Immunogenicity of mumps virus vaccine candidates matching circulating genotypes in the United States and China

Standard definition of a clinical case of mumps and diagnostic effectiveness of the test systems used in the modern period

Introduction. Registration of regular epidemic outbreaks of mumps infection among young people, difficulties in the clinical diagnosis of the disease, the presence of specific clinical manifestations in adults with a severe course of infection make it necessary the improvement of the quality of diagnosis of the disease. The aim of the work is to develop a standard definition of a clinical case of mumps and to conduct a comparative assessment of the effectiveness of the diagnostic test systems used for mumps diagnostics based on the determination of their sensitivity and specificity. Materials and methods. To develop a standard definition of a clinical case of mumps based on ten combined clinical and laboratory parameters, a mathematical model was built using the logistic regression method. The study included 84 patients with mumps infection (main group) and 66 patients with non-epidemic sialoadenitis (comparison group). For a comparative evaluation of the diagnostic systems VectoParotitis-IgM, VectoParotitis-IgG, ELISA-Mumps-IgM, ELISA-Mumps-IgG, Anti-Mumps Virus ELISA-IgM, and Anti-Mumps Virus ELISA-IgG, a blood serum samples from patients (n = 41) with a diagnosis mumps? were tested in dynamics to assess their sensitivity, specificity, and diagnostic effectiveness. Results. The clinical symptom dry mouth increased the chance of diagnosing mumps by 13.7 times, the presence of bilateral lesions of the salivary glands by 6.5 times, the increase in the level of diastase in the urine by 3.2 times. The coefficient of determination R2 was 61.1; the sensitivity was 93% and the specificity 67%; p 0.001. Diagnostic effectiveness of Anti-Mumps Virus ELISA-IgG test system was 84.4%, ELISA-Mumps-IgG 87.2%, and "VectoParotitis-IgG" 88.5%. Conclusions. Based on the combination of following clinical symptoms observed simultaneously in patient, of the general weakness, dry mouth, bilateral lesions of the salivary glands, an increase in the level of diastase in the urine, it is possible to establish a clinical diagnosis of mumps with a probability of 81%. The highest diagnostic effectiveness of domestically manufactured test systems for quantitation of IgG antibodies to mumps virus in sick people has been demonstrted.

Establishment of a model to assess mumps virus neurovirulence in neonatal Wistar rats

Mumps virus (MuV) is highly neurotropic and neurovirulent, hence, the neurovirulence of virus seeds used in the production of mumps vaccines must be tested. The previous neurovirulence evaluation method involves measuring the area of the cavity in the Lewis neonatal rat brain caused by MuV through paraffin sectioning and hematoxylin-eosin (HE) staining. However, the processes of paraffin sectioning and HE staining are time consuming and complicated. To solve this problem, in this study, a vibratome sectioning system was first deployed to evaluate MuV neurovirulence in the rat brain instead of paraffin sectioning and HE staining. The results showed that the vibratome sectioning method could assess the neurovirulence potential of MuV more objectively and efficiently. In addition, the effects of different MuV doses and the ages of the rats in days on this evaluation method were explored. The results indicate that MuV at no less than 10 50 % cell culture infective dose (CCID₅₀) could cause obvious cavity formation in 1-day-old rat brains. The neonatal rat model developed in this study could evaluate the neurovirulence of different MuV strains with high sensitivity and good repeatability.

Immunogenicity of Mumps Virus Genotype G Vaccine Candidates in Jeryl Lynn-Immunized Mice

Mumps virus (MuV) causes a highly contagious human disease characterized by the enlargement of the parotid glands. In severe cases, mumps can lead to neurological complications such as aseptic meningitis and encephalitis. Vaccination with the attenuated Jeryl Lynn (JL) MuV vaccine has dramatically reduced the incidence of MuV infection. Recently, large outbreaks have occurred in vaccinated populations. The vaccine strain JL was generated from genotype A, while most current circulating strains belong to genotype G. In this study, we examined the immunogenicity and longevity of genotype G-based vaccines. We found that our recombinant genotype G-based vaccines provide robust neutralizing titers toward genotype G for up to 1 year in mice. In addition, we demonstrated that a third dose of a genotype G-based vaccine following two doses of JL immunization significantly increases neutralizing titers toward the genotype G strain. Our data suggest that after two doses of JL vaccination, which most people have received, a third dose of a genotype G-based vaccine can generate immunity against a genotype G strain. IMPORTANCE At present, most individuals have received two doses of the measles, mumps, and rubella (MMR) vaccine, which contains genotype A mumps vaccine. One hurdle in developing a new mumps vaccine against circulating genotype G virus is whether the new genotype G vaccine can generate immunity in humans that are immunized against genotype A virus. This work demonstrates that a novel genotype G-based vaccine can be effective in animals which received two doses of genotype A-based vaccine, suggesting that the lead genotype G vaccine may induce anti-G immunity in humans who have received two doses of the current vaccine, providing support for testing this vaccine in humans.

Development of Improved Mumps Vaccine Candidates by Mutating Viral mRNA Cap Methyltransferase Sites in the Large Polymerase Protein

Although a live attenuated vaccine is available for controlling mumps virus (MuV), mumps still outbreaks frequently worldwide. The attenuated MuV vaccine strain S79 is widely used in mumps vaccination in China, but still with many shortcomings, among which the most prominent are the side effects and decreased immunity. Therefore, there is a need to further improve the safety and efficacy of the current MuV vaccine. In the present study, we further attenuated MuV S79 vaccine strain by inhibiting viral mRNA methyltransferase (MTase). We generated a panel of eight recombinant MuVs (rMuVs) carrying mutations in the MTase catalytic site or S-adenosylmethionine (SAM) binding site in the large (L) polymerase protein. These rMuVs are genetically stable and seven rMuVs are more attenuated in replication in cell culture and five rMuVs are more attenuated in replication in lungs of cotton rats compared with the parental vaccine strain S79. Importantly, cotton rats vaccinated with these seven rMuV mutants produced high levels of serum neutralizing antibodies and were completely protected against challenge with a wild-type MuV strain (genotype F). Therefore, our results demonstrate that alteration in the MTase catalytic site or SAM binding site in MuV L protein improves the safety or the immunogenicity of the MuV vaccine and thus mRNA cap MTase may be an effective target for the development of new vaccine candidates for MuV.

Epidemiological and Phylogenetic Analysis of Mumps Virus Isolated from 2016 to 2019 in Henan Province, China

Routine vaccination has proven to be highly effective in reducing the incidence of mumps. However, sporadic cases and/or mumps outbreaks have been reported in children and adolescents younger than 15 years of age, particularly among those aged 5-9 years. To explore the characteristics of such outbreaks in the Henan Province, clinical data of patients infected with mumps virus (MuV) were collected, and the isolated strains were phylogenetically analyzed. Of the total 426 samples analyzed, MuV RNA targeting the small hydrophobic (SH) gene was detected in 153 samples. MuV-positive cases in age groups <5 years, 5-9 years, 10-15 years, 16-19 years, and ≥20 years accounted for 1%, 17%, 12%, 2%, and 4% of the total number of cases, respectively. Phylogenetic analysis based on the SH gene sequences indicated that all of the isolated strains were of genotype F, and isolates in the same subcluster and with identical SH gene sequences tended to be derived from the same community or municipalities when analyzed alongside epidemiological data. In conclusion, the incidence of mumps in the Henan Province was high. The data provided in this study might promote further research in the clarification of the specific causes of mumps outbreaks, which can facilitate the implementation of effective prevention and control measures.

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.

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.

Immunogenicity and safety of the new MMR vaccine containing measles AIK-C, rubella Takahashi, and mumps RIT4385 strains in Japanese children: a randomized phase I/II clinical trial

Domestic measles, mumps, and rubella combined (MMR) vaccines were discontinued in 1993 in Japan because of the unexpected high incidence of aseptic meningitis. The introduction of an effective MMR vaccine with lower reactogenicity has been expected. A new MMR vaccine (JVC-001) was developed, using mumps RIT4385 strain in combination with Japanese measles AIK-C strain and rubella Takahashi strain (MR) vaccine. An open-label, randomized, phase I/II clinical study was conducted in 100 healthy Japanese children equally randomized to a JVC-001 group and an MR with monovalent mumps vaccine (Hoshino strain) group. Immunogenicity was assessed using a neutralization test (NT) for measles, hemagglutination inhibition (HI) test for rubella, and NT and enzyme-linked immune-sorbent assay (ELISA) for mumps strain with different genotypes (genotype A, B, D and G) on Day 0 and Day 42–56. Solicited and unsolicited adverse events (AEs) were recorded. Seroconversion rates of measles and rubella were both 100%. JVC-001 induced higher immunogenicity against mumps virus genotype G with seroconversion rate of 77.1% (95% confidence interval [CI]: 62.7–88.0%) compared to 65.3% (95% CI: 50.4–78.3%) in the control group. Geometric mean titer (GMT) was 12.5 (95% CI: 8.6–18.3) in the JVC-001 group and 7.1 (95% CI: 5.0–10.1) in the control group. JVC-001 also induced good immunogenicity against other genotypes (A, B and D). There was no apparent difference in the incidence of AEs between JVC-001 and the control groups. JVC-001 is safe and induces effective immunogenicity against measles, mumps, and rubella compared with the currently marketed vaccines in Japan.

Differences in antigenic sites and other functional regions between genotype A and G mumps virus surface proteins

The surface proteins of the mumps virus, the fusion protein (F) and haemagglutinin-neuraminidase (HN), are key factors in mumps pathogenesis and are important targets for the immune response during mumps virus infection. We compared the predicted amino acid sequences of the F and HN genes from Dutch mumps virus samples from the pre-vaccine era (1957-1982) with mumps virus genotype G strains (from 2004 onwards). Genotype G is the most frequently detected mumps genotype in recent outbreaks in vaccinated communities, especially in Western Europe, the USA and Japan. Amino acid differences between the Jeryl Lynn vaccine strains (genotype A) and genotype G strains were predominantly located in known B-cell epitopes and in N-linked glycosylation sites on the HN protein. There were eight variable amino acid positions specific to genotype A or genotype G sequences in five known B-cell epitopes of the HN protein. These differences may account for the reported antigenic differences between Jeryl Lynn and genotype G strains. We also found amino acid differences in and near sites on the HN protein that have been reported to play a role in mumps virus pathogenesis. These differences may contribute to the occurrence of genotype G outbreaks in vaccinated communities.

Mumps outbreaks: A problem in need of solutions

OBJECTIVES

To discuss what is presently known about recent mumps outbreaks and what solutions can be suggested to ensure more complete protection against mumps.

METHODS

PubMed was used to search for all of the studies published over the last 15 years using the key words "mumps" or "mumps virus" or "mumps vaccine". More than 1500 articles were found, but only those published in English or providing evidence-based data were included in the evaluation.

RESULTS

Prevention of mumps remains an unsolved problem. Available vaccines are effective but the protection they evoke declines over time. The use of booster doses can control outbreaks but it is not precisely defined whether they can prevent them. The rapid decline of antibody levels could limit the impact of the introduction of a third dose in the recommended immunization schedule. Furthermore, in most of the areas, mumps viral strains that are genetically different from those included in the vaccines are emerging and this might favour vaccine escape. However, also for this problem, its real relevance in favouring outbreak development is not precisely defined.

CONCLUSIONS

The true reasons for the development of mumps outbreaks in people with very high vaccination coverage are not clearly understood. The use of a booster dose or the preparation of vaccines containing the emerging serotypes are possible solutions, but both have some limitations. Further studies mainly devoted to improve our knowledge of the immune response to mumps vaccines are needed before long-term effective mumps vaccines can be prepared and outbreaks can be avoided.