The Human CD4+ T Cell Response against Mumps Virus Targets a Broadly Recognized Nucleoprotein Epitope

Single-dose mucosal replicon-particle vaccine protects against lethal Nipah virus infection up to 3 days after vaccination

Nipah virus (NiV) causes a highly lethal disease in humans who present with acute respiratory or neurological signs. No vaccines against NiV have been approved to date. Here, we report on the clinical impact of a novel NiV-derived nonspreading replicon particle lacking the fusion (F) protein gene (NiVΔF) as a vaccine in three small animal models of disease. A broad antibody response was detected that included immunoglobulin G (IgG) and IgA subtypes with demonstrable Fc-mediated effector function targeting multiple viral antigens. Single-dose intranasal vaccination up to 3 days before challenge prevented clinical signs and reduced virus levels in hamsters and immunocompromised mice; decreases were seen in tissues and mucosal secretions, critically decreasing potential for virus transmission. This virus replicon particle system provides a vital tool to the field and demonstrates utility as a highly efficacious and safe vaccine candidate that can be administered parenterally or mucosally to protect against lethal Nipah disease.

Nationwide and long-term molecular epidemiologic studies of mumps viruses that circulated in Japan between 1986 and 2017

In Japan, major mumps outbreaks still occur every 4–5 years because of low mumps vaccine coverage (30–40%) owing to the voluntary immunization program. Herein, to prepare for a regular immunization program, we aimed to reveal the nationwide and long-term molecular epidemiological trends of the mumps virus (MuV) in Japan. Additionally, we performed whole-genome sequencing (WGS) using next-generation sequencing to assess results from conventional genotyping using MuV sequences of the small-hydrophobic (SH) gene. We analyzed 1,064 SH gene sequences from mumps clinical samples and MuV isolates collected from 25 prefectures from 1986 to 2017. The results showed that six genotypes, namely B (110), F (1), G (900), H (3), J (41), and L (9) were identified, and the dominant genotypes changed every decade in Japan since the 1980s. Genotype G has been exclusively circulating since the early 2000s. Seven clades were identified for genotype G using SH sequence-based classification. To verify the results, we performed WGS on 77 representative isolates of genotype G using NGS and phylogenetically analyzed them. Five clades were identified with high bootstrap values and designated as Japanese clade (JPC)-1, -2, -3, -4, -5. JPC-1 and -3 accounted for over 80% of the total genotype G isolates (68.3 and 13.8%, respectively). Of these, JPC-2 and -5, were newly identified clades in Japan through this study. This is the first report describing the nationwide and long-term molecular epidemiology of MuV in Japan. The results provide information about Japanese domestic genotypes, which is essential for evaluating the mumps elimination progress in Japan after the forthcoming introduction of the mumps vaccine into Japan’s regular immunization program. Furthermore, the study shows that WGS analysis using NGS is more accurate than results obtained from conventional SH sequence-based classification and is a powerful tool for accurate molecular epidemiology studies.

CD4+ Cytotoxic T cells - Phenotype, Function and Transcriptional Networks Controlling Their Differentiation Pathways

The two major subsets of peripheral T cells are classically divided into the CD4⁺ T helper cells and the cytotoxic CD8⁺ T cell lineage. However, the appearance of some effector CD4⁺ T cell populations displaying cytotoxic activity, in particular during viral infections, has been observed, thus breaking the functional dichotomy of CD4⁺ and CD8⁺ T lymphocytes. The strong association of the appearance of CD4⁺ cytotoxic T lymphocytes (CD4 CTLs) with viral infections suggests an important role of this subset in antiviral immunity by controlling viral replication and infection. Moreover, CD4 CTLs have been linked with anti-tumor activity and might also cause immunopathology in autoimmune diseases. This raises interest into the molecular mechanisms regulating CD4 CTL differentiation, which are poorly understood in comparison to differentiation pathways of other Th subsets. In this review, we provide a brief overview about key features of CD4 CTLs, including their role in viral infections and cancer immunity, and about the link between CD4 CTLs and immune-mediated diseases. Subsequently, we will discuss the current knowledge about transcriptional and epigenetic networks controlling CD4 CTL differentiation and highlight recent data suggesting a role for histone deacetylases in the generation of CD4 CTLs.

The Role of Nucleoprotein in Immunity to Human Negative-Stranded RNA Viruses—Not Just Another Brick in the Viral Nucleocapsid

Negative-stranded RNA viruses (NSVs) are important human pathogens, including emerging and reemerging viruses that cause respiratory, hemorrhagic and other severe illnesses. Vaccine design traditionally relies on the viral surface glycoproteins. However, surface glycoproteins rarely elicit effective long-term immunity due to high variability. Therefore, an alternative approach is to include conserved structural proteins such as nucleoprotein (NP). NP is engaged in myriad processes in the viral life cycle: coating and protection of viral RNA, regulation of transcription/replication processes and induction of immunosuppression of the host. A broad heterosubtypic T-cellular protection was ascribed very early to this protein. In contrast, the understanding of the humoral immunity to NP is very limited in spite of the high titer of non-neutralizing NP-specific antibodies raised upon natural infection or immunization. In this review, the data with important implications for the understanding of the role of NP in the immune response to human NSVs are revisited. Major implications of the elicited T-cell immune responses to NP are evaluated, and the possible multiple mechanisms of the neglected humoral response to NP are discussed. The intention of this review is to remind that NP is a very promising target for the development of future vaccines.

Longitudinal Characterization of the Mumps-Specific HLA-A2 Restricted T-Cell Response after Mumps Virus Infection

Waning of the mumps virus (MuV)-specific humoral response after vaccination has been suggested as a cause for recent mumps outbreaks in vaccinated young adults, although it cannot explain all cases. Moreover, CD8+ T cells may play an important role in the response against MuV; however, little is known about the characteristics and dynamics of the MuV-specific CD8+ T-cell response after MuV infection. Here, we had the opportunity to follow the CD8+ T-cell response to three recently identified HLA-A2*02:01-restricted MuV-specific epitopes from 1.5 to 36 months post-MuV infection in five previously vaccinated and three unvaccinated individuals. The infection-induced CD8+ T-cell response was dominated by T cells specific for the ALDQTDIRV and LLDSSTTRV epitopes, while the response to the GLMEGQIVSV epitope was subdominant. MuV-specific CD8+ T-cell frequencies in the blood declined between 1.5 and 9 months after infection. This decline was not explained by changes in the expression of inhibitory receptors or homing markers. Despite the ongoing changes in the frequencies and phenotype of MuV-specific CD8+ T cells, TCRβ analyses revealed a stable MuV-specific T-cell repertoire over time. These insights in the maintenance of the cellular response against mumps may provide hallmarks for optimizing vaccination strategies towards a long-term cellular memory response.

Novel mumps virus epitopes reveal robust cytotoxic T cell responses after natural infection but not after vaccination

Mumps is nowadays re-emerging despite vaccination. The contribution of T cell immunity to protection against mumps has not been clearly defined. Previously, we described a set of 41 peptides that were eluted from human leukocyte antigen (HLA) class I molecules of mumps virus (MuV)-infected cells. Here, we confirmed immunogenicity of five novel HLA-B*07:02- and HLA-A*01:01-restricted MuV T cell epitopes from this set of peptides. High frequencies of T cells against these five MuV epitopes could be detected ex vivo in all tested mumps patients. Moreover, these epitope-specific T cells derived from mumps patients displayed strong cytotoxic activity. In contrast, only marginal T cell responses against these novel MuV epitopes could be detected in recently vaccinated persons, corroborating earlier findings. Identifying which MuV epitopes are dominantly targeted in the mumps-specific CD8⁺ T- response is an important step towards better understanding in the discrepancies between natural infection or vaccination-induced cell-mediated immune protection.

Genetic Analysis Reveals Differences in CD8+ T Cell Epitope Regions That May Impact Cross-Reactivity of Vaccine-Induced T Cells against Wild-Type Mumps Viruses

Nowadays, mumps is re-emerging in highly vaccinated populations. Waning of vaccine-induced immunity plays a role, but antigenic differences between vaccine and mumps outbreak strains could also contribute to reduced vaccine effectiveness. CD8⁺ T cells play a critical role in immunity to viruses. However, limited data are available about sequence variability in CD8⁺ T cell epitope regions of mumps virus (MuV) proteins. Recently, the first set of naturally presented human leukocyte antigen Class I (HLA-I) epitopes of MuV was identified by us. In the present study, sequences of 40 CD8⁺ T cell epitope candidates, including previously and newly identified, obtained from Jeryl–Lynn mumps vaccine strains were compared with genomes from 462 circulating MuV strains. In 31 epitope candidates (78%) amino acid differences were detected, and in 17 (43%) of the epitope candidates the corresponding sequences in wild-type strains had reduced predicted HLA-I-binding compared to the vaccine strains. These findings suggest that vaccinated persons may have reduced T cell immunity to circulating mumps viruses due to antigenic differences.

A Third Dose of Measles-Mumps-Rubella Vaccine to Improve Immunity Against Mumps in Young Adults

BACKGROUND

Waning of vaccine-induced immunity is considered to play a central role in the reemergence of mumps among vaccinated young adults. The aim of the present study was to investigate antibody responses and safety of a third dose of measles-mumps-rubella vaccine (MMR-3) in 150 young adults. Antibody levels were related to a surrogate of protection based on preoutbreak serum antibody levels in 31 persons with and 715 without serological evidence of mumps.

METHODS

Mumps virus-specific immunoglobulin G (IgG) antibody responses and mumps virus-neutralizing antibody responses (based on the focus-reduction neutralizing test) against both the Jeryl Lynn mumps virus vaccine strain (hereafter, the "vaccine strain") and the MuVi/Utrecht.NLD/40.10 outbreak strain (hereafter, the "outbreak strain") were determined, and vaccine safety was evaluated.

RESULTS

Four weeks following MMR-3 receipt, levels of IgG, anti-vaccine strain, and anti-outbreak strain antibodies increased by a factor of 1.65, 1.34, and 1.35, respectively. Although antibody levels decreased 1 year later, they were still above the baseline level by a factor of 1.37, 1.15, and 1.27, respectively. Based on the surrogate protective antibody cutoff, significantly more participants were protected against mumps virus infection up to 1 year after vaccination (ie, they had antibody levels above the presumed threshold for herd immunity).

CONCLUSIONS

MMR-3 receipt increased antibody levels that may protect against mumps virus infection for longer than previously assumed and is expected to be a good and safe intervention for controlling a mumps outbreak.

CLINICAL TRIALS REGISTRATION

2016-001104-36; NTR5911.

Identification of Naturally Processed Mumps Virus Epitopes by Mass Spectrometry: Confirmation of Multiple CD8+ T-Cell Responses in Mumps Patients

BACKGROUND

The re-emergence of mumps among vaccinated young adults has become a global issue. Besides waning of antibody responses, suboptimal induction of T-cell responses may reduce protection. In a recent study, we observed a dominant polyfunctional CD8+ T-cell response after natural mumps virus (MuV) infection that was not present after vaccination. Unraveling the MuV epitope repertoire can provide insight in the specificity, functionality, and breadth of the T-cell response against MuV.

METHODS

Peptides were eluted from human leukocyte antigen (HLA) class I molecules of MuV-infected cells and characterized by advanced mass spectrometry. Selected identified MuV peptides were tested for in vitro and ex vivo immunogenicity.

RESULTS

In this study, we identified a broad landscape of 83 CD8+ T-cell epitopes of MuV, 41 of which were confirmed based on synthetic peptide standards. For 6 epitopes, we showed induction of an HLA-A*02-restriced CD8+ T-cell response. Moreover, robust T-cell responses against 5 selected MuV epitopes could be detected in all tested mumps patients using peptide/HLA-A*02:01 dextramers.

CONCLUSIONS

The identified CD8+ T-cell epitopes will help to further characterize MuV-specific T-cell immunity after natural MuV infection or vaccination. These MuV epitopes may provide clues for a better understanding of, and possibly for preventing, mumps vaccine failure.We identified for the first time 41 mumps virus (MuV)-specific HLA-A*02 epitopes. For 6 epitopes, CD8+ T-cell responses were confirmed in T cells derived from several mumps cases, and MuV-specific CD8+ T cells could be identified by peptide/dextramer staining.

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 association between short-term exposure to ambient air pollution and the incidence of mumps in Wuhan, China: A time-series study

BACKGROUND

Previous studies have estimated the association between meteorological factors and mumps outbreaks without assessing the influence of air pollution. In this research, we explored the effects of short-term exposure to air pollution on the incidence of mumps.

METHODS

Our time-series analysis was conducted using data collected in Wuhan, China from 2015 to 2017. Daily number of mumps cases was obtained from Disease Reporting System in Hubei Provincial Center for Disease Control and Prevention. Data on air pollution was obtained from 10 national air quality monitoring stations, including nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ground-level ozone (O₃), particulate matter less than or equal to 10 μm in aerodynamic diameter (PM₁₀), and particulate matter less than or equal to 2.5 μm in aerodynamic diameter (PM_2.5). Daily meteorological data including temperature and relative humidity were obtained from Hubei Meteorological Bureau. We performed a Poisson regression in generalized additive models (GAM) to explore the association between the incidence of mumps and exposure to air pollution.

RESULTS

We observed that the effects of air pollutants were statistically significant mainly in two periods, lag 0 to lag 5 and lag 20 to lag 25, with the strongest effects appearing at lag 2 and lag 23. The cumulative effects were stronger than single-day lag effects. The stratified analysis showed the effect of pollutants during the hot season was stronger than that during the cold season, especially for NO₂ and SO₂.

CONCLUSIONS

We found that exposure to NO₂ and SO₂ was significantly associated with higher risk of developing mumps. Our findings could help deepen the understanding of how air pollution exposure affects the incidence of mumps.