protection From Clinical Mumps Disease During a 2017 Mumps Outbreak Among Military Service Members

Background

In 2017, a mumps outbreak occurred in a US military barracks. Serum collected at service entry was used to compare pre-exposure with presumptive vaccine-induced antibody levels from persons who developed mumps (cases) and potentially exposed persons who did not develop mumps (non-cases). Sufficient information to determine levels of exposure during the outbreak was not available.

Methods

Pre-outbreak serum samples from the Department of Defense Serum Repository were available from 254 potentially exposed service members. Twelve developed clinical symptoms and had post-outbreak serum collected. All sera were tested with a mumps-specific enzyme immunoassay for immunoglobulin M, immunoglobulin G (IgG), and IgG avidity. The neutralizing antibodies to vaccine strain (Jeryl Lynn [JL], genotype A) and wildtype virus (genotype G) was assessed by a plaque reduction neutralization test. A Fisher exact test and receiver operator characteristic curve were used to analyze the antibody response for non-cases and mumps cases.

Results

Eight mumps cases were laboratory confirmed. Pre-outbreak neutralizing antibody titers to JL and genotype G mumps virus and pre-outbreak IgG index values were proportionately lower for most cases as compared with exposed non-cases. When compared with potentially exposed non-cases, cases with clinical symptoms had greater odds of having a pre-outbreak JL titer <41 and a genotype G titer <16.

Conclusions

We identified potential correlates of protection for mumps neutralizing antibody titers against JL and genotype G mumps viruses.

Robust immune responses are observed after one dose of BNT162b2 mRNA vaccine dose in SARS-CoV-2-experienced individuals

The use of coronavirus disease 2019 (COVID-19) vaccines will play the major role in helping to end the pandemic that has killed millions worldwide. COVID-19 vaccines have resulted in robust humoral responses and protective efficacy in human trials, but efficacy trials excluded individuals with a prior diagnosis of COVID-19. As a result, little is known about how immune responses induced by mRNA vaccines differ in individuals who recovered from COVID-19. Here, we evaluated longitudinal immune responses to two-dose BNT162b2 mRNA vaccination in 15 adults who had experienced COVID-19, compared to 21 adults who did not have prior COVID-19. Consistent with prior studies of mRNA vaccines, we observed robust cytotoxic CD8+ T cell responses in both cohorts after the second dose. Furthermore, SARS-CoV-2–naive individuals had progressive increases in humoral and antigen-specific antibody-secreting cell (ASC) responses after each dose of vaccine, whereas SARS-CoV-2–experienced individuals demonstrated strong humoral and antigen-specific ASC responses to the first dose but these responses were not further enhanced after the second dose of the vaccine at the time points studied. Together, these data highlight the relevance of immunological history for understanding vaccine immune responses and may have implications for personalizing mRNA vaccination regimens used to prevent COVID-19, including for the deployment of booster shots.

Robust immune responses after one dose of BNT162b2 mRNA vaccine dose in SARS-CoV-2 experienced individuals

The use of COVID-19 vaccines will play the major role in helping to end the pandemic that has killed millions worldwide. COVID-19 vaccines have resulted in robust humoral responses and protective efficacy in human trials, but efficacy trials excluded individuals with a prior diagnosis of COVID-19. As a result, little is known about how immune responses induced by mRNA vaccines differ in individuals who recovered from COVID-19. Here, we evaluated longitudinal immune responses to two-dose BNT162b2 mRNA vaccination in 15 adults who recovered from COVID-19, compared to 21 adults who did not have prior COVID-19 diagnosis. Consistent with prior studies of mRNA vaccines, we observed robust cytotoxic CD8+ T cell responses in both cohorts following the second dose. Furthermore, SARS-CoV-2-naive individuals had progressive increases in humoral and antigen-specific antibody-secreting cell (ASC) responses following each dose of vaccine, whereas SARS-CoV-2-experienced individuals demonstrated strong humoral and antigen-specific ASC responses to the first dose but muted responses to the second dose of the vaccine at the time points studied. Together, these data highlight the relevance of immunological history for understanding vaccine immune responses and may have significant implications for personalizing mRNA vaccination regimens used to prevent COVID-19, including booster shots.

Mumps Outbreaks in Vaccinated Populations-Is It Time to Re-assess the Clinical Efficacy of Vaccines?

History illustrates the remarkable public health impact of mass vaccination, by dramatically improving life expectancy and reducing the burden of infectious diseases and co-morbidities worldwide. It has been perceived that if an individual adhered to the MMR vaccine schedule that immunity to mumps virus (MuV) would be lifelong. Recent mumps outbreaks in individuals who had received two doses of the Measles Mumps Rubella (MMR) vaccine has challenged the efficacy of the MMR vaccine. However, clinical symptoms, complications, viral shedding and transmission associated with mumps infection has been shown to be reduced in vaccinated individuals, demonstrating a benefit of this vaccine. Therefore, the question of what constitutes a good mumps vaccine and how its impact is assessed in this modern era remains to be addressed. Epidemiology of the individuals most affected by the outbreaks (predominantly young adults) and variance in the circulating MuV genotype have been well-described alluding to a collection of influences such as vaccine hesitancy, heterogeneous vaccine uptake, primary, and/or secondary vaccine failures. This review aims to discuss in detail the interplay of factors thought to be contributing to the current mumps outbreaks seen in highly vaccinated populations. In addition, how mumps diagnoses has progressed and impacted the understanding of mumps infection since a mumps vaccine was first developed, the limitations of current laboratory tests in confirming protection in vaccinated individuals and how vaccine effectiveness is quantified are also considered. By highlighting knowledge gaps within this area, this state-of-the-art review proposes a change of perspective regarding the impact of a vaccine in a highly vaccinated population from a clinical, diagnostic and public perspective, highlighting a need for a paradigm shift on what is considered vaccine immunity.

The variability of the serological response to SARS-corona virus-2: Potential resolution of ambiguity through determination of avidity (functional affinity)

Data on the serological response toward severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in 16 recent reports were analyzed and a high degree of variability was shown. Immunoglobulin M (IgM) responses were either found earlier than IgG, or together with IgG, later than IgG, or were missing. Therefore, clear distinctions between early, intermediate, and past infections are obviously not possible merely on the basis of IgM and IgG determinations. A review of publications on the serology of other virus groups shows that variable IgM responses can be found as well and therefore are not unique for SARS‐CoV‐2 infections. A model to explain this variability is proposed. The inclusion of avidity determination into regular diagnostic procedures has allowed to resolve such “atypical” serological constellations. The potential use of avidity determination for the diagnosis of COVID‐19, for risk assessment, epidemiological studies, analysis of cross reactions, as well as for the control of vaccination programs is suggested and discussed.

The serological response to SARS CoV‐2 infection is highly variable.

The mere detection of specific IgM and IgG does not allow to distinguish between acute and past infection.

The variable IgM and IgG responses after SARS CoV‐2 infection are analogous to serological findings in other virus systems.

Variable IgM and IgG responses can be rationally explained by models that describe immunoglobulin production by the immune system.

Avidity determination of SARS CoV‐2 IgG is suggested for resolution of diagnostic ambiguity.

Mumps: an Update on Outbreaks, Vaccine Efficacy, and Genomic Diversity

Mumps is an acute viral infection characterized by inflammation of the parotid and other salivary glands. Persons with mumps are infectious from 2 days before through 5 days after parotitis onset, and transmission is through respiratory droplets. Despite the success of mumps vaccination programs in the United States and parts of Europe, a recent increase in outbreaks of mumps virus infections among fully vaccinated populations has been reported. Although the effectiveness of the mumps virus component of the measles-mumps-rubella (MMR) vaccine is suboptimal, a range of contributing factors has led to these outbreaks occurring in high-vaccination-coverage settings, including the intensity of exposure, the possibility of vaccine strain mismatch, delayed implementation of control measures due to the timeliness of reporting, a lack of use of appropriate laboratory tests (such as reverse transcription-PCR), and time since last vaccination. The resurgence of mumps virus infections among previously vaccinated individuals over the past decade has prompted discussions about new strategies to mitigate the risk of future outbreaks. The decision to implement a third dose of the MMR vaccine in response to an outbreak should be considered in discussions with local public health agencies. Traditional public health measures, including the isolation of infectious persons, timely contact tracing, and effective communication and awareness education for the public and medical community, should remain key interventions for outbreak control. Maintaining high mumps vaccination coverage remains key to U.S. and global efforts to reduce disease incidence and rates of complications.

Decreased humoral immunity to mumps in young adults immunized with MMR vaccine in childhood

In the past decade, multiple mumps outbreaks have occurred in the United States, primarily in close-contact, high-density settings such as colleges, with a high attack rate among young adults, many of whom had the recommended 2 doses of mumps-measles-rubella (MMR) vaccine. Waning humoral immunity and the circulation of divergent wild-type mumps strains have been proposed as contributing factors to mumps resurgence. Blood samples from 71 healthy 18- to 23-year-old college students living in a non-outbreak area were assayed for antibodies and memory B cells (MBCs) to mumps, measles, and rubella. Seroprevalence rates of mumps, measles, and rubella determined by IgG enzyme-linked immunosorbent assay (ELISA) were 93, 93, and 100%, respectively. The index standard ratio indicated that the concentration of IgG was significantly lower for mumps than rubella. High IgG avidity to mumps Enders strain was detected in sera of 59/71 participants who had sufficient IgG levels. The frequency of circulating mumps-specific MBCs was 5 to 10 times lower than measles and rubella, and 10% of the participants had no detectable MBCs to mumps. Geometric mean neutralizing antibody titers (GMTs) by plaque reduction neutralization to the predominant circulating wild-type mumps strain (genotype G) were 6-fold lower than the GMTs against the Jeryl Lynn vaccine strain (genotype A). The majority of the participants (80%) received their second MMR vaccine ≥10 years prior to study participation. Additional efforts are needed to fully characterize B and T cell immune responses to mumps vaccine and to develop strategies to improve the quality and durability of vaccine-induced immunity.

Viral mumps: Increasing occurrences in the vaccinated population

Before the introduction of the vaccine, mumps was the most common salivary gland disease and was one of the most common infectious diseases in children globally. Following the introduction of the mumps vaccine in 1967, the disease was almost nonexistent in the United States and was only found to occur in nonvaccinated patients, and even then, it did not present in epidemic portions because of the extent of vaccination in the population at large. Beginning in the early 2000s, viral mumps began to present itself in vaccinated populations, and currently, outbreaks are continuing to increase in number. This article presents information on the various outbreaks, a review of the virus and the disease, including symptoms and comorbidities, and new recommendations for management. Dental practitioners should be aware of the increasing incidence and prevalence of this disease, be able to recognize it, and make appropriate referrals for management.

Development and Use of an Endpoint Titration Assay To Characterize Mumps IgG Avidity following Measles, Mumps, and Rubella Vaccination and Wild-Type Mumps Infection

Waning mumps IgG antibody and incomplete IgG avidity maturation may increase susceptibility to mumps virus infection in some vaccinees. To measure mumps IgG avidity, serum specimens serially diluted to the endpoint were incubated on a commercial mumps-specific IgG enzyme immunoassay and treated with the protein denaturant diethylamine (60 mM, pH 10). End titer avidity indices (etAIs [percent ratio of detected diethylamine-resistant IgG at endpoint]) were calculated. Unpaired serum specimens (n = 108) from 15-month-old children living in a low-incidence setting were collected 1 month and 2 years after the first measles, mumps, and rubella vaccine dose (MMR1) and tested for mumps avidity. Per the receiver operating characteristic curve, the avidity assay is accurate (area under the curve, 0.994; 95% confidence interval [CI], 0.956 to 1.000), 96.5% sensitive (95% CI, 87.9 to 99.6%), and 92.2% specific (95% CI, 81.1 to 97.8%) at an etAI of 30%. When 9 sets of paired serum specimens collected 1 to 60 months post-MMR1 were tested for mumps and measles IgG avidity using comparable methods, the mumps etAI increased from 11% to 40 to 60% in 6 months. From 6 to 60 months, avidity was sustained at a mean etAI of 50% (95% CI, 46 to 54%), significantly lower (P  < 0.0001) than the mean measles etAI of 80% (95% CI, 74 to 86%). Mean etAIs in children 2 years post-MMR1 (n = 51), unvaccinated adults with distant mumps disease (n = 29), and confirmed mumps cases (n = 23) were 54, 62, and 57%, respectively. A mumps-specific endpoint avidity assay was developed and validated, and mumps avidity was determined to be generally sustained at etAIs of 40 to 60%, reaching etAIs of >80% in some individuals.IMPORTANCE Numerous outbreaks of mumps have occurred in the United States among two-dose measles-mumps-rubella (MMR)-vaccinated populations since 2006. The avidity of mumps-specific IgG antibodies may affect susceptibility to mumps virus infection in some vaccinated individuals. To accurately measure mumps avidity, we developed and validated a mumps-specific IgG avidity assay that determines avidity at the endpoint titer of serially diluted serum specimens, providing results that are independent of IgG concentration. At low antibody titers, endpoint methods are considered more accurate than methods that determine avidity at a single dilution. We determined that 6 months after the first MMR dose, mumps IgG avidity is high and generally sustained at avidity indices of 40 to 60%, reaching values of >80% in some individuals. Additionally, 4% (4/103) of individuals had avidity indices of ≤30% (low avidity) 2 years after vaccination. Inadequate mumps avidity maturation may be one factor influencing susceptibility to mumps virus infection among previously vaccinated or naturally infected individuals.

Mumps epidemiology in Cuba between 2004 and 2015

Vaccination with the measles, mumps and rubella vaccine decreased the mumps incidence in Cuba, but in 2006 and 2007 an outbreak with more than 1000 laboratory confirmed cases occurred, mainly among high school and university students. The objective of the study was to investigate mumps epidemiology in Cuba between 2004 and 2015 and provide an in-depth laboratory characterization of selected samples from mumps patients. Samples from 116 cases (throat swabs, urines, paired acute and convalescent serum samples) were tested for mumps-specific IgM antibodies by ELISA, in a hemagglutination inhibition assay (HIA) or by RT-PCR. IgM antibodies were found in 80.2% of cases. 48.3% of first sera were positive, 30 of which were collected within two days after symptom onset. Testing of all 116 paired sera by HIA showed seroconversion in 55.2% individuals and an at least fourfold increase in antibodies in 44.8% of cases. In 18 out of the 111 vaccinated people (16.2%) no IgM antibodies were detected, neither in the acute nor the convalescent sera, but 14 of them showed seroconversion by HIA and 4 had an at least fourfold increase of hemagglutinin antibody titers. In the RT-PCR, 23 acute phase sera, 4 throat swabs and 5 urines were positive. Detection of mumps-specific IgM antibodies by ELISA and additional diagnostic methods may be required in settings with high vaccination coverage rates.

Knowledge gaps persist and hinder progress in eliminating mumps

Mumps, a common childhood disease in the pre-vaccine era that causes swelling of the parotid salivary glands, can lead to orchitis, viral meningitis, and sensorineural deafness. While the incidence of disease decreased dramatically after the vaccine was added to standard vaccination schedules, the disease has made a substantial resurgence in recent years. As a result, it becomes critical to examine the factors involved in recurring outbreaks. Although low and incomplete vaccination coverage may be a key reason, it does not fully explain the issue due to the high rate of occurrence in populations with high vaccination coverage rates. Multiple studies suggest that waning immunity and secondary vaccine failure play a large role, the effects of which were previously masked by subclinical boosting. Significant knowledge gaps persist around the exact role and mechanism of waning immunity and demonstrate the need for more research in this area, as well as a reevaluation of mumps vaccine policy.

Utility of neutralization test for laboratory diagnosis of suspected mumps

Mumps is an infectious disease caused by mumps virus (MuV), which belongs to the family Paramyxoviridae and genus Rubulavirus. Typical symptoms of mumps include fever and swelling of the parotid glands; however, mumps can be asymptomatic. Mumps is diagnosed by molecular and serological methods (i.e., PCR and Enzyme Immunoassay [EIA]); however, both methods have pros and cons. This study was performed to compare the diagnostic utility of a focus reduction neutralization test (FRNT) to that of MuV-specific commercial IgM and IgG antibody EIA in patients suspected of having mumps. One hundred-eighty six samples collected during mumps outbreak in 2012-16 were studied. Samples (n = 80) were tested by all the three serological assays and showed 70.4%, 83% and 92.5% positivity by IgM EIA, IgG and FRNT, respectively. In all, 58.8% samples (n = 47) tested positive in all three assays. Concordance between mumps RT-PCR and IgM EIA was highest during the first 2-5 days and decreased with increasing time post-onset. Mumps FRNT results agreed with those of RT-PCR/IgM EIA from the second week onwards, whereas the results of mumps IgG EIA agreed with those of RT-PCR/IgM EIA from post-onset days 3-10. These findings suggest the utility of a FRNT for laboratory diagnosis of mumps in countries whose populations are not immunized against this infection.

Serological survey of mumps antibodies in adults in the Czech Republic and the need for changes to the vaccination strategy

Mumps outbreaks, especially in adolescents and young adults, have been reported in the Czech Republic. The aim of the presented study was to determine the seroprevalence of specific IgG antibodies against mumps in the adult population of the Czech Republic. The study was designed as a multicenter serological survey of adults aged 18 years and over. Specific IgG antibodies against mumps were detected in blood samples using an enzyme-linked immunosorbent assay (ELISA). A total of 1,911 serum samples were examined. The overall seropositivity reached 55.3%. In individual age groups, the highest seropositivity 63% (63.5-65.2%) was recorded in adults aged 40 years and over; the lowest seropositivity was found in adults aged 18-29 years (27.4%). The difference in seropositivity rate between the 18-29 years age group and the 40 years and over age groups was statistically significant (p < 0.001). Only the 18-29 years age group included both vaccinated and unvaccinated (born in the pre-vaccine era) individuals. In vaccinated individuals, seropositivity was reported in only 19.1% of persons; in unvaccinated individuals, seropositivity reached 48.2%. Our results demonstrate the long-term persistence of antibodies following natural infection and the decrease in seropositivity that occurs after vaccination over time. This immunity waning may account for the higher susceptibility of adolescents and young adults to mumps. Therefore, the current vaccination program in the Czech Republic could be considered as less effective. It will be modified with the shifting of the second dose of vaccine from two years of age to the preschool age.

Mumps in the Eastern Bohemia Region of the Czech Republic - a Serological Survey 2008-2012

BACKGROUND

The incidence of mumps has decreased in many countries since the introduction of vaccination programmes, however, in the past decade a rapid increase in the disease occurrence has been reported worldwide. The reason for this situation is still not clear. We present the results of a serological survey carried out in the Eastern Bohemia Region of the Czech Republic during the years 2008-2012.

METHODS

In total, 2,536 samples of 2,034 patients were examined during the study period. The study cohort was divided into two groups, one consisted of individuals born before the introduction of mandatory vaccination and the other one comprised individuals born after mandatory vaccination started. For the serology analyses the ELISA kits RIDASCREEN Mumpsvirus IgM and IgG (R-Biopharm®, Germany) were used.

RESULTS

Out of 2,536 samples (including paired sera), 23.9% (n=606) were positive and 12% (n=304) had equivocal results. Most of the positive samples were obtained from patients aged 17-20 years. Significantly more (p<0.05) positive patients were born after the start of the national vaccination programme (patient group 2) (22.8%) compared to those born before its start (patient group 1) (13.7%). Interestingly, the analysis of data showed that 75.3% of patients falling into group 1 had anti-mumps IgG antibodies, which means that they had contracted mumps, whilst 23.5% of patients of group 2 had undetectable IgG antibodies, even though they should have been vaccinated.

CONCLUSION

The data from our study, with a low number of positive samples in the first years of the study and an increase in the last two years, could suggest the occurrence of outbreaks every 4-6 years.

Cellular and humoral immunity after vaccination or natural mumps infection

BACKGROUND

This study measured cell-mediated immunity (CMI) and serum antibody to clarify the basis of breakthrough after vaccination and reinfection after mumps.

METHODS

From a pool of 54 college students, 17 seronegative subjects and 14 subjects with intermediate level of antibodies against mumps were vaccinated with a monovalent mumps vaccine, and CMI was assessed using interferon-γ release assay.

RESULTS

CMI positivity according to pre-existing antibody level, defined as titer <2.0 index units, negative; 2.0-3.9 index units, intermediate; and ≥4.0 index units, positive, was 8/17 (47.1%), 9/14 (64.3%) and 19/23 (82.6%) before vaccination, respectively. Of the 17 seronegative subjects, seven (41.2%) had a history of vaccination and/or natural infection, four (57.1%) of whom were CMI positive or intermediate. Ten (71%) of 14 subjects with intermediate antibody level had a history of vaccination or natural infection, eight (80%) of whom were CMI positive or intermediate. After vaccination the interferon (IFN)-γ and antibody titers increased significantly, but seven (41.2%) of the 17 seronegative subjects and 13 (92.9%) of the 14 intermediate-level subjects tested positive for both antibody and CMI. In a comparison of the natural infection group (confirmed as IgG seropositive and/or CMI positive without vaccination) versus the vaccination group, IgG antibody titer (mean ± SD) was 14.4 ± 8.0 versus 3.6 ± 2.4 index units (P < 0.01) and IFN-γ was 122.7 ± 90.0 pg/mL versus 59.5 ± 37.8 pg/mL (P > 0.05), respectively.

CONCLUSION

Vaccination or even natural mumps infection did not always induce both cellular and humoral immunity.

Immunogenicity and Protective Efficacy against Enterotoxigenic Escherichia coli Colonization following Intradermal, Sublingual, or Oral Vaccination with EtpA Adhesin

Enterotoxigenic Escherichia coli (ETEC) strains are a common cause of diarrhea. Extraordinary antigenic diversity has prompted a search for conserved antigens to complement canonical approaches to ETEC vaccine development. EtpA, an immunogenic extracellular ETEC adhesin relatively conserved in the ETEC pathovar, has previously been shown to be a protective antigen following intranasal immunization. These studies were undertaken to explore alternative routes of EtpA vaccination that would permit use of a double mutant (R192G L211A) heat-labile toxin (dmLT) adjuvant. Here, oral vaccination with EtpA adjuvanted with dmLT afforded significant protection against small intestinal colonization, and the degree of protection correlated with fecal IgG, IgA, or total fecal antibody responses to EtpA. Sublingual vaccination yielded compartmentalized mucosal immune responses with significant increases in anti-EtpA fecal IgG and IgA, and mice vaccinated via this route were also protected against colonization. In contrast, while intradermal (i.d.) vaccination achieved high levels of both serum and fecal antibodies against both EtpA and dmLT, mice vaccinated via the i.d. route were not protected against subsequent colonization and the avidity of serum IgG and IgA EtpA-specific antibodies was significantly lower after i.d. immunization compared to other routes. Finally, we demonstrate that antiserum from vaccinated mice significantly impairs binding of LT to cognate GM1 receptors and shows near complete neutralization of toxin delivery by ETEC in vitro Collectively, these data provide further evidence that EtpA could complement future vaccine strategies but also suggest that additional effort will be required to optimize its use as a protective immunogen.

How to assess the binding strength of antibodies elicited by vaccination against HIV and other viruses

Vaccines that protect against viral infections generally induce neutralizing antibodies. When vaccines are evaluated, the need arises to assess the affinity maturation of the antibody responses. Binding titers of polyclonal sera depend not only on the affinities of the constituent antibodies but also on their individual concentrations, which are difficult to ascertain. Therefore an assay based on chaotrope disruption of antibody-antigen complexes was designed for measuring binding strength. This assay works well with many viral antigens but gives differential results depending on the conformational dependence of epitopes on complex antigens such as the envelope glycoprotein of HIV-1. Kinetic binding assays might offer alternatives, since they can measure average off-rate constants for polyclonal antibodies in a serum. Here, potentials and fallacies of these techniques are discussed.

A Mumps Outbreak in Vojvodina, Serbia, in 2012 Underlines the Need for Additional Vaccination Opportunities for Young Adults

In 2012, mumps was introduced from Bosnia and Herzegovina to Vojvodina, causing an outbreak with 335 reported cases. The present manuscript analyses the epidemiological and laboratory characteristics of this outbreak, identifies its main causes and suggests potential future preventive measures. Sera of 133 patients were tested for mumps-specific antibodies by ELISA and 15 nose/throat swabs were investigated for mumps virus RNA by RT-PCR. IgG antibodies were found in 127 patients (95.5%). Mumps infection was laboratory-confirmed in 53 patients, including 44 IgM and 9 PCR positive cases. All other 282 cases were classified as epidemiologically-confirmed. More than half of the patients (n = 181, 54%) were 20–29 years old, followed by the 15–19 age bracket (n = 95, 28.4%). Twice as many males as females were affected (67% versus 33%). Disease complications were reported in 13 cases (3.9%), including 9 patients with orchitis and 4 with pancreatitis. According to medical records or anamnestic data, 190 patients (56.7%) were immunized with two doses and 35 (10.4%) with one dose of mumps-containing vaccine. The Serbian sequences corresponded to a minor genotype G variant detected during the 2011/2012 mumps outbreak in Bosnia and Herzegovina. Vaccine failures, the initial one-dose immunization policy and a vaccine shortage between 1999 and 2002 contributed to the outbreak. Additional vaccination opportunities should be offered to young adults during transition periods in their life trajectories.

What Do Chaotrope-Based Avidity Assays for Antibodies to HIV-1 Envelope Glycoproteins Measure?

When HIV-1 vaccine candidates that include soluble envelope glycoproteins (Env) are tested in humans and other species, the resulting antibody responses to Env are sifted for correlates of protection or risk. One frequently used assay measures the reduction in antibody binding to Env antigens by an added chaotrope (such as thiocyanate). Based on that assay, an avidity index was devised for assessing the affinity maturation of antibodies of unknown concentration in polyclonal sera. Since a high avidity index was linked to protection in animal models of HIV-1 infection, it has become a criterion for evaluating antibody responses to vaccine candidates. But what does the assay measure and what does an avidity index mean? Here, we have used a panel of monoclonal antibodies to well-defined epitopes on Env (gp120, gp41, and SOSIP.664 trimers) to explore how the chaotrope acts. We conclude that the chaotrope sensitivity of antibody binding to Env depends on several properties of the epitopes (continuity versus tertiary- and quaternary-structural dependence) and that the avidity index has no simple relationship to antibody affinity for functional Env spikes on virions. We show that the binding of broadly neutralizing antibodies against quaternary-structural epitopes is particularly sensitive to chaotrope treatment, whereas antibody binding to epitopes in variable loops and to nonneutralization epitopes in gp41 is generally resistant. As a result of such biases, the avidity index may at best be a mere surrogate for undefined antibody or other immune responses that correlate weakly with protection.

IMPORTANCE

An effective HIV-1 vaccine is an important goal. Such a vaccine will probably need to induce antibodies that neutralize typically transmitted variants of HIV-1, preventing them from infecting target cells. Vaccine candidates have so far failed to induce such antibody responses, although some do protect weakly against infection in animals and, possibly, humans. In the search for responses associated with protection, an avidity assay based on chemical disruption is often used to measure the strength of antibody binding. We have analyzed this assay mechanistically and found that the epitope specificity of an antibody has a greater influence on the outcome than does its affinity. As a result, the avidity assay is biased toward the detection of some antibody specificities while disfavoring others. We conclude that the assay may yield merely indirect correlations with weak protection, specifically when Env vaccination has failed to induce broad neutralizing responses.

Establishment of an antibody avidity test to differentiate vaccinated cattle from those naturally infected with Mycoplasma bovis

Mycoplasma bovis is a major pathogen of bovine respiratory disease (BRD) in China and a live attenuated vaccine has recently been developed. This study aimed to establish an IgG avidity test to differentiate between naturally infected and vaccinated animals. An indirect ELISA (iELISA) was first established in the laboratory to detect antibodies specific to M. bovis using whole cell proteins as coating antigens and serum samples from experimentally infected cattle. The specificity and sensitivity of the iELISA was confirmed using a commercial ELISA kit as a reference standard. Both tests showed substantial agreement as indicated by a κ value of 0.78 (95% confidence interval, CI, 0.62, 0.93), and an overall 92.0% (80/87) agreement between the two tests. Based on the laboratory iELISA, a sodium thiocyanate (NaSCN) competitive iELISA was then developed for the detection of IgG avidity, expressed as relative avidity index (AI). Two-hundred and one experimentally immunised and naturally infected animals were used. These comprised 36 immunised calves, 38 negative control calves, 37 naturally infected calves, 87 calves of unknown status, and an additional three immunised calves that were used for a time trial. By testing true positive and negative antisera from either naturally infected or immunised calves, the AI cut-off value was defined as 70.4%. The diagnostic accuracy of the in-house NaSCN competitive iELISA was determined using serum samples collected from the experimental animals. The IgG avidity test demonstrated 96.0% sensitivity (95% CI 80.5%, 99.3%) and 95.8% specificity (95% CI 79.8%, 99.3%), and was successfully established as a valuable first test for differentiating vaccinated animals from those infected with M. bovis. This test may be a useful tool for clarifying the magnitude of M. bovis infection and in assessing the efficacy of vaccination in exposed animal populations.

Assessing mumps outbreak risk in highly vaccinated populations using spatial seroprevalence data

Mumps is a potentially severe viral infection. The incidence of mumps has declined dramatically in high-income countries since the introduction of mumps antigen-containing vaccines. However, recent large outbreaks of mumps in highly vaccinated populations suggest waning of vaccine-induced immunity and primary vaccine failure. In this paper we present a simple method for identifying geographic regions with high outbreak potential, demonstrated using 2006 mumps seroprevalence data from Belgium and Belgian vaccination coverage data. Predictions of the outbreak potential in terms of the effective reproduction number in future years signal an increased risk of new mumps outbreaks. Literature reviews on serological information for both primary vaccine failure and waning immunity provide essential information for our predictions. Tailor-made additional vaccination campaigns would be valuable for decreasing local pockets of susceptibility, thereby reducing the risk of future large-scale mumps outbreaks.

TcVac3 induced control of Trypanosoma cruzi infection and chronic myocarditis in mice

We characterized the immune responses elicited by a DNA-prime/MVA-boost vaccine (TcVac3) constituted of antigenic candidates (TcG2 and TcG4), shown to be recognized by B and T cell responses in Trypanosoma cruzi (Tc) infected multiple hosts. C57BL/6 mice immunized with TcVac3 elicited a strong antigen-specific, high-avidity, trypanolytic antibody response (IgG2b>IgG1); and a robust antigen- and Tc-specific CD8⁺T cell response with type-1 cytokine (IFN-γ⁺TNF-α>IL-4⁺IL-10) and cytolytic effector (CD8⁺CD107a⁺IFN-γ⁺Perforin⁺) phenotype. The vaccine-induced effector T cells significantly expanded upon challenge infection and provided >92% control of T. cruzi. Co-delivery of IL-12 and GMCSF cytokine adjuvants didn’t enhance the TcVac3-induced resistance to T. cruzi. In chronic phase, vaccinated/infected mice exhibited a significant decline (up to 70%) in IFN-γ⁺CD8⁺T cells, a predominance of immunoregulatory IL-10⁺/CD4⁺T and IL10⁺/CD8⁺T cells, and presented undetectable tissue parasitism, inflammatory infiltrate, and fibrosis in vaccinated/infected mice. In comparison, control mice responded to challenge infection by a low antibody response, mixed cytokine profile, and consistent activation of pro-inflammatory CD8⁺T cells associated with parasite persistence and pathologic damage in the heart. We conclude that TcVac3 elicited type-1 effector T cell immunity that effectively controlled T. cruzi infection, and subsequently, predominance of anti-inflammatory responses prevented chronic inflammation and myocarditis in chagasic mice.

Clinical utility of avidity assays

IgM may persist for months, presenting a risk of an erroneous diagnosis where serology is the only available tool. Indeed, IgM may be detected in secondary infection as a result of crossreactivity and/or nonspecific stimulation of the immune system. One test that can aid the serologist is IgG avidity testing, in that the avidity of IgG is low early in infection with the avidity of IgG antibodies increasing over time. Congenital toxoplasmosis can induce serious sequelae. Detectable IgM usually persists long after the acute infection. IgG avidity can be an important aid in diagnosis and assessing the risk to the fetus. Another infection that is of concern in pregnancy is cytomegalovirus (CMV). In pregnant women it is very important to differentiate primary from secondary infection, as primary infection presents the highest risk to the fetus. Serologic detection of IgM alone is not a specific marker of primary CMV infection. IgG avidity can have utility in identifying or excluding primary CMV infections during pregnancy. Outside of pregnancy, IgG avidity testing is increasingly recognized as a valuable tool. During the recent West Nile virus (WNV) epidemic in the US, it was recognized that WNV-specific IgM may persist for 6 - 12 months following exposure. Thus, a person presenting to their clinician with nonspecific symptoms may be tested and return a positive WNV IgM that may be the product of exposure during the previous period. In this environment, WNV IgG avidity testing is able to provide some assistance. IgG avidity testing should not be used alone and without an understanding of the limitations of the technique. Serology remains an important tool for the diagnosis and management of infectious disease. Classically, IgM is defined as a marker of acute infection and IgG, in the absence of clinical disease, is often considered a marker of past infection. However, the clinical reality can be quite different.

Comparison of the sensitivity of laboratory diagnostic methods from a well-characterized outbreak of mumps in New York city in 2009

A mumps outbreak in upstate New York in 2009 at a summer camp for Orthodox Jewish boys spread into Orthodox Jewish communities in the Northeast, including New York City. The availability of epidemiologic information, including vaccination records and parotitis onset dates, allowed an enhanced analysis of laboratory methods for mumps testing. Serum and buccal swab samples were collected from 296 confirmed cases with onsets from September through December 2009. All samples were tested using the Centers for Disease Control and Prevention (CDC) capture IgM enzyme immunoassay (EIA) and a real-time reverse transcription-PCR (rRT-PCR) that targets the short hydrophobic gene. A subset of the samples (n = 205) was used to evaluate 3 commercial mumps IgM assays and to assess the sensitivity of using an alternative target gene (nucleoprotein) in the rRT-PCR protocol. Among 115 cases of mumps with 2 documented doses of measles, mumps, and rubella (MMR) vaccine, the CDC capture IgM EIA detected IgM in 51% of serum samples compared to 9% to 24% using three commercial IgM assays. The rRT-PCR that targeted the nucleoprotein gene increased RNA detection by 14% compared to that obtained with the original protocol. The ability to detect IgM improved when serum was collected 3 days or more after symptom onset, whereas sensitivity of RNA detection by rRT-PCR declined when buccal swabs were collected later than 2 days after onset. Selection of testing methods and timing of sample collection are important factors in the ability to confirm infection among vaccinated persons. These results reinforce the need to use virus detection assays in addition to serologic tests.

Clinical features of mumps orchitis in vaccinated postpubertal males: a single-center series of 62 patients

Purpose

Although the measles-mumps-rubella vaccination covers most children against mumps in Korea, the development of mumps has been reported. However, the clinical manifestations of mumps orchitis in postpubertal vaccinated patients have never been investigated. Herein we report the clinical features of mumps orchitis in postpubertal vaccinated patients.

Materials and Methods

This study included a total of 62 postpubertal males who developed acute mumps orchitis from 2005 to 2010. The clinical manifestations such as the incubation period, febrile duration, and the mean duration of orchitis were retrospectively investigated. The laboratory and sonographic findings were also reviewed and compared with the features of previously reported cases of unvaccinated postpubertal mumps orchitis.

Results

The mean age of the 62 patients was 17.56 years (range, 15 to 29 years). All patients were serologically confirmed with acute mumps infection (positive immunoglobulin [Ig] M and negative or positive IgG). The mean incubation period was 5.39 days (range, 0 to 23 days), with a febrile duration of 1.8 days (range, 0.5 to 3 days), and a mean duration of orchitis of 4.96 days (range, 0 to 17 days). Sonography revealed unilateral orchitis in 58 patients (93.6%) and bilateral orchitis in only 6 (6.4%).

Conclusions

In our study, mumps orchitis in postpubertal vaccinated patients showed a relatively shorter febrile duration. In addition, less scrotal swelling and a lower incidence of bilaterality were found upon physical examination and ultrasonography. In the future, additional long-term follow-up is needed to determine the features of mumps orchitis in postpubertal vaccinated males, and an additional booster vaccination should be considered.

Study of avidity of antigen-specific antibody as a means of understanding development of long-term immunological memory after Vibrio cholerae O1 infection

The avidity of antibodies to specific antigens and the relationship of avidity to memory B cell responses to these antigens have not been studied in patients with cholera or those receiving oral cholera vaccines. We measured the avidity of antibodies to cholera toxin B subunit (CTB) and Vibrio cholerae O1 lipopolysaccharide (LPS) in Bangladeshi adult cholera patients (n = 30), as well as vaccinees (n = 30) after administration of two doses of a killed oral cholera vaccine. We assessed antibody and memory B cell responses at the acute stage in patients or prior to vaccination in vaccinees and then in follow-up over a year. Both patients and vaccinees mounted CTB-specific IgG and IgA antibodies of high avidity. Patients showed longer persistence of these antibodies than vaccinees, with persistence lasting in patients up to day 270 to 360. The avidity of LPS-specific IgG and IgA antibodies in patients remained elevated up to 180 days of follow-up. Vaccinees mounted highly avid LPS-specific antibodies at day 17 (3 days after the second dose of vaccine), but the avidity waned rapidly to baseline by 30 days. We examined the correlation between antigen-specific memory B cell responses and avidity indices for both antigens. We found that numbers of CTB- and LPS-specific memory B cells significantly correlated with the avidity indices of the corresponding antibodies (P < 0.05; Spearman's ρ = 0.28 to 0.45). These findings suggest that antibody avidity after infection and immunization is a good correlate of the development and maintenance of memory B cell responses to Vibrio cholerae O1 antigens.

Development and application of a GuHCl-modified ELISA to measure the avidity of anti-HPV L1 VLP antibodies in vaccinated individuals

Antibody responses against infectious agents are an important component in the prevention of disease. The avidity of antibodies for their antigens relates to their functional efficiency, and is a fundamental aspect in the investigation of humoral responses. Modified ELISAs are used to estimate avidity through the use of chaotropic agents and the measurement of the degree to which they disrupt the interaction between antibody and antigen. The theory behind the assay is the higher the avidity of an interaction the less susceptible it is to the effects of the chaotropic agent. The goal of this study was to generate a modified ELISA where a complex, multimeric coating-antigen, human papillomavirus (HPV) virus-like particles (VLP), was used to measure the avidity of anti-HPV antibodies generated following vaccination with HPV VLPs. A series of chaotropic agents were evaluated in the assay for their effectiveness in measuring avidity. Guanidine hydrochloride (GuHCl) was selected as a chaotropic reagent with the ability to disrupt antibody and antigen interactions, while not affecting the integrity of the plate-bound VLP. Two methods of determining the avidity index were assessed and shown to be comparable. This assay was then successfully applied to measure the avidity of anti-HPV VLP serum antibodies in samples from an HPV L1 VLP vaccine clinical trial. Overall, the assay was highly reproducible and captured a wide range of antibody avidities. Therefore, a GuHCl-modified ELISA is an acceptable method that can be used to determine HPV-specific antibody avidity indices within a clinical trial setting.

Enzyme-linked immunospot assay detection of mumps-specific antibody-secreting B cells as an alternative method of laboratory diagnosis

Although high measles, mumps, and rubella (MMR) vaccination coverage has been successful in dramatically reducing mumps disease in the United States, mumps (re)infections occasionally occur in individuals who have been either previously vaccinated or naturally infected. Standard diagnostics that detect virus or virus-specific antibody are dependable for confirming primary mumps infection in immunologically naïve persons, but these methods perform inconsistently for individuals with prior immune exposure. We hypothesized that detection of activated mumps-specific antibody-secreting B cells (ASCs) by enzyme-linked immunospot (ELISPOT) assay could be used as a more reliable diagnostic. To test this, a time course of virus-specific ASC responses was measured by ELISPOT assay following MMR vaccination of 16 previously vaccinated or naturally exposed adult volunteers. Mumps-specific ASCs were detectable in 68% of these individuals at some point during the first 3 weeks following revaccination. In addition, mumps-specific ASCs were detected in 7/7 previously vaccinated individuals who recently had been infected as part of a confirmed mumps outbreak. These data suggest that ELISPOT detection of mumps-specific ASCs has the potential for use as an alternative method of diagnosis when suspect cases cannot be confirmed by detection of IgM or virus. In addition, it was determined that mumps-specific memory B cells are detected at a much lower frequency than measles- or rubella-specific cells, suggesting that mumps infection may not generate robust B-cell memory.

Reemergence of mumps

The mumps virus is a single-stranded, non-segmented, negative-sense RNA virus belonging to the Paramyxoviridae family. Mumps is characterized by bilateral or unilateral swelling of the parotid gland. Aseptic meningitis is a common complication, and orchitis is also common in adolescents and adult men. Diagnosis is based on clinical findings, but because of high vaccination coverage, clinical findings alone are not sufficient for diagnosis, and laboratory confirmation is needed. Mumps is preventable by vaccination, but despite high vaccination coverage, epidemics occur in several countries, including Korea. Many hypotheses are suggested for these phenomena. In this review, we investigate the reason for the epidemics, optimal methods of diagnosis, and surveillance of immunization status for the prevention of future epidemics.

Investigation of a mumps outbreak among university students with two measles-mumps-rubella (MMR) vaccinations, Virginia, September-December 2006

Following the clinical diagnosis of the first case of mumps on September 22, 2006 at the University of Virginia (UVA), 52 suspected cases were identified through active surveillance for mumps by the end of December 2006. Samples were collected from 47 students who presented with parotitis despite a documented history of two doses of measles, mumps, and rubella (MMR) vaccine. Six of 47 serum samples (13%) were positive for mumps IgM, and 46/47 specimens were positive for mumps IgG. Endpoint titration of acute phase serum samples from laboratory-confirmed cases did not provide evidence that elevated serum IgG is a consistent marker for infection among cases due to secondary vaccine failure. Buccal swab samples from 39 of the 47 students were tested by real-time reverse transcription-polymerase chain reaction (RT-PCR) and/or viral culture. Mumps virus or mumps RNA was detected in 12 of 39 buccal samples (31%). Genetic analysis of the virus from the outbreak at UVA indicated that the outbreak was not linked to the large mumps outbreak in the Midwestern US that occurred earlier in 2006. Our findings support the use of viral detection to improve laboratory diagnosis of mumps among persons who have received two doses of MMR.

Characterization of large mumps outbreak among vaccinated Palestinian refugees

During a large mumps virus (MuV) outbreak which occurred in the Palestinian refugee camps of the West Bank, 68.1% (2,636/3,871) of the cases were vaccinated with one dose of trivalent measles, mumps, and rubella (MMR) vaccine. Attack rates by camp ranged from less than 1 case per 1,000 people in the population to 43/1,000 (overall, 11/1,000). The outbreak lasted from December 2003 to June 2005, with two peaks, one from April to May 2004 and the other from March to April 2005. To control the outbreak, a mass MMR vaccination campaign was conducted in May 2005. Evaluation of the immune status of cases (n=59) and healthy controls (n=51) revealed high levels of mumps immunoglobulin G (IgG) and a low MuV-specific IgM in clinical cases indicative of a booster immune response. This suggested a secondary rather than a primary infection due to the insufficient protection conferred by the single vaccine dose included in the vaccination program. This prediction was further confirmed by the low seroprevalence (68.6%) found in the healthy control group, which was below the threshold level required for MuV herd immunity. Mumps diagnosis was established mainly by reverse transcription-PCR in clinical samples obtained within 48 h from the onset of disease. Of the parotid fluids and nasopharyngeal aspirates analyzed, 92% were positive for MuV RNA, while only 33% of the urine samples were positive. Phylogenetic analysis of the MuV SH gene identified the outbreak strain as the H genotype, which has been in circulation worldwide at least since 1989.

Mumps: a resurgent disease with protean manifestations

Mumps has re-emerged as an infection in the developed world. Its epidemiology has changed, with the majority of cases now primarily affecting adolescents and adults. While mumps is easily suspected if parotitis is present, parotitis is absent in 10%-30% of symptomatic cases. Mumps is a systemic infection with a variety of extra-parotid complications. In Australia, mumps diagnosis is confirmed by antibody testing and reverse transcriptase-polymerase chain reaction techniques. Suitable specimens for testing are serum, saliva, urine and cerebrospinal fluid. Treatment is generally supportive, although intravenous immunoglobulin therapy may have a future role in mumps management. Interferon alpha-2b treatment may be considered specifically for mumps epididymo-orchitis. Mumps vaccine is included in the measles-mumps-rubella (MMR) vaccine. In Australia, this vaccine is routinely administered at the ages of 1 and 4 years. Serious reactions to the mumps components of the MMR vaccine are rare.

Immune responses to mumps vaccine in adults who were vaccinated in childhood

BACKGROUND

In a mumps outbreak in the United States, many infected individuals were adults who had received 2 doses of mumps vaccine. The persistence of cellular immunity to mumps vaccine has not been defined.

METHODS

This was an observational, nonrandomized cohort study evaluating cell-mediated and humoral immunity to mumps in 10 vaccinated and 10 naturally immune adults. Mumps-specific T cell activation and interferon (IFN)-gamma production were measured using lymphoproliferative and flow cytometry assays, and mumps immunoglobulin (Ig) G was measured using enzyme-linked immunosorbent assay.

RESULTS

T cell immunity to mumps was high in both groups; 70% of vaccinated and 80% of naturally immune individuals had a positive (> or =3) stimulation index (SI) (P = 1.0). The mean percentages of mumps-specific CD4+ T cells that expressed CD69 and produced IFN-gamma were equivalent in the 2 groups: 0.06% and 0.12%, respectively (P = .11). The mean SIs in the groups were also equivalent, although IFN-gamma concentrations from cultures stimulated with mumps antigen were higher in naturally immune adults than in vaccinated adults (P < or = .01). All adults were positive for mumps IgG.

CONCLUSION

T and B cell immunity to mumps was detected in adults at least 10 years after immunization. Except for IFN-gamma release, responses in vaccinated adults paralleled those observed in naturally immune individuals.

Long-term persistence of mumps antibody after receipt of 2 measles-mumps-rubella (MMR) vaccinations and antibody response after a third MMR vaccination among a university population

BACKGROUND

High attack rates among vaccinated young adults reported during the 2006 mumps outbreak in the United States heightened concerns regarding mumps vaccine failure.

METHODS

Serum specimens from university students and staff were tested for mumps immunoglobulin (Ig) G by enzyme immunoassay (EIA). A subset of participants vaccinated for < or =5 years and > or =15 years were tested by neutralizing antibody (NA) assay. Persons seronegative by EIA were offered a third dose of measles-mumps-rubella vaccine (MMR3), and serum specimens were obtained 7-10 days and 2-3 months after its administration.

RESULTS

Overall, 94% (95% confidence interval [CI], 91%-96%) of the 440 participants were seropositive. No differences existed in seropositivity rates by sex, age, age at receipt of the second dose of MMR vaccine (MMR2), or time since receipt of MMR2 (P = .568). The geometric mean titer (GMT) of NA among persons vaccinated with MMR2 during the previous 1-5 years was 97 (95% CI, 64-148), whereas, among those vaccinated > or =15 years before blood collection, the GMT was 58 (95% CI, 44-76) (P = .065). After MMR3, 82% (14/17) and 91% (10/11) seroconverted in 7-10 days and 2-3 months, respectively.

CONCLUSIONS

Lower levels of NA observed among persons who received MMR2 > or =15 years ago demonstrates antibody decay over time. MMR3 vaccination of most seronegative persons marked the capacity to mount an anamnestic response.

Visiting sick people: is it really detrimental to our health?

Intuitively, keeping ones distance from a source of infection would appear to be the best way to limit the occurrence of disease. However, this overlooks the importance of repeated infections in maintaining efficient immune defenses. When acquired immunity has partly waned, re-exposure to the pathogenic agent may lead to mild disease that boosts the immune system. This prevents the total loss of immunity that would lead to classical disease in cases of re-infection. Here, using a mathematical model, we show that avoiding the pathogenic agent is detrimental in some situations, e.g. for pathogens that are highly transmissible, are not excessively lethal and that induce rapidly waning immunity. Reducing exposure to pathogenic agents is among the objectives of most, if not all, public health measures. A better understanding of the factors influencing the severity of a disease is required before applying measures that reduce the circulation of pathogenic agents.

Mumps virus reinfection is not a rare event confirmed by reverse transcription loop-mediated isothermal amplification

Clinically apparent mumps reinfection is considered extremely rare, but several cases have been suspected of reinfection in an out-patient clinic. In this study, virological examination, virus isolation, the reverse transcription loop-mediated isothermal amplification (RT-LAMP), and IgG and IgM EIA antibodies, were examined in order to identify mumps reinfection. Patients were divided into three categories; the reinfection group comprised 29 patients with a history of natural infection, the vaccine-failure group consisted of 37 patients with an immunization history, and two patients had histories of both immunization and mumps infection. Another 25 patients were enrolled as a primary infection group. Mumps virus was isolated in 5 (17%) and the genome was detected in 12 (41%) of 29 in the reinfection group. Reinfection was confirmed in 21/28, demonstrating high avidity of IgG EIA. Mumps virus was isolated in 15 (41%) and there was a higher positivity of genome amplification in 25 (68%) of 37 patients in the vaccine-failure group. Among these, 23 were confirmed as secondary vaccine failure by high avidity IgG EIA serology. In the primary infection group, the isolation rate and genome detection rate was higher in 16 (64%) and in 18 (72%) of 25 patients, respectively. There was no significant difference in virus load among the three groups but high mumps virus load was suspected in the IgM EIA-positive group based on the shorter amplification time on RT-LAMP. Mumps virus reinfection was confirmed by RT-LAMP and an IgG avidity test and was not a rare event.

Mumps

Mumps is a common childhood infection caused by the mumps virus. The hallmark of infection is swelling of the parotid gland. Aseptic meningitis and encephalitis are common complications of mumps together with orchitis and oophoritis, which can arise in adult men and women, respectively; other complications include deafness and pancreatitis. Clinical diagnosis can be based on the classic parotid swelling; however, this feature is not present in all cases of mumps and can also occur in various other disorders. Laboratory diagnosis is based on isolation of virus, detection of viral nucleic acid, or serological confirmation (generally presence of IgM mumps antibodies). Mumps is vaccine-preventable, and one dose of mumps vaccine is about 80% effective against the disease. Routine vaccination has proven highly effective in reducing the incidence of mumps, and is presently used by most developed countries; however, there have been outbreaks of disease in vaccinated populations. In 2005, a large epidemic peaked in the UK, and in 2006 the American midwest had several outbreaks. In both countries, the largest proportion of cases was in young adults. In the UK, susceptible cohorts too old to have been vaccinated and too young to have been exposed to natural infections were the primary cause of the mumps epidemic. In the USA, effectiveness and uptake in combination appear not to have been sufficient to obtain herd immunity for mumps in populations such as college students.

[Measles, mumps and rubella virus infection in pregnancy. Possible adverse effects on pregnant women, pregnancy outcome and the fetus]

Measles, mumps and rubella are common childhood diseases. Therefore, frequent and intense contact with children of preschool age may be associated with a higher infection risk for childcare providers. This overview summarizes current knowledge on possible adverse effects of these infections on pregnant women, pregnancy outcome and the fetus. Acute rubella or mumps virus infections are apparently not more severe in pregnant than non-pregnant women. In contrast, measles virus infection in pregnancy is linked to a higher incidence of pneumonitis and hospitalization. Evidence of congenital defects due to fetal infection is only provided in case of rubella virus infection in early pregnancy. Following rubella virus infection in the first trimester an increased fetal loss rate was reported. In 1966, a prospective study showed also a significant association between maternal mumps in the first trimester and an increased risk of abortion. But other investigators could not confirm this association. Measles and rubella but not mumps virus infections are linked to an increased premature birth rate. Occurring in late pregnancy, all three infections can result in birth of an infected infant. But severe disease occurs rarely and is mostly reported for premature infants with early neonatal measles. Preventive measures, aimed to reduce the risk of infection or severe complications for pregnant childcare providers, should consider the individual history of the employee (e.g. previous immunizations or antibody test results), the current epidemiological situation and possible interventions like passive immunization in case of exposure to measles.

Effectiveness of previous mumps vaccination during a summer camp outbreak

OBJECTIVES

Mumps is a vaccine-preventable disease that may cause outbreaks. In July 2005, an outbreak of mumps occurred during a children's summer camp in upstate New York. An investigation was initiated to describe the cases and evaluate vaccine effectiveness.

METHODS

A retrospective cohort study was conducted among 541 children from the United States and abroad who attended a 1- or 2-month overnight summer camp. Patients with mumps were interviewed; serologic analysis was conducted for 6 case patients. Vaccine effectiveness was calculated by retrospective review of immunization records for 507 attendees who were eligible for vaccination and had verified immunization history.

RESULTS

Thirty-one camp attendees were identified as having mumps (attack rate: 5.7%); 5 (83%) of 6 patients tested had positivity for mumps immunoglobulin M. Of the 507 participants (including 29 patients) with available immunization history, 440 (including 16 [87%] patients) were 2-dose recipients of mumps vaccine (attack rate: 3.6%); 46 participants (including 4 [9%] patients) were 1-dose recipients (attack rate: 8.7%); and 21 (including 9 [4%] patients) were unvaccinated (attack rate: 42.9%). Vaccine effectiveness was 92% for 2 doses and 80% for 1 dose.

CONCLUSIONS

Outbreaks of mumps in settings such as summer camps can occur despite high vaccination rates. Vaccine effectiveness for 2 mumps vaccinations was greater than vaccine effectiveness for 1 mumps vaccination. Therefore, recommendation of 2 mumps vaccinations for summer camp participants continues to be appropriate. Control of mumps disease relies on broad vaccination coupled with correct clinical diagnosis and strict control measures.

Mumps outbreaks in Canada and the United States: time for new thinking on mumps vaccines

Mumps epidemics in Canada and the United States prompted us to review evidence for the effectiveness of 5 different vaccine strains. Early trials with the Jeryl Lynn vaccine strain demonstrated an efficacy of approximately 95%, but in epidemic conditions, the effectiveness has been as low as 62%; this is still considerably better than the effectiveness of another safe strain, Rubini (which has an effectiveness of close to 0% in epidemic conditions). The Urabe vaccine strain has an effectiveness of 54%-87% but is prone to cause aseptic meningitis. Little epidemiological information is available for other vaccines. The Leningrad-Zagreb vaccine strain, which is widely used in developing countries and costs a fraction of what vaccines cost in the developed world, seems to have encouraging results; in 1 study, the effectiveness of this vaccine exceeded 95%. Aseptic meningitis has also been reported in association with this vaccine, but the benign nature of the associated meningitis was shown recently in Croatia. Also, the Leningrad-3 strain seems to be effective but causes less-benign meningitis. No mumps vaccine equals the best vaccines in quality, but the virtually complete safety of some strains may not offset their low effectiveness. Epidemiological data are pivotal in mumps, because serological testing is subject to many interpretation problems.

Investigation of mumps vaccine failures in Minsk, Belarus, 2001–2003

The purpose of this study was to investigate mumps vaccine failures (VF) in a highly vaccinated population of Minsk, Belarus, and to investigate a possible role for virus strain-specific immunity. During our 3-year study period, 22 adults were admitted to the Infectious Diseases Hospital in Minsk with a diagnosis of mumps. A genotype H1 mumps virus (MuV) strain was identified in all patients. Of 15 patients from whom the paired sera were collected, 9 were confirmed to have been previously vaccinated. Serological examinations indicated primary VF in seven of these cases and secondary VF in two. Despite almost all vaccinated patients possessing MuV specific IgG, few possessed neutralizing antibody to the vaccine strain and titers were nominal. Importantly, none of the sera were able to neutralize a genotype H MuV strain. Our results demonstrate the importance of assaying for neutralizing antibody and support the assertion that antigenic differences between wild type and vaccine MuV strains may play a role in cases of breakthrough infection in vaccinees.

Mumps vaccine failure investigation in Novosibirsk, Russia, 2002-2004

The aims of this study were to estimate the importance of vaccine failure (VF) in cases of mumps during 2002-2004 in the city of Novosibirsk, Western Siberia, Russia, and to genotype the responsible virus strain. Mumps virus-specific RT-PCR testing of saliva was performed for 18 cases of mumps. Sera were tested for IgM and IgG, IgG avidity, and the ability to neutralise a panel of mumps viruses, including the Leningrad-3 mumps vaccine virus. Of the 12 patients for whom vaccination status was positively determined, 11 showed serological evidence of primary VF. Sequence analysis of virus RNA amplified from saliva revealed a genotype C2 virus in 2002, a genotype H2 virus in 2003, and both genotypes in 2004. Although several vaccinated patients were positive for mumps virus IgG at the time of first sampling, only nominal levels of neutralising antibody were detected, and these were effective in neutralising the vaccine strain, but not genotype C and H mumps virus strains. These results suggest that the majority of cases of mumps in vaccinees are caused by primary VF, defined as either a lack of seroconversion or a lack of IgG maturity, as based on avidity testing. The results also support the hypothesis that sera of low neutralising antibody titre have a limited ability to neutralise heterologous mumps virus strains, suggesting that antigenic differences between circulating and mumps vaccine virus strains may play a role in cases of breakthrough infection. Consistent with previous reports, mumps virus genotypes C and H continue to circulate in Novosibirsk.

Mumps outbreak in a highly vaccinated school population: assessment of secondary vaccine failure using IgG avidity measurements

From March to April 2006, an outbreak of mumps occurred in Gyeonggi, Korea. The aim of this study was to describe and discriminate between primary and secondary vaccine failure in a highly vaccinated population for mumps using IgG avidity testing. Fifteen clinical mumps cases occurred among 41 students. Among these 15 patients, 11 vaccinated patients were considered secondary vaccine failures with high IgG titers and a high avidity index (AI, > or =32%); an unvaccinated patient was considered to have primary infection with high IgG titers and low AI, and three vaccinated patients were considered as other infections with low IgG titers and low AI. Among 26 unaffected students, 5 vaccinated patients were retrospectively diagnosed as sub-clinical infection with high IgG titers and high AI; the remaining students had low IgG titers and low AI except for one previously infected student. The results of this study show that secondary vaccine failure played an important role in this mumps outbreak. Therefore, booster immunization for mumps should be considered in immunized adolescents to prevent further outbreaks.