Use of MLST in the epidemiology of meningococci

1. Use of MLST in the epidemiology of meningococci Mary Ramsay

2. Caused by the bacteria Neisseria meningitidis Disease can take two forms meningitis (inflammation of the brain) septicaemia (blood poisoning) High case fatality rate High level of public anxiety Meningococcal disease

4. Notifications of meningococcal diseaseEngland and Wales 1912-1998

5. N. meningitidis is an extremely variable organism N. meningitidis is a common organism found in nasopharynx of health people Most invasive disease is caused by a smaller number of virulent strains Historical description of the diversity of N. meningitidis isolates based mainly on serogrouping of capsular polysaccharide sero/sub-typing of outer membrane proteins Background

6. Neisseria meningitidis- characterisation & typing targets Polysaccharide capsule Serogroup porAclass 1 OMP Sero-subtype VR1, VR2, VR3 porB class 2 OMP Serotype DNA porB class 3 OMP Serotype

7. Virulent strains tend to cluster into small number of clonal complexes with same genetic lineage Broad correlation between routine phenotypic description and and sequence type, but Within each clonal complex strains can maintain different capsular polysaccharides different PorA and PorB proteins Within each phenotype strains can arise from different genetic lineages Current knowledge about meningococci

8. Establishing links between cases in outbreaks Vast majority of disease is sporadic Establishing diversity of meningococci as part of national and international surveillance Deciding on the use of conjugate vaccines in an individual or on a population basis serogroup determination for conjugate vaccines Establishing the need for group B vaccines based on OMPs sero/sub-type determination by phenotyping Por A sequencing Public health objectives of typing

9. Consistent and comparable data from different countries No problems with availability / use of monoclonal antibodies Potential use in culture negative specimens What does MLST add to sequence typing of major surface proteins (eg. Por A)? National and international surveillanceAdvantages of sequence based-typing

10. Sequence 450-500bp internal fragment of seven “house-keeping” genes abcZ, adk, aroE, fumC, gdh, pdhC, pgm Distinct alleles at each loci are assigned a number to produce a seven digit allelic profile Electronic interrogation of database (http://www.mlst.net) allows sequence type (ST) and clonal complex (CC) to be assigned Slow accumulation of genetic changes Determines genetic (clonal) relationship between meningococci Multi-Locus Sequence Typing (MLST)

11. Detection of newly emergent variants Currently identified by phenotypic markers ST could identify new genetic variant which non-typeable by standard methods MLST could identify new genetic variant with same antigenic properties as current strain What is public health significance of detecting a new genetic lineage? If it “escapes” current vaccine protection If it is hyper-virulent eg. hyper-transmissable / high CFR The role of MLST in public health surveillance

12. Case fatality ratio by serogroup Confirmed cases in EU - 1999

13. Confirmed Group W135 Meningococcal DiseaseEngland & Wales - Cumulative Cases by Week

14. Emergence of phenotypically distinct variant observed Epidemiologically associated with Hajj Variant associated with high case fatality rate Higher than endemic W135, similar to group C MLST indicated strains belonged to ST-11 complex Same as majority of group C infections in UK Associated with high case fatality rate Changed recommendation for Hajj vaccination Indicated potential importance of clonal complex Summary

15. Sentinel surveillance of Hajj W135 strainEuropean Union, Sept 2000-2001 Hajj 2001

16. Builds on existing DG-SANCO network Epidemiological and clinical database Phenotypic data Linked to DG-XII research network (EU-MENNET) European MLST centre Linked database Describe diversity of invasive meningococci in EU Determine most virulent organisms Monitor the impact of group C conjugate vaccines European MLST project

17. Distribution of clonal complexesEurope 2000-2002

18. Virulence of meningococci

19. Clonal complexes which normally express group C polysaccharide Can be associated with other capsules (group B/ W135) Pressure from group C vaccination may increase propensity for ST-11 strains to express non-vaccine preventable serogroups increase in group B ST-11 strains Lead to increase in cases High virulence, high CFR, not vaccine preventable Public health uses of MLSTMonitor capsule switching

20. Cases of culture-confirmed serogroup C England & Wales, Ireland and Spain (combined) by age group and year, 1999-2002

21. C-conjugate vaccine Polysaccharide A+C vaccination Possible evidence of capsule switching of meningococci in Spain B:2b and B:2a strains 1995-2002 Slide courtesy of Julio Vazquez, ISCII Madrid

22. Fair correlation between ST-11 and serotype 2a Increase in B2a seen in Spain, not in Ireland and UK England and Wales MLST being applied to non-C 2a strains MLST applied to group B deaths MLST applied to group B non-culture strains Development of SNP assay for ST-11 European monitoring of group B ST-11 in vaccine and non-vaccine countries being commenced Strains with phenotypic markers to be sent for MLST Role of MLST in monitoring capsule switching

23. Continue to collect data To determine changes in EU epidemiology To review the impact of conjugate group C vaccines Further develop into web-enabled database (www.euibis.org) Link to information on MLST project Standard queries being developed Inform European vaccination policy Role of capsule switching Future plans

24. Web-based epidemiological queries (www.euibis.org)

25. All contributing partners Sarah and Caroline at CDSC Ankur and Jon at CPHL Steve, Ed and Andrew at MRU Martin Maiden and Keith Jolley at Oxford Matthias Frosch (EU MEN-NET) European Union DG SANCO Acknowledgements