Natural immunity against capsular group X N. meningitidis following an outbreak in Togo, 2007
Gunnstein Norheim1, Judith E Mueller2, Berthe-Marie Njanpop-Lafourcade3
1Oxford Vaccine Group, Department of Paediatrics, University of Oxford, and the NIHR Oxford Biomedical Research Centre, Oxford, UK; Norwegian Institute of Public Health, Oslo, Norway.
Background:
Capsular group X N. meningitidis (MenX) has emerged as a cause of localized disease outbreaks in sub-Saharan Africa, but the human immune response following exposure to MenX antigens is poorly described. We therefore assessed the natural immunity against MenX in individuals who were living in an area affected by a MenX outbreak during 2007 in Togo, West Africa. During 2009, 300 healthy individuals (100 aged 3-5 years, 100 aged 13-19 years and 100 aged 20-25 years) were included in the study, and serum responses were compared with sera from age-matched controls from the U.K. and Burkina Faso.
Methods:
MenX serum bactericidal antibody (SBA) was measured using rabbit complement, and antibodies against MenX polysaccharide (XPS) and outer membrane vesicles (XOMVs) were quantified by ELISA.
Results:
The proportion of Togolese individuals with an SBA titer of ≥8 against the MenX strain was 29% (95% confidence interval (CI) 18-41) among those aged 3-5 years, 34% (95% CI 9-60) among those aged 13-19 years and 32% (95% CI 24-40) among those aged 20-25 years. These were significantly higher than observed in the control populations from the U.K (range 13-16%) and Burkina Faso (range 2-6%).
Conclusion:
In Togolese individuals, the concentration of serum IgG against XPS was higher among the two older age groups as compared to the youngest age group. Antibody concentrations against MenX PS correlated significantly with SBA titers. This supports further development of a MenX PS based conjugate vaccine. Further studies are needed to verify the ability of MenX PS to induce SBA in humans.
Insights
Natural immunity against Neisseria meningitidis serogroup X (MenX) was assessed in Togo. Togolese individuals showed higher MenX serum bactericidal antibody (SBA) levels than UK and Burkina Faso controls, supporting MenX vaccine development.
Area of Science:
- Immunology
- Microbiology
- Vaccinology
Background:
- Neisseria meningitidis serogroup X (MenX) causes outbreaks in sub-Saharan Africa.
- Natural human immune responses to MenX antigens are not well understood.
- Study assessed natural immunity in Togo following a 2007 MenX outbreak.
Purpose of the Study:
- To evaluate natural immunity against MenX in Togolese individuals.
- To compare immune responses in different age groups and with control populations.
- To inform the development of MenX vaccines.
Main Methods:
- Serum bactericidal antibody (SBA) titers against MenX were measured.
- Antibodies against MenX polysaccharide (XPS) and outer membrane vesicles (XOMVs) were quantified using ELISA.
- Togolese participants (n=300) were compared to UK and Burkina Faso controls.
Main Results:
- 29-34% of Togolese individuals had MenX SBA titers ≥8, significantly higher than controls (2-16%).
- Serum IgG concentrations against XPS were higher in older Togolese age groups.
- MenX polysaccharide antibody levels correlated significantly with SBA titers.
Conclusions:
- Togolese individuals exhibit higher natural immunity to MenX compared to control populations.
- MenX polysaccharide shows potential for conjugate vaccine development.
- Further research is needed to confirm MenX polysaccharide's ability to induce SBA in humans.
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