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Serologic Cross-Reactivity between the Mumps Virus Vaccine Genotype A Strain and the Circulating Genotype G Strain
Sabaparvin Shaikh1,2, Michael Carpenter2, Lisa Lin2
1Department of Medical Microbiology and Infectious Diseases, Faculty of Health Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
Abstract:
Recent mumps outbreaks have been observed in vaccinated young adults due to the mumps virus (MuV) of genotype G, whereas the current vaccine is a mixture of two genotype A strains. These outbreaks could be attributed to waning vaccine immunity or the antigenic differences between the HN and F glycoproteins in the vaccine and circulating MuV. These glycoproteins are essential targets for the immune system, and antigenic variations may reduce the recognition of mumps antibodies, rendering the population susceptible to the MuV. We established stable cell lines expressing the MuV glycoproteins to study cross-reactivity between genotype A and genotype G. Cross-reactivity between the genotypes was evaluated via immunofluorescence using patient sera from vaccinated individuals, infected individuals, and vaccinated individuals infected with genotype G. Titer ratios showed that the vaccinated individuals exhibited a titer 3.68 times higher for the HN protein and 2.3 times higher for the F protein when comparing genotype A with genotype G. In contrast, the infected individuals showed a lower titer for genotype A compared with genotype G, at 0.43 and 0.33 for the HN and F proteins, respectively. No difference in titer ratio was observed for individuals vaccinated and subsequently infected with mumps. These findings suggest that antigenic variations between the two genotypes may potentially result in immune escape of the circulating strain, resulting in individuals susceptible to the MuV.
Insights
Mumps virus (MuV) genotype G outbreaks in vaccinated adults may stem from antigenic differences between vaccine (genotype A) and circulating strains. This suggests potential immune escape and reduced vaccine effectiveness against newer mumps strains.
Area of Science:
- Virology
- Immunology
- Vaccinology
Background:
- Recent mumps outbreaks occur in vaccinated young adults, primarily caused by mumps virus (MuV) genotype G.
- Current mumps vaccines contain genotype A strains, raising questions about vaccine effectiveness against other genotypes.
- Antigenic drift in MuV glycoproteins (HN and F) may impact antibody recognition and vaccine-induced immunity.
Purpose of the Study:
- To investigate the cross-reactivity of immune responses between mumps virus genotypes A and G.
- To evaluate the impact of antigenic differences in HN and F glycoproteins on vaccine effectiveness.
Main Methods:
- Established stable cell lines expressing MuV HN and F glycoproteins from genotypes A and G.
- Utilized immunofluorescence assays with sera from vaccinated, infected, and breakthrough-infected individuals.
- Quantified antibody titers against genotype A and G glycoproteins.
Main Results:
- Vaccinated individuals showed higher antibody titers against genotype A than genotype G.
- In contrast, infected individuals exhibited higher titers against genotype G than genotype A.
- Individuals with breakthrough infections showed no significant difference in titer ratios between genotypes.
Conclusions:
- Antigenic variations between MuV genotypes A and G may contribute to immune escape.
- These variations could reduce the efficacy of current genotype A-based vaccines against circulating genotype G strains.
- Waning immunity and antigenic differences are potential factors in mumps outbreaks among vaccinated populations.
